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Lange TE, Naji A, van der Hoeven R, Liang H, Zhou Y, Hammond GR, Hancock JF, Cho KJ. MTMR regulates KRAS function by controlling plasma membrane levels of phospholipids. J Cell Biol 2025; 224:e202403126. [PMID: 40314454 PMCID: PMC12047185 DOI: 10.1083/jcb.202403126] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/21/2024] [Revised: 09/08/2024] [Accepted: 10/18/2024] [Indexed: 05/03/2025] Open
Abstract
KRAS, a small GTPase involved in cell proliferation and differentiation, frequently gains activating mutations in human cancers. For KRAS to function, it must bind the plasma membrane (PM) via interactions between its membrane anchor and phosphatidylserine (PtdSer). Therefore, depleting PM PtdSer abrogates KRAS PM binding and activity. From a genome-wide siRNA screen to identify genes regulating KRAS PM localization, we identified a set of phosphatidylinositol (PI) 3-phosphatases: myotubularin-related proteins (MTMR) 2, 3, 4, and 7. Here, we show that silencing MTMR 2/3/4/7 disrupts KRAS PM interactions by reducing PM PI 4-phosphate (PI4P) levels, thereby disrupting the localization and operation of ORP5, a lipid transfer protein maintaining PM PtdSer enrichment. Concomitantly, silencing MTMR 2/3/4/7 elevates PM PI3P levels while reducing PM and total PtdSer levels. We also observed MTMR 2/3/4/7 expression is interdependent. We propose that the PI 3-phosphatase activity of MTMR is required for generating PM PI, necessary for PM PI4P synthesis, promoting the PM localization of PtdSer and KRAS.
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Affiliation(s)
- Taylor E. Lange
- Department of Biochemistry and Molecular Biology, Boonshoft School of Medicine, Wright State University, Dayton, OH, USA
| | - Ali Naji
- Department of Diagnostic and Biomedical Sciences, School of Dentistry, The University of Texas Health Science Center at Houston, Houston, TX, USA
| | - Ransome van der Hoeven
- Department of Diagnostic and Biomedical Sciences, School of Dentistry, The University of Texas Health Science Center at Houston, Houston, TX, USA
| | - Hong Liang
- Department of Integrative Biology and Pharmacology, McGovern Medical School, University of Texas Health Science Center, Houston, TX, USA
| | - Yong Zhou
- Department of Integrative Biology and Pharmacology, McGovern Medical School, University of Texas Health Science Center, Houston, TX, USA
| | - Gerald R.V. Hammond
- Department of Cell Biology, University of Pittsburgh School of Medicine, Pittsburgh, PA, USA
| | - John F. Hancock
- Department of Integrative Biology and Pharmacology, McGovern Medical School, University of Texas Health Science Center, Houston, TX, USA
| | - Kwang-jin Cho
- Department of Biochemistry and Molecular Biology, Boonshoft School of Medicine, Wright State University, Dayton, OH, USA
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Jiang Y, Wu B, Zhang X, Yang L, Wang S, Li H, Zhou S, Qian Y, Wang H. Thirteen New Patients of PPP2R5D Gene Mutation and the Fine Profile of Genotype-Phenotype Correlation Unraveling the Pathogenic Mechanism Underlying Macrocephaly Phenotype. CHILDREN (BASEL, SWITZERLAND) 2024; 11:897. [PMID: 39201832 PMCID: PMC11352527 DOI: 10.3390/children11080897] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 06/17/2024] [Revised: 07/21/2024] [Accepted: 07/22/2024] [Indexed: 09/03/2024]
Abstract
BACKGROUND Neurodevelopmental disorders (NDDs) are a group of diseases that severely affect the physical and mental health of children. The PPP2R5D gene encodes B56δ, the regulatory subunit of protein phosphatase 2A (PP2A). NDDs related to the PPP2R5D gene have recently been defined as Houge-Janssens syndrome 1. METHODS Clinical/whole exome sequencing was performed on approximately 3000 patients with NDDs from 2017 to 2023. In vitro experiments were performed to assess the impairment of variants to protein expression and the assembly of PP2A holoenzyme. The genetic information and phenotypes of the reported patients, as well as patients in this study, were summarized, and the genotype-phenotype relationship was analyzed. The probability of pathogenic missense variants in PPP2R5D was predicted using AlphaMissense (AM), and the relationship between certain phenotype and 3D protein structural features were analyzed. RESULTS Thirteen new patients carrying twelve PPP2R5D gene variants were detected, including five novel missense variants and one novel frameshift variant. In vitro experiments revealed that the frameshift variant p.H463Mfs*3 resulted in a ~50 kDa truncated protein with lower expression level. Except for E420K and T536R, other missense variants impaired holoenzyme assembly. Furthermore, we found that pathogenic/likely pathogenic (P/LP) variants that have been reported so far were all missense variants and clustered in three conserved regions, and the likelihood of P/LP mutations located in these conserved regions was extremely high. In addition, the macrocephaly phenotype was related to negatively charged residues involved in substrate recruitment. CONCLUSIONS We reported thirteen new patients with PPP2R5D gene variants and expanded the PPP2R5D variant spectrum. We confirmed the pathogenicity of novel variants through in vitro experiments. Our findings in genotype-phenotype relationship provide inspiration for genetic counseling and interpretation of variants. We also provide directions for further research on the mechanism of macrocephaly phenotype.
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Affiliation(s)
- Yinmo Jiang
- Center for Molecular Medicine, Pediatrics Research Institute, Children’s Hospital of Fudan University, National Children’s Medical Center, 399 Wanyuan Road, Shanghai 201102, China; (Y.J.); (X.Z.)
| | - Bingbing Wu
- Center for Molecular Medicine, Pediatrics Research Institute, Children’s Hospital of Fudan University, National Children’s Medical Center, 399 Wanyuan Road, Shanghai 201102, China; (Y.J.); (X.Z.)
| | - Xi Zhang
- Center for Molecular Medicine, Pediatrics Research Institute, Children’s Hospital of Fudan University, National Children’s Medical Center, 399 Wanyuan Road, Shanghai 201102, China; (Y.J.); (X.Z.)
| | - Lin Yang
- Center for Molecular Medicine, Pediatrics Research Institute, Children’s Hospital of Fudan University, National Children’s Medical Center, 399 Wanyuan Road, Shanghai 201102, China; (Y.J.); (X.Z.)
| | - Sujuan Wang
- Department of Rehabilitation, Children’s Hospital of Fudan University, Shanghai 201102, China
| | - Huiping Li
- Department of Child Health Care, Children’s Hospital of Fudan University, National Children’s Medical Center, 399 Wanyuan Road, Shanghai 201102, China
| | - Shuizhen Zhou
- Neurology Department, Children’s Hospital of Fudan University, National Children’s Medical Center, 399 Wanyuan Road, Shanghai 201102, China
| | - Yanyan Qian
- Center for Molecular Medicine, Pediatrics Research Institute, Children’s Hospital of Fudan University, National Children’s Medical Center, 399 Wanyuan Road, Shanghai 201102, China; (Y.J.); (X.Z.)
| | - Huijun Wang
- Center for Molecular Medicine, Pediatrics Research Institute, Children’s Hospital of Fudan University, National Children’s Medical Center, 399 Wanyuan Road, Shanghai 201102, China; (Y.J.); (X.Z.)
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Zhang Y, Jiang Q, Liang X, Qian Q, Xiong J, Liu C, Xu J, Wang N, Xu Y, Zhou P, Lu S, Zhou Q, Yuan Y, Fan X, Liu J, Chen S. Coagulation Factor VII Fine-tunes Hepatic Steatosis by Blocking AKT-CD36-Mediated Fatty Acid Uptake. Diabetes 2024; 73:682-700. [PMID: 38394642 DOI: 10.2337/db23-0814] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/11/2023] [Accepted: 02/13/2024] [Indexed: 02/25/2024]
Abstract
Nonalcoholic fatty liver disease (NAFLD) is considered a risk factor for cardiovascular and cerebrovascular disease owing to its close association with coagulant disturbances. However, the precise biological functions and mechanisms that connect coagulation factors to NAFLD pathology remain inadequately understood. Herein, with unbiased bioinformatics analyses followed by functional testing, we demonstrate that hepatic expression of coagulation factor VII (FVII) decreases in patients and mice with NAFLD/nonalcoholic steatohepatitis (NASH). By using adenovirus-mediated F7-knockdown and hepatocyte-specific F7-knockout mouse models, our mechanistic investigations unveil a noncoagulant function of hepatic FVII in mitigating lipid accumulation and lipotoxicity. This protective effect is achieved through the suppression of fatty acid uptake, orchestrated via the AKT-CD36 pathway. Interestingly, intracellular FVII directly interacts with AKT and PP2A, thereby promoting their association and triggering the dephosphorylation of AKT. Therapeutic intervention through adenovirus-mediated liver-specific overexpression of F7 results in noteworthy improvements in liver steatosis, inflammation, injury, and fibrosis in severely afflicted NAFLD mice. In conclusion, our findings highlight coagulation factor FVII as a critical regulator of hepatic steatosis and a potential target for the treatment of NAFLD and NASH. ARTICLE HIGHLIGHTS
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Affiliation(s)
- Yao Zhang
- Shanghai Diabetes Institute, Department of Endocrinology and Metabolism, Shanghai Sixth People's Hospital Affiliated to Shanghai Jiao Tong University School of Medicine, Shanghai, China
| | - Quanxin Jiang
- Shanghai Diabetes Institute, Department of Endocrinology and Metabolism, Shanghai Sixth People's Hospital Affiliated to Shanghai Jiao Tong University School of Medicine, Shanghai, China
| | | | - Qiqi Qian
- Shanghai Diabetes Institute, Department of Endocrinology and Metabolism, Shanghai Sixth People's Hospital Affiliated to Shanghai Jiao Tong University School of Medicine, Shanghai, China
| | - Jie Xiong
- Shanghai Diabetes Institute, Department of Endocrinology and Metabolism, Shanghai Sixth People's Hospital Affiliated to Shanghai Jiao Tong University School of Medicine, Shanghai, China
| | - Chuchu Liu
- Shanghai Diabetes Institute, Department of Endocrinology and Metabolism, Shanghai Sixth People's Hospital Affiliated to Shanghai Jiao Tong University School of Medicine, Shanghai, China
| | - Junting Xu
- Shanghai Diabetes Institute, Department of Endocrinology and Metabolism, Shanghai Sixth People's Hospital Affiliated to Shanghai Jiao Tong University School of Medicine, Shanghai, China
| | - Ning Wang
- Shanghai Diabetes Institute, Department of Endocrinology and Metabolism, Shanghai Sixth People's Hospital Affiliated to Shanghai Jiao Tong University School of Medicine, Shanghai, China
| | - Ying Xu
- Shanghai Diabetes Institute, Department of Endocrinology and Metabolism, Shanghai Sixth People's Hospital Affiliated to Shanghai Jiao Tong University School of Medicine, Shanghai, China
| | - Peihui Zhou
- Shanghai Diabetes Institute, Department of Endocrinology and Metabolism, Shanghai Sixth People's Hospital Affiliated to Shanghai Jiao Tong University School of Medicine, Shanghai, China
| | - Sijia Lu
- Shanghai Diabetes Institute, Department of Endocrinology and Metabolism, Shanghai Sixth People's Hospital Affiliated to Shanghai Jiao Tong University School of Medicine, Shanghai, China
| | - Qian Zhou
- Shanghai Diabetes Institute, Department of Endocrinology and Metabolism, Shanghai Sixth People's Hospital Affiliated to Shanghai Jiao Tong University School of Medicine, Shanghai, China
| | - Yanmei Yuan
- Shanghai Diabetes Institute, Department of Endocrinology and Metabolism, Shanghai Sixth People's Hospital Affiliated to Shanghai Jiao Tong University School of Medicine, Shanghai, China
| | - Xuemei Fan
- Department of Biochemistry and Molecular Cell Biology, Key Laboratory of Cell Differentiation and Apoptosis of Chinese Ministry of Education, Shanghai Jiao Tong University School of Medicine, Shanghai, China
| | - Junli Liu
- Shanghai Diabetes Institute, Department of Endocrinology and Metabolism, Shanghai Sixth People's Hospital Affiliated to Shanghai Jiao Tong University School of Medicine, Shanghai, China
| | - Suzhen Chen
- Shanghai Diabetes Institute, Department of Endocrinology and Metabolism, Shanghai Sixth People's Hospital Affiliated to Shanghai Jiao Tong University School of Medicine, Shanghai, China
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Hou G, Hu W, Sang Y, Gan X, Xu H, Hu Q, Cao X. Corynoxine triggers cell death via activating PP2A and regulating AKT-mTOR/GSK3β axes in NSCLC. Biochem Pharmacol 2024; 222:116110. [PMID: 38460908 DOI: 10.1016/j.bcp.2024.116110] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/17/2023] [Revised: 02/16/2024] [Accepted: 03/05/2024] [Indexed: 03/11/2024]
Abstract
This study investigates the anticancer activity and pharmacological mechanisms of Corynoxine (Cory) in non-small cell lung cancer (NSCLC). Cory, a natural product derived from the Chinese herbal medicine Uncaria rhynchophylla, demonstrates promising pharmacological activity. Cell proliferation and viability were evaluated via MTT and colony formation assays. Flow cytometry was employed to analyze cell apoptosis, cycle distribution, and mitochondrial membrane potential. Autophagy was detected using fluorescence microscopy and electron microscopy. Western blotting, protein overexpression, gene knockdown, co-immunoprecipitation, and bioinformatics characterized Cory's impact on signaling pathways. The research indicates that Cory inhibits the proliferation of NSCLC cells in vivo and in vitro. Cory enhances PP2A activity, inhibits the AKT/mTOR signaling pathway triggering autophagy, while suppressing the AKT/GSK3β signaling pathway to induce cellular apoptosis in NSCLC. Notably, the activation of PP2A plays a crucial role in Cory's antitumor effects by inhibiting AKT. In vivo experiments validated Cory's efficacy in NSCLC treatment. These findings highlight the promising role of Cory as a lead compound for drug development in NSCLC therapy, providing a viable option for addressing this challenging disease.
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Affiliation(s)
- Guoqing Hou
- School of Basic Medicine, Tongji Medical College, Huazhong University of Science and Technology, Wuhan 430030, Hubei, China; School of Medicine, Taizhou University, Taizhou 318000, Zhejiang, China
| | - Weihua Hu
- Department of Orthopedics, Tongji Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan 430030, Hubei, China
| | - Yazhou Sang
- School of Basic Medicine, Tongji Medical College, Huazhong University of Science and Technology, Wuhan 430030, Hubei, China
| | - Xiaocai Gan
- School of Basic Medicine, Tongji Medical College, Huazhong University of Science and Technology, Wuhan 430030, Hubei, China
| | - Hui Xu
- School of Basic Medicine, Tongji Medical College, Huazhong University of Science and Technology, Wuhan 430030, Hubei, China
| | - Qiongying Hu
- School of Medicine, Taizhou University, Taizhou 318000, Zhejiang, China.
| | - Xuan Cao
- School of Basic Medicine, Tongji Medical College, Huazhong University of Science and Technology, Wuhan 430030, Hubei, China; School of Medicine, Taizhou University, Taizhou 318000, Zhejiang, China.
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Nadel G, Yao Z, Hacohen-Lev-Ran A, Wainstein E, Maik-Rachline G, Ziv T, Naor Z, Admon A, Seger R. Phosphorylation of PP2Ac by PKC is a key regulatory step in the PP2A-switch-dependent AKT dephosphorylation that leads to apoptosis. Cell Commun Signal 2024; 22:154. [PMID: 38419089 PMCID: PMC10900696 DOI: 10.1186/s12964-024-01536-7] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/17/2023] [Accepted: 02/17/2024] [Indexed: 03/02/2024] Open
Abstract
BACKGROUND Although GqPCR activation often leads to cell survival by activating the PI3K/AKT pathway, it was previously shown that in several cell types AKT activity is reduced and leads to JNK activation and apoptosis. The mechanism of AKT inactivation in these cells involves an IGBP1-coupled PP2Ac switch that induces the dephosphorylation and inactivation of both PI3K and AKT. However, the machinery involved in the initiation of PP2A switch is not known. METHODS We used phospho-mass spectrometry to identify the phosphorylation site of PP2Ac, and raised specific antibodies to follow the regulation of this phosphorylation. Other phosphorylations were monitored by commercial antibodies. In addition, we used coimmunoprecipitation and proximity ligation assays to follow protein-protein interactions. Apoptosis was detected by a TUNEL assay as well as PARP1 cleavage using SDS-PAGE and Western blotting. RESULTS We identified Ser24 as a phosphorylation site in PP2Ac. The phosphorylation is mediated mainly by classical PKCs (PKCα and PKCβ) but not by novel PKCs (PKCδ and PKCε). By replacing the phosphorylated residue with either unphosphorylatable or phosphomimetic residues (S24A and S24E), we found that this phosphorylation event is necessary and sufficient to mediate the PP2A switch, which ultimately induces AKT inactivation, and a robust JNK-dependent apoptosis. CONCLUSION Our results show that the PP2A switch is induced by PKC-mediated phosphorylation of Ser24-PP2Ac and that this phosphorylation leads to apoptosis upon GqPCR induction of various cells. We propose that this mechanism may provide an unexpected way to treat some cancer types or problems in the endocrine machinery.
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Affiliation(s)
- Guy Nadel
- Department of Immunology and Regenerative Biology, the Weizmann Institute of Science, Rehovot, Israel
| | - Zhong Yao
- Department of Immunology and Regenerative Biology, the Weizmann Institute of Science, Rehovot, Israel
| | - Avital Hacohen-Lev-Ran
- Department of Immunology and Regenerative Biology, the Weizmann Institute of Science, Rehovot, Israel
| | - Ehud Wainstein
- Department of Immunology and Regenerative Biology, the Weizmann Institute of Science, Rehovot, Israel
| | - Galia Maik-Rachline
- Department of Immunology and Regenerative Biology, the Weizmann Institute of Science, Rehovot, Israel
| | - Tamar Ziv
- Smoler Proteomic Center, Technion-Israel Institute of Technology, Haifa, Israel
| | - Zvi Naor
- Department of Biochemistry and Molecular Biology, Tel Aviv University, Tel Aviv, Israel
| | - Arie Admon
- Faculty of Biology, Technion-Israel Institute of Technology, Haifa, Israel
| | - Rony Seger
- Department of Immunology and Regenerative Biology, the Weizmann Institute of Science, Rehovot, Israel.
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Hogg EKJ, Findlay GM. Functions of SRPK, CLK and DYRK kinases in stem cells, development, and human developmental disorders. FEBS Lett 2023; 597:2375-2415. [PMID: 37607329 PMCID: PMC10952393 DOI: 10.1002/1873-3468.14723] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/05/2023] [Revised: 07/08/2023] [Accepted: 07/18/2023] [Indexed: 08/24/2023]
Abstract
Human developmental disorders encompass a wide range of debilitating physical conditions and intellectual disabilities. Perturbation of protein kinase signalling underlies the development of some of these disorders. For example, disrupted SRPK signalling is associated with intellectual disabilities, and the gene dosage of DYRKs can dictate the pathology of disorders including Down's syndrome. Here, we review the emerging roles of the CMGC kinase families SRPK, CLK, DYRK, and sub-family HIPK during embryonic development and in developmental disorders. In particular, SRPK, CLK, and DYRK kinase families have key roles in developmental signalling and stem cell regulation, and can co-ordinate neuronal development and function. Genetic studies in model organisms reveal critical phenotypes including embryonic lethality, sterility, musculoskeletal errors, and most notably, altered neurological behaviours arising from defects of the neuroectoderm and altered neuronal signalling. Further unpicking the mechanisms of specific kinases using human stem cell models of neuronal differentiation and function will improve our understanding of human developmental disorders and may provide avenues for therapeutic strategies.
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Affiliation(s)
- Elizabeth K. J. Hogg
- The MRC Protein Phosphorylation and Ubiquitylation Unit, School of Life SciencesUniversity of DundeeUK
| | - Greg M. Findlay
- The MRC Protein Phosphorylation and Ubiquitylation Unit, School of Life SciencesUniversity of DundeeUK
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Peris I, Romero-Murillo S, Vicente C, Narla G, Odero MD. Regulation and role of the PP2A-B56 holoenzyme family in cancer. Biochim Biophys Acta Rev Cancer 2023; 1878:188953. [PMID: 37437699 DOI: 10.1016/j.bbcan.2023.188953] [Citation(s) in RCA: 7] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/14/2023] [Revised: 07/07/2023] [Accepted: 07/08/2023] [Indexed: 07/14/2023]
Abstract
Protein phosphatase 2A (PP2A) inactivation is common in cancer, leading to sustained activation of pro-survival and growth-promoting pathways. PP2A consists of a scaffolding A-subunit, a catalytic C-subunit, and a regulatory B-subunit. The functional complexity of PP2A holoenzymes arises mainly through the vast repertoire of regulatory B-subunits, which determine both their substrate specificity and their subcellular localization. Therefore, a major challenge for developing more effective therapeutic strategies for cancer is to identify the specific PP2A complexes to be targeted. Of note, the development of small molecules specifically directed at PP2A-B56α has opened new therapeutic avenues in both solid and hematological tumors. Here, we focus on the B56/PR61 family of PP2A regulatory subunits, which have a central role in directing PP2A tumor suppressor activity. We provide an overview of the mechanisms controlling the formation and regulation of these complexes, the pathways they control, and the mechanisms underlying their deregulation in cancer.
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Affiliation(s)
- Irene Peris
- Department of Biochemistry and Genetics, University of Navarra, Pamplona, Spain; Centro de Investigación Médica Aplicada (CIMA), University of Navarra, Pamplona, Spain; Instituto de Investigación Sanitaria de Navarra (IdiSNA), Pamplona, Spain.
| | - Silvia Romero-Murillo
- Department of Biochemistry and Genetics, University of Navarra, Pamplona, Spain; Centro de Investigación Médica Aplicada (CIMA), University of Navarra, Pamplona, Spain
| | - Carmen Vicente
- Centro de Investigación Médica Aplicada (CIMA), University of Navarra, Pamplona, Spain; Instituto de Investigación Sanitaria de Navarra (IdiSNA), Pamplona, Spain
| | - Goutham Narla
- Division of Genetic Medicine, Department of Internal Medicine, The University of Michigan Medical School, Ann Arbor, MI, USA
| | - Maria D Odero
- Department of Biochemistry and Genetics, University of Navarra, Pamplona, Spain; Centro de Investigación Médica Aplicada (CIMA), University of Navarra, Pamplona, Spain; Instituto de Investigación Sanitaria de Navarra (IdiSNA), Pamplona, Spain; CIBERONC, Instituto de Salud Carlos III, Madrid, Spain.
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Nadel G, Maik-Rachline G, Seger R. JNK Cascade-Induced Apoptosis-A Unique Role in GqPCR Signaling. Int J Mol Sci 2023; 24:13527. [PMID: 37686335 PMCID: PMC10487481 DOI: 10.3390/ijms241713527] [Citation(s) in RCA: 6] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/27/2023] [Revised: 08/27/2023] [Accepted: 08/28/2023] [Indexed: 09/10/2023] Open
Abstract
The response of cells to extracellular signals is mediated by a variety of intracellular signaling pathways that determine stimulus-dependent cell fates. One such pathway is the cJun-N-terminal Kinase (JNK) cascade, which is mainly involved in stress-related processes. The cascade transmits its signals via a sequential activation of protein kinases, organized into three to five tiers. Proper regulation is essential for securing a proper cell fate after stimulation, and the mechanisms that regulate this cascade may involve the following: (1) Activatory or inhibitory phosphorylations, which induce or abolish signal transmission. (2) Regulatory dephosphorylation by various phosphatases. (3) Scaffold proteins that bring distinct components of the cascade in close proximity to each other. (4) Dynamic change of subcellular localization of the cascade's components. (5) Degradation of some of the components. In this review, we cover these regulatory mechanisms and emphasize the mechanism by which the JNK cascade transmits apoptotic signals. We also describe the newly discovered PP2A switch, which is an important mechanism for JNK activation that induces apoptosis downstream of the Gq protein coupled receptors. Since the JNK cascade is involved in many cellular processes that determine cell fate, addressing its regulatory mechanisms might reveal new ways to treat JNK-dependent pathologies.
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Affiliation(s)
| | | | - Rony Seger
- Department of Immunology and Regenerative Biology, Weizmann Institute of Science, Rehovot 7610001, Israel; (G.N.); (G.M.-R.)
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Norberto S, Assalin HB, Guadagnini D, Tobar N, Boer PA, Kang MC, Saad MJA, Kim YB, Prada PO. CLK2 in GABAergic neurons is critical in regulating energy balance and anxiety-like behavior in a gender-specific fashion. Front Endocrinol (Lausanne) 2023; 14:1172835. [PMID: 37635967 PMCID: PMC10449579 DOI: 10.3389/fendo.2023.1172835] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/23/2023] [Accepted: 07/24/2023] [Indexed: 08/29/2023] Open
Abstract
Introduction Cdc2-like kinase (CLK2) is a member of CLK kinases expressed in hypothalamic neurons and is activated in response to refeeding, leptin, or insulin. Diet-induced obesity and leptin receptor-deficient db/db mice lack CLK2 signal in the hypothalamic neurons. The neurotransmiter gamma-aminobutyric acid (GABA) is among the most prevalent in the central nervous system (CNS), particularly in the hypothalamus. Given the abundance of GABA-expressing neurons and their potential influence on regulating energy and behavioral homeostasis, we aimed to explore whether the deletion of CLK2 in GABAergic neurons alters energy homeostasis and behavioral and cognitive functions in both genders of mice lacking CLK2 in Vgat-expressing neurons (Vgat-Cre; Clk2loxP/loxP) on chow diet. Methods We generated mice lacking Clk2 in Vgat-expressing neurons (Vgat-Cre; Clk2loxP/loxP) by mating Clk2loxP/loxP mice with Vgat-IRES-Cre transgenic mice and employed behavior, and physiological tests, and molecular approaches to investigate energy metabolism and behavior phenotype of both genders. Results and discussion We showed that deletion of CLK2 in GABAergic neurons increased adiposity and food intake in females. The mechanisms behind these effects were likely due, at least in part, to hypothalamic insulin resistance and upregulation of hypothalamic Npy and Agrp expression. Besides normal insulin and pyruvate sensitivity, Vgat-Cre; Clk2loxP/loxP females were glucose intolerant. Male Vgat-Cre; Clk2loxP/loxP mice showed an increased energy expenditure (EE). Risen EE may account for avoiding weight and fat mass gain in male Vgat-Cre; Clk2loxP/loxP mice. Vgat-Cre; Clk2loxP/loxP mice had no alteration in cognition or memory functions in both genders. Interestingly, deleting CLK2 in GABAergic neurons changed anxiety-like behavior only in females, not males. These findings suggest that CLK2 in GABAergic neurons is critical in regulating energy balance and anxiety-like behavior in a gender-specific fashion and could be a molecular therapeutic target for combating obesity associated with psychological disorders in females.
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Affiliation(s)
- Sónia Norberto
- Department of Internal Medicine, School of Medical Science, University of Campinas (UNICAMP), Campinas, SP, Brazil
| | - Heloisa Balan Assalin
- Department of Internal Medicine, School of Medical Science, University of Campinas (UNICAMP), Campinas, SP, Brazil
| | - Dioze Guadagnini
- Department of Internal Medicine, School of Medical Science, University of Campinas (UNICAMP), Campinas, SP, Brazil
| | - Natália Tobar
- Department of Radiology, University of Campinas (UNICAMP), Campinas, SP, Brazil
| | - Patrícia Aline Boer
- Department of Internal Medicine, Fetal Programming Laboratory, School of Medical Science, University of Campinas (UNICAMP), Campinas, SP, Brazil
| | - Min-Cheol Kang
- Division of Endocrinology, Diabetes and Metabolism, Department of Medicine, Beth Israel Deaconess Medical Center, Harvard Medical School, Boston, MA, United States
- Research Group of Food Processing, Korea Food Research Instute, Jeollabuk-do, Wanju, Republic of Korea
| | - Mario Jose Abdalla Saad
- Department of Internal Medicine, School of Medical Science, University of Campinas (UNICAMP), Campinas, SP, Brazil
| | - Young-Bum Kim
- Division of Endocrinology, Diabetes and Metabolism, Department of Medicine, Beth Israel Deaconess Medical Center, Harvard Medical School, Boston, MA, United States
| | - Patricia Oliveira Prada
- Department of Internal Medicine, School of Medical Science, University of Campinas (UNICAMP), Campinas, SP, Brazil
- School of Applied Sciences, University of Campinas (UNICAMP), Limeira, SP, Brazil
- Max-Planck Institute for Metabolism Research, Köln, Germany
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10
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Song M, Pang L, Zhang M, Qu Y, Laster KV, Dong Z. Cdc2-like kinases: structure, biological function, and therapeutic targets for diseases. Signal Transduct Target Ther 2023; 8:148. [PMID: 37029108 PMCID: PMC10082069 DOI: 10.1038/s41392-023-01409-4] [Citation(s) in RCA: 25] [Impact Index Per Article: 12.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/04/2022] [Revised: 03/15/2023] [Accepted: 03/20/2023] [Indexed: 04/09/2023] Open
Abstract
The CLKs (Cdc2-like kinases) belong to the dual-specificity protein kinase family and play crucial roles in regulating transcript splicing via the phosphorylation of SR proteins (SRSF1-12), catalyzing spliceosome molecular machinery, and modulating the activities or expression of non-splicing proteins. The dysregulation of these processes is linked with various diseases, including neurodegenerative diseases, Duchenne muscular dystrophy, inflammatory diseases, viral replication, and cancer. Thus, CLKs have been considered as potential therapeutic targets, and significant efforts have been exerted to discover potent CLKs inhibitors. In particular, clinical trials aiming to assess the activities of the small molecules Lorecivivint on knee Osteoarthritis patients, and Cirtuvivint and Silmitasertib in different advanced tumors have been investigated for therapeutic usage. In this review, we comprehensively documented the structure and biological functions of CLKs in various human diseases and summarized the significance of related inhibitors in therapeutics. Our discussion highlights the most recent CLKs research, paving the way for the clinical treatment of various human diseases.
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Affiliation(s)
- Mengqiu Song
- Department of Pathophysiology, School of Basic Medical Sciences, College of Medicine, Zhengzhou University, Zhengzhou, Henan, 450001, China
- China-US (Henan) Hormel Cancer Institute, No.127, Dongming Road, Jinshui District, Zhengzhou, Henan, 450008, China
- State Key Laboratory of Esophageal Cancer Prevention and Treatment, Zhengzhou University, Zhengzhou, Henan, China
| | - Luping Pang
- State Key Laboratory of Esophageal Cancer Prevention and Treatment, Zhengzhou University, Zhengzhou, Henan, China
- Academy of Medical Sciences, College of Medicine, Zhengzhou University, Zhengzhou, Henan, 450001, China
- Research Center of Basic Medicine, Academy of Medical Sciences, College of Medicine, Zhengzhou University, Zhengzhou, Henan, 450001, China
| | - Mengmeng Zhang
- Department of Pathophysiology, School of Basic Medical Sciences, College of Medicine, Zhengzhou University, Zhengzhou, Henan, 450001, China
- Academy of Medical Sciences, College of Medicine, Zhengzhou University, Zhengzhou, Henan, 450001, China
| | - Yingzi Qu
- Department of Pathophysiology, School of Basic Medical Sciences, College of Medicine, Zhengzhou University, Zhengzhou, Henan, 450001, China
- Academy of Medical Sciences, College of Medicine, Zhengzhou University, Zhengzhou, Henan, 450001, China
| | - Kyle Vaughn Laster
- China-US (Henan) Hormel Cancer Institute, No.127, Dongming Road, Jinshui District, Zhengzhou, Henan, 450008, China
| | - Zigang Dong
- Department of Pathophysiology, School of Basic Medical Sciences, College of Medicine, Zhengzhou University, Zhengzhou, Henan, 450001, China.
- China-US (Henan) Hormel Cancer Institute, No.127, Dongming Road, Jinshui District, Zhengzhou, Henan, 450008, China.
- State Key Laboratory of Esophageal Cancer Prevention and Treatment, Zhengzhou University, Zhengzhou, Henan, China.
- Academy of Medical Sciences, College of Medicine, Zhengzhou University, Zhengzhou, Henan, 450001, China.
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11
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Shao Z, Zhao B, Kotla P, Burns JG, Tran J, Ke M, Chen X, Browning KS, Qiao H. Phosphorylation status of Bβ subunit acts as a switch to regulate the function of phosphatase PP2A in ethylene-mediated root growth inhibition. THE NEW PHYTOLOGIST 2022; 236:1762-1778. [PMID: 36073540 PMCID: PMC9828452 DOI: 10.1111/nph.18467] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 05/12/2022] [Accepted: 08/25/2022] [Indexed: 05/20/2023]
Abstract
The various combinations and regulations of different subunits of phosphatase PP2A holoenzymes underlie their functional complexity and importance. However, molecular mechanisms governing the assembly of PP2A complex in response to external or internal signals remain largely unknown, especially in Arabidopsis thaliana. We found that the phosphorylation status of Bβ of PP2A acts as a switch to regulate the activity of PP2A. In the absence of ethylene, phosphorylated Bβ leads to an inactivation of PP2A; the substrate EIR1 remains to be phosphorylated, preventing the EIR1-mediated auxin transport in epidermis, leading to normal root growth. Upon ethylene treatment, the dephosphorylated Bβ mediates the formation of the A2-C4-Bβ protein complex to activate PP2A, resulting in the dephosphorylation of EIR1 to promote auxin transport in epidermis of elongation zone, leading to root growth inhibition. Altogether, our research revealed a novel molecular mechanism by which the dephosphorylation of Bβ subunit switches on PP2A activity to dephosphorylate EIR1 to establish EIR1-mediated auxin transport in the epidermis in elongation zone for root growth inhibition in response to ethylene.
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Affiliation(s)
- Zhengyao Shao
- Institute for Cellular and Molecular BiologyThe University of Texas at AustinAustinTX78712USA
- Department of Molecular BiosciencesThe University of Texas at AustinAustinTX78712USA
| | - Bo Zhao
- Institute for Cellular and Molecular BiologyThe University of Texas at AustinAustinTX78712USA
- Department of Molecular BiosciencesThe University of Texas at AustinAustinTX78712USA
| | - Prashanth Kotla
- Institute for Cellular and Molecular BiologyThe University of Texas at AustinAustinTX78712USA
| | - Jackson G. Burns
- Institute for Cellular and Molecular BiologyThe University of Texas at AustinAustinTX78712USA
| | - Jaclyn Tran
- Institute for Cellular and Molecular BiologyThe University of Texas at AustinAustinTX78712USA
- Department of Molecular BiosciencesThe University of Texas at AustinAustinTX78712USA
| | - Meiyu Ke
- Haixia Institute of Science and Technology, Horticultural Plant Biology and Metabolomics CenterFujian Agriculture and Forestry UniversityFuzhouFujian350002China
| | - Xu Chen
- Haixia Institute of Science and Technology, Horticultural Plant Biology and Metabolomics CenterFujian Agriculture and Forestry UniversityFuzhouFujian350002China
| | - Karen S. Browning
- Institute for Cellular and Molecular BiologyThe University of Texas at AustinAustinTX78712USA
- Department of Molecular BiosciencesThe University of Texas at AustinAustinTX78712USA
| | - Hong Qiao
- Institute for Cellular and Molecular BiologyThe University of Texas at AustinAustinTX78712USA
- Department of Molecular BiosciencesThe University of Texas at AustinAustinTX78712USA
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12
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Sule A, Golding SE, Ahmad SF, Watson J, Ahmed MH, Kellogg GE, Bernas T, Koebley S, Reed JC, Povirk LF, Valerie K. ATM phosphorylates PP2A subunit A resulting in nuclear export and spatiotemporal regulation of the DNA damage response. Cell Mol Life Sci 2022; 79:603. [PMID: 36434396 PMCID: PMC9700600 DOI: 10.1007/s00018-022-04550-5] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/24/2022] [Revised: 08/30/2022] [Accepted: 09/07/2022] [Indexed: 11/26/2022]
Abstract
Ataxia telangiectasia mutated (ATM) is a serine-threonine protein kinase and important regulator of the DNA damage response (DDR). One critical ATM target is the structural subunit A (PR65-S401) of protein phosphatase 2A (PP2A), known to regulate diverse cellular processes such as mitosis and cell growth as well as dephosphorylating many proteins during the recovery from the DDR. We generated mouse embryonic fibroblasts expressing PR65-WT, -S401A (cannot be phosphorylated), and -S401D (phospho-mimetic) transgenes. Significantly, S401 mutants exhibited extensive chromosomal aberrations, impaired DNA double-strand break (DSB) repair and underwent increased mitotic catastrophe after radiation. Both S401A and the S401D cells showed impaired DSB repair (nonhomologous end joining and homologous recombination repair) and exhibited delayed DNA damage recovery, which was reflected in reduced radiation survival. Furthermore, S401D cells displayed increased ERK and AKT signaling resulting in enhanced growth rate further underscoring the multiple roles ATM-PP2A signaling plays in regulating prosurvival responses. Time-lapse video and cellular localization experiments showed that PR65 was exported to the cytoplasm after radiation by CRM1, a nuclear export protein, in line with the very rapid pleiotropic effects observed. A putative nuclear export sequence (NES) close to S401 was identified and when mutated resulted in aberrant PR65 shuttling. Our study demonstrates that the phosphorylation of a single, critical PR65 amino acid (S401) by ATM fundamentally controls the DDR, and balances DSB repair quality, cell survival and growth by spatiotemporal PR65 nuclear-cytoplasmic shuttling mediated by the nuclear export receptor CRM1.
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Affiliation(s)
- Amrita Sule
- Department of Radiation Oncology, Virginia Commonwealth University, Richmond, VA, 23298-0058, USA
- Department of Biochemistry and Molecular Biology, Virginia Commonwealth University, Richmond, VA, 23298, USA
| | - Sarah E Golding
- Department of Radiation Oncology, Virginia Commonwealth University, Richmond, VA, 23298-0058, USA
| | - Syed F Ahmad
- Department of Radiation Oncology, Virginia Commonwealth University, Richmond, VA, 23298-0058, USA
- Department of Biochemistry and Molecular Biology, Virginia Commonwealth University, Richmond, VA, 23298, USA
| | - James Watson
- Department of Radiation Oncology, Virginia Commonwealth University, Richmond, VA, 23298-0058, USA
| | - Mostafa H Ahmed
- Department of Medicinal Chemistry, Virginia Commonwealth University, Richmond, VA, 23298, USA
| | - Glen E Kellogg
- Department of Medicinal Chemistry, Virginia Commonwealth University, Richmond, VA, 23298, USA
- Massey Cancer Center, Virginia Commonwealth University, Richmond, VA, 23298, USA
| | - Tytus Bernas
- Department of Anatomy, Virginia Commonwealth University, Richmond, VA, 23298, USA
| | - Sean Koebley
- Department of Physics, Virginia Commonwealth University, Richmond, VA, 23298, USA
| | - Jason C Reed
- Department of Physics, Virginia Commonwealth University, Richmond, VA, 23298, USA
- Massey Cancer Center, Virginia Commonwealth University, Richmond, VA, 23298, USA
| | - Lawrence F Povirk
- Department of Pharmacology and Toxicology, Virginia Commonwealth University, Richmond, VA, 23298, USA
- Massey Cancer Center, Virginia Commonwealth University, Richmond, VA, 23298, USA
| | - Kristoffer Valerie
- Department of Radiation Oncology, Virginia Commonwealth University, Richmond, VA, 23298-0058, USA.
- Department of Biochemistry and Molecular Biology, Virginia Commonwealth University, Richmond, VA, 23298, USA.
- Massey Cancer Center, Virginia Commonwealth University, Richmond, VA, 23298, USA.
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13
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Støle TP, Lunde M, Shen X, Martinsen M, Lunde PK, Li J, Lockwood F, Sjaastad I, Louch WE, Aronsen JM, Christensen G, Carlson CR. The female syndecan-4−/− heart has smaller cardiomyocytes, augmented insulin/pSer473-Akt/pSer9-GSK-3β signaling, and lowered SCOP, pThr308-Akt/Akt and GLUT4 levels. Front Cell Dev Biol 2022; 10:908126. [PMID: 36092718 PMCID: PMC9452846 DOI: 10.3389/fcell.2022.908126] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/30/2022] [Accepted: 07/06/2022] [Indexed: 11/13/2022] Open
Abstract
Background: In cardiac muscle, the ubiquitously expressed proteoglycan syndecan-4 is involved in the hypertrophic response to pressure overload. Protein kinase Akt signaling, which is known to regulate hypertrophy, has been found to be reduced in the cardiac muscle of exercised male syndecan-4−/− mice. In contrast, we have recently found that pSer473-Akt signaling is elevated in the skeletal muscle (tibialis anterior, TA) of female syndecan-4−/− mice. To determine if the differences seen in Akt signaling are sex specific, we have presently investigated Akt signaling in the cardiac muscle of sedentary and exercised female syndecan-4−/− mice. To get deeper insight into the female syndecan-4−/− heart, alterations in cardiomyocyte size, a wide variety of different extracellular matrix components, well-known syndecan-4 binding partners and associated signaling pathways have also been investigated.Methods: Left ventricles (LVs) from sedentary and exercise trained female syndecan-4−/− and WT mice were analyzed by immunoblotting and real-time PCR. Cardiomyocyte size and phosphorylated Ser473-Akt were analyzed in isolated adult cardiomyocytes from female syndecan-4−/− and WT mice by confocal imaging. LV and skeletal muscle (TA) from sedentary male syndecan-4−/− and WT mice were immunoblotted with Akt antibodies for comparison. Glucose levels were measured by a glucometer, and fasting blood serum insulin and C-peptide levels were measured by ELISA.Results: Compared to female WT hearts, sedentary female syndecan-4−/− LV cardiomyocytes were smaller and hearts had higher levels of pSer473-Akt and its downstream target pSer9-GSK-3β. The pSer473-Akt inhibitory phosphatase PHLPP1/SCOP was lowered, which may be in response to the elevated serum insulin levels found in the female syndecan-4−/− mice. We also observed lowered levels of pThr308-Akt/Akt and GLUT4 in the female syndecan-4−/− heart and an increased LRP6 level after exercise. Otherwise, few alterations were found. The pThr308-Akt and pSer473-Akt levels were unaltered in the cardiac and skeletal muscles of sedentary male syndecan-4−/− mice.Conclusion: Our data indicate smaller cardiomyocytes, an elevated insulin/pSer473-Akt/pSer9-GSK-3β signaling pathway, and lowered SCOP, pThr308-Akt/Akt and GLUT4 levels in the female syndecan-4−/− heart. In contrast, cardiomyocyte size, and Akt signaling were unaltered in both cardiac and skeletal muscles from male syndecan-4−/− mice, suggesting important sex differences.
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Affiliation(s)
- Thea Parsberg Støle
- Institute for Experimental Medical Research, Oslo University Hospital and University of Oslo, Oslo, Norway
- *Correspondence: Thea Parsberg Støle,
| | - Marianne Lunde
- Institute for Experimental Medical Research, Oslo University Hospital and University of Oslo, Oslo, Norway
- K. G. Jebsen Center for Cardiac Research, University of Oslo, Oslo, Norway
| | - Xin Shen
- Institute for Experimental Medical Research, Oslo University Hospital and University of Oslo, Oslo, Norway
- K. G. Jebsen Center for Cardiac Research, University of Oslo, Oslo, Norway
| | - Marita Martinsen
- Institute for Experimental Medical Research, Oslo University Hospital and University of Oslo, Oslo, Norway
- K. G. Jebsen Center for Cardiac Research, University of Oslo, Oslo, Norway
| | - Per Kristian Lunde
- Institute for Experimental Medical Research, Oslo University Hospital and University of Oslo, Oslo, Norway
- K. G. Jebsen Center for Cardiac Research, University of Oslo, Oslo, Norway
| | - Jia Li
- Institute for Experimental Medical Research, Oslo University Hospital and University of Oslo, Oslo, Norway
- K. G. Jebsen Center for Cardiac Research, University of Oslo, Oslo, Norway
| | - Francesca Lockwood
- Institute for Experimental Medical Research, Oslo University Hospital and University of Oslo, Oslo, Norway
- K. G. Jebsen Center for Cardiac Research, University of Oslo, Oslo, Norway
| | - Ivar Sjaastad
- Institute for Experimental Medical Research, Oslo University Hospital and University of Oslo, Oslo, Norway
- K. G. Jebsen Center for Cardiac Research, University of Oslo, Oslo, Norway
| | - William Edward Louch
- Institute for Experimental Medical Research, Oslo University Hospital and University of Oslo, Oslo, Norway
- K. G. Jebsen Center for Cardiac Research, University of Oslo, Oslo, Norway
| | - Jan Magnus Aronsen
- Institute for Experimental Medical Research, Oslo University Hospital and University of Oslo, Oslo, Norway
- Department of Molecular Medicine, Institute of Basic Medical Sciences, University of Oslo, Oslo, Norway
| | - Geir Christensen
- Institute for Experimental Medical Research, Oslo University Hospital and University of Oslo, Oslo, Norway
- K. G. Jebsen Center for Cardiac Research, University of Oslo, Oslo, Norway
| | - Cathrine Rein Carlson
- Institute for Experimental Medical Research, Oslo University Hospital and University of Oslo, Oslo, Norway
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14
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Nadel G, Yao Z, Wainstein E, Cohen I, Ben-Ami I, Schajnovitz A, Maik-Rachline G, Naor Z, Horwitz BA, Seger R. GqPCR-stimulated dephosphorylation of AKT is induced by an IGBP1-mediated PP2A switch. Cell Commun Signal 2022; 20:5. [PMID: 34998390 PMCID: PMC8742922 DOI: 10.1186/s12964-021-00805-z] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/12/2021] [Accepted: 11/18/2021] [Indexed: 11/10/2022] Open
Abstract
BACKGROUND G protein-coupled receptors (GPCRs) usually regulate cellular processes via activation of intracellular signaling pathways. However, we have previously shown that in several cell lines, GqPCRs induce immediate inactivation of the AKT pathway, which leads to JNK-dependent apoptosis. This apoptosis-inducing AKT inactivation is essential for physiological functions of several GqPCRs, including those for PGF2α and GnRH. METHODS Here we used kinase activity assays of PI3K and followed phosphorylation state of proteins using specific antibodies. In addition, we used coimmunoprecipitation and proximity ligation assays to follow protein-protein interactions. Apoptosis was detected by TUNEL assay and PARP1 cleavage. RESULTS We identified the mechanism that allows the unique stimulated inactivation of AKT and show that the main regulator of this process is the phosphatase PP2A, operating with the non-canonical regulatory subunit IGBP1. In resting cells, an IGBP1-PP2Ac dimer binds to PI3K, dephosphorylates the inhibitory pSer608-p85 of PI3K and thus maintains its high basal activity. Upon GqPCR activation, the PP2Ac-IGBP1 dimer detaches from PI3K and thus allows the inhibitory dephosphorylation. At this stage, the free PP2Ac together with IGBP1 and PP2Aa binds to AKT, causing its dephosphorylation and inactivation. CONCLUSION Our results show a stimulated shift of PP2Ac from PI3K to AKT termed "PP2A switch" that represses the PI3K/AKT pathway, providing a unique mechanism of GPCR-stimulated dephosphorylation. Video Abstract.
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Affiliation(s)
- Guy Nadel
- Departments of Biological Regulation, The Weizmann Institute of Science, Rehovot, Israel
| | - Zhong Yao
- Departments of Biological Regulation, The Weizmann Institute of Science, Rehovot, Israel
| | - Ehud Wainstein
- Departments of Biological Regulation, The Weizmann Institute of Science, Rehovot, Israel
| | - Izel Cohen
- Departments of Biological Regulation, The Weizmann Institute of Science, Rehovot, Israel
| | - Ido Ben-Ami
- Departments of Biological Regulation, The Weizmann Institute of Science, Rehovot, Israel.,IVF and Fertility Unit, Department of OB/GYN, Shaare Zedek Medical Center and The Hebrew University Medical School, Jerusalem, Israel
| | - Amir Schajnovitz
- Departments of Biological Regulation, The Weizmann Institute of Science, Rehovot, Israel
| | - Galia Maik-Rachline
- Departments of Biological Regulation, The Weizmann Institute of Science, Rehovot, Israel
| | - Zvi Naor
- Department of Biochemistry and Molecular Biology, Tel Aviv University, Tel Aviv, Israel
| | - Benjamin A Horwitz
- Departments of Biological Regulation, The Weizmann Institute of Science, Rehovot, Israel.,Faculty of Biology, Technion-Israel Institute of Technology, Haifa, Israel
| | - Rony Seger
- Departments of Biological Regulation, The Weizmann Institute of Science, Rehovot, Israel.
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15
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Naro C, Bielli P, Sette C. Oncogenic dysregulation of pre-mRNA processing by protein kinases: challenges and therapeutic opportunities. FEBS J 2021; 288:6250-6272. [PMID: 34092037 PMCID: PMC8596628 DOI: 10.1111/febs.16057] [Citation(s) in RCA: 34] [Impact Index Per Article: 8.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/09/2021] [Revised: 05/13/2021] [Accepted: 06/04/2021] [Indexed: 12/12/2022]
Abstract
Alternative splicing and polyadenylation represent two major steps in pre-mRNA-processing, which ensure proper gene expression and diversification of human transcriptomes. Deregulation of these processes contributes to oncogenic programmes involved in the onset, progression and evolution of human cancers, which often result in the acquisition of resistance to existing therapies. On the other hand, cancer cells frequently increase their transcriptional rate and develop a transcriptional addiction, which imposes a high stress on the pre-mRNA-processing machinery and establishes a therapeutically exploitable vulnerability. A prominent role in fine-tuning pre-mRNA-processing mechanisms is played by three main families of protein kinases: serine arginine protein kinase (SRPK), CDC-like kinase (CLK) and cyclin-dependent kinase (CDK). These kinases phosphorylate the RNA polymerase, splicing factors and regulatory proteins involved in cleavage and polyadenylation of the nascent transcripts. The activity of SRPKs, CLKs and CDKs can be altered in cancer cells, and their inhibition was shown to exert anticancer effects. In this review, we describe key findings that have been reported on these topics and discuss challenges and opportunities of developing therapeutic approaches targeting splicing factor kinases.
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Affiliation(s)
- Chiara Naro
- Department of NeuroscienceSection of Human AnatomyCatholic University of the Sacred HeartRomeItaly
- Fondazione Policlinico Universitario A. GemelliIRCCSRomeItaly
| | - Pamela Bielli
- Department of Biomedicine and PreventionUniversity of Rome Tor VergataItaly
- Fondazione Santa LuciaIRCCSRomeItaly
| | - Claudio Sette
- Department of NeuroscienceSection of Human AnatomyCatholic University of the Sacred HeartRomeItaly
- Fondazione Santa LuciaIRCCSRomeItaly
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16
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Nishimura Y, Yamakawa D, Uchida K, Shiromizu T, Watanabe M, Inagaki M. Primary cilia and lipid raft dynamics. Open Biol 2021; 11:210130. [PMID: 34428960 PMCID: PMC8385361 DOI: 10.1098/rsob.210130] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/13/2023] Open
Abstract
Primary cilia, antenna-like structures of the plasma membrane, detect various extracellular cues and transduce signals into the cell to regulate a wide range of functions. Lipid rafts, plasma membrane microdomains enriched in cholesterol, sphingolipids and specific proteins, are also signalling hubs involved in a myriad of physiological functions. Although impairment of primary cilia and lipid rafts is associated with various diseases, the relationship between primary cilia and lipid rafts is poorly understood. Here, we review a newly discovered interaction between primary cilia and lipid raft dynamics that occurs during Akt signalling in adipogenesis. We also discuss the relationship between primary cilia and lipid raft-mediated Akt signalling in cancer biology. This review provides a novel perspective on primary cilia in the regulation of lipid raft dynamics.
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Affiliation(s)
- Yuhei Nishimura
- Department of Integrative Pharmacology, Mie University Graduate School of Medicine, Tsu, Mie, Japan
| | - Daishi Yamakawa
- Department of Physiology, Mie University Graduate School of Medicine, Tsu, Mie, Japan
| | - Katsunori Uchida
- Department of Oncologic Pathology, Mie University Graduate School of Medicine, Tsu, Mie, Japan
| | - Takashi Shiromizu
- Department of Integrative Pharmacology, Mie University Graduate School of Medicine, Tsu, Mie, Japan
| | - Masatoshi Watanabe
- Department of Oncologic Pathology, Mie University Graduate School of Medicine, Tsu, Mie, Japan
| | - Masaki Inagaki
- Department of Physiology, Mie University Graduate School of Medicine, Tsu, Mie, Japan
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17
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Trafficking to the Cell Surface of Amino Acid Transporter SLC6A14 Upregulated in Cancer Is Controlled by Phosphorylation of SEC24C Protein by AKT Kinase. Cells 2021; 10:cells10071800. [PMID: 34359969 PMCID: PMC8307180 DOI: 10.3390/cells10071800] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/17/2021] [Revised: 07/07/2021] [Accepted: 07/14/2021] [Indexed: 01/24/2023] Open
Abstract
Cancer cells need a constant supply of nutrients. SLC6A14, an amino acid transporter B0,+ (ATB0,+) that is upregulated in many cancers, transports all but acidic amino acids. In its exit from the endoplasmic reticulum (ER), it is recognized by the SEC24C subunit of coatomer II (COPII) for further vesicular trafficking to the plasma membrane. SEC24C has previously been shown to be phosphorylated by protein kinase B/AKT, which is hyper-activated in cancer; therefore, we analyzed the influence of AKT on SLC6A14 trafficking to the cell surface. Studies on overexpressed and endogenous transporters in the breast cancer cell line MCF-7 showed that AKT inhibition with MK-2206 correlated with a transient increase of the transporter in the plasma membrane, not resulting from the inhibition of ER-associated protein degradation. Two-dimensional electrophoresis demonstrated the decreased phosphorylation of SLC6A14 and SEC24C upon AKT inhibition. A proximity ligation assay confirmed this conclusion: AKT inhibition is correlated with decreased SLC6A14 phosphothreonine and SEC24C phosphoserine. Augmented levels of SLC6A14 in plasma membrane led to increased leucine transport. These results show that the inactivation of AKT can rescue amino acid delivery through SLC6A14 trafficking to the cell surface, supporting cancer cell survival. The regulation of the ER export of the amino acid transporter seems to be a novel function of AKT.
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18
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Pleiotropic and Potentially Beneficial Effects of Reactive Oxygen Species on the Intracellular Signaling Pathways in Endothelial Cells. Antioxidants (Basel) 2021; 10:antiox10060904. [PMID: 34205032 PMCID: PMC8229098 DOI: 10.3390/antiox10060904] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/29/2021] [Revised: 05/28/2021] [Accepted: 05/31/2021] [Indexed: 02/06/2023] Open
Abstract
Endothelial cells (ECs) are exposed to molecular dioxygen and its derivative reactive oxygen species (ROS). ROS are now well established as important signaling messengers. Excessive production of ROS, however, results in oxidative stress, a significant contributor to the development of numerous diseases. Here, we analyze the experimental data and theoretical concepts concerning positive pro-survival effects of ROS on signaling pathways in endothelial cells (ECs). Our analysis of the available experimental data suggests possible positive roles of ROS in induction of pro-survival pathways, downstream of the Gi-protein-coupled receptors, which mimics insulin signaling and prevention or improvement of the endothelial dysfunction. It is, however, doubtful, whether ROS can contribute to the stabilization of the endothelial barrier.
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19
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Systematic Identification of Survival-Associated Alternative Splicing Events in Kidney Renal Clear Cell Carcinoma. COMPUTATIONAL AND MATHEMATICAL METHODS IN MEDICINE 2021; 2021:5576933. [PMID: 33959190 PMCID: PMC8075682 DOI: 10.1155/2021/5576933] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 02/24/2021] [Revised: 03/29/2021] [Accepted: 04/05/2021] [Indexed: 11/18/2022]
Abstract
There is growing evidence that aberrant alternative splicing (AS) is highly correlated with driving tumorigenesis, but its function in kidney renal clear cell carcinoma (KIRC) remains to be discovered. In this study, we obtained the level-3 RNA sequencing and clinical data of KIRC from The Cancer Genome Atlas (TGCA). Combining with the splicing event detail information from TGCA SpliceSeq database, we established the independent prognosis signatures for KIRC with the univariate and multivariate Cox regression analyses. Then, we used the Kaplan-Meier analysis and receiver operating characteristic curves (ROCs) to assess the accuracy of prognosis signatures. We also constructed the regulatory network of splicing factors (SFs) and AS events. Our results showed that a total of 12029 survival-associated AS events of 5761 genes were found in 524 KIRC patients. All types of prognosis signatures displayed a satisfactory ability to reliably predict, especially in exon skip model which the area under curve of ROC was 0.802. Moreover, 18 splicing factors (SFs) highly correlated to AS events were identified. With the construction of the SF-AS interactive network, we found that SF powerfully promotes the occurrence of abnormal AS and may have a profound role in KIRC. Collectively, we screened survival-associated AS events and established prognosis signatures for KIRC, coupling with the SF-AS interactive network, which might provide a key perspective to clarify the potential mechanism of AS in KIRC.
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20
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Papke CM, Smolen KA, Swingle MR, Cressey L, Heng RA, Toporsian M, Deng L, Hagen J, Shen Y, Chung WK, Kettenbach AN, Honkanen RE. A disorder-related variant (E420K) of a PP2A-regulatory subunit (PPP2R5D) causes constitutively active AKT-mTOR signaling and uncoordinated cell growth. J Biol Chem 2021; 296:100313. [PMID: 33482199 PMCID: PMC7952134 DOI: 10.1016/j.jbc.2021.100313] [Citation(s) in RCA: 31] [Impact Index Per Article: 7.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/10/2020] [Revised: 01/13/2021] [Accepted: 01/15/2021] [Indexed: 02/08/2023] Open
Abstract
Functional genomic approaches have facilitated the discovery of rare genetic disorders and improved efforts to decipher their underlying etiology. PPP2R5D-related disorder is an early childhood onset condition characterized by intellectual disability, hypotonia, autism-spectrum disorder, macrocephaly, and dysmorphic features. The disorder is caused by de novo single nucleotide changes in PPP2R5D, which generate heterozygous dominant missense variants. PPP2R5D is known to encode a B'-type (B'56δ) regulatory subunit of a PP2A-serine/threonine phosphatase. To help elucidate the molecular mechanisms altered in PPP2R5D-related disorder, we used a CRISPR-single-base editor to generate HEK-293 cells in which a single transition (c.1258G>A) was introduced into one allele, precisely recapitulating a clinically relevant E420K variant. Unbiased quantitative proteomic and phosphoproteomic analyses of endogenously expressed proteins revealed heterozygous-dominant changes in kinase/phosphatase signaling. These data combined with orthogonal validation studies revealed a previously unrecognized interaction of PPP2R5D with AKT in human cells, leading to constitutively active AKT-mTOR signaling, increased cell size, and uncoordinated cellular growth in E420K-variant cells. Rapamycin reduced cell size and dose-dependently reduced RPS6 phosphorylation in E420K-variant cells, suggesting that inhibition of mTOR1 can suppress both the observed RPS6 hyperphosphorylation and increased cell size. Together, our findings provide a deeper understanding of PPP2R5D and insight into how the E420K-variant alters signaling networks influenced by PPP2R5D. Our comprehensive approach, which combines precise genome editing, isobaric tandem mass tag labeling of peptides generated from endogenously expressed proteins, and concurrent liquid chromatography-mass spectrometry (LC-MS3), also provides a roadmap that can be used to rapidly explore the etiologies of additional genetic disorders.
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Affiliation(s)
- Cinta M Papke
- Department of Biochemistry and Molecular Biology, University of South Alabama, Mobile, Alabama, USA
| | - Kali A Smolen
- Department of Biochemistry and Cell Biology, Geisel School of Medicine at Dartmouth, Hanover, New Hampshire, USA; Norris Cotton Cancer Center, Geisel School of Medicine at Dartmouth, Lebanon, New Hampshire, USA
| | - Mark R Swingle
- Department of Biochemistry and Molecular Biology, University of South Alabama, Mobile, Alabama, USA
| | - Lauren Cressey
- Department of Biochemistry and Cell Biology, Geisel School of Medicine at Dartmouth, Hanover, New Hampshire, USA; Norris Cotton Cancer Center, Geisel School of Medicine at Dartmouth, Lebanon, New Hampshire, USA
| | - Richard A Heng
- Department of Biochemistry and Molecular Biology, University of South Alabama, Mobile, Alabama, USA
| | - Mourad Toporsian
- Department of Biochemistry and Molecular Biology, University of South Alabama, Mobile, Alabama, USA
| | - Liyong Deng
- Department of Pediatrics, Columbia University Irving Medical Center, New York, New York, USA
| | - Jacob Hagen
- Department of Pediatrics, Columbia University Irving Medical Center, New York, New York, USA
| | - Yufeng Shen
- Department of Systems Biology, Columbia University Irving Medical Center, New York, New York, USA
| | - Wendy K Chung
- Department of Pediatrics, Columbia University Irving Medical Center, New York, New York, USA; Herbert Irving Comprehensive Cancer Center, Columbia University Medical Center, New York, New York, USA; Department of Medicine, Columbia University Medical Center, New York, New York, USA
| | - Arminja N Kettenbach
- Department of Biochemistry and Cell Biology, Geisel School of Medicine at Dartmouth, Hanover, New Hampshire, USA; Norris Cotton Cancer Center, Geisel School of Medicine at Dartmouth, Lebanon, New Hampshire, USA.
| | - Richard E Honkanen
- Department of Biochemistry and Molecular Biology, University of South Alabama, Mobile, Alabama, USA.
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21
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Bao Y, Oguz G, Lee WC, Lee PL, Ghosh K, Li J, Wang P, Lobie PE, Ehmsen S, Ditzel HJ, Wong A, Tan EY, Lee SC, Yu Q. EZH2-mediated PP2A inactivation confers resistance to HER2-targeted breast cancer therapy. Nat Commun 2020; 11:5878. [PMID: 33208750 PMCID: PMC7674491 DOI: 10.1038/s41467-020-19704-x] [Citation(s) in RCA: 28] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/17/2020] [Accepted: 10/23/2020] [Indexed: 12/13/2022] Open
Abstract
HER2-targeted therapy has yielded a significant clinical benefit in patients with HER2+ breast cancer, yet disease relapse due to intrinsic or acquired resistance remains a significant challenge in the clinic. Here, we show that the protein phosphatase 2A (PP2A) regulatory subunit PPP2R2B is a crucial determinant of anti-HER2 response. PPP2R2B is downregulated in a substantial subset of HER2+ breast cancers, which correlates with poor clinical outcome and resistance to HER2-targeted therapies. EZH2-mediated histone modification accounts for the PPP2R2B downregulation, resulting in sustained phosphorylation of PP2A targets p70S6K and 4EBP1 which leads to resistance to inhibition by anti-HER2 treatments. Genetic depletion or inhibition of EZH2 by a clinically-available EZH2 inhibitor restores PPP2R2B expression, abolishes the residual phosphorylation of p70S6K and 4EBP1, and resensitizes HER2+ breast cancer cells to anti-HER2 treatments both in vitro and in vivo. Furthermore, the same epigenetic mechanism also contributes to the development of acquired resistance through clonal selection. These findings identify EZH2-dependent PPP2R2B suppression as an epigenetic control of anti-HER2 resistance, potentially providing an opportunity to mitigate anti-HER2 resistance with EZH2 inhibitors.
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Affiliation(s)
- Yi Bao
- Cancer Science Institute of Singapore, Yong Loo Lin School of Medicine, National University of Singapore, Singapore, 117597, Singapore.,Cancer Precision Medicine, Genome Institute of Singapore, Agency for Science, Technology, and Research, Biopolis, Singapore, 138672, Singapore
| | - Gokce Oguz
- Cancer Precision Medicine, Genome Institute of Singapore, Agency for Science, Technology, and Research, Biopolis, Singapore, 138672, Singapore
| | - Wee Chyan Lee
- Cancer Precision Medicine, Genome Institute of Singapore, Agency for Science, Technology, and Research, Biopolis, Singapore, 138672, Singapore
| | - Puay Leng Lee
- Cancer Precision Medicine, Genome Institute of Singapore, Agency for Science, Technology, and Research, Biopolis, Singapore, 138672, Singapore
| | - Kakaly Ghosh
- Cancer Precision Medicine, Genome Institute of Singapore, Agency for Science, Technology, and Research, Biopolis, Singapore, 138672, Singapore
| | - Jiayao Li
- Cancer Research Institute, Jinan University, Guangzhou, China
| | - Panpan Wang
- Cancer Research Institute, Jinan University, Guangzhou, China
| | - Peter E Lobie
- Cancer Science Institute of Singapore, Yong Loo Lin School of Medicine, National University of Singapore, Singapore, 117597, Singapore.,Tsinghua-Berkeley Shenzhen Institute, Guangdong Province and Shenzhen Bay Laboratory, Tsinghua University, Shenzhen, Guangdong Province, China
| | - Sidse Ehmsen
- Department of Oncology, Odense University Hospital, Institute of Clinical Research, University of Southern Denmark, 5230, Odense, Denmark
| | - Henrik J Ditzel
- Department of Oncology, Odense University Hospital, Institute of Clinical Research, University of Southern Denmark, 5230, Odense, Denmark.,Department of Cancer and Inflammation Research, Institute of Molecular Medicine, University of Southern Denmark, 5230, Odense, Denmark
| | - Andrea Wong
- Department of Haematology-Oncology, National University Cancer Institute, National University Health System, Singapore, 119047, Singapore
| | - Ern Yu Tan
- Department of General Surgery, Tan Tock Seng Hospital, Singapore, Singapore
| | - Soo Chin Lee
- Cancer Science Institute of Singapore, Yong Loo Lin School of Medicine, National University of Singapore, Singapore, 117597, Singapore. .,Department of Haematology-Oncology, National University Cancer Institute, National University Health System, Singapore, 119047, Singapore.
| | - Qiang Yu
- Cancer Precision Medicine, Genome Institute of Singapore, Agency for Science, Technology, and Research, Biopolis, Singapore, 138672, Singapore. .,Department of Physiology, Yong Loo Lin School of Medicine, National University of Singapore, Singapore, 117597, Singapore. .,Cancer and Stem Cell Biology, DUKE-NUS Graduate Medical School of Singapore, Singapore, 169857, Singapore.
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22
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Park SY, Mittal S, Dong J, Jeong K, Martinez-Ledesma E, Piao Y, Khan S, Henry V, Verhaak RGW, Majd N, Balasubramaniyan V, de Groot JF. Depletion of CLK2 sensitizes glioma stem-like cells to PI3K/mTOR and FGFR inhibitors. Am J Cancer Res 2020; 10:3765-3783. [PMID: 33294266 PMCID: PMC7716149] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/19/2020] [Accepted: 09/10/2020] [Indexed: 06/12/2023] Open
Abstract
The Cdc2-like kinases (CLKs) regulate RNA splicing and have been shown to suppress cell growth. Knockdown of CLK2 was found to block glioma stem-like cell (GSC) growth in vivo through the AKT/FOXO3a/p27 pathway without activating mTOR and MAPK signaling, suggesting that these pathways mediate resistance to CLK2 inhibition. We identified CLK2 binding partners using immunoprecipitation assays and confirmed their interactions in vitro in GSCs. We then tested the cellular viability of several signaling inhibitors in parental and CLK2 knockdown GSCs. Our results demonstrate that CLK2 binds to 14-3-3τ isoform and prevents its ubiquitination in GSCs. Stable CLK2 knockdown increased PP2A activity and activated PI3K signaling. Treatment with a PI3K/mTOR inhibitor in CLK2 knockdown cells led to a modest reduction in cell viability compared to drug treatment alone at a lower dose. However, FGFR inhibitor in CLK2 knockdown cells led to a decrease in cell viability and increased apoptosis. Reduced expression of CLK2 in glioblastoma, in combination with FGFR inhibitors, led to synergistic apoptosis induction and cell cycle arrest compared to blockade or either kinase alone.
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Affiliation(s)
- Soon Young Park
- Department of Cell Developmental and Cancer Biology, Oregon Health and Science UniversityPortland, Oregon, USA
| | - Sandeep Mittal
- Department of Neuro-Oncology, The University of Texas MD Anderson Cancer CenterHouston, Texas, USA
| | - Jianwen Dong
- Department of Neuro-Oncology, The University of Texas MD Anderson Cancer CenterHouston, Texas, USA
| | - Kangjin Jeong
- Department of Cell Developmental and Cancer Biology, Oregon Health and Science UniversityPortland, Oregon, USA
| | | | - Yuji Piao
- Department of Neuro-Oncology, The University of Texas MD Anderson Cancer CenterHouston, Texas, USA
| | - Sabbir Khan
- Department of Neuro-Oncology, The University of Texas MD Anderson Cancer CenterHouston, Texas, USA
| | - Verlene Henry
- Department of Neuro-Surgery, The University of Texas MD Anderson Cancer CenterHouston, Texas, USA
| | - Roel GW Verhaak
- The Jackson Laboratory for Genomic MedicineFarmington, Connecticut, USA
| | - Nazanin Majd
- Department of Neuro-Oncology, The University of Texas MD Anderson Cancer CenterHouston, Texas, USA
| | | | - John F de Groot
- Department of Neuro-Oncology, The University of Texas MD Anderson Cancer CenterHouston, Texas, USA
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23
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Gil-Ranedo J, Gonzaga E, Jaworek KJ, Berger C, Bossing T, Barros CS. STRIPAK Members Orchestrate Hippo and Insulin Receptor Signaling to Promote Neural Stem Cell Reactivation. Cell Rep 2020; 27:2921-2933.e5. [PMID: 31167138 PMCID: PMC6581792 DOI: 10.1016/j.celrep.2019.05.023] [Citation(s) in RCA: 42] [Impact Index Per Article: 8.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/13/2018] [Revised: 04/14/2019] [Accepted: 05/03/2019] [Indexed: 12/19/2022] Open
Abstract
Adult stem cells reactivate from quiescence to maintain tissue homeostasis and in response to injury. How the underlying regulatory signals are integrated is largely unknown. Drosophila neural stem cells (NSCs) also leave quiescence to generate adult neurons and glia, a process that is dependent on Hippo signaling inhibition and activation of the insulin-like receptor (InR)/PI3K/Akt cascade. We performed a transcriptome analysis of individual quiescent and reactivating NSCs harvested directly from Drosophila brains and identified the conserved STRIPAK complex members mob4, cka, and PP2A (microtubule star, mts). We show that PP2A/Mts phosphatase, with its regulatory subunit Widerborst, maintains NSC quiescence, preventing premature activation of InR/PI3K/Akt signaling. Conversely, an increase in Mob4 and Cka levels promotes NSC reactivation. Mob4 and Cka are essential to recruit PP2A/Mts into a complex with Hippo kinase, resulting in Hippo pathway inhibition. We propose that Mob4/Cka/Mts functions as an intrinsic molecular switch coordinating Hippo and InR/PI3K/Akt pathways and enabling NSC reactivation. Transcriptional profiling of reactivating versus quiescent NSCs identifies STRIPAK members PP2A/Mts phosphatase inhibits Akt activation, maintaining NSC quiescence Mob4 and Cka target Mts to Hippo to inhibit its activity and promote NSC reactivation Mob4/Cka/Mts coordinate Hippo and InR/PI3K/Akt signaling in NSCs
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Affiliation(s)
- Jon Gil-Ranedo
- Faculty of Medicine and Dentistry, University of Plymouth, PL6 8BU Plymouth, UK
| | - Eleanor Gonzaga
- Faculty of Medicine and Dentistry, University of Plymouth, PL6 8BU Plymouth, UK
| | - Karolina J Jaworek
- Faculty of Medicine and Dentistry, University of Plymouth, PL6 8BU Plymouth, UK
| | - Christian Berger
- Institute of Genetics, Johannes Gutenberg University, 55099 Mainz, Germany
| | - Torsten Bossing
- Faculty of Medicine and Dentistry, University of Plymouth, PL6 8BU Plymouth, UK
| | - Claudia S Barros
- Faculty of Medicine and Dentistry, University of Plymouth, PL6 8BU Plymouth, UK.
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24
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Huang P, Chen K, Ma T, Cao N, Weng D, Xu C, Xu L. The effects of short-term treatment of microcystin-LR on the insulin pathway in both the HL7702 cell line and livers of mice. ENVIRONMENTAL TOXICOLOGY 2020; 35:727-737. [PMID: 32073747 DOI: 10.1002/tox.22907] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/17/2019] [Revised: 12/07/2019] [Accepted: 01/17/2020] [Indexed: 06/10/2023]
Abstract
Our previous work indicated exposure of Human liver cell 7702 (HL7702) cells to Microcystin-leucine-arginine (MC-LR) for 24 hours can disrupt insulin (INS) signaling by the hyperphosphorylation of specific proteins. For further exploring the time-dependent effect posed by MC-LR on this pathway, in the current study, HL7702 cells together with mice were exposed to the MC-LR with different concentrations under short-term treatment, and then, protein phosphatase 2A (PP2A) activity and expression of proteins related to INS signaling, as well as the characteristics of their action in the liver, were investigated. The results indicated, in HL7702 cells with 0.5, 1, and 6 hours of treatment by MC-LR, PP2A activity showed an obvious decrease in a time and concentration-dependent manner. While the total protein level of Akt, glycogen synthase kinase 3 (GSK-3), and glycogen synthase remained unchanged, GSK-3 and Akt phosphorylation increased significantly. In livers of mice with 1 hour of intraperitoneal injection with MC-LR, a similar change in these proteins was observed. In addition, the levels of total IRS1 and p-IRS1 at serine sites showed decreasing and increasing trends,respectively, and the hematoxylin and eosin staining showed that liver tissues of mice in the maximum-dose group exhibited obvious hepatocyte degeneration and hemorrhage. Our results further proved that short-term treatment with MC-LR can inhibit PP2A activity and disrupt INS signaling proteins' phosphorylation level, thereby interfering with the INS pathway. Our findings provide a helpful understanding of the toxic effects posed by MC-LR on the glucose metabolism of liver via interference with the INS signaling pathway.
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Affiliation(s)
- Pu Huang
- Department of Biochemistry, School of Medicine, Zhejiang University, Hangzhou, China
| | - Kele Chen
- Department of Biochemistry, School of Medicine, Zhejiang University, Hangzhou, China
| | - Tianfeng Ma
- Department I of Clinical Medicine, First Affiliated Hospital, School of Medicine, Zhejiang University, Hangzhou, China
| | - Naifang Cao
- Department I of Clinical Medicine, First Affiliated Hospital, School of Medicine, Zhejiang University, Hangzhou, China
| | - Dengpo Weng
- Department of Biochemistry, School of Medicine, Zhejiang University, Hangzhou, China
| | - Chun Xu
- Department of Endocrinology, The Third Medical Center of Chinese PLA General Hospital, Beijing, China
| | - Lihong Xu
- Department of Biochemistry, School of Medicine, Zhejiang University, Hangzhou, China
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25
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Zhu J, Shi L, Du G, Li L, Liu M. Upregulated SET Promotes Cell Survival Through Activating Akt/NF-κB Signal in Colorectal Carcinoma. Cancer Manag Res 2020; 12:4735-4745. [PMID: 32606964 PMCID: PMC7310974 DOI: 10.2147/cmar.s255930] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/03/2020] [Accepted: 06/09/2020] [Indexed: 12/12/2022] Open
Abstract
Purpose SET has been proven to be an oncogene, which promotes the initiation and progression in several kinds of malignant carcinomas. However, the expression and its functional roles in colorectal carcinoma (CRC) remained unknown. Materials and Methods CRC tissues samples, CRC cell lines and xenograft mouse tumors were used in this study. The mRNA and protein expressions were detected by quantitative real-time polymerase chain reaction (qRT-PCR), immunohistochemistry (IHC), and Western blot (WB), respectively. siRNAs were used to silence the gene expression. Cell viability, cell proliferation, colony formation, and apoptosis were measured by MTS assay, EdU incorporation assay, plated colony formation assay, and flow cytometry, respectively. Western blot was applied to evaluate the levels of Akt, p-Akt, c-Myc and cyclin D1. Xenograft mouse model was performed to observe the role of SET in vivo. Results Our results revealed that SET was up-regulated in CRC, and the expression of SET was increased with the development of CRC. SET knockdown in vitro attenuated cell proliferation activity, and increased cell apoptosis in CRC cells. Moreover, the knockdown of SET reduces tumorigenic potential in nude mice. For the mechanism, knockdown of SET promoted the dephosphorylation of Akt, followed by suppressing the translocation of NF-κB to nucleus. In addition, SET knockdown-mediated dephosphorylation of Akt downregulated the expression of c-Myc and Cyclin D1, which inhibited the cell survival in CRC. Conclusion Our results indicated that SET promoted cell survival via activating Akt/NF-κB signaling pathway in CRC, which strongly suggested that SET might be a potential therapeutic target in the colorectal carcinoma treatment.
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Affiliation(s)
- Jianjun Zhu
- Department of Medical Cellular Biology and Genetics, Shanxi Medical University, Taiyuan 030001, People's Republic of China
| | - Lihong Shi
- Department of Human Anatomy, School of Basic Medicine, Shanxi Medical University, Taiyuan 030001, People's Republic of China
| | - Genlai Du
- Department of Medical Cellular Biology and Genetics, Shanxi Medical University, Taiyuan 030001, People's Republic of China
| | - Li Li
- Department of Medical Cellular Biology and Genetics, Shanxi Medical University, Taiyuan 030001, People's Republic of China
| | - Ming Liu
- Department of Medical Cellular Biology and Genetics, Shanxi Medical University, Taiyuan 030001, People's Republic of China
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26
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Biswas D, Cary W, Nolta JA. PPP2R5D-Related Intellectual Disability and Neurodevelopmental Delay: A Review of the Current Understanding of the Genetics and Biochemical Basis of the Disorder. Int J Mol Sci 2020; 21:ijms21041286. [PMID: 32074998 PMCID: PMC7072873 DOI: 10.3390/ijms21041286] [Citation(s) in RCA: 33] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/11/2019] [Revised: 02/03/2020] [Accepted: 02/10/2020] [Indexed: 12/14/2022] Open
Abstract
Protein Phosphatase 2 Regulatory Subunit B′ Delta (PPP2R5D)-related intellectual disability (ID) and neurodevelopmental delay results from germline de novo mutations in the PPP2R5D gene. This gene encodes the protein PPP2R5D (also known as the B56 delta subunit), which is an isoform of the subunit family B56 of the enzyme serine/threonine-protein phosphatase 2A (PP2A). Clinical signs include intellectual disability (ID); autism spectrum disorder (ASD); epilepsy; speech problems; behavioral challenges; and ophthalmologic, skeletal, endocrine, cardiac, and genital malformations. The association of defective PP2A activity in the brain with a wide range of severity of ID, along with its role in ASD, Alzheimer’s disease, and Parkinson’s-like symptoms, have recently generated the impetus for further research into mutations within this gene. PP2A, together with protein phosphatase 1 (PP1), accounts for more than 90% of all phospho-serine/threonine dephosphorylations in different tissues. The specificity for a wide variety of substrates is determined through nearly 100 different PP2A holoenzymes that are formed by at least 23 types of regulatory B subunits, and two isoforms each of the catalytic subunit C and the structural subunit A. In the mammalian brain, PP2A-mediated protein dephosphorylation plays an important role in learning and memory. The PPP2R5D subunit is highly expressed in the brain and the PPP2A–PPP2R5D holoenzyme plays an important role in maintaining neurons and regulating neuronal signaling. From 2015 to 2017, 25 individuals with PPP2R5D-related developmental disorder were diagnosed. Since then, Whole-Exome Sequencing (WES) has helped to identify more unrelated individuals clinically diagnosed with a neurodevelopmental disorder with pathological variants of PPP2R5D. In this review, we discuss the current understanding of the clinical and genetic aspects of the disorder in the context of the known functions of the PP2A–PPP2R5D holoenzyme in the brain, as well as the pathogenic mutations in PPP2R5D that lead to deficient PP2A–PPP2R5D dephosphorylation and their implications during development and in the etiology of autism, Parkinson’s disease, Alzheimer’s disease, and so forth. In the future, tools such as transgenic animals carrying pathogenic PPP2R5D mutations, and patient-derived induced pluripotent stem cell lines need to be developed in order to fully understand the effects of these mutations on different neural cell types.
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Affiliation(s)
- Dayita Biswas
- SPARK Program Scholar, Institute for Regenerative Cures, University of California, Sacramento, CA 95817, USA;
| | - Whitney Cary
- Stem Cell Program, UC Davis School of Medicine. The University of California, Sacramento, CA 95817, USA
- UC Davis Gene Therapy Program, University of California, Sacramento, CA 95817, USA
- Correspondence: (W.C.); (J.A.N.)
| | - Jan A. Nolta
- SPARK Program Scholar, Institute for Regenerative Cures, University of California, Sacramento, CA 95817, USA;
- Stem Cell Program, UC Davis School of Medicine. The University of California, Sacramento, CA 95817, USA
- UC Davis Gene Therapy Program, University of California, Sacramento, CA 95817, USA
- Correspondence: (W.C.); (J.A.N.)
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27
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Guo B, Wu S, Zhu X, Zhang L, Deng J, Li F, Wang Y, Zhang S, Wu R, Lu J, Zhou Y. Micropeptide CIP2A-BP encoded by LINC00665 inhibits triple-negative breast cancer progression. EMBO J 2020; 39:e102190. [PMID: 31755573 PMCID: PMC6939193 DOI: 10.15252/embj.2019102190] [Citation(s) in RCA: 168] [Impact Index Per Article: 33.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/06/2019] [Revised: 10/10/2019] [Accepted: 10/15/2019] [Indexed: 01/22/2023] Open
Abstract
TGF-β signaling pathway plays a key role in breast cancer metastasis. Recent studies suggest that TGF-β regulates tumor progression and invasion not only via transcriptional regulation, but also via translational regulation. Using both bioinformatics and experimental tools, we identified a micropeptide CIP2A-BP encoded by LINC00665, whose translation was downregulated by TGF-β in breast cancer cell lines. Using TNBC cell lines, we showed that TGF-β-activated Smad signaling pathway induced the expression of translation inhibitory protein 4E-BP1, which inhibited eukaryote translation initiation factor elF4E, leading to reduced translation of CIP2A-BP from LINC00665. CIP2A-BP directly binds tumor oncogene CIP2A to replace PP2A's B56γ subunit, thus releasing PP2A activity, which inhibits PI3K/AKT/NFκB pathway, resulting in decreased expression levels of MMP-2, MMP-9, and Snail. Downregulation of CIP2A-BP in TNBC patients was significantly associated with metastasis and poor overall survival. In the MMTV-PyMT model, either introducing CIP2A-BP gene or direct injection of CIP2A-BP micropeptide significantly reduced lung metastases and improved overall survival. In conclusion, we provide evidence that CIP2A-BP is both a prognostic marker and a novel therapeutic target for TNBC.
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Affiliation(s)
- Binbin Guo
- Department of GeneticsMedical College of Soochow UniversitySuzhouChina
| | - Siqi Wu
- Department of GeneticsMedical College of Soochow UniversitySuzhouChina
| | - Xun Zhu
- Department of General SurgeryThe Second Affiliated Hospital of Soochow UniversitySuzhouChina
| | - Liyuan Zhang
- Department of Radiotherapy & OncologyThe Second Affiliated Hospital of Soochow UniversitySuzhouChina
| | - Jieqiong Deng
- Department of GeneticsMedical College of Soochow UniversitySuzhouChina
| | - Fang Li
- Department of GeneticsMedical College of Soochow UniversitySuzhouChina
| | - Yirong Wang
- Department of GeneticsMedical College of Soochow UniversitySuzhouChina
| | - Shenghua Zhang
- Department of GeneticsMedical College of Soochow UniversitySuzhouChina
| | - Rui Wu
- Department of GeneticsMedical College of Soochow UniversitySuzhouChina
| | - Jiachun Lu
- The State Key Lab of Respiratory DiseaseThe First Affiliated HospitalThe School of Public HealthGuangzhou Medical UniversityGuangzhouChina
| | - Yifeng Zhou
- Department of GeneticsMedical College of Soochow UniversitySuzhouChina
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28
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Hribal ML, Mancuso E, Arcidiacono GP, Greco A, Musca D, Procopio T, Ruffo M, Sesti G. The Phosphatase PHLPP2 Plays a Key Role in the Regulation of Pancreatic Beta-Cell Survival. Int J Endocrinol 2020; 2020:1027386. [PMID: 32411219 PMCID: PMC7199632 DOI: 10.1155/2020/1027386] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/30/2019] [Revised: 11/03/2019] [Accepted: 12/10/2019] [Indexed: 02/06/2023] Open
Abstract
Currently available antidiabetic treatments fail to halt, and may even exacerbate, pancreatic β-cell exhaustion, a key feature of type 2 diabetes pathogenesis; thus, strategies to prevent, or reverse, β-cell failure should be actively sought. The serine threonine kinase Akt has a key role in the regulation of β-cell homeostasis; among Akt modulators, a central role is played by pleckstrin homology domain leucine-rich repeat protein phosphatase (PHLPP) family. Here, taking advantage of an in vitro model of chronic exposure to high glucose, we demonstrated that PHLPPs, particularly the second family member called PHLPP2, are implicated in the ability of pancreatic β cells to deal with glucose toxicity. We observed that INS-1 rat pancreatic β cell line maintained for 12-15 passages at high (30 mM) glucose concentrations (INS-1 HG) showed increased expression of PHLPP2 and PHLPP1 both at mRNA and protein level as compared to INS-1 maintained for the same number of passages in the presence of normal glucose levels (INS-1 NG). These changes were paralleled by decreased phosphorylation of Akt and by increased expression of apoptotic and autophagic markers. To investigate if PHLPPs had a casual role in the alteration of INS-1 homeostasis observed upon chronic exposure to high glucose concentrations, we took advantage of shRNA technology to specifically knock-down PHLPPs. We obtained proof-of-concept evidence that modulating PHLPPs expression may help to restore a healthy β cell mass, as the reduced expression of PHLPP2/1 was accompanied by a recovered balance between pro- and antiapoptotic factor levels. In conclusion, our data provide initial support for future studies aimed to identify pharmacological PHLPPs modulator to treat beta-cell survival impairment. They also contribute to shed some light on β-cell dysfunction, a complex and unsatisfactorily characterized phenomenon that has a central causative role in the pathogenesis of type 2 diabetes.
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Affiliation(s)
- Marta Letizia Hribal
- Department of Medical and Surgical Sciences, University Magna Græcia of Catanzaro, Catanzaro, Italy
| | - Elettra Mancuso
- Department of Medical and Surgical Sciences, University Magna Græcia of Catanzaro, Catanzaro, Italy
| | - Gaetano Paride Arcidiacono
- Department of Medical and Surgical Sciences, University Magna Græcia of Catanzaro, Catanzaro, Italy
- Department of Medicine, University of Padua, Padua, Italy
| | - Annalisa Greco
- Department of Medical and Surgical Sciences, University Magna Græcia of Catanzaro, Catanzaro, Italy
| | - Donatella Musca
- Department of Medical and Surgical Sciences, University Magna Græcia of Catanzaro, Catanzaro, Italy
| | - Teresa Procopio
- Department of Medical and Surgical Sciences, University Magna Græcia of Catanzaro, Catanzaro, Italy
| | - Mariafrancesca Ruffo
- Department of Medical and Surgical Sciences, University Magna Græcia of Catanzaro, Catanzaro, Italy
- Department of Medicine, Ausl of Bologna, Bologna, Italy
| | - Giorgio Sesti
- Department of Medical and Surgical Sciences, University Magna Græcia of Catanzaro, Catanzaro, Italy
- Department of Clinical and Molecular Medicine, University of Rome La Sapienza, Rome, Italy
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29
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Li J, An R, Lai S, Li L, Liu S, Xu H. Dysregulation of PP2A-Akt interaction contributes to Sucrose non-fermenting related kinase (SNRK) deficiency induced insulin resistance in adipose tissue. Mol Metab 2019; 28:26-35. [PMID: 31420304 PMCID: PMC6822176 DOI: 10.1016/j.molmet.2019.07.009] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/16/2019] [Revised: 07/23/2019] [Accepted: 07/30/2019] [Indexed: 12/16/2022] Open
Abstract
Objective We previously identified Sucrose non-fermenting related kinase (SNRK) as a regulator of adipose inflammation and energy homeostasis. In this study, we aimed to investigate the role of SNRK in insulin signaling in white (WAT) and brown adipose tissue (BAT). Methods Adipose tissue specific (SNRK deficiency in both WAT and BAT) and BAT specific knockout mouse models were employed. Phosphoproteomic studies were conducted to identify the novel SNRK pathway regulating insulin signaling in adipose tissue. Results SNRK ablation is sufficient to inhibit insulin-stimulated AKT phosphorylation and glucose uptake in both WAT and BAT. Phosphoproteomic study using SNRK deficient versus wild type BAT samples revealed 99% reduction of phosphorylation on Serine 80 of PPP2R5D, the regulatory subunit of Protein phosphatase 2A (PP2A). Drastic (142.5-fold) induction of phosphorylation on Serine 80 of PPP2R5D was observed in SNRK-deficient primary brown adipocytes overexpressing SNRK compared to control protein. In vitro phosphorylation reaction followed by targeted phosphoproteomic detection further confirms that human recombinant SNRK is able to phosphorylate human recombinant PPP2R5D. Dephosphorylated PPP2R5D promotes constitutive assembly of PP2A-AKT complex, therefore inhibits insulin-induced AKT phosphorylation and subsequent glucose uptake in both BAT and WAT. Knockdown of PPP2R5D in adipocytes can improve insulin sensitivity in adipocytes without SNRK expression. Conclusions Our findings demonstrate that SNRK regulates insulin signaling through controlling PPP2R5D phosphorylation, which subsequently impacts PP2A activity and then AKT phosphorylation in both WAT and BAT. SNRK may represent a promising potential target for treating insulin resistance-related metabolic disorders. SNRK is essential for insulin-stimulated AKT phosphorylation in adipose tissue. SNRK ablation causes insulin resistance in both white and brown adipose tissue. Phosphoproteomic studies identify PPP2R5D as a novel substrate of SNRK. SNRK regulates PP2A-AKT interaction through PPP2R5D phosphorylation. Enhanced PP2A activity by SNRK ablation inhibits AKT phosphorylation.
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Affiliation(s)
- Jie Li
- Department of Epidemiology, Brown University, Providence, RI, USA; Center for Global Cardiometabolic Health, Brown University, Providence, RI, USA; National Key Discipline, Department of Nutrition and Food Hygiene, School of Public Health, Harbin Medical University, Harbin, China
| | - Ran An
- Department of Epidemiology, Brown University, Providence, RI, USA; Center for Global Cardiometabolic Health, Brown University, Providence, RI, USA; Department of Pharmaceutical Analysis and Analytical Chemistry, College of Pharmacy, Harbin Medical University, Harbin, China
| | - Shuiqing Lai
- Department of Endocrinology, Guangdong Provincial People's Hospital, Guangdong Academy of Medical Sciences, Guangzhou, China; Department of Epidemiology, Brown University, Providence, RI, USA; Center for Global Cardiometabolic Health, Brown University, Providence, RI, USA
| | - Linlin Li
- Department of Epidemiology, Brown University, Providence, RI, USA; Center for Global Cardiometabolic Health, Brown University, Providence, RI, USA; Department of Epidemiology & Biostatistics, School of Public Health, Zhengzhou University, China
| | - Simin Liu
- Department of Epidemiology, Brown University, Providence, RI, USA; Center for Global Cardiometabolic Health, Brown University, Providence, RI, USA
| | - Haiyan Xu
- Department of Epidemiology, Brown University, Providence, RI, USA; Center for Global Cardiometabolic Health, Brown University, Providence, RI, USA.
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30
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Virgirinia RP, Jahan N, Okada M, Takebayashi‐Suzuki K, Yoshida H, Nakamura M, Akao H, Yoshimoto Y, Fatchiyah F, Ueno N, Suzuki A. Cdc2‐like kinase 2 (Clk2) promotes early neural development inXenopusembryos. Dev Growth Differ 2019; 61:365-377. [DOI: 10.1111/dgd.12619] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/06/2018] [Revised: 04/24/2019] [Accepted: 04/25/2019] [Indexed: 12/13/2022]
Affiliation(s)
- Regina Putri Virgirinia
- Amphibian Research Center Graduate School of Science Hiroshima University Higashi-Hiroshima Japan
| | - Nusrat Jahan
- Amphibian Research Center Graduate School of Science Hiroshima University Higashi-Hiroshima Japan
| | - Maya Okada
- Amphibian Research Center Graduate School of Science Hiroshima University Higashi-Hiroshima Japan
| | | | - Hitoshi Yoshida
- Amphibian Research Center Graduate School of Science Hiroshima University Higashi-Hiroshima Japan
| | - Makoto Nakamura
- Amphibian Research Center Graduate School of Science Hiroshima University Higashi-Hiroshima Japan
| | - Hajime Akao
- Amphibian Research Center Graduate School of Science Hiroshima University Higashi-Hiroshima Japan
| | - Yuta Yoshimoto
- Amphibian Research Center Graduate School of Science Hiroshima University Higashi-Hiroshima Japan
| | - Fatchiyah Fatchiyah
- Department of Biology Faculty of Mathematics and Natural Sciences Brawijaya University Malang Indonesia
| | - Naoto Ueno
- Division of Morphogenesis National Institute for Basic Biology Okazaki Japan
| | - Atsushi Suzuki
- Amphibian Research Center Graduate School of Science Hiroshima University Higashi-Hiroshima Japan
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31
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Sugiyama MG, Fairn GD, Antonescu CN. Akt-ing Up Just About Everywhere: Compartment-Specific Akt Activation and Function in Receptor Tyrosine Kinase Signaling. Front Cell Dev Biol 2019; 7:70. [PMID: 31131274 PMCID: PMC6509475 DOI: 10.3389/fcell.2019.00070] [Citation(s) in RCA: 94] [Impact Index Per Article: 15.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/20/2019] [Accepted: 04/09/2019] [Indexed: 12/12/2022] Open
Abstract
The serine/threonine kinase Akt is a master regulator of many diverse cellular functions, including survival, growth, metabolism, migration, and differentiation. Receptor tyrosine kinases are critical regulators of Akt, as a result of activation of phosphatidylinositol-3-kinase (PI3K) signaling leading to Akt activation upon receptor stimulation. The signaling axis formed by receptor tyrosine kinases, PI3K and Akt, as well as the vast range of downstream substrates is thus central to control of cell physiology in many different contexts and tissues. This axis must be tightly regulated, as disruption of PI3K-Akt signaling underlies the pathology of many diseases such as cancer and diabetes. This sophisticated regulation of PI3K-Akt signaling is due in part to the spatial and temporal compartmentalization of Akt activation and function, including in specific nanoscale domains of the plasma membrane as well as in specific intracellular membrane compartments. Here, we review the evidence for localized activation of PI3K-Akt signaling by receptor tyrosine kinases in various specific cellular compartments, as well as that of compartment-specific functions of Akt leading to control of several fundamental cellular processes. This spatial and temporal control of Akt activation and function occurs by a large number of parallel molecular mechanisms that are central to regulation of cell physiology.
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Affiliation(s)
- Michael G. Sugiyama
- Department of Chemistry and Biology, Ryerson University, Toronto, ON, Canada
- Keenan Research Centre for Biomedical Science, St. Michael’s Hospital, Toronto, ON, Canada
| | - Gregory D. Fairn
- Keenan Research Centre for Biomedical Science, St. Michael’s Hospital, Toronto, ON, Canada
- Department of Surgery, University of Toronto, Toronto, ON, Canada
| | - Costin N. Antonescu
- Department of Chemistry and Biology, Ryerson University, Toronto, ON, Canada
- Keenan Research Centre for Biomedical Science, St. Michael’s Hospital, Toronto, ON, Canada
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32
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Uchida E, Suwa S, Yoshimoto R, Watanabe K, Kasama T, Miura O, Fukuda T. TOPK is regulated by PP2A and BCR/ABL in leukemia and enhances cell proliferation. Int J Oncol 2019; 54:1785-1796. [PMID: 30864683 DOI: 10.3892/ijo.2019.4740] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/10/2018] [Accepted: 01/21/2019] [Indexed: 11/06/2022] Open
Abstract
Although treatment of chronic myeloid leukemia (CML) has improved with the development of tyrosine kinase inhibitors (TKIs), patients develop fatal blast crisis (BC) whilst receiving TKI treatment. Alternative treatments for cases resistant to TKIs are required. A serine/threonine protein kinase, T‑lymphokine‑activated killer cell‑originated protein kinase (TOPK), is highly expressed in various malignant tumors. Binding of peptides to human leukocyte antigen was assessed via mass spectrometry in K562 CML cells. TOPK expression was assessed in various CML cell lines and in clinical samples obtained from patients with CML using reverse transcription‑quantitative polymerase chain reaction and western blot assays. It was observed that TOPK was expressed abundantly in BCR/ABL‑positive cell lines and at significantly higher levels in CML clinical samples compared with healthy donor samples. Overexpression of BCR/ABL or the presence of its inhibitor imatinib upregulated and downregulated TOPK expression, respectively, indicating that TOPK may be a target of BCR/ABL. TOPK inhibitor OTS514 suppressed proliferation of BCR/ABL‑positive cell lines and colony formation of CD34‑positive cells from patients with CML compared with lymphoma patients without bone marrow involvement. Furthermore, phosphorylation of TOPK was increased by protein phosphatase 2A (PP2A) inhibitor okadaic acid and was decreased in the presence of PP2A activator FTY720 compared with untreated samples. As constitutive BCR/ABL activity and inhibition of PP2A are key mechanisms of CML development, TOPK may be a crucial signaling molecule for this disease. Inhibition of TOPK may control disease status of CML, even in cases resistant to TKIs.
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Affiliation(s)
- Emi Uchida
- Department of Hematology, Tokyo Medical and Dental University, Tokyo 113‑8519, Japan
| | - Shihoko Suwa
- Department of Hematology, Tokyo Medical and Dental University, Tokyo 113‑8519, Japan
| | - Ryoto Yoshimoto
- Department of Hematology, Tokyo Medical and Dental University, Tokyo 113‑8519, Japan
| | - Ken Watanabe
- Department of Hematology, Tokyo Medical and Dental University, Tokyo 113‑8519, Japan
| | - Takeshi Kasama
- Research Center for Medical and Dental Sciences, Tokyo Medical and Dental University, Tokyo 113‑8519, Japan
| | - Osamu Miura
- Department of Hematology, Tokyo Medical and Dental University, Tokyo 113‑8519, Japan
| | - Tetsuya Fukuda
- Department of Hematology, Tokyo Medical and Dental University, Tokyo 113‑8519, Japan
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33
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Kubiniok P, Finicle BT, Piffaretti F, McCracken AN, Perryman M, Hanessian S, Edinger AL, Thibault P. Dynamic Phosphoproteomics Uncovers Signaling Pathways Modulated by Anti-oncogenic Sphingolipid Analogs. Mol Cell Proteomics 2019; 18:408-422. [PMID: 30482847 PMCID: PMC6398214 DOI: 10.1074/mcp.ra118.001053] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/23/2018] [Revised: 10/23/2018] [Indexed: 12/31/2022] Open
Abstract
The anti-neoplastic sphingolipid analog SH-BC-893 starves cancer cells to death by down-regulating cell surface nutrient transporters and blocking lysosomal trafficking events. These effects are mediated by the activation of protein phosphatase 2A (PP2A). To identify putative PP2A substrates, we used quantitative phosphoproteomics to profile the temporal changes in protein phosphorylation in FL5.12 cells following incubation with SH-BC-893 or the specific PP2A inhibitor LB-100. These analyses enabled the profiling of more than 15,000 phosphorylation sites, of which 958 sites on 644 proteins were dynamically regulated. We identified 114 putative PP2A substrates including several nutrient transporter proteins, GTPase regulators (e.g. Agap2, Git1), and proteins associated with actin cytoskeletal remodeling (e.g. Vim, Pxn). To identify SH-BC-893-induced cell signaling events that disrupt lysosomal trafficking, we compared phosphorylation profiles in cells treated with SH-BC-893 or C2-ceramide, a non-vacuolating sphingolipid that does not impair lysosomal fusion. These analyses combined with functional assays uncovered the differential regulation of Akt and Gsk3b by SH-BC-893 (vacuolating) and C2-ceramide (non-vacuolating). Dynamic phosphoproteomics of cells treated with compounds affecting PP2A activity thus enabled the correlation of cell signaling with phenotypes to rationalize their mode of action.
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Affiliation(s)
- Peter Kubiniok
- From the ‡Institute for Research in Immunology and Cancer, Université de Montréal, C.P. 6128, Succursale centre-ville, Montréal, Québec, H3C 3J7, Canada
- §Department of Chemistry, Université de Montréal, Quebec, H3C 3J7, Canada
| | - Brendan T Finicle
- ¶Department of Developmental and Cell Biology, University of California Irvine, Irvine CA 92697
| | - Fanny Piffaretti
- From the ‡Institute for Research in Immunology and Cancer, Université de Montréal, C.P. 6128, Succursale centre-ville, Montréal, Québec, H3C 3J7, Canada
| | - Alison N McCracken
- ¶Department of Developmental and Cell Biology, University of California Irvine, Irvine CA 92697
| | - Michael Perryman
- §Department of Chemistry, Université de Montréal, Quebec, H3C 3J7, Canada
| | - Stephen Hanessian
- §Department of Chemistry, Université de Montréal, Quebec, H3C 3J7, Canada
| | - Aimee L Edinger
- ¶Department of Developmental and Cell Biology, University of California Irvine, Irvine CA 92697;
| | - Pierre Thibault
- From the ‡Institute for Research in Immunology and Cancer, Université de Montréal, C.P. 6128, Succursale centre-ville, Montréal, Québec, H3C 3J7, Canada;
- §Department of Chemistry, Université de Montréal, Quebec, H3C 3J7, Canada
- ‖Department of Biochemistry, Université de Montréal, C.P. 6128, Succursale centre-ville, Montréal, Québec, H3C 3J7, Canada
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Fowle H, Zhao Z, Graña X. PP2A holoenzymes, substrate specificity driving cellular functions and deregulation in cancer. Adv Cancer Res 2019; 144:55-93. [PMID: 31349904 PMCID: PMC9994639 DOI: 10.1016/bs.acr.2019.03.009] [Citation(s) in RCA: 53] [Impact Index Per Article: 8.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Abstract
PP2A is a highly conserved eukaryotic serine/threonine protein phosphatase of the PPP family of phosphatases with fundamental cellular functions. In cells, PP2A targets specific subcellular locations and substrates by forming heterotrimeric holoenzymes, where a core dimer consisting of scaffold (A) and catalytic (C) subunits complexes with one of many B regulatory subunits. PP2A plays a key role in positively and negatively regulating a myriad of cellular processes, as it targets a very sizable fraction of the cellular substrates phosphorylated on Ser/Thr residues. This review focuses on insights made toward the understanding on how the subunit composition and structure of PP2A holoenzymes mediates substrate specificity, the role of substrate modulation in the signaling of cellular division, growth, and differentiation, and its deregulation in cancer.
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Affiliation(s)
- Holly Fowle
- Fels Institute for Cancer Research and Molecular Biology and Temple University Lewis Katz School of Medicine, Philadelphia, PA, United States
| | - Ziran Zhao
- Fels Institute for Cancer Research and Molecular Biology and Temple University Lewis Katz School of Medicine, Philadelphia, PA, United States
| | - Xavier Graña
- Fels Institute for Cancer Research and Molecular Biology and Temple University Lewis Katz School of Medicine, Philadelphia, PA, United States.
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35
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Madigan JP, Hou F, Ye L, Hu J, Dong A, Tempel W, Yohe ME, Randazzo PA, Jenkins LMM, Gottesman MM, Tong Y. The tuberous sclerosis complex subunit TBC1D7 is stabilized by Akt phosphorylation-mediated 14-3-3 binding. J Biol Chem 2018; 293:16142-16159. [PMID: 30143532 DOI: 10.1074/jbc.ra118.003525] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/17/2018] [Revised: 08/13/2018] [Indexed: 01/19/2023] Open
Abstract
The tuberous sclerosis complex (TSC) is a negative regulator of mTOR complex 1, a signaling node promoting cellular growth in response to various nutrients and growth factors. However, several regulators in TSC signaling still await discovery and characterization. Using pulldown and MS approaches, here we identified the TSC complex member, TBC1 domain family member 7 (TBC1D7), as a binding partner for PH domain and leucine-rich repeat protein phosphatase 1 (PHLPP1), a negative regulator of Akt kinase signaling. Most TBC domain-containing proteins function as Rab GTPase-activating proteins (RabGAPs), but the crystal structure of TBC1D7 revealed that it lacks residues critical for RabGAP activity. Sequence analysis identified a putative site for both Akt-mediated phosphorylation and 14-3-3 binding at Ser-124, and we found that Akt phosphorylates TBC1D7 at Ser-124. However, this phosphorylation had no effect on the binding of TBC1D7 to TSC1, but stabilized TBC1D7. Moreover, 14-3-3 protein both bound and stabilized TBC1D7 in a growth factor-dependent manner, and a phospho-deficient substitution, S124A, prevented this interaction. The crystal structure of 14-3-3ζ in complex with a phospho-Ser-124 TBC1D7 peptide confirmed the direct interaction between 14-3-3 and TBC1D7. The sequence immediately upstream of Ser-124 aligned with a canonical β-TrCP degron, and we found that the E3 ubiquitin ligase β-TrCP2 ubiquitinates TBC1D7 and decreases its stability. Our findings reveal that Akt activity determines the phosphorylation status of TBC1D7 at the phospho-switch Ser-124, which governs binding to either 14-3-3 or β-TrCP2, resulting in increased or decreased stability of TBC1D7, respectively.
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Affiliation(s)
| | - Feng Hou
- the Structural Genomics Consortium and
| | - Linlei Ye
- Department of Pharmacology and Toxicology, University of Toronto, Toronto, Ontario M5G 1L7, Canada, and
| | | | | | | | | | - Paul A Randazzo
- Laboratory of Cell and Molecular Biology, Center for Cancer Research, NCI, National Institutes of Health, Bethesda, Maryland 20892
| | | | | | - Yufeng Tong
- the Structural Genomics Consortium and .,the Department of Chemistry and Biochemistry, University of Windsor, Windsor, Ontario N9B 3P4, Canada
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36
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Nakatsumi H, Oka T, Higa T, Shirane M, Nakayama KI. Nuclear-cytoplasmic shuttling protein PP2A B56 contributes to mTORC1-dependent dephosphorylation of FOXK1. Genes Cells 2018; 23:599-605. [PMID: 29845697 DOI: 10.1111/gtc.12597] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/12/2018] [Accepted: 04/24/2018] [Indexed: 12/17/2022]
Abstract
Mammalian target of rapamycin complex 1 (mTORC1) kinase is a master regulator of the cellular response to nutrition-related signals such as insulin and amino acids. mTORC1 is activated on the lysosomal membrane and induces phosphorylation of a variety of downstream molecules. We previously showed that activated mTORC1 induces protein phosphatase 2A (PP2A)-mediated dephosphorylation of the transcription factor forkhead box K1 (FOXK1). The mechanism underlying the signal transduction from the cytoplasmic mTORC1 to the nuclear FOXK1 has remained unclear, however, we now show that a nuclear-cytoplasmic transport system is necessary for the mTORC1-FOXK1 signal transduction. This reaction is mediated by a shuttling protein B56, which is a regulatory subunit of PP2A and plays an essential role in the mTORC1-dependent dephosphorylation of FOXK1. These results suggest that PP2AB56 phosphatase contributes to the signaling for mTORC1-dependent transcriptional regulation.
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Affiliation(s)
- Hirokazu Nakatsumi
- Department of Molecular and Cellular Biology, Medical Institute of Bioregulation, Kyushu University, Fukuoka, Japan.,Department of Molecular Biology, Graduate School of Pharmaceutical Sciences, Nagoya City University, Nagoya, Japan
| | - Takeru Oka
- Department of Molecular and Cellular Biology, Medical Institute of Bioregulation, Kyushu University, Fukuoka, Japan
| | - Tsunaki Higa
- Department of Molecular and Cellular Biology, Medical Institute of Bioregulation, Kyushu University, Fukuoka, Japan
| | - Michiko Shirane
- Department of Molecular and Cellular Biology, Medical Institute of Bioregulation, Kyushu University, Fukuoka, Japan.,Department of Molecular Biology, Graduate School of Pharmaceutical Sciences, Nagoya City University, Nagoya, Japan
| | - Keiichi I Nakayama
- Department of Molecular and Cellular Biology, Medical Institute of Bioregulation, Kyushu University, Fukuoka, Japan
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37
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Yu S, Li L, Wu Q, Dou N, Li Y, Gao Y. PPP2R2D, a regulatory subunit of protein phosphatase 2A, promotes gastric cancer growth and metastasis via mechanistic target of rapamycin activation. Int J Oncol 2018; 52:2011-2020. [PMID: 29568966 DOI: 10.3892/ijo.2018.4329] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/12/2017] [Accepted: 03/15/2018] [Indexed: 11/06/2022] Open
Abstract
Protein phosphatase 2A (PP2A) is an essential serine/threonine protein phosphatase that regulates the basic activities of eukaryotes by dephosphorylating its substrates. The function and substrate specificity of PP2A are generally determined by its regulatory subunits. In the present study, the clinical significance and roles of PPP2R2D, one of the regulatory subunits of PP2A, were demonstrated in gastric cancer (GC) carcinogenesis. Through a tissue microarray and quantitative polymerase chain reaction analysis, it was demonstrated that PPP2R2D was commonly upregulated in GC samples. This upregulation was positively correlated with the patients' tumor stage (P<0.01), T classification (P<0.01) and N classification (P=0.01). Furthermore, a high expression of PPP2R2D was closely associated with poor prognosis of patients. Knockdown of PPP2R2D significantly inhibited the proliferation and migration of GC cells in vitro, as well as the tumorigenicity and metastasis in vivo in an animal GC model. By contrast, overexpression of PPP2R2D promoted GC cell proliferation and migration in vitro. The analysis of underlying mechanisms indicated that PPP2R2D silencing decreased the phosphorylation level of mechanistic target of rapamycin (mTOR), thereby implicating that PPP2R2D is involved in the regulation of mTOR activity during tumorigenesis. Thus, the findings of the present study suggested that PPP2R2D may serve as a potential oncogene in GC and as a novel target for therapeutic strategies against this disease.
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Affiliation(s)
- Shijun Yu
- Department of Oncology, Shanghai East Hospital, Tongji University School of Medicine, Shanghai 200120, P.R. China
| | - Li Li
- Department of Oncology, Shanghai East Hospital, Tongji University School of Medicine, Shanghai 200120, P.R. China
| | - Qiong Wu
- Department of Oncology, Shanghai East Hospital, Tongji University School of Medicine, Shanghai 200120, P.R. China
| | - Ning Dou
- Department of Oncology, Shanghai East Hospital, Tongji University School of Medicine, Shanghai 200120, P.R. China
| | - Yandong Li
- Department of Oncology, Shanghai East Hospital, Tongji University School of Medicine, Shanghai 200120, P.R. China
| | - Yong Gao
- Department of Oncology, Shanghai East Hospital, Tongji University School of Medicine, Shanghai 200120, P.R. China
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38
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Rodriguez-Martinez A, Ayala R, Posma JM, Neves AL, Gauguier D, Nicholson JK, Dumas ME. MetaboSignal: a network-based approach for topological analysis of metabotype regulation via metabolic and signaling pathways. Bioinformatics 2018; 33:773-775. [PMID: 28011775 PMCID: PMC5408820 DOI: 10.1093/bioinformatics/btw697] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/01/2016] [Accepted: 11/03/2016] [Indexed: 12/31/2022] Open
Abstract
Summary MetaboSignal is an R package that allows merging metabolic and signaling pathways reported in the Kyoto Encyclopaedia of Genes and Genomes (KEGG). It is a network-based approach designed to navigate through topological relationships between genes (signaling- or metabolic-genes) and metabolites, representing a powerful tool to investigate the genetic landscape of metabolic phenotypes. Availability and Implementation MetaboSignal is available from Bioconductor: https://bioconductor.org/packages/MetaboSignal/ Supplementary information Supplementary data are available at Bioinformatics online.
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Affiliation(s)
- Andrea Rodriguez-Martinez
- Computational and Systems Medicine, Department of Surgery and Cancer, Faculty of Medicine, Imperial College London, SW7 2AZ London, UK
| | - Rafael Ayala
- Computational and Systems Medicine, Department of Surgery and Cancer, Faculty of Medicine, Imperial College London, SW7 2AZ London, UK
| | - Joram M Posma
- Computational and Systems Medicine, Department of Surgery and Cancer, Faculty of Medicine, Imperial College London, SW7 2AZ London, UK
| | - Ana L Neves
- Computational and Systems Medicine, Department of Surgery and Cancer, Faculty of Medicine, Imperial College London, SW7 2AZ London, UK
| | - Dominique Gauguier
- Computational and Systems Medicine, Department of Surgery and Cancer, Faculty of Medicine, Imperial College London, SW7 2AZ London, UK.,Sorbonne Universities, University Pierre & Marie Curie, University Paris Descartes, Sorbonne Paris Cité, INSERMUMR_S 1138, Cordeliers Research Centre, 75006 Paris, France
| | - Jeremy K Nicholson
- Computational and Systems Medicine, Department of Surgery and Cancer, Faculty of Medicine, Imperial College London, SW7 2AZ London, UK
| | - Marc-Emmanuel Dumas
- Computational and Systems Medicine, Department of Surgery and Cancer, Faculty of Medicine, Imperial College London, SW7 2AZ London, UK
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39
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Park SY, Piao Y, Thomas C, Fuller GN, de Groot JF. Cdc2-like kinase 2 is a key regulator of the cell cycle via FOXO3a/p27 in glioblastoma. Oncotarget 2018; 7:26793-805. [PMID: 27050366 PMCID: PMC5042015 DOI: 10.18632/oncotarget.8471] [Citation(s) in RCA: 22] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/23/2015] [Accepted: 03/10/2016] [Indexed: 01/09/2023] Open
Abstract
Cdc2-like kinase 2 (CLK2) is known as a regulator of RNA splicing that ultimately controls multiple physiological processes. However, the function of CLK2 in glioblastoma progression has not been described. Reverse-phase protein array (RPPA) was performed to identify proteins differentially expressed in CLK2 knockdown cells compared to controls. The RPPA results indicated that CLK2 knockdown influenced the expression of survival-, proliferation-, and cell cycle-related proteins in GSCs. Thus, knockdown of CLK2 expression arrested the cell cycle at the G1 and S checkpoints in multiple GSC lines. Depletion of CLK2 regulated the dephosphorylation of AKT and decreased phosphorylation of Forkhead box O3a (FOXO3a), which not only translocated to the nucleus but also increased p27 expression. In two glioblastoma xenograft models, the survival duration of mice with CLK2-knockdown GSCs was significantly longer than mice with control tumors. Additionally, tumor volumes were significantly smaller in CLK2-knockdown mice than in controls. Knockdown of CLK2 expression reduced the phosphorylation of FOXO3a and decreased Ki-67 in vivo. Finally, high expression of CLK2 protien was significantly associated with worse patient survival. These findings suggest that CLK2 plays a critical role in controlling the cell cycle and survival of glioblastoma via FOXO3a/p27.
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Affiliation(s)
- Soon Young Park
- Department of Neuro-Oncology, The University of Texas MD Anderson Cancer Center, Houston, Texas, USA
| | - Yuji Piao
- Department of Neuro-Oncology, The University of Texas MD Anderson Cancer Center, Houston, Texas, USA
| | - Craig Thomas
- Department of Neuro-Oncology, The University of Texas MD Anderson Cancer Center, Houston, Texas, USA
| | - Gregory N Fuller
- Department of Pathology, The University of Texas MD Anderson Cancer Center, Houston, Texas, USA
| | - John F de Groot
- Department of Neuro-Oncology, The University of Texas MD Anderson Cancer Center, Houston, Texas, USA
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40
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Haeusler RA, McGraw TE, Accili D. Biochemical and cellular properties of insulin receptor signalling. Nat Rev Mol Cell Biol 2018; 19:31-44. [PMID: 28974775 PMCID: PMC5894887 DOI: 10.1038/nrm.2017.89] [Citation(s) in RCA: 475] [Impact Index Per Article: 67.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
Abstract
The mechanism of insulin action is a central theme in biology and medicine. In addition to the rather rare condition of insulin deficiency caused by autoimmune destruction of pancreatic β-cells, genetic and acquired abnormalities of insulin action underlie the far more common conditions of type 2 diabetes, obesity and insulin resistance. The latter predisposes to diseases ranging from hypertension to Alzheimer disease and cancer. Hence, understanding the biochemical and cellular properties of insulin receptor signalling is arguably a priority in biomedical research. In the past decade, major progress has led to the delineation of mechanisms of glucose transport, lipid synthesis, storage and mobilization. In addition to direct effects of insulin on signalling kinases and metabolic enzymes, the discovery of mechanisms of insulin-regulated gene transcription has led to a reassessment of the general principles of insulin action. These advances will accelerate the discovery of new treatment modalities for diabetes.
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Affiliation(s)
- Rebecca A Haeusler
- Columbia University College of Physicians and Surgeons, Department of Pathology and Cell Biology, New York, New York 10032, USA
| | - Timothy E McGraw
- Weill Cornell Medicine, Departments of Biochemistry and Cardiothoracic Surgery, New York, New York 10065, USA
| | - Domenico Accili
- Columbia University College of Physicians & Surgeons, Department of Medicine, New York, New York 10032, USA
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41
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Hatting M, Tavares CDJ, Sharabi K, Rines AK, Puigserver P. Insulin regulation of gluconeogenesis. Ann N Y Acad Sci 2017; 1411:21-35. [PMID: 28868790 DOI: 10.1111/nyas.13435] [Citation(s) in RCA: 354] [Impact Index Per Article: 44.3] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/03/2017] [Revised: 06/16/2017] [Accepted: 06/26/2017] [Indexed: 12/11/2022]
Abstract
The coordinated regulation between cellular glucose uptake and endogenous glucose production is indispensable for the maintenance of constant blood glucose concentrations. The liver contributes significantly to this process by altering the levels of hepatic glucose release, through controlling the processes of de novo glucose production (gluconeogenesis) and glycogen breakdown (glycogenolysis). Various nutritional and hormonal stimuli signal to alter hepatic gluconeogenic flux, and suppression of this metabolic pathway during the postprandial state can, to a significant extent, be attributed to insulin. Here, we review some of the molecular mechanisms through which insulin modulates hepatic gluconeogenesis, thus controlling glucose production by the liver to ultimately maintain normoglycemia. Various signaling pathways governed by insulin converge at the level of transcriptional regulation of the key hepatic gluconeogenic genes PCK1 and G6PC, highlighting this as one of the focal mechanisms through which gluconeogenesis is modulated. In individuals with compromised insulin signaling, such as insulin resistance in type 2 diabetes, insulin fails to suppress hepatic gluconeogenesis, even in the fed state; hence, an insight into these insulin-moderated pathways is critical for therapeutic purposes.
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Affiliation(s)
- Maximilian Hatting
- Department of Cancer Biology, Dana-Farber Cancer Institute, Boston, Massachusetts.,Department of Cell Biology, Harvard Medical School, Boston, Massachusetts
| | - Clint D J Tavares
- Department of Cancer Biology, Dana-Farber Cancer Institute, Boston, Massachusetts.,Department of Cell Biology, Harvard Medical School, Boston, Massachusetts
| | - Kfir Sharabi
- Department of Cancer Biology, Dana-Farber Cancer Institute, Boston, Massachusetts.,Department of Cell Biology, Harvard Medical School, Boston, Massachusetts
| | - Amy K Rines
- Department of Cancer Biology, Dana-Farber Cancer Institute, Boston, Massachusetts.,Department of Cell Biology, Harvard Medical School, Boston, Massachusetts
| | - Pere Puigserver
- Department of Cancer Biology, Dana-Farber Cancer Institute, Boston, Massachusetts.,Department of Cell Biology, Harvard Medical School, Boston, Massachusetts
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42
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Li HY, Wang T, Yang YP, Geng SL, Xu WH. TGF-β signaling regulates p-Akt levels via PP2A during diapause entry in the cotton bollworm, Helicoverpa armigera. INSECT BIOCHEMISTRY AND MOLECULAR BIOLOGY 2017; 87:165-173. [PMID: 28720534 DOI: 10.1016/j.ibmb.2017.07.003] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/10/2017] [Revised: 07/13/2017] [Accepted: 07/14/2017] [Indexed: 06/07/2023]
Abstract
Akt, which is a key kinase in the insulin signaling pathway, plays important roles in glucose metabolism, cell proliferation, transcription and cell migration. Our previous studies indicated that low insulin levels and high p-Akt levels are present in diapause-destined individuals. Here, we show that PI3K, which is upstream of Akt, is low in diapause-destined pupal brains but high in p-Akt levels, implying that p-Akt is modified by factors other than the insulin signaling pathway. Protein phosphatase 2A (PP2A), which is a key regulator in the TGF-β signaling pathway, can directly bind to and dephosphorylate Akt. Low PP2A expression and activity in diapause-destined individuals suggest that a weak Akt dephosphorylation contributes to p-Akt accumulation. In addition, transforming growth factor-β receptor I (TβRI), which is upstream of PP2A, increases the activity of PP2A and decreases the p-Akt levels. These results show that TGF-β signaling decreases p-Akt levels by increasing the activity of PP2A. This is the first report showing that TGF-β signaling negatively regulates the insulin pathway in insect development or diapause.
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Affiliation(s)
- Hai-Yin Li
- State Key Laboratory of Biocontrol, School of Life Sciences, Sun Yat-sen University, Guangzhou 510006, China
| | - Tao Wang
- State Key Laboratory of Biocontrol, School of Life Sciences, Sun Yat-sen University, Guangzhou 510006, China
| | - Yong-Pan Yang
- State Key Laboratory of Biocontrol, School of Life Sciences, Sun Yat-sen University, Guangzhou 510006, China
| | - Shao-Lei Geng
- State Key Laboratory of Biocontrol, School of Life Sciences, Sun Yat-sen University, Guangzhou 510006, China
| | - Wei-Hua Xu
- State Key Laboratory of Biocontrol, School of Life Sciences, Sun Yat-sen University, Guangzhou 510006, China.
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43
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Kim LW. Dual TORCs driven and B56 orchestrated signaling network guides eukaryotic cell migration. BMB Rep 2017; 50:437-444. [PMID: 28571594 PMCID: PMC5625690 DOI: 10.5483/bmbrep.2017.50.9.091] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/23/2017] [Indexed: 11/20/2022] Open
Abstract
Different types of eukaryotic cells may adopt seemingly distinct modes of directional cell migration. However, several core aspects are regarded common whether the movement is either ameoboidal or mesenchymal. The region of cells facing the attractive signal is often termed leading edge where lamellipodial structures dominates and the other end of the cell called rear end is often mediating cytoskeletal F-actin contraction involving Myosin-II. Dynamic remodeling of cell-to-matrix adhesion involving integrin is also evident in many types of migrating cells. All these three aspects of cell migration are significantly affected by signaling networks of TorC2, TorC1, and PP2A/B56. Here we review the current views of the mechanistic understanding of these regulatory signaling networks and how these networks affect eukaryotic cell migration.
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Affiliation(s)
- Lou W Kim
- Department of Biological Sciences, Florida International University, Miami, FL 33199, USA
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44
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Czubaty A, Piekiełko-Witkowska A. Protein kinases that phosphorylate splicing factors: Roles in cancer development, progression and possible therapeutic options. Int J Biochem Cell Biol 2017; 91:102-115. [PMID: 28552434 DOI: 10.1016/j.biocel.2017.05.024] [Citation(s) in RCA: 42] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/15/2017] [Revised: 05/16/2017] [Accepted: 05/18/2017] [Indexed: 11/30/2022]
Abstract
Disturbed alternative splicing is a common feature of human tumors. Splicing factors that control alternative splicing are phosphorylated by multiple kinases, including these that specifically add phosphoryl groups to serine-arginine rich proteins (e.g. SR-protein kinases, cdc2-like kinases, topoisomerase 1), and protein kinases that govern key cellular signaling pathways (i.e. AKT). Phosphorylation of splicing factors regulates their subcellular localization and interactions with target transcripts and protein partners, and thus significantly contributes the final result of splicing reactions. In this review we aim to summarize the current knowledge on the role of splicing kinases in cancer. Published studies and recently released data of The Cancer Genome Atlas demonstrate that expressions and activities of splicing kinases are commonly disturbed in cancers. Aberrant functioning of splicing kinases results in changed alternative splicing of tumor suppressors (e.g. p53) and regulators of cell signaling (e.g. MAPKs), apoptosis (e.g. MCL), and angiogenesis (VEGF). Splicing kinases act in complicated regulatory networks in which they mutually affect each other's activity to provide tight control of cellular signaling. Dysregulation of these regulatory networks contributes to oncogenic transformation, uncontrolled proliferation, enhanced migration and invasion. Furthermore, the activities of splicing kinases significantly contribute to cellular responses to genotoxic stress. In conclusion, published data provide strong evidence that splicing kinases emerge as important regulators of key processes governing malignant transformation, progression, and response to therapeutic treatments, suggesting their potential as clinically relevant targets.
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Affiliation(s)
- Alicja Czubaty
- Department of Molecular Biology, Faculty of Biology, University of Warsaw, ul. Miecznikowa 1, 02-096 Warsaw, Poland
| | - Agnieszka Piekiełko-Witkowska
- Department of Biochemistry and Molecular Biology, Centre of Postgraduate Medical Education, ul. Marymoncka 99/103, 01-813 Warsaw, Poland.
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45
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Luo K, Li Y, Yin Y, Li L, Wu C, Chen Y, Nowsheen S, Hu Q, Zhang L, Lou Z, Yuan J. USP49 negatively regulates tumorigenesis and chemoresistance through FKBP51-AKT signaling. EMBO J 2017; 36:1434-1446. [PMID: 28363942 DOI: 10.15252/embj.201695669] [Citation(s) in RCA: 68] [Impact Index Per Article: 8.5] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/06/2016] [Revised: 02/24/2017] [Accepted: 03/08/2017] [Indexed: 12/21/2022] Open
Abstract
The AKT pathway is a fundamental signaling pathway that mediates multiple cellular processes, such as cell proliferation and survival, angiogenesis, and glucose metabolism. We recently reported that the immunophilin FKBP51 is a scaffolding protein that can enhance PHLPP-AKT interaction and facilitate PHLPP-mediated dephosphorylation of AKT at Ser473, negatively regulating AKT activation. However, the regulation of FKBP51-PHLPP-AKT pathway remains unclear. Here we report that a deubiquitinase, USP49, is a new regulator of the AKT pathway. Mechanistically, USP49 deubiquitinates and stabilizes FKBP51, which in turn enhances PHLPP's capability to dephosphorylate AKT Furthermore, USP49 inhibited pancreatic cancer cell proliferation and enhanced cellular response to gemcitabine in a FKBP51-AKT-dependent manner. Clinically, decreased expression of USP49 in patients with pancreatic cancer was associated with decreased FKBP51 expression and increased AKT phosphorylation. Overall, our findings establish USP49 as a novel regulator of AKT pathway with a critical role in tumorigenesis and chemo-response in pancreatic cancer.
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Affiliation(s)
- Kuntian Luo
- Research Center for Translational Medicine, East Hospital, Tongji University School of Medicine, Shanghai, China.,Key Laboratory of Arrhythmias of the Ministry of Education of China, East Hospital, Tongji University School of Medicine, Shanghai, China.,Department of Oncology, Mayo Clinic, Rochester, MN, USA
| | - Yunhui Li
- Research Center for Translational Medicine, East Hospital, Tongji University School of Medicine, Shanghai, China.,Key Laboratory of Arrhythmias of the Ministry of Education of China, East Hospital, Tongji University School of Medicine, Shanghai, China
| | - Yujiao Yin
- Research Center for Translational Medicine, East Hospital, Tongji University School of Medicine, Shanghai, China.,Key Laboratory of Arrhythmias of the Ministry of Education of China, East Hospital, Tongji University School of Medicine, Shanghai, China
| | - Lei Li
- Research Center for Translational Medicine, East Hospital, Tongji University School of Medicine, Shanghai, China.,Key Laboratory of Arrhythmias of the Ministry of Education of China, East Hospital, Tongji University School of Medicine, Shanghai, China
| | - Chenming Wu
- Research Center for Translational Medicine, East Hospital, Tongji University School of Medicine, Shanghai, China.,Key Laboratory of Arrhythmias of the Ministry of Education of China, East Hospital, Tongji University School of Medicine, Shanghai, China
| | - Yuping Chen
- Research Center for Translational Medicine, East Hospital, Tongji University School of Medicine, Shanghai, China.,Key Laboratory of Arrhythmias of the Ministry of Education of China, East Hospital, Tongji University School of Medicine, Shanghai, China
| | - Somaira Nowsheen
- Medical Scientist Training Program, Mayo Clinic School of Medicine, Mayo Clinic Graduate School of Biomedical Sciences, Rochester, MN, USA
| | - Qi Hu
- Department of Biochemistry and Molecular Biology, Mayo Clinic, Rochester, MN, USA
| | - Lizhi Zhang
- Department of Laboratory Medicine and Pathology, Mayo Clinic, Rochester, MN, USA
| | - Zhenkun Lou
- Department of Oncology, Mayo Clinic, Rochester, MN, USA
| | - Jian Yuan
- Research Center for Translational Medicine, East Hospital, Tongji University School of Medicine, Shanghai, China .,Key Laboratory of Arrhythmias of the Ministry of Education of China, East Hospital, Tongji University School of Medicine, Shanghai, China.,Department of Oncology, Mayo Clinic, Rochester, MN, USA
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46
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Adipose Tissue CLK2 Promotes Energy Expenditure during High-Fat Diet Intermittent Fasting. Cell Metab 2017; 25:428-437. [PMID: 28089567 PMCID: PMC5299049 DOI: 10.1016/j.cmet.2016.12.007] [Citation(s) in RCA: 42] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/06/2016] [Revised: 11/04/2016] [Accepted: 12/10/2016] [Indexed: 01/06/2023]
Abstract
A promising approach to treating obesity is to increase diet-induced thermogenesis in brown adipose tissue (BAT), but the regulation of this process remains unclear. Here we find that CDC-like kinase 2 (CLK2) is expressed in BAT and upregulated upon refeeding. Mice lacking CLK2 in adipose tissue exhibit exacerbated obesity and decreased energy expenditure during high-fat diet intermittent fasting. Additionally, tissue oxygen consumption and protein levels of UCP1 are reduced in CLK2-deficient BAT. Phosphorylation of CREB, a transcriptional activator of UCP1, is markedly decreased in BAT cells lacking CLK2 due to enhanced CREB dephosphorylation. Mechanistically, CREB dephosphorylation is rescued by the inhibition of PP2A, a phosphatase that targets CREB. Our results suggest that CLK2 is a regulatory component of diet-induced thermogenesis in BAT through increased CREB-dependent expression of UCP1.
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47
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ARPP-16 Is a Striatal-Enriched Inhibitor of Protein Phosphatase 2A Regulated by Microtubule-Associated Serine/Threonine Kinase 3 (Mast 3 Kinase). J Neurosci 2017; 37:2709-2722. [PMID: 28167675 DOI: 10.1523/jneurosci.4559-15.2017] [Citation(s) in RCA: 28] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/21/2015] [Revised: 01/20/2017] [Accepted: 01/25/2017] [Indexed: 12/27/2022] Open
Abstract
ARPP-16 (cAMP-regulated phospho-protein of molecular weight 16 kDa) is one of several small acid-soluble proteins highly expressed in medium spiny neurons of striatum that are phosphorylated in response to dopamine acting via D1 receptor/protein kinase A (PKA) signaling. We show here that ARPP-16 is also phosphorylated in vitro and in vivo by microtubule-associated serine/threonine kinase 3 (MAST3 kinase), an enzyme of previously unknown function that is enriched in striatum. We find that ARPP-16 interacts directly with the scaffolding A subunit of the serine/threonine protein phosphatase, PP2A, and that phosphorylation of ARPP-16 at Ser46 by MAST3 kinase converts the protein into a selective inhibitor of B55α- and B56δ-containing heterotrimeric forms of PP2A. Ser46 of ARPP-16 is phosphorylated to a high basal stoichiometry in striatum, suggestive of basal inhibition of PP2A in striatal neurons. In support of this hypothesis, conditional knock-out of ARPP-16 in CaMKIIα::cre/floxed ARPP-16/19 mice results in dephosphorylation of a subset of PP2A substrates including phospho-Thr75-DARPP-32, phospho-T308-Akt, and phospho-T202/Y204-ERK. Conditional knock-out of ARPP-16/19 is associated with increased motivation measured on a progressive ratio schedule of food reinforcement, yet an attenuated locomotor response to acute cocaine. Our previous studies have shown that ARPP-16 is phosphorylated at Ser88 by PKA. Activation of PKA in striatal slices leads to phosphorylation of Ser88, and this is accompanied by marked dephosphorylation of Ser46. Together, these studies suggest that phospho-Ser46-ARPP-16 acts to basally control PP2A in striatal medium spiny neurons but that dopamine acting via PKA inactivates ARPP-16 leading to selective potentiation of PP2A signaling.SIGNIFICANCE STATEMENT We describe a novel mechanism of signal transduction enriched in medium spiny neurons of striatum that likely mediates effects of the neurotransmitter dopamine acting on these cells. We find that the protein ARPP-16, which is highly expressed in striatal medium spiny neurons, acts as a selective inhibitor of certain forms of the serine/threonine protein phosphatase, PP2A, when phosphorylated by the kinase, MAST3. Under basal conditions, ARPP-16 is phosphorylated by MAST3 to a very high stoichiometry. However, the actions of MAST3 are antagonized by dopamine and cAMP-regulated signaling leading to disinhibition of ARPP-16 and increased PP2A action.
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48
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Booker MA, DeLong A. Atypical Protein Phosphatase 2A Gene Families Do Not Expand via Paleopolyploidization. PLANT PHYSIOLOGY 2017; 173:1283-1300. [PMID: 28034953 PMCID: PMC5291013 DOI: 10.1104/pp.16.01768] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/20/2016] [Accepted: 12/23/2016] [Indexed: 05/22/2023]
Abstract
Protein phosphatase 2A (PP2A) presents unique opportunities for analyzing molecular mechanisms of functional divergence between gene family members. The canonical PP2A holoenzyme regulates multiple eukaryotic signaling pathways by dephosphorylating target proteins and contains a catalytic (C) subunit, a structural/scaffolding (A) subunit, and a regulatory (B) subunit. Genes encoding PP2A subunits have expanded into multigene families in both flowering plants and mammals, and the extent to which different isoform functions may overlap is not clearly understood. To gain insight into the diversification of PP2A subunits, we used phylogenetic analyses to reconstruct the evolutionary histories of PP2A gene families in Arabidopsis (Arabidopsis thaliana). Genes encoding PP2A subunits in mammals represent ancient lineages that expanded early in vertebrate evolution, while flowering plant PP2A subunit lineages evolved much more recently. Despite this temporal difference, our data indicate that the expansion of PP2A subunit gene families in both flowering plants and animals was driven by whole-genome duplications followed by nonrandom gene loss. Selection analysis suggests that the expansion of one B subunit gene family (B56/PPP2R5) was driven by functional diversification rather than by the maintenance of gene dosage. We also observed reduced expansion rates in three distinct B subunit subclades. One of these subclades plays a highly conserved role in cell division, while the distribution of a second subclade suggests a specialized function in supporting beneficial microbial associations. Thus, while whole-genome duplications have driven the expansion and diversification of most PP2A gene families, members of functionally specialized subclades quickly revert to singleton status after duplication events.
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Affiliation(s)
- Matthew A Booker
- Department of Molecular Biology, Cell Biology, and Biochemistry, Brown University, Providence, Rhode Island 02912
| | - Alison DeLong
- Department of Molecular Biology, Cell Biology, and Biochemistry, Brown University, Providence, Rhode Island 02912
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49
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Beg M, Srivastava A, Shankar K, Varshney S, Rajan S, Gupta A, Kumar D, Gaikwad AN. PPP2R5B, a regulatory subunit of PP2A, contributes to adipocyte insulin resistance. Mol Cell Endocrinol 2016; 437:97-107. [PMID: 27521959 DOI: 10.1016/j.mce.2016.08.016] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/11/2016] [Revised: 07/04/2016] [Accepted: 08/09/2016] [Indexed: 12/29/2022]
Abstract
Insulin resistance is associated with deregulation of insulin signaling owing to the chronic exposure of insulin (hyperinsulinemia) to the tissues. Phosphorylation and dephosphorylation events in insulin signaling pathway play an essential role in signal transduction and glucose uptake. Amongst all, Akt protein is considered to be central to the overall insulin signaling proteins. In glucose responsive tissues like adipose and muscles, activation of Akt is responsible for triggering GLUT4 translocation and glucose transport. Several phosphatases such as PTEN, PP2A have been reported to be involved in dephosphorylation and inactivation of Akt protein. We have identified increased PP2A activity during state of chronic hyperinsulinemia exposure along-with development of adipocyte insulin resistance. This increased phosphatase activity leads activation of cAMP/PKA axis, which in turn increased cAMP levels in insulin resistant (IR) adipocytes. Okadaic acid, an inhibitor of PP2A restored and increased insulin stimulated glucose uptake in insulin resistant (IR) and insulin sensitive (IS) adipocytes respectively. In IS adipocyte, chemical activation of PP2A through MG132 and FTY720 showed decreased insulin sensitivity corroborated with decreased Akt phosphorylation and glucose uptake. We also observed an increased expression of PP2A-B (regulatory) subunit in IR adipocytes. We found PPP2R5B, a regulatory subunit of PP2A is responsible for the dephosphorylation and inactivation of Akt protein. Increased expression of PPP2R5B was also confirmed in white adipose tissue of high fat diet induced IR mice model. Overexpression and suppression strategies confirmed the role of PPP2R5B in regulating insulin signaling. Thus, we conclude that PPP2R5B, a B subunit of PP2A is a negative regulator of Akt phosphorylation contributing partly to the chronic hyperinsulinemia induced insulin resistance in adipocytes.
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Affiliation(s)
- Muheeb Beg
- Division of Pharmacology, CSIR-Central Drug Research Institute, Lucknow, 226031, India
| | - Ankita Srivastava
- Division of Pharmacology, CSIR-Central Drug Research Institute, Lucknow, 226031, India; Academy of Scientific and Innovative Research, CSIR-CDRI, India
| | - Kripa Shankar
- Division of Pharmacology, CSIR-Central Drug Research Institute, Lucknow, 226031, India
| | - Salil Varshney
- Division of Pharmacology, CSIR-Central Drug Research Institute, Lucknow, 226031, India
| | - Sujith Rajan
- Division of Pharmacology, CSIR-Central Drug Research Institute, Lucknow, 226031, India; Academy of Scientific and Innovative Research, CSIR-CDRI, India
| | - Abhishek Gupta
- Division of Pharmacology, CSIR-Central Drug Research Institute, Lucknow, 226031, India
| | - Durgesh Kumar
- Division of Pharmacology, CSIR-Central Drug Research Institute, Lucknow, 226031, India; Academy of Scientific and Innovative Research, CSIR-CDRI, India
| | - Anil N Gaikwad
- Division of Pharmacology, CSIR-Central Drug Research Institute, Lucknow, 226031, India; Academy of Scientific and Innovative Research, CSIR-CDRI, India.
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50
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The broken "Off" switch in cancer signaling: PP2A as a regulator of tumorigenesis, drug resistance, and immune surveillance. BBA CLINICAL 2016; 6:87-99. [PMID: 27556014 PMCID: PMC4986044 DOI: 10.1016/j.bbacli.2016.08.002] [Citation(s) in RCA: 118] [Impact Index Per Article: 13.1] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 07/02/2016] [Revised: 08/01/2016] [Accepted: 08/02/2016] [Indexed: 12/31/2022]
Abstract
Aberrant activation of signal transduction pathways can transform a normal cell to a malignant one and can impart survival properties that render cancer cells resistant to therapy. A diverse set of cascades have been implicated in various cancers including those mediated by serine/threonine kinases such RAS, PI3K/AKT, and PKC. Signal transduction is a dynamic process involving both "On" and "Off" switches. Activating mutations of RAS or PI3K can be viewed as the switch being stuck in the "On" position resulting in continued signaling by a survival and/or proliferation pathway. On the other hand, inactivation of protein phosphatases such as the PP2A family can be seen as the defective "Off" switch that similarly can activate these pathways. A problem for therapeutic targeting of PP2A is that the enzyme is a hetero-trimer and thus drug targeting involves complex structures. More importantly, since PP2A isoforms generally act as tumor suppressors one would want to activate these enzymes rather than suppress them. The elucidation of the role of cellular inhibitors like SET and CIP2A in cancer suggests that targeting these proteins can have therapeutic efficacy by mechanisms involving PP2A activation. Furthermore, drugs such as FTY-720 can activate PP2A isoforms directly. This review will cover the current state of knowledge of PP2A role as a tumor suppressor in cancer cells and as a mediator of processes that can impact drug resistance and immune surveillance.
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