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Lian Y, Bodian D, Shehu A. Elucidating the Role of Wildtype and Variant FGFR2 Structural Dynamics in (Dys)Function and Disorder. Int J Mol Sci 2024; 25:4523. [PMID: 38674107 PMCID: PMC11050683 DOI: 10.3390/ijms25084523] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/12/2024] [Revised: 04/12/2024] [Accepted: 04/17/2024] [Indexed: 04/28/2024] Open
Abstract
The fibroblast growth factor receptor 2 (FGFR2) gene is one of the most extensively studied genes with many known mutations implicated in several human disorders, including oncogenic ones. Most FGFR2 disease-associated gene mutations are missense mutations that result in constitutive activation of the FGFR2 protein and downstream molecular pathways. Many tertiary structures of the FGFR2 kinase domain are publicly available in the wildtype and mutated forms and in the inactive and activated state of the receptor. The current literature suggests a molecular brake inhibiting the ATP-binding A loop from adopting the activated state. Mutations relieve this brake, triggering allosteric changes between active and inactive states. However, the existing analysis relies on static structures and fails to account for the intrinsic structural dynamics. In this study, we utilize experimentally resolved structures of the FGFR2 tyrosine kinase domain and machine learning to capture the intrinsic structural dynamics, correlate it with functional regions and disease types, and enrich it with predicted structures of variants with currently no experimentally resolved structures. Our findings demonstrate the value of machine learning-enabled characterizations of structure dynamics in revealing the impact of mutations on (dys)function and disorder in FGFR2.
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Affiliation(s)
- Yiyang Lian
- School of Systems Biology, George Mason University, Manassas, VA 20110, USA;
| | - Dale Bodian
- Diamond Age Data Science, Boston, MA 02143, USA;
| | - Amarda Shehu
- School of Systems Biology, George Mason University, Manassas, VA 20110, USA;
- Department of Computer Science, George Mason University, Fairfax, VA 22030, USA
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2
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Yao Y, Wang Y, Yang F, Wang C, Mao M, Gai Q, He J, Qin Y, Yao X, Lan X, Zhu J, Lu H, Zeng H, Yao X, Bian X, Wang Y. Targeting AKT and CK2 represents a novel therapeutic strategy for SMO constitutive activation-driven medulloblastoma. CNS Neurosci Ther 2022; 28:1033-1044. [PMID: 35419951 PMCID: PMC9160449 DOI: 10.1111/cns.13835] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/28/2022] [Revised: 03/17/2022] [Accepted: 03/20/2022] [Indexed: 11/29/2022] Open
Abstract
AIMS Sonic hedgehog subtype medulloblastoma is featured with overactivation of hedgehog pathway and can be targeted by SMO-specific inhibitors. However, the resistance is frequently developed leading to treatment failure of SMO inhibitors. W535L mutation of SMO (SMOW535L ) is thought to be an oncogenic driver for Sonic hedgehog subtype MB and confer resistance to SMO inhibitors. The regulation network of SMOW535L remains to be explored in comparison with wild-type SMO (SMOWT ). METHODS In this study, we profiled transcriptomes, methylomes, and interactomes of MB cells expression SMOWT or SMOW535L in the treatment of DMSO or SMO inhibitor, respectively. RESULTS Analysis of transcriptomic data indicated that SMO inhibitor disrupted processes of endocytosis and cilium organization in MB cells with SMOWT , which are necessary for SMO activation. In MB cells with SMOW535L , however, SMO inhibitor did not affect the two processes-related genes, implying resistance of SMOW535L toward SMO inhibitor. Moreover, we noticed that SMO inhibitor significantly inhibited metabolism-related pathways. Our metabolic analysis indicated that nicotinate and nicotinamide metabolism, glycerolipid metabolism, beta-alanine metabolism, and synthesis and degradation of ketone bodies might be involved in SMOW535L function maintenance. Interactomic analysis revealed casein kinase II (CK2) as an important SMO-associated protein. Finally, we linked CK2 and AKT together and found combination of inhibitors targeting CK2 and AKT showed synergetic effects to inhibit the growth of MB cells with SMO constitutive activation mutation. CONCLUSIONS Taken together, our work described SMO-related transcriptomes, metabolomes, and interactomes under different SMO status and treatment conditions, identifying CK2 and AKT as therapeutic targets for SHH-subtype MB cells with SMO inhibitor resistance.
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Affiliation(s)
- Yue‐Liang Yao
- Institute of Pathology and Southwest Cancer CenterSouthwest HospitalArmy Medical University (Third Military Medical University)ChongqingChina
- Fuzhou Medical College of Nanchang UniversityFuzhouChina
| | - Yan‐Xia Wang
- Institute of Pathology and Southwest Cancer CenterSouthwest HospitalArmy Medical University (Third Military Medical University)ChongqingChina
| | - Fei‐Cheng Yang
- Institute of Pathology and Southwest Cancer CenterSouthwest HospitalArmy Medical University (Third Military Medical University)ChongqingChina
| | - Chuan Wang
- Institute of Pathology and Southwest Cancer CenterSouthwest HospitalArmy Medical University (Third Military Medical University)ChongqingChina
| | - Min Mao
- Institute of Pathology and Southwest Cancer CenterSouthwest HospitalArmy Medical University (Third Military Medical University)ChongqingChina
| | - Qu‐Jing Gai
- Institute of Pathology and Southwest Cancer CenterSouthwest HospitalArmy Medical University (Third Military Medical University)ChongqingChina
| | - Jiang He
- Institute of Pathology and Southwest Cancer CenterSouthwest HospitalArmy Medical University (Third Military Medical University)ChongqingChina
| | - Yan Qin
- Institute of Pathology and Southwest Cancer CenterSouthwest HospitalArmy Medical University (Third Military Medical University)ChongqingChina
| | - Xiao‐Xue Yao
- Institute of Pathology and Southwest Cancer CenterSouthwest HospitalArmy Medical University (Third Military Medical University)ChongqingChina
| | - Xi Lan
- Institute of Pathology and Southwest Cancer CenterSouthwest HospitalArmy Medical University (Third Military Medical University)ChongqingChina
| | - Jiang Zhu
- Institute of Pathology and Southwest Cancer CenterSouthwest HospitalArmy Medical University (Third Military Medical University)ChongqingChina
| | - Hui‐Min Lu
- Institute of Pathology and Southwest Cancer CenterSouthwest HospitalArmy Medical University (Third Military Medical University)ChongqingChina
| | - Hui Zeng
- Institute of Pathology and Southwest Cancer CenterSouthwest HospitalArmy Medical University (Third Military Medical University)ChongqingChina
| | - Xiao‐Hong Yao
- Institute of Pathology and Southwest Cancer CenterSouthwest HospitalArmy Medical University (Third Military Medical University)ChongqingChina
| | - Xiu‐Wu Bian
- Institute of Pathology and Southwest Cancer CenterSouthwest HospitalArmy Medical University (Third Military Medical University)ChongqingChina
| | - Yan Wang
- Institute of Pathology and Southwest Cancer CenterSouthwest HospitalArmy Medical University (Third Military Medical University)ChongqingChina
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3
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Gahankari A, Dong C, Bartoletti G, Galazo M, He F. Deregulated Rac1 Activity in Neural Crest Controls Cell Proliferation, Migration and Differentiation During Midbrain Development. Front Cell Dev Biol 2021; 9:704769. [PMID: 34557485 PMCID: PMC8452869 DOI: 10.3389/fcell.2021.704769] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/03/2021] [Accepted: 08/18/2021] [Indexed: 11/13/2022] Open
Abstract
Mutations in RAC1 allele are implicated in multiple brain tumors, indicating a rigorous control of Rac1 activity is required for neural tissue normal development and homeostasis. To understand how elevated Rac1 activity affects neural crest cells (NCCs) development, we have generated Rac1 CA ;Wnt1-Cre2 mice, in which a constitutively active Rac1 G12V mutant is expressed specifically in NCCs derivatives. Our results revealed that augmented Rac1 activity leads to enlarged midbrain and altered cell density, accompanied by increased NCCs proliferation rate and misrouted cell migration. Interestingly, our experimental data also showed that elevated Rac1 activity in NCCs disrupts regionalization of dopaminergic neuron progenitors in the ventral midbrain and impairs their differentiation. These findings shed light on the mechanisms of RAC1 mutation correlated brain tumor at the cellular and molecular level.
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Affiliation(s)
- Apurva Gahankari
- Department of Cell and Molecular Biology, Tulane University, New Orleans, LA, United States
| | - Chunmin Dong
- Department of Cell and Molecular Biology, Tulane University, New Orleans, LA, United States
| | - Garrett Bartoletti
- Department of Cell and Molecular Biology, Tulane University, New Orleans, LA, United States
| | - Maria Galazo
- Department of Cell and Molecular Biology, Tulane University, New Orleans, LA, United States.,Tulane Brain Institute, Tulane University, New Orleans, LA, United States
| | - Fenglei He
- Department of Cell and Molecular Biology, Tulane University, New Orleans, LA, United States
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4
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Panneerselvam S, Wang J, Zhu W, Dai H, Pappas JG, Rabin R, Low KJ, Rosenfeld JA, Emrick L, Xiao R, Xia F, Yang Y, Eng CM, Anderson A, Chau V, Soler-Alfonso C, Streff H, Lalani SR, Mercimek-Andrews S, Bi W. PPP3CA truncating variants clustered in the regulatory domain cause early-onset refractory epilepsy. Clin Genet 2021; 100:227-233. [PMID: 33963760 DOI: 10.1111/cge.13979] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/01/2021] [Revised: 05/04/2021] [Accepted: 05/04/2021] [Indexed: 12/27/2022]
Abstract
PPP3CA encodes the catalytic subunit of calcineurin, a calcium-calmodulin-regulated serine-threonine phosphatase. Loss-of-function (LoF) variants in the catalytic domain have been associated with epilepsy, while gain-of-function (GoF) variants in the auto-inhibitory domain cause multiple congenital abnormalities. We herein report five new patients with de novo PPP3CA variants. Interestingly, the two frameshift variants in this study and the six truncating variants reported previously are all located within a 26-amino acid region in the regulatory domain (RD). Patients with a truncating variant had more severe earlier onset seizures compared to patients with a LoF missense variant, while autism spectrum disorder was a more frequent feature in the latter. Expression studies of a truncating variant showed apparent RNA expression from the mutant allele, but no detectable mutant protein. Our data suggest that PPP3CA truncating variants clustered in the RD, causing more severe early-onset refractory epilepsy and representing a type of variants distinct from LoF or GoF missense variants.
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Affiliation(s)
- Sugi Panneerselvam
- Department of Molecular and Human Genetics, Baylor College of Medicine, Houston, Texas, USA
| | - Julia Wang
- Medical Scientist Training Program and Developmental Biology, Baylor College of Medicine, Houston, Texas, USA
| | - Wenmiao Zhu
- Baylor Genetics Laboratories, Houston, Texas, USA
| | - Hongzheng Dai
- Department of Molecular and Human Genetics, Baylor College of Medicine, Houston, Texas, USA
- Baylor Genetics Laboratories, Houston, Texas, USA
| | - John G Pappas
- Department of Pediatrics, Clinical Genetic Services, NYU School of Medicine, New York, New York, USA
| | - Rachel Rabin
- Department of Pediatrics, Clinical Genetic Services, NYU School of Medicine, New York, New York, USA
| | - Karen J Low
- University Hospital Bristol NHS Foundation Trust, Bristol, UK
| | - Jill A Rosenfeld
- Department of Molecular and Human Genetics, Baylor College of Medicine, Houston, Texas, USA
| | - Lisa Emrick
- Texas Children's Hospital, Houston, Texas, USA
| | - Rui Xiao
- Department of Molecular and Human Genetics, Baylor College of Medicine, Houston, Texas, USA
- Baylor Genetics Laboratories, Houston, Texas, USA
| | - Fan Xia
- Department of Molecular and Human Genetics, Baylor College of Medicine, Houston, Texas, USA
- Baylor Genetics Laboratories, Houston, Texas, USA
| | - Yaping Yang
- Department of Molecular and Human Genetics, Baylor College of Medicine, Houston, Texas, USA
- Baylor Genetics Laboratories, Houston, Texas, USA
| | - Christine M Eng
- Department of Molecular and Human Genetics, Baylor College of Medicine, Houston, Texas, USA
- Baylor Genetics Laboratories, Houston, Texas, USA
| | - Anne Anderson
- Department of Molecular and Human Genetics, Baylor College of Medicine, Houston, Texas, USA
- Texas Children's Hospital, Houston, Texas, USA
| | - Vann Chau
- Division of Neurology, Department of Pediatrics, University of Toronto, The Hospital for Sick Children, Toronto, Ontario, Canada
| | - Claudia Soler-Alfonso
- Department of Molecular and Human Genetics, Baylor College of Medicine, Houston, Texas, USA
- Texas Children's Hospital, Houston, Texas, USA
| | - Haley Streff
- Department of Molecular and Human Genetics, Baylor College of Medicine, Houston, Texas, USA
- Texas Children's Hospital, Houston, Texas, USA
| | - Seema R Lalani
- Department of Molecular and Human Genetics, Baylor College of Medicine, Houston, Texas, USA
- Texas Children's Hospital, Houston, Texas, USA
| | - Saadet Mercimek-Andrews
- Division of Clinical and Metabolic Genetics, Department of Pediatrics, University of Toronto, The Hospital for Sick Children, Toronto, Ontario, Canada
- Department of Medical Genetics, University of Alberta, Stollery Children's Hospital, Edmonton, Alberta, Canada
| | - Weimin Bi
- Department of Molecular and Human Genetics, Baylor College of Medicine, Houston, Texas, USA
- Baylor Genetics Laboratories, Houston, Texas, USA
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Abstract
BACKGROUND Signal transducer and activator of transcription (STAT) proteins are cytoplasmic transcription factors that transmit the signal of cytokines, hormones and growth factors. STAT proteins control fundamental cellular processes including survival, proliferation and differentiation. Inappropriate activation of STATs might contribute to cellular transformation and leukaemogenesis. About 70% of all solid and haematological tumours exhibit aberrant STAT3 expression and/or activation, highlighting its essential role in tumourigenesis. Aberrant STAT3 activation has been found in several solid tumours and haematologic malignancies. Importantly, constitutive activation of STAT proteins has been found in several leukaemias including acute myeloid leukaemia, acute promyelocytic leukaemia, acute lymphoblastic leukaemia, chronic myeloid leukaemia and chronic lymphocytic leukaemia (CLL). Constitutively activated STAT3 plays an important role in CLL biology. CLL cells harbour constitutive phosphorylation on S727 and acetylation on K685 and transient phosphorylation on Y705 residues. Moreover, STAT3 messenger RNA expression is significantly higher in CLL cells compared to healthy B-lymphocytes. Interestingly, STAT3 inhibition was disclosed as an important by-product of ibrutinib treatment in CLL patients. PURPOSE The purpose of this review is to describe the consequences of STAT3 dysregulation in CLL cells. Here, we discuss aberrantly modified processes by STAT3 activation in CLL cells such as proliferation, apoptosis, B cell receptor signalling, cytokine secretion, immune checkpoint regulation, microRNA regulation, free fatty acid metabolism and electron transport chain in the mitochondria.
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Ma H, Liu Z, Zhong CQ, Liu Y, Zhang Z, Liang Y, Li J, Han S, Han J. Inactivation of Cyclic AMP Response Element Transcription Caused by Constitutive p38 Activation Is Mediated by Hyperphosphorylation-Dependent CRTC2 Nucleocytoplasmic Transport. Mol Cell Biol 2019; 39:e00554-18. [PMID: 30782776 DOI: 10.1128/MCB.00554-18] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/27/2018] [Accepted: 02/01/2019] [Indexed: 01/05/2023] Open
Abstract
The p38 signal transduction pathway can be activated transiently or constitutively, depending on the contexts in which the activation occurs. However, the biological consequence of constitutive activation of p38 is largely unknown. After screening 300 transcriptional cofactors, we identified CRTC2 as a downstream substrate of constitutively activated p38. Constitutive, rather than transient, activation of p38 led to hyperphosphorylation of CRTC2, resulting in CRTC2 cytosolic relocation and subsequent inactivation of cyclic AMP response element (CRE)-mediated transcription. Interestingly, the cytosolic translocation of CRTC2 depended on phosphorylation accumulation at multiple sites (≥11 phosphoserine/phosphothreonine residues) but not on specific sites. The hyperphosphorylation-driven nucleocytoplasmic transport of CRTC2 may not be a rare case of nuclear export of proteins, as we also observed that constitutively activated p38 promoted FOS nuclear export in a hyperphosphorylation-dependent manner. Collectively, our study uncovered a previously unknown mechanism of inactivation of selected transcription, which results from hyperphosphorylation-driven nucleocytoplasmic transport of cofactors or transcription factors mediated by constitutively active kinase.
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7
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Sheehe JL, Bonev AD, Schmoker AM, Ballif BA, Nelson MT, Moon TM, Dostmann WR. Oxidation of cysteine 117 stimulates constitutive activation of the type Iα cGMP-dependent protein kinase. J Biol Chem 2018; 293:16791-16802. [PMID: 30206122 DOI: 10.1074/jbc.ra118.004363] [Citation(s) in RCA: 27] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/10/2018] [Revised: 09/04/2018] [Indexed: 12/22/2022] Open
Abstract
The type I cGMP-dependent protein kinase (PKG I) is an essential regulator of vascular tone. It has been demonstrated that the type Iα isoform can be constitutively activated by oxidizing conditions. However, the amino acid residues implicated in this phenomenon are not fully elucidated. To investigate the molecular basis for this mechanism, we studied the effects of oxidation using recombinant WT, truncated, and mutant constructs of PKG I. Using an in vitro assay, we observed that oxidation with hydrogen peroxide (H2O2) resulted in constitutive, cGMP-independent activation of PKG Iα. PKG Iα C42S and a truncation construct that does not contain Cys-42 (Δ53) were both constitutively activated by H2O2 In contrast, oxidation of PKG Iα C117S maintained its cGMP-dependent activation characteristics, although oxidized PKG Iα C195S did not. To corroborate these results, we also tested the effects of our constructs on the PKG Iα-specific substrate, the large conductance potassium channel (KCa 1.1). Application of WT PKG Iα activated by either cGMP or H2O2 increased the open probabilities of the channel. Neither cGMP nor H2O2 activation of PKG Iα C42S significantly increased channel open probabilities. Moreover, cGMP-stimulated PKG Iα C117S increased KCa 1.1 activity, but this effect was not observed under oxidizing conditions. Finally, we observed that PKG Iα C42S caused channel flickers, indicating dramatically altered KCa 1.1 channel characteristics compared with channels exposed to WT PKG Iα. Cumulatively, these results indicate that constitutive activation of PKG Iα proceeds through oxidation of Cys-117 and further suggest that the formation of a sulfur acid is necessary for this phenotype.
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Affiliation(s)
- Jessica L Sheehe
- From the Department of Pharmacology, Larner College of Medicine, and
| | - Adrian D Bonev
- From the Department of Pharmacology, Larner College of Medicine, and
| | - Anna M Schmoker
- the Department of Biology, University of Vermont, Burlington, Vermont 05405 and
| | - Bryan A Ballif
- the Department of Biology, University of Vermont, Burlington, Vermont 05405 and
| | - Mark T Nelson
- From the Department of Pharmacology, Larner College of Medicine, and
| | - Thomas M Moon
- the Department of Chemistry and Biochemistry, University of Arizona, Tucson, Arizona 85721
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Li B, Chen M, Liu X, Guo SW. Constitutive and tumor necrosis factor-α-induced activation of nuclear factor-κB in adenomyosis and its inhibition by andrographolide. Fertil Steril 2013; 100:568-77. [PMID: 23706331 DOI: 10.1016/j.fertnstert.2013.04.028] [Citation(s) in RCA: 47] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/09/2012] [Revised: 04/03/2013] [Accepted: 04/15/2013] [Indexed: 12/31/2022]
Abstract
OBJECTIVE To investigate the action of nuclear factor (NF)-κB in adenomyosis and evaluate the potential therapeutic effect of andrographolide on tumor necrosis factor (TNF)-α-induced expression of NF-κB-mediated genes cyclooxygease-2 (COX-2), vascular endothelial growth factor (VEGF), and tissue factor (TF) in adenomyotic stromal cells. DESIGN Laboratory study using human tissues. SETTING Academic hospital. PATIENT(S) Twenty-nine patients (cases) with histologically confirmed adenomyosis and 14 (controls) without adenomyosis or endometriosis. INTERVENTION(S) Endometrial stromal cells derived from tissue samples harvested from both cases and controls were subjected to electrophoretic mobility shift assay, and gene and protein expression analyses. MAIN OUTCOME MEASURE(S) The NF-κB DNA-binding activity and protein levels of NF-κB subunits p50 and p65 and the messenger RNA (mRNA) and protein levels of NF-κB-mediated genes COX-2, VEGF, and TF in cases and controls, and their changes after stimulation with TNF-α and treatment with andrographolide. RESULT(S) The constitutive NF-κB DNA-binding activity and protein expression levels of p50 and p65, and mRNA and protein levels of COX-2, VEGF, and TF in cases were significantly higher than that of controls. The binding activity level correlated positively with dysmenorrhea severity in cases. The TNF-α stimulation further increased the binding activity, and the mRNA and protein levels of COX-2, VEGF, and TF, but treatment with andrographolide significantly reduced them. CONCLUSION(S) NF-κB may be a pivotal transcription factor involved in the development of adenomyosis. Targeting NF-κB with inhibitors, like andrographolide, may hold promises of treating adenomyosis.
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Affiliation(s)
- Bin Li
- Shanghai Obstetrics and Gynecology Hospital, Fudan University, Shanghai, People's Republic of China
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9
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Yi YW, Kang HJ, Kim HJ, Hwang JS, Wang A, Bae I. Inhibition of constitutively activated phosphoinositide 3-kinase/AKT pathway enhances antitumor activity of chemotherapeutic agents in breast cancer susceptibility gene 1-defective breast cancer cells. Mol Carcinog 2012; 52:667-75. [PMID: 22488590 DOI: 10.1002/mc.21905] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/14/2011] [Revised: 02/21/2012] [Accepted: 03/07/2012] [Indexed: 12/24/2022]
Abstract
Loss or decrease of wild type BRCA1 function, by either mutation or reduced expression, has a role in hereditary and sporadic human breast and ovarian cancers. We report here that the PI3K/AKT pathway is constitutively active in BRCA1-defective human breast cancer cells. Levels of phospho-AKT are sustained even after serum starvation in breast cancer cells carrying deleterious BRCA1 mutations. Knockdown of BRCA1 in MCF7 cells increases the amount of phospho-AKT and sensitizes cells to small molecule protein kinase inhibitors (PKIs) targeting the PI3K/AKT pathway. Restoration of wild type BRCA1 inhibits the activated PI3K/AKT pathway and de-sensitizes cells to PKIs targeting this pathway in BRCA1 mutant breast cancer cells, regardless of PTEN mutations. In addition, clinical PI3K/mTOR inhibitors, PI-103, and BEZ235, showed anti-proliferative effects on BRCA1 mutant breast cancer cell lines and synergism in combination with chemotherapeutic drugs, cisplatin, doxorubicin, topotecan, and gemcitabine. BEZ235 synergizes with the anti-proliferative effects of gemcitabine by enhancing caspase-3/7 activity. Our results suggest that the PI3K/AKT pathway can be an important signaling pathway for the survival of BRCA1-defective breast cancer cells and pharmacological inhibition of this pathway is a plausible treatment for a subset of breast cancers.
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Affiliation(s)
- Yong Weon Yi
- Department of Oncology, Lombardi Comprehensive Cancer Center, Georgetown University, Washington, DC 20057, USA
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10
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Abstract
Activating mutations in the luteinizing hormone receptor (LHR) gene are one of the most common mutations found in the gonadotropin receptor genes. Human males with these mutations exhibit precocious puberty while females do not have an obvious phenotype. To better understand the pathophysiology of premature LHR activation, transgenic mice have been generated with an activating mutation in LHR and a genetically engineered ligand-activated LHR. This review will summarize the major findings obtained with these two genetically modified mouse models and briefly discuss the similarities and differences between them and with the human phenotype.
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Affiliation(s)
| | - Prema Narayan
- * Corresponding author: Department of Physiology,
School of Medicine, Southern Illinois University, Life Science III, Mailcode
6523, Carbondale IL, 62901, USA, Tel: 618-453-1567, Fax: 618-453-1517,
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11
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Abstract
The L457(3.43)R mutation of the hLHR was initially identified in a Brazilian boy with gonadotropin-independent precocious puberty. As would be expected, L457(3.43)R, when expressed in 293 cells, caused a marked elevation in basal cAMP levels. Interestingly, in spite of the fact that the elevated basal levels of cAMP elicited by L457R were not as great as those elicited by the wild-type hLHR when stimulated with hCG, L457(3.43)R cells were unresponsive to further hormonal stimulation. We have since determined that the L457(3.43)R mutant, as well as other constitutively active mutants of the hLHR, causes an increase in phosphodiesterase activity that attenuates the target cell to hormonal stimulation of the wild-type hLHR or other Gs-coupled GPCRs. We have also shown that the constitutive activity and lack of hormonal responsiveness of L457(3.43)R are due to the formation of a salt bridge between the introduced arginine in the mid portion of helix 3 with D578(6.44) in the mid portion of helix 6. The formation of this salt bridge results in the disruption of interactions between the cytoplasmic ends of helices 3 and 6 that are associated in general with activation of the hLHR. As such, this mutant has provided novel insights into the properties of target cells expressing activating hLHR mutants and into the structural basis for hLHR activation.
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Affiliation(s)
- Ana Claudia Latronico
- Developmental Endocrinology Unit, Hormone and Molecular Genetics Laboratory, Clinical Hospital, Sao Paulo University Medical School, Sao Paulo, Brazil
| | - Deborah L. Segaloff
- Department of Physiology and Biophysics, The Roy J. and Lucille A. Carver College of Medicine, The University of Iowa, Iowa City, IA, USA
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12
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Matsumoto J, Kaneda M, Tada M, Hamada JI, Okushiba S, Kondo S, Katoh H, Moriuchi T. Differential mechanisms of constitutive Akt/PKB activation and its influence on gene expression in pancreatic cancer cells. Jpn J Cancer Res 2002; 93:1317-26. [PMID: 12495471 PMCID: PMC5926936 DOI: 10.1111/j.1349-7006.2002.tb01240.x] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022] Open
Abstract
Activated Akt/protein kinase B transmits oncogenic signals leading to inhibition of apoptosis, cellular proliferation, and tolerance to hypoxia. Presently, mutational inactivation of PTEN and activation of Ras are considered to be the major causes of Akt activation. Here we report differential mechanisms of constitutive Akt activation in 4 human pancreatic cancer cell lines (KMP-3, KMP-4, PCI-66, and PCI-68). These 4 cell lines displayed phosphorylation and functional activation of Akt both in the presence and absence of serum, while three control cell lines (PCI-79, KMP-8, and PSN-1) did so only in the presence of serum in culture. All the 7 cell lines harbored K-Ras activated by mutations at codon 12 resulting in MAP kinase kinase (MEK1/2) phosphorylation, and all except one (KMP-8) had p53 mutations, indicating that these mutations are not sufficient for constitutive Akt activation. KMP-3 and KMP-4 had lost PTEN function owing to loss of expression or a mutation, but PCI-66 and PCI-68 retained wild-type PTEN. Phosphorylation of Akt was inhibited by the phosphatidylinositol-3-kinase (PI3K) inhibitor LY294002 and the tyrosine kinase inhibitor genistein in KMP-3 and KMP-4 cells, indicating that upstream signals are required for Akt activation in these two cell lines. In contrast, neither LY294002 nor genistein inhibited Akt activation in PCI-66 and PCI-68 cells, indicating the involvement of another unknown mechanism of Akt activation independent of PI3K-mediated signaling to Akt. Irrespective of the differential mechanisms, the 4 cell lines showed similar mRNA expression patterns of 49 genes assessed by cDNA array as compared to the 3 cell lines without Akt activation, suggesting that the mechanisms have the same consequences on the downstream signaling of the constitutive Akt activation.
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Affiliation(s)
- Joe Matsumoto
- Division of Cancer-related Genes, Institute for Genetic Medicine, Hokkaido University, Kita-ku, Sapporo 060-0815, Japan
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13
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Kim JM, Altenbach C, Thurmond RL, Khorana HG, Hubbell WL. Structure and function in rhodopsin: rhodopsin mutants with a neutral amino acid at E134 have a partially activated conformation in the dark state. Proc Natl Acad Sci U S A 1997; 94:14273-8. [PMID: 9405602 PMCID: PMC24937 DOI: 10.1073/pnas.94.26.14273] [Citation(s) in RCA: 81] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023] Open
Abstract
The Glu-134-Arg-135 residues in rhodopsin, located near the cytoplasmic end of the C helix, are involved in G protein binding, or activation, or both. Furthermore, the charge-neutralizing mutation Glu-134 to Gln-134 produces hyperactivity in the activated state and produces constitutive activity in opsin. The Glu/Asp-Arg charge pair is highly conserved in equivalent positions in other G protein-coupled receptors. To investigate the structural consequences of charge-neutralizing mutations at Glu-134 and Arg-135 in rhodopsin, single spin-labeled side chains were introduced at sites in the cytoplasmic domains of helices C (140), E (227), F (250), or G (316) to serve as "molecular sensors" of the local helix bundle conformation. In each of the spin-labeled rhodopsins, a Gln substitution was introduced at either Glu-134 or Arg-135, and the electron paramagnetic resonance spectrum of the spin label was used to monitor the structural response of the helix bundle. The results indicate that a Gln substitution at Glu-134 induces a photoactivated conformation around helices C and G even in the dark state, an observation of potential relevance to the hyperactivity and constitutive activity of the mutant. In contrast, little change is induced in helix F, which has been shown to undergo a dominant motion upon photoactivation. This result implies that the multiple helix motions accompanying photoactivation are not strongly coupled and can be induced to take place independently. Gln substitution at Arg-135 produces only minor structural changes in the dark- or light-activated conformation, suggesting that this residue is not a determinant of structure in the regions investigated, although it may be functionally important.
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Affiliation(s)
- J M Kim
- Department of Biology, Massachusetts Institute of Technology, 77 Massachusetts Avenue, Cambridge, MA 02139, USA
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