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Chetwynd SA, Andrews S, Inglesfield S, Delon C, Ktistakis NT, Welch HCE. Functions and mechanisms of the GPCR adaptor protein Norbin. Biochem Soc Trans 2023; 51:1545-1558. [PMID: 37503670 PMCID: PMC10586782 DOI: 10.1042/bst20221349] [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] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/08/2023] [Revised: 06/27/2023] [Accepted: 07/07/2023] [Indexed: 07/29/2023]
Abstract
Norbin (Neurochondrin, NCDN) is a highly conserved 79 kDa adaptor protein that was first identified more than a quarter of a century ago as a gene up-regulated in rat hippocampus upon induction of long-term potentiation. Most research has focussed on the role of Norbin in the nervous system, where the protein is highly expressed. Norbin regulates neuronal morphology and synaptic plasticity, and is essential for normal brain development and homeostasis. Dysregulation of Norbin is linked to a variety of neurological conditions. Recently, Norbin was shown to be expressed in myeloid cells as well as neurons. Myeloid-cell specific deletion revealed an important role of Norbin as a suppressor of neutrophil-derived innate immunity. Norbin limits the ability of neutrophils to clear bacterial infections by curbing the responsiveness of these cells to inflammatory and infectious stimuli. Mechanistically, Norbin regulates cell responses through binding to its interactors, in particular to a wide range of G protein-coupled receptors (GPCRs). Norbin association with GPCRs controls GPCR trafficking and signalling. Other important Norbin interactors are the Rac guanine-nucleotide exchange factor P-Rex1 and protein kinase A. Downstream signalling pathways regulated by Norbin include ERK, Ca2+ and the small GTPase Rac. Here, we review the current understanding of Norbin structure, expression and its roles in health and disease. We also explore Norbin signalling through its interactors, with a particular focus on GPCR trafficking and signalling. Finally, we discuss avenues that could be pursued in the future to increase our understanding of Norbin biology.
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Affiliation(s)
| | - Simon Andrews
- Bioinformatics Facility, Babraham Institute, Cambridge, U.K
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Pan J, Liu M, Su H, Hu H, Chen H, Ma L. Pharmacological Inhibition of P-Rex1/Rac1 Axis Blocked Angiotensin II-Induced Cardiac Fibrosis. Cardiovasc Drugs Ther 2023:10.1007/s10557-023-07442-3. [PMID: 36892683 DOI: 10.1007/s10557-023-07442-3] [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] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Accepted: 02/15/2023] [Indexed: 03/10/2023]
Abstract
PURPOSE Phosphatidylinositol-3,4,5-trisphosphate-dependent Rac exchange factor-1 (P-Rex1), as one of the members of Rac-GEFs, has been proven to play a critical role in cancer progression and metastasis. Nonetheless, its role in cardiac fibrosis remains elusive. In the present study, we aimed to investigate whether and how the P-Rex1 mediates AngII-induced cardiac fibrosis. METHOD A cardiac fibrosis mouse model was established by chronic AngII perfusion. The heart structure, function, pathological changes of myocardial tissues, oxidative stress, and cardiac fibrotic protein expression were determined in an AngII induced mouse model. To provide a molecular mechanism for P-Rex1 involvement in cardiac fibrosis, a specific inhibitor or siRNA was used to block P-Rex1, and target the relationship between Rac1-GTPase and its downstream effector. RESULTS Blocking P-Rex1 showed down-regulation of its downstream effectors such as the profibrotic transcriptional regulator Paks, ERK1/2, and ROS generation. Intervention treatment with P-Rex1 inhibitor 1A-116 ameliorated AngII-induced abnormalities in heart structure and function. Moreover, pharmacological inhibition of the P-Rex1/Rac1 axis showed a protective effect in AngII-induced cardiac fibrosis through the down-regulation of collagen1, CTGF, and α-SMA expression. CONCLUSION Our findings demonstrated for the first time that P-Rex1 was an essential signaling mediator in CFs activation and subsequent cardiac fibrosis, and 1A-116 could be a potential pharmacological development drug.
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Affiliation(s)
- Jianyuan Pan
- Department of Cardiology, The First Affiliated Hospital of USTC, Division of Life Sciences and Medicine, University of Science and Technology of China, No.17 Lujiang Road, Hefei, Anhui, 230001, People's Republic of China
| | - Ming Liu
- Department of Cardiology, The First Affiliated Hospital of USTC, Division of Life Sciences and Medicine, University of Science and Technology of China, No.17 Lujiang Road, Hefei, Anhui, 230001, People's Republic of China
| | - Huimin Su
- Department of Cardiology, The First Affiliated Hospital of USTC, Division of Life Sciences and Medicine, University of Science and Technology of China, No.17 Lujiang Road, Hefei, Anhui, 230001, People's Republic of China
| | - Hao Hu
- Department of Cardiology, The First Affiliated Hospital of USTC, Division of Life Sciences and Medicine, University of Science and Technology of China, No.17 Lujiang Road, Hefei, Anhui, 230001, People's Republic of China
| | - Hongwu Chen
- Department of Cardiology, The First Affiliated Hospital of USTC, Division of Life Sciences and Medicine, University of Science and Technology of China, No.17 Lujiang Road, Hefei, Anhui, 230001, People's Republic of China
| | - Likun Ma
- Department of Cardiology, The First Affiliated Hospital of USTC, Division of Life Sciences and Medicine, University of Science and Technology of China, No.17 Lujiang Road, Hefei, Anhui, 230001, People's Republic of China.
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Kumarasinghe L, Garcia-Gimeno MA, Ramirez J, Mayor U, Zugaza JL, Sanz P. P-Rex1 is a novel substrate of the E3 ubiquitin ligase Malin associated with Lafora disease. Neurobiol Dis 2023; 177:105998. [PMID: 36638890 PMCID: PMC10682699 DOI: 10.1016/j.nbd.2023.105998] [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] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/01/2022] [Revised: 12/29/2022] [Accepted: 01/09/2023] [Indexed: 01/12/2023] Open
Abstract
Laforin and Malin are two proteins that are encoded by the genes EPM2A and EPM2B, respectively. Laforin is a glucan phosphatase and Malin is an E3-ubiquitin ligase, and these two proteins function as a complex. Mutations occurring at the level of one of the two genes lead to the accumulation of an aberrant form of glycogen meant to cluster in polyglucosans that go under the name of Lafora bodies. Individuals affected by the appearance of these polyglucosans, especially at the cerebral level, experience progressive neurodegeneration and several episodes of epilepsy leading to the manifestation of a fatal form of a rare disease called Lafora disease (LD), for which, to date, no treatment is available. Despite the different dysfunctions described for this disease, many molecular aspects still demand elucidation. An effective way to unknot some of the nodes that prevent the achievement of better knowledge of LD is to focus on the substrates that are ubiquitinated by the E3-ubiquitin ligase Malin. Some substrates have already been provided by previous studies based on protein-protein interaction techniques and have been associated with some alterations that mark the disease. In this work, we have used an unbiased alternative approach based on the activity of Malin as an E3-ubiquitin ligase. We report the discovery of novel bonafide substrates of Malin and have characterized one of them more deeply, namely PIP3-dependent Rac exchanger 1 (P-Rex1). The analysis conducted upon this substrate sets the genesis of the delineation of a molecular pathway that leads to altered glucose uptake, which could be one of the origin of the accumulation of the polyglucosans present in the disease.
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Affiliation(s)
- L Kumarasinghe
- Instituto de Biomedicina de Valencia, IBV-CSIC, 46010, Valencia, Spain; Centro de Investigación Biomédica en Red de Enfermedades Raras (CIBERER)-ISCIII, 28029 Madrid, Spain
| | - M A Garcia-Gimeno
- Department of Biotechnology, Escuela Técnica Superior de Ingeniería Agronómica y del Medio Natural (ETSIAMN), Universitat Politécnica de València, 46022, Valencia, Spain
| | - J Ramirez
- Department of Biochemistry and Molecular Biology, Faculty of Science and Technology, UPV/EHU, Leioa, Bizkaia, Spain
| | - U Mayor
- Department of Biochemistry and Molecular Biology, Faculty of Science and Technology, UPV/EHU, Leioa, Bizkaia, Spain; Ikerbasque, Basque Foundation for Science, Plaza Euskadi, 48009 Bilbao, Spain
| | - J L Zugaza
- Ikerbasque, Basque Foundation for Science, Plaza Euskadi, 48009 Bilbao, Spain; Achucarro Basque Center for Neuroscience, Scientific Park UPV/EHU, 48940 Leioa, Bizkaia, Spain; Department of Genetics, Physical Anthropology and Animal Physiology, Faculty of Science and Technology, UPV/EHU, 48940 Leioa, Bizkaia, Spain
| | - P Sanz
- Instituto de Biomedicina de Valencia, IBV-CSIC, 46010, Valencia, Spain; Centro de Investigación Biomédica en Red de Enfermedades Raras (CIBERER)-ISCIII, 28029 Madrid, Spain.
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Lawson CD, Hornigold K, Pan D, Niewczas I, Andrews S, Clark J, Welch HCE. Small-molecule inhibitors of P-Rex guanine-nucleotide exchange factors. Small GTPases 2022; 13:307-326. [PMID: 36342857 PMCID: PMC9645260 DOI: 10.1080/21541248.2022.2131313] [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] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022] Open
Abstract
P-Rex1 and P-Rex2 are guanine-nucleotide exchange factors (GEFs) that activate Rac small GTPases in response to the stimulation of G protein-coupled receptors and phosphoinositide 3-kinase. P-Rex Rac-GEFs regulate the morphology, adhesion and migration of various cell types, as well as reactive oxygen species production and cell cycle progression. P-Rex Rac-GEFs also have pathogenic roles in the initiation, progression or metastasis of several types of cancer. With one exception, all P-Rex functions are known or assumed to be mediated through their catalytic Rac-GEF activity. Thus, inhibitors of P-Rex Rac-GEF activity would be valuable research tools. We have generated a panel of small-molecule P-Rex inhibitors that target the interface between the catalytic DH domain of P-Rex Rac-GEFs and Rac. Our best-characterized compound, P-Rex inhibitor 1 (PREX-in1), blocks the Rac-GEF activity of full-length P-Rex1 and P-Rex2, and of their isolated catalytic domains, in vitro at low-micromolar concentration, without affecting the activities of several other Rho-GEFs. PREX-in1 blocks the P-Rex1 dependent spreading of PDGF-stimulated endothelial cells and the production of reactive oxygen species in fMLP-stimulated mouse neutrophils. Structure-function analysis revealed critical structural elements of PREX-in1, allowing us to develop derivatives with increased efficacy, the best with an IC50 of 2 µM. In summary, we have developed PREX-in1 and derivative small-molecule compounds that will be useful laboratory research tools for the study of P-Rex function. These compounds may also be a good starting point for the future development of more sophisticated drug-like inhibitors aimed at targeting P-Rex Rac-GEFs in cancer.
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Affiliation(s)
- CD Lawson
- Signalling Programme, The Babraham Institute, Babraham Research Campus, CambridgeCB22 3AT, UK
| | - K Hornigold
- Signalling Programme, The Babraham Institute, Babraham Research Campus, CambridgeCB22 3AT, UK
| | - D Pan
- Signalling Programme, The Babraham Institute, Babraham Research Campus, CambridgeCB22 3AT, UK
| | - I Niewczas
- Biological Chemistry Facility, The Babraham Institute, Babraham Research Campus, CambridgeCB22 3AT, UK
| | - S Andrews
- Bioinformatics Facility, The Babraham Institute, Babraham Research Campus, CambridgeCB22 3AT, UK
| | - J Clark
- Biological Chemistry Facility, The Babraham Institute, Babraham Research Campus, CambridgeCB22 3AT, UK
| | - HCE Welch
- Signalling Programme, The Babraham Institute, Babraham Research Campus, CambridgeCB22 3AT, UK,CONTACT HCE Welch Signalling Programme, The Babraham Institute, Babraham Research Campus, CambridgeCB22 3ATUK
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Hampson E, Tsonou E, Baker MJ, Hornigold DC, Hubbard RE, Massey A, Welch HCE. P-Rex1 Controls Sphingosine 1-Phosphate Receptor Signalling, Morphology, and Cell-Cycle Progression in Neuronal Cells. Cells 2021; 10:2474. [PMID: 34572121 DOI: 10.3390/cells10092474] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/03/2021] [Accepted: 09/15/2021] [Indexed: 11/30/2022] Open
Abstract
P-Rex1 is a guanine-nucleotide exchange factor (GEF) that activates Rac-type small G proteins in response to the stimulation of a range of receptors, particularly G protein-coupled receptors (GPCRs), to control cytoskeletal dynamics and other Rac-dependent cell responses. P-Rex1 is mainly expressed in leukocytes and neurons. Whereas its roles in leukocytes have been studied extensively, relatively little is known about its functions in neurons. Here, we used CRISPR/Cas9-mediated P-Rex1 deficiency in neuronal PC12 cells that stably overexpress the GPCR S1PR1, a receptor for sphingosine 1-phosphate (S1P), to investigate the role of P-Rex1 in neuronal GPCR signalling and cell responses. We show that P-Rex1 is required for the S1P-stimulated activation of Rac1 and Akt, basal Rac3 activity, and constitutive cAMP production in PC12-S1PR1 cells. The constitutive cAMP production was not due to increased expression levels of major neuronal adenylyl cyclases, suggesting that P-Rex1 may regulate adenylyl cyclase activity. P-Rex1 was required for maintenance of neurite protrusions and spreading in S1P-stimulated PC12-S1PR1 cells, as well as for cell-cycle progression and proliferation. In summary, we identified novel functional roles of P-Rex1 in neuronal Rac, Akt and cAMP signalling, as well as in neuronal cell-cycle progression and proliferation.
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6
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Liang Q, Chang Y, Liu J, Yu Y, Qiu W, Li J, Yang X, Sun G. P-Rex1 Cooperates With TGFβR2 to Drive Lung Fibroblast Migration in Pulmonary Fibrosis. Front Pharmacol 2021; 12:678733. [PMID: 34349645 PMCID: PMC8326510 DOI: 10.3389/fphar.2021.678733] [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] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/11/2021] [Accepted: 06/21/2021] [Indexed: 11/13/2022] Open
Abstract
Pulmonary fibrosis is a kind of interstitial lung disease with progressive pulmonary scar formation, leading to irreversible loss of lung functions. The TGF-β1/Smad signaling pathway plays a key role in fibrogenic processes. It is associated with the increased synthesis of extracellular matrix, enhanced proliferation of fibroblasts, and transformation of alveolar epithelial cells into interstitial cells. We investigated P-Rex1, a PIP3-Gβγ-dependent guanine nucleotide exchange factor (GEF) for Rac, for its potential role in TGF-β1-induced pulmonary fibrosis. A high expression level of P-Rex1 was identified in the lung tissue of patients with pulmonary fibrosis than that from healthy donors. Using the P-Rex1 knockdown and overexpression system, we established a novel player of P-Rex1 in mouse lung fibroblast migration. P-Rex1 contributed to fibrogenic processes in lung fibroblasts by targeting the TGF-β type Ⅱ receptor (TGFβR2). The RNA-seq analysis for expression profiling confirmed the modulation of P-Rex1 in cell migration and the involvement of P-Rex1 in TGF-β1 signaling. These results identified P-Rex1 as a signaling molecule involved in TGF-β1-induced pulmonary fibrosis, suggesting that P-Rex1 may be a potential target for pulmonary fibrosis treatment.
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Affiliation(s)
- Qing Liang
- Department of Pharmacy, Shanghai Fifth People's Hospital, Fudan University, Shanghai, China
| | - Yanhua Chang
- Department of Pathology, The Affiliated Wuxi People's Hospital of Nanjing Medical University, Wuxi, China
| | - Jing Liu
- Department of Pharmacy, Shanghai Fifth People's Hospital, Fudan University, Shanghai, China
| | - Yan Yu
- Department of Pharmacy, Shanghai Fifth People's Hospital, Fudan University, Shanghai, China
| | - Wancheng Qiu
- Department of Pharmacy, Shanghai Fifth People's Hospital, Fudan University, Shanghai, China
| | - Jiajia Li
- Department of Pharmacy, Shanghai Fifth People's Hospital, Fudan University, Shanghai, China
| | - Xu Yang
- Department of Pharmacy, Shanghai Fifth People's Hospital, Fudan University, Shanghai, China
| | - Guangchun Sun
- Department of Pharmacy, Shanghai Fifth People's Hospital, Fudan University, Shanghai, China
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Cervantes-Villagrana RD, Beltrán-Navarro YM, García-Jiménez I, Adame-García SR, Olguín-Olguín A, Reyes-Cruz G, Vázquez-Prado J. Gβγ recruits and activates P-Rex1 via two independent binding interfaces. Biochem Biophys Res Commun 2021; 539:20-27. [PMID: 33412417 DOI: 10.1016/j.bbrc.2020.12.089] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/27/2020] [Accepted: 12/26/2020] [Indexed: 12/19/2022]
Abstract
Gβγ marks the inner side of the plasma membrane where chemotactic GPCRs activate Rac to lead the assembly of actin filaments that push the cell to move forward. Upon dissociation from heterotrimeric Gi, Gβγ recruits and activates P-Rex1, a Rac guanine nucleotide exchange factor (RacGEF). This cytosolic chemotactic effector is kept inactive by intramolecular interactions. The mechanism by which Gβγ stimulates P-Rex1 has been debated. We hypothesized that Gβγ activates P-Rex1 by a two-step mechanism based on independent interaction interfaces to recruit and unroll this RacGEF. Using pulldown assays, we found that Gβγ binds P-Rex1-DH/PH as well as PDZ-PDZ domains. These domains and the DEP-DEP tandem interact among them and dissociate upon binding with Gβγ, arguing for a stimulatory allosteric effect. In addition, P-Rex1 catalytic activity is inhibited by its C-terminal domain. To discern P-Rex1 recruitment from activation, we studied Q-Rhox, a synthetic RhoGEF having the PDZ-RhoGEF catalytic DH/PH module, insensitive to Gβγ, swapped into P-Rex1. Gβγ recruited Q-Rhox to the plasma membrane, indicating that Gβγ/PDZ-PDZ interaction interface plays a role on P-Rex1 recruitment. In conclusion, we reconcile previous findings and propose a mechanistic model of P-Rex1 activation; accordingly, Gβγ recruits P-Rex1 via the Gβγ/PDZ-PDZ interface followed by a second contact involving the Gβγ/DH/PH interface to unleash P-Rex1 RacGEF activity at the plasma membrane.
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8
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Qiu W, Chang Y, Liu J, Yang X, Yu Y, Li J, Liang Q, Sun G. Identification of P-Rex1 in the Regulation of Liver Cancer Cell Proliferation and Migration via HGF/c-Met/Akt Pathway. Onco Targets Ther 2020; 13:9481-9495. [PMID: 33061433 PMCID: PMC7522411 DOI: 10.2147/ott.s265592] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [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: 06/10/2020] [Accepted: 08/21/2020] [Indexed: 12/19/2022] Open
Abstract
Background Rho-GTPases and their activators, guanine nucleotide exchange factors (GEFs), are increasingly being recognized as essential mediators of oncogenic signaling. Although it is known that P-Rex1, a member of the Dbl family of GEFs for the Rac small GTPase, contributes to the migration of cancer cells, its exact role in liver cancer and the underlying mechanisms remain unclear. Materials and Methods Public datasets from the Gene Expression Omnibus database (GEO) and clinical liver cancer samples were analyzed to explore the expression of P-Rex1. P-Rex1 knockdown and overexpression cell lines were established using a recombinant lentiviral transfection system. BrdU and colony formation assays were performed to determine cell viability. Migratory capacity was analyzed using a transwell migration assay and an in vitro wound-healing assay. Nude mice bearing subcutaneous xenograft tumors were established to determine the effects of P-Rex1 on tumorigenesis in vivo. The role of P-Rex1 in hepatocarcinogenesis was determined through Western blot and co-immunoprecipitation. Results Induced expression of endogenous P-Rex1 was identified in liver cancer tumors when compared with adjacent nonmalignant tissues from clinical data. In response to HGF treatment, P-Rex1-knockdown cells displayed reduced proliferation and migration in vitro as well as reduced xenograft tumor growth in vivo. Overexpression of P-Rex1 promoted liver cancer cell proliferation and migration. P-Rex1 primarily acts as a downstream effector of GPCR signaling. This study demonstrated that downregulation of P-Rex1 led to a significant decrease in the phosphorylation of Akt and Erk1/2 by reducing the phosphorylation of the tyrosine kinase receptor c-Met. Furthermore, a physical association between P-Rex1 and c-Met was observed after HGF treatment, suggesting that P-Rex1 may be involved in the HGF/c-Met signaling pathway. Conclusion These results support the role of P-Rex1 as a novel player in liver cancer, which suggest that targeting P-Rex1 may provide a potential strategy for liver cancer treatment.
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Affiliation(s)
- Wancheng Qiu
- Department of Pharmacy, Shanghai Fifth People's Hospital, Fudan University, Shanghai, People's Republic of China
| | - Yanhua Chang
- Department of Pathology, The Affiliated Wuxi People's Hospital of Nanjing Medical University, Wuxi, Jiangsu Province, People's Republic of China
| | - Jing Liu
- Department of Pharmacy, Shanghai Fifth People's Hospital, Fudan University, Shanghai, People's Republic of China
| | - Xu Yang
- Department of Pharmacy, Shanghai Fifth People's Hospital, Fudan University, Shanghai, People's Republic of China
| | - Yan Yu
- Department of Pharmacy, Shanghai Fifth People's Hospital, Fudan University, Shanghai, People's Republic of China
| | - Jiajia Li
- Department of Pharmacy, Shanghai Fifth People's Hospital, Fudan University, Shanghai, People's Republic of China
| | - Qing Liang
- Department of Pharmacy, Shanghai Fifth People's Hospital, Fudan University, Shanghai, People's Republic of China
| | - Guangchun Sun
- Department of Pharmacy, Shanghai Fifth People's Hospital, Fudan University, Shanghai, People's Republic of China
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9
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Baker MJ, Abba MC, Garcia-Mata R, Kazanietz MG. P-REX1-Independent, Calcium-Dependent RAC1 Hyperactivation in Prostate Cancer. Cancers (Basel). 2020;12. [PMID: 32092966 PMCID: PMC7072377 DOI: 10.3390/cancers12020480] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/21/2019] [Revised: 02/07/2020] [Accepted: 02/17/2020] [Indexed: 12/15/2022] Open
Abstract
The GTPase Rac1 is a well-established master regulator of cell motility and invasiveness contributing to cancer metastasis. Dysregulation of the Rac1 signaling pathway, resulting in elevated motile and invasive potential, has been reported in multiple cancers. However, there are limited studies on the regulation of Rac1 in prostate cancer. Here, we demonstrate that aggressive androgen-independent prostate cancer cells display marked hyperactivation of Rac1. This hyperactivation is independent of P-Rex1 activity or its direct activators, the PI3K product PIP3 and Gβγ subunits. Furthermore, we demonstrate that the motility and invasiveness of PC3 prostate cancer cells is independent of P-Rex1, supporting the analysis of publicly available datasets indicating no correlation between high P-Rex1 expression and cancer progression in patients. Rac1 hyperactivation was not related to the presence of activating Rac1 mutations and was insensitive to overexpression of a Rac-GAP or the silencing of specific Rac-GEFs expressed in prostate cancer cells. Interestingly, active Rac1 levels in these cells were markedly reduced by elevations in intracellular calcium or by serum stimulation, suggesting the presence of an alternative means of Rac1 regulation in prostate cancer that does not involve previously established paradigms.
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10
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Li Q, Wang L, Ma Y, Yue W, Zhang D, Li J. P-Rex1 Overexpression Results in Aberrant Neuronal Polarity and Psychosis-Related Behaviors. Neurosci Bull 2019; 35:1011-1023. [PMID: 31286410 DOI: 10.1007/s12264-019-00408-2] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.0] [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: 01/26/2019] [Accepted: 03/21/2019] [Indexed: 12/22/2022] Open
Abstract
Neuronal polarity is involved in multiple developmental stages, including cortical neuron migration, multipolar-to-bipolar transition, axon initiation, apical/basal dendrite differentiation, and spine formation. All of these processes are associated with the cytoskeleton and are regulated by precise timing and by controlling gene expression. The P-Rex1 (phosphatidylinositol-3,4,5-trisphosphate dependent Rac exchange factor 1) gene for example, is known to be important for cytoskeletal reorganization, cell motility, and migration. Deficiency of P-Rex1 protein leads to abnormal neuronal migration and synaptic plasticity, as well as autism-related behaviors. Nonetheless, the effects of P-Rex1 overexpression on neuronal development and higher brain functions remain unclear. In the present study, we explored the effect of P-Rex1 overexpression on cerebral development and psychosis-related behaviors in mice. In utero electroporation at embryonic day 14.5 was used to assess the influence of P-Rex1 overexpression on cell polarity and migration. Primary neuron culture was used to explore the effects of P-Rex1 overexpression on neuritogenesis and spine morphology. In addition, P-Rex1 overexpression in the medial prefrontal cortex (mPFC) of mice was used to assess psychosis-related behaviors. We found that P-Rex1 overexpression led to aberrant polarity and inhibited the multipolar-to-bipolar transition, leading to abnormal neuronal migration. In addition, P-Rex1 overexpression affected the early development of neurons, manifested as abnormal neurite initiation with cytoskeleton change, reduced the axon length and dendritic complexity, and caused excessive lamellipodia in primary neuronal culture. Moreover, P-Rex1 overexpression decreased the density of spines with increased height, width, and head area in vitro and in vivo. Behavioral tests showed that P-Rex1 overexpression in the mouse mPFC caused anxiety-like behaviors and a sensorimotor gating deficit. The appropriate P-Rex1 level plays a critical role in the developing cerebral cortex and excessive P-Rex1 might be related to psychosis-related behaviors.
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Affiliation(s)
- Qiongwei Li
- Peking University Institute of Mental Health, Peking University Sixth Hospital, Beijing, 100191, China.,National Health Center Key Laboratory of Mental Health (Peking University), Beijing, 100191, China.,National Clinical Research Center for Mental Disorders, Peking University Sixth Hospital, Beijing, 100191, China
| | - Lifang Wang
- Peking University Institute of Mental Health, Peking University Sixth Hospital, Beijing, 100191, China.,National Health Center Key Laboratory of Mental Health (Peking University), Beijing, 100191, China.,National Clinical Research Center for Mental Disorders, Peking University Sixth Hospital, Beijing, 100191, China
| | - Yuanlin Ma
- Peking University Institute of Mental Health, Peking University Sixth Hospital, Beijing, 100191, China.,National Health Center Key Laboratory of Mental Health (Peking University), Beijing, 100191, China.,National Clinical Research Center for Mental Disorders, Peking University Sixth Hospital, Beijing, 100191, China
| | - Weihua Yue
- Peking University Institute of Mental Health, Peking University Sixth Hospital, Beijing, 100191, China.,National Health Center Key Laboratory of Mental Health (Peking University), Beijing, 100191, China.,National Clinical Research Center for Mental Disorders, Peking University Sixth Hospital, Beijing, 100191, China.,PKU-IDG/McGovern Institute for Brain Research, Peking University, Beijing, 100871, China
| | - Dai Zhang
- Peking University Institute of Mental Health, Peking University Sixth Hospital, Beijing, 100191, China. .,National Health Center Key Laboratory of Mental Health (Peking University), Beijing, 100191, China. .,National Clinical Research Center for Mental Disorders, Peking University Sixth Hospital, Beijing, 100191, China. .,Peking-Tsinghua Center for Life Sciences, Peking University, Beijing, 100871, China. .,PKU-IDG/McGovern Institute for Brain Research, Peking University, Beijing, 100871, China.
| | - Jun Li
- Peking University Institute of Mental Health, Peking University Sixth Hospital, Beijing, 100191, China. .,National Health Center Key Laboratory of Mental Health (Peking University), Beijing, 100191, China. .,National Clinical Research Center for Mental Disorders, Peking University Sixth Hospital, Beijing, 100191, China.
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Abstract
Rac-GTPases and their Rac-GEF activators play important roles in the recruitment and host defence functions of neutrophils. These proteins control the activation of adhesion molecules and the cytoskeletal dynamics that enable the adhesion, migration and tissue recruitment of neutrophils. They also regulate the effector functions that allow neutrophils to kill bacterial and fungal pathogens, and to clear debris. This review focuses on the roles of Rac-GTPases and Rac-GEFs in neutrophil adhesion, migration and recruitment.
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Barrio-Real L, Lopez-Haber C, Casado-Medrano V, Goglia AG, Toettcher JE, Caloca MJ, Kazanietz MG. P-Rex1 is dispensable for Erk activation and mitogenesis in breast cancer. Oncotarget 2018; 9:28612-24. [PMID: 29983884 DOI: 10.18632/oncotarget.25584] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/27/2017] [Accepted: 05/19/2018] [Indexed: 12/21/2022] Open
Abstract
Phosphatidylinositol-3,4,5-Trisphosphate Dependent Rac Exchange Factor 1 (P-Rex1) is a key mediator of growth factor-induced activation of Rac1, a small GTP-binding protein widely implicated in actin cytoskeleton reorganization. This Guanine nucleotide Exchange Factor (GEF) is overexpressed in human luminal breast cancer, and its expression associates with disease progression, metastatic dissemination and poor outcome. Despite the established contribution of P-Rex1 to Rac activation and cell locomotion, whether this Rac-GEF has any relevant role in mitogenesis has been a subject of controversy. To tackle the discrepancies among various reports, we carried out an exhaustive analysis of the potential involvement of P-Rex1 on the activation of the mitogenic Erk pathway. Using a range of luminal breast cancer cellular models, we unequivocally showed that silencing P-Rex1 (transiently, stably, using multiple siRNA sequences) had no effect on the phospho-Erk response upon stimulation with growth factors (EGF, heregulin, IGF-I) or a GPCR ligand (SDF-1). The lack of involvement of P-Rex1 in Erk activation was confirmed at the single cell level using a fluorescent biosensor of Erk kinase activity. Depletion of P-Rex1 from breast cancer cells failed to affect cell cycle progression, cyclin D1 induction, Akt activation and apoptotic responses. In addition, mammary-specific P-Rex1 transgenic mice (MMTV-P-Rex1) did not show any obvious hyperproliferative phenotype. Therefore, despite its crucial role in Rac1 activation and cell motility, P-Rex1 is dispensable for mitogenic or survival responses in breast cancer cells.
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Montero JC, Seoane S, García-Alonso S, Pandiella A. Multisite phosphorylation of P-Rex1 by protein kinase C. Oncotarget 2018; 7:77937-77949. [PMID: 27788493 PMCID: PMC5363633 DOI: 10.18632/oncotarget.12846] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [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: 06/30/2016] [Accepted: 10/12/2016] [Indexed: 02/07/2023] Open
Abstract
P-Rex proteins are guanine nucleotide exchange factors (GEFs) that act on the Rho/Rac family of GTP binding proteins. The activity of P-Rex proteins is regulated by several extracellular stimuli. In fact, activation of growth factor receptors has been reported to activate a phosphorylation/dephosphorylation cycle of P-Rex1. Such cycle includes dephosphorylation of serines 313 and 319 which negatively regulate the GEF activity of P-Rex1, together with phosphorylation of serines 605 and 1169 which favour P-Rex1 GEF activity. However, the kinases that regulate phosphorylation at these different regulatory sites are largely unknown. Here we have investigated the potential regulatory action of several kinases on the phosphorylation of P-Rex1 at S313, S319, S605 and S1169. We show that activation of protein kinase C (PKC) caused phosphorylation of S313, S319 and S1169. Activation of growth factor receptors induced phosphorylation of S1169 through a mechanism that was independent of PKC, indicating that distinct kinases and mechanisms control the phosphorylation of P-Rex1 at different regulatory serines. Genetic and biochemical studies confirmed that the PKC isoform PKCδ was able to directly phosphorylate P-Rex1 at S313. Functional studies using cells with very low endogenous P-Rex1 expression, transfected with wild type P-Rex1 or a mutant form in which S313 was substituted by alanine, indicated that phosphorylation at that residue negatively regulated P-Rex1 exchange activity. We suggest that control of P-Rex1 activity depends on a highly dynamic interplay among distinct signalling routes and its multisite phosphorylation is controlled by the action of different kinases.
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Affiliation(s)
- Juan Carlos Montero
- Instituto de Biología Molecular y Celular del Cáncer, CSIC-Universidad de Salamanca, Spain
| | - Samuel Seoane
- Instituto de Biología Molecular y Celular del Cáncer, CSIC-Universidad de Salamanca, Spain
| | - Sara García-Alonso
- Instituto de Biología Molecular y Celular del Cáncer, CSIC-Universidad de Salamanca, Spain
| | - Atanasio Pandiella
- Instituto de Biología Molecular y Celular del Cáncer, CSIC-Universidad de Salamanca, Spain
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Barrio-Real L, Wertheimer E, Garg R, Abba MC, Kazanietz MG. Characterization of a P-Rex1 gene signature in breast cancer cells. Oncotarget 2018; 7:51335-51348. [PMID: 27351228 PMCID: PMC5239479 DOI: 10.18632/oncotarget.10285] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.0] [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: 02/18/2016] [Accepted: 06/12/2016] [Indexed: 01/29/2023] Open
Abstract
The Rac nucleotide Exchange Factor (Rac-GEF) P-Rex1 is highly expressed in breast cancer, specifically in the luminal subtype, and is an essential mediator of actin cytoskeleton reorganization and cell migratory responses induced by stimulation of ErbB and other tyrosine-kinase receptors. Heregulin (HRG), a growth factor highly expressed in mammary tumors, causes the activation of P-Rex1 and Rac1 in breast cancer cells via ErbB3, leading to a motile response. Since there is limited information about P-Rex1 downstream effectors, we carried out a microarray analysis to identify genes regulated by this Rac-GEF after stimulation of ErbB3 with HRG. In T-47D breast cancer cells, HRG treatment caused major changes in gene expression, including genes associated with motility, adhesion, invasiveness and metastasis. Silencing P-Rex1 expression from T-47D cells using RNAi altered the induction and repression of a subset of HRG-regulated genes, among them genes associated with extracellular matrix organization, migration, and chemotaxis. HRG induction of MMP10 (matrix metalloproteinase 10) was found to be highly sensitive both to P-Rex1 depletion and inhibition of Rac1 function by the GTPase Activating Protein (GAP) β2-chimaerin, suggesting the dependence of the P-Rex1/Rac1 pathway for the induction of genes critical for breast cancer invasiveness. Notably, there is a significant association in the expression of P-Rex1 and MMP10 in human luminal breast cancer, and their co-expression is indicative of poor prognosis.
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Affiliation(s)
- Laura Barrio-Real
- Department of Systems Pharmacology and Translational Therapeutics, Perelman School of Medicine, University of Pennsylvania, Philadelphia, USA
| | - Eva Wertheimer
- Centro de Estudios Farmacológicos y Botánicos (CEFYBO), Universidad de Buenos Aires, Buenos Aires, Argentina
| | - Rachana Garg
- Department of Systems Pharmacology and Translational Therapeutics, Perelman School of Medicine, University of Pennsylvania, Philadelphia, USA
| | - Martin C Abba
- Centro de Investigaciones Inmunológicas Básicas y Aplicadas (CINIBA), Facultad de Ciencias Médicas, Universidad Nacional de La Plata, La Plata, Argentina
| | - Marcelo G Kazanietz
- Department of Systems Pharmacology and Translational Therapeutics, Perelman School of Medicine, University of Pennsylvania, Philadelphia, USA
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15
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Kazanietz MG, Barrio-Real L, Casado-Medrano V, Baker MJ, Lopez-Haber C. The P-Rex1/Rac signaling pathway as a point of convergence for HER/ErbB receptor and GPCR responses. Small GTPases 2016; 9:297-303. [PMID: 27588611 DOI: 10.1080/21541248.2016.1221273] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022] Open
Abstract
Guanine nucleotide Exchange Factors (GEFs) are responsible for mediating GDP/GTP exchange for specific small G proteins, such as Rac. There has been substantial evidence for the involvement of Rac-GEFs in the control of cancer cell migration and metastatic progression. We have previously established that the Rac-GEF P-Rex1 is a mediator of actin cytoskeleton rearrangements and cell motility in breast cancer cells downstream of HER/ErbB receptors and the G-Protein Coupled Receptor (GPCR) CXCR4. P-Rex1 is highly expressed in luminal A and B breast cancer compared to normal mammary tissue, whereas expression is very low in basal breast cancer, and its expression correlates with the appearance of metastasis in patients. Here, we discuss the involvement of P-Rex1 as an effector of oncogenic/metastatic receptors in breast cancer and underscore its relevance in the convergence of receptor-triggered motile signals. In addition, we provide an overview of our recent findings describing a cross-talk between HER/ErbB receptors and CXCR4, and how this impacts on the activation of P-Rex1/Rac1 signaling, as well as highlight challenges that lie ahead. We propose a model in which P-Rex1 acts as a crucial node for the integration of upstream inputs from HER/ErbB receptors and CXCR4 in luminal breast cancer cells.
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Affiliation(s)
- Marcelo G Kazanietz
- a Department of Systems Pharmacology and Translational Therapeutics , Perelman School of Medicine, University of Pennsylvania , Philadelphia , PA , USA
| | - Laura Barrio-Real
- a Department of Systems Pharmacology and Translational Therapeutics , Perelman School of Medicine, University of Pennsylvania , Philadelphia , PA , USA
| | - Victoria Casado-Medrano
- a Department of Systems Pharmacology and Translational Therapeutics , Perelman School of Medicine, University of Pennsylvania , Philadelphia , PA , USA
| | - Martin J Baker
- a Department of Systems Pharmacology and Translational Therapeutics , Perelman School of Medicine, University of Pennsylvania , Philadelphia , PA , USA
| | - Cynthia Lopez-Haber
- a Department of Systems Pharmacology and Translational Therapeutics , Perelman School of Medicine, University of Pennsylvania , Philadelphia , PA , USA
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Marei H, Carpy A, Macek B, Malliri A. Proteomic analysis of Rac1 signaling regulation by guanine nucleotide exchange factors. Cell Cycle 2016; 15:1961-74. [PMID: 27152953 PMCID: PMC4968972 DOI: 10.1080/15384101.2016.1183852] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.8] [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: 03/18/2016] [Revised: 04/13/2016] [Accepted: 04/22/2016] [Indexed: 10/30/2022] Open
Abstract
The small GTPase Rac1 is implicated in various cellular processes that are essential for normal cell function. Deregulation of Rac1 signaling has also been linked to a number of diseases, including cancer. The diversity of Rac1 functioning in cells is mainly attributed to its ability to bind to a multitude of downstream effectors following activation by Guanine nucleotide Exchange Factors (GEFs). Despite the identification of a large number of Rac1 binding partners, factors influencing downstream specificity are poorly defined, thus hindering the detailed understanding of both Rac1's normal and pathological functions. In a recent study, we demonstrated a role for 2 Rac-specific GEFs, Tiam1 and P-Rex1, in mediating Rac1 anti- versus pro-migratory effects, respectively. Importantly, via conducting a quantitative proteomic screen, we identified distinct changes in the Rac1 interactome following activation by either GEF, indicating that these opposing effects are mediated through GEF modulation of the Rac1 interactome. Here, we present the full list of identified Rac1 interactors together with functional annotation of the differentially regulated Rac1 binding partners. In light of this data, we also provide additional insights into known and novel signaling cascades that might account for the GEF-mediated Rac1-driven cellular effects.
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Affiliation(s)
- Hadir Marei
- Cell Signaling Group, Cancer Research UK Manchester Institute, The University of Manchester, Manchester, UK
| | - Alejandro Carpy
- Proteome Center Tuebingen, Interfaculty Institute for Cell Biology, University of Tuebingen, Tuebingen, Germany
| | - Boris Macek
- Proteome Center Tuebingen, Interfaculty Institute for Cell Biology, University of Tuebingen, Tuebingen, Germany
| | - Angeliki Malliri
- Cell Signaling Group, Cancer Research UK Manchester Institute, The University of Manchester, Manchester, UK
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17
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Li J, Chai A, Wang L, Ma Y, Wu Z, Yu H, Mei L, Lu L, Zhang C, Yue W, Xu L, Rao Y, Zhang D. Synaptic P-Rex1 signaling regulates hippocampal long-term depression and autism-like social behavior. Proc Natl Acad Sci U S A 2015; 112:E6964-72. [PMID: 26621702 DOI: 10.1073/pnas.1512913112] [Citation(s) in RCA: 47] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022] Open
Abstract
Autism spectrum disorders (ASDs) are a group of highly inheritable mental disorders associated with synaptic dysfunction, but the underlying cellular and molecular mechanisms remain to be clarified. Here we report that autism in Chinese Han population is associated with genetic variations and copy number deletion of P-Rex1 (phosphatidylinositol-3,4,5-trisphosphate-dependent Rac exchange factor 1). Genetic deletion or knockdown of P-Rex1 in the CA1 region of the hippocampus in mice resulted in autism-like social behavior that was specifically linked to the defect of long-term depression (LTD) in the CA1 region through alteration of AMPA receptor endocytosis mediated by the postsynaptic PP1α (protein phosphase 1α)-P-Rex1-Rac1 (Ras-related C3 botulinum toxin substrate 1) signaling pathway. Rescue of the LTD in the CA1 region markedly alleviated autism-like social behavior. Together, our findings suggest a vital role of P-Rex1 signaling in CA1 LTD that is critical for social behavior and cognitive function and offer new insight into the etiology of ASDs.
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Lucato CM, Halls ML, Ooms LM, Liu HJ, Mitchell CA, Whisstock JC, Ellisdon AM. The Phosphatidylinositol (3,4,5)-Trisphosphate-dependent Rac Exchanger 1·Ras-related C3 Botulinum Toxin Substrate 1 ( P-Rex1·Rac1) Complex Reveals the Basis of Rac1 Activation in Breast Cancer Cells. J Biol Chem 2015; 290:20827-20840. [PMID: 26112412 DOI: 10.1074/jbc.m115.660456] [Citation(s) in RCA: 41] [Impact Index Per Article: 4.6] [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: 04/22/2015] [Indexed: 12/16/2022] Open
Abstract
The P-Rex (phosphatidylinositol (3,4,5)-trisphosphate (PIP3)-dependent Rac exchanger) family (P-Rex1 and P-Rex2) of the Rho guanine nucleotide exchange factors (Rho GEFs) activate Rac GTPases to regulate cell migration, invasion, and metastasis in several human cancers. The family is unique among Rho GEFs, as their activity is regulated by the synergistic binding of PIP3 and Gβγ at the plasma membrane. However, the molecular mechanism of this family of multi-domain proteins remains unclear. We report the 1.95 Å crystal structure of the catalytic P-Rex1 DH-PH tandem domain in complex with its cognate GTPase, Rac1 (Ras-related C3 botulinum toxin substrate-1). Mutations in the P-Rex1·Rac1 interface revealed a critical role for this complex in signaling downstream of receptor tyrosine kinases and G protein-coupled receptors. The structural data indicated that the PIP3/Gβγ binding sites are on the opposite surface and markedly removed from the Rac1 interface, supporting a model whereby P-Rex1 binding to PIP3 and/or Gβγ releases inhibitory C-terminal domains to expose the Rac1 binding site.
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Affiliation(s)
- Christina M Lucato
- Department of Biochemistry and Molecular Biology, School of Biomedical Sciences, Monash University, Clayton, Victoria 3800, Australia; Australian Research Council Centre of Excellence in Advanced Molecular Imaging, Monash University, Clayton, Victoria 3800, Australia
| | - Michelle L Halls
- Monash Institute of Pharmaceutical Sciences, Monash University, Parkville, Victoria 3052, Australia
| | - Lisa M Ooms
- Department of Biochemistry and Molecular Biology, School of Biomedical Sciences, Monash University, Clayton, Victoria 3800, Australia
| | - Heng-Jia Liu
- Department of Biochemistry and Molecular Biology, School of Biomedical Sciences, Monash University, Clayton, Victoria 3800, Australia
| | - Christina A Mitchell
- Department of Biochemistry and Molecular Biology, School of Biomedical Sciences, Monash University, Clayton, Victoria 3800, Australia.
| | - James C Whisstock
- Department of Biochemistry and Molecular Biology, School of Biomedical Sciences, Monash University, Clayton, Victoria 3800, Australia; Australian Research Council Centre of Excellence in Advanced Molecular Imaging, Monash University, Clayton, Victoria 3800, Australia.
| | - Andrew M Ellisdon
- Department of Biochemistry and Molecular Biology, School of Biomedical Sciences, Monash University, Clayton, Victoria 3800, Australia; Australian Research Council Centre of Excellence in Advanced Molecular Imaging, Monash University, Clayton, Victoria 3800, Australia.
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Abstract
The P-Rex family are Dbl-type guanine-nucleotide exchange factors for Rac family small G proteins. They are distinguished from other Rac-GEFs through their synergistic mode of activation by the lipid second messenger phosphatidyl inositol (3,4,5) trisphosphate and the Gβγ subunits of heterotrimeric G proteins, thus acting as coincidence detectors for phosphoinositide 3-kinase and G protein coupled receptor signaling. Work in genetically-modified mice has shown that P-Rex1 has physiological importance in the inflammatory response and the migration of melanoblasts during development, whereas P-Rex2 controls the dendrite morphology of cerebellar Purkinje neurons as well as glucose homeostasis in liver and adipose tissue. Deregulation of P-Rex1 and P-Rex2 expression occurs in many types of cancer, and P-Rex2 is frequently mutated in melanoma. Both GEFs promote tumor growth or metastasis. This review critically evaluates the P-Rex literature and tools available and highlights exciting recent developments and open questions.
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