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Dwyer MB, Aumiller JL, Wedegaertner PB. Going Rogue: Mechanisms, Regulation, and Roles of Mutationally Activated G α in Human Cancer. Mol Pharmacol 2024; 106:198-215. [PMID: 39187387 DOI: 10.1124/molpharm.124.000743] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/01/2024] [Revised: 08/19/2024] [Accepted: 08/21/2024] [Indexed: 08/28/2024] Open
Abstract
G protein-coupled receptors (GPCRs) couple to heterotrimeric G proteins, comprised of α and βγ subunits, to convert extracellular signals into activation of intracellular signaling pathways. Canonically, GPCR-mediated activation results in the exchange of GDP for GTP on G protein α subunits (Gα) and the dissociation of Gα-GTP and G protein βγ subunits (Gβγ), both of which can regulate a variety of signaling pathways. Hydrolysis of bound GTP by Gα returns the protein to Gα-GDP and allows reassociation with Gβγ to reform the inactive heterotrimer. Naturally occurring mutations in Gα have been found at conserved glutamine and arginine amino acids that disrupt the canonical G protein cycle by inhibiting GTP hydrolysis, rendering these mutants constitutively active. Interestingly, these dysregulated Gα mutants are found in many different cancers due to their ability to sustain aberrant signaling without a need for activation by GPCRs. This review will highlight an increased recognition of the prevalence of such constitutively activating Gα mutations in cancers and the signaling pathways activated. In addition, we will discuss new knowledge regarding how these constitutively active Gα are regulated, how different mutations are biochemically distinct, and how mutationally activated Gα are unique compared with GPCR-activated Gα Lastly, we will discuss recent progress in developing inhibitors directly targeting constitutively active Gα mutants. SIGNIFICANCE STATEMENT: Constitutively activating mutations in G protein α subunits (Gα) widely occur in and contribute to the development of many human cancers. To develop ways to inhibit dysregulated, oncogenic signaling by these mutant Gα, it is crucial to better understand mechanisms that lead to constitutive Gα activation and unique mechanisms that regulate mutationally activated Gα in cells. The prevalence of activating mutations in Gα in various cancers makes Gα proteins compelling targets for the development of therapeutics.
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Affiliation(s)
- Morgan B Dwyer
- Department of Biochemistry and Molecular Biology, Sidney Kimmel Medical College, Thomas Jefferson University, Philadelphia, Pennsylvania
| | - Jenna L Aumiller
- Department of Biochemistry and Molecular Biology, Sidney Kimmel Medical College, Thomas Jefferson University, Philadelphia, Pennsylvania
| | - Philip B Wedegaertner
- Department of Biochemistry and Molecular Biology, Sidney Kimmel Medical College, Thomas Jefferson University, Philadelphia, Pennsylvania
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2
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Wu Z, Liu Q, Zhao Y, Fang C, Zheng W, Zhao Z, Zhang N, Yang X. Rhogef17: A novel target for endothelial barrier function. Biomed Pharmacother 2024; 170:115983. [PMID: 38134633 DOI: 10.1016/j.biopha.2023.115983] [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: 10/18/2023] [Revised: 11/29/2023] [Accepted: 12/02/2023] [Indexed: 12/24/2023] Open
Abstract
ARHGEF17 encodes the protein RhoGEF17, which is highly expressed in vascular endothelial cells. It is a guanine nucleotide exchange factor (GEF) that accelerates the exchange of GDP with GTP on many small GTPases through its Dbl homology (DH) domain, enabling the activation of Rho-GTPases such as RhoA, RhoB, and RhoC. Rho GTPase-regulated changes in the actin cytoskeleton and cell adhesion kinetics are the main mechanisms mediating many endothelial cell (EC) alterations, including cell morphology, migration, and division changes, which profoundly affect EC barrier function. This review focuses on ARHGEF17 expression, activation and biological functions in ECs, linking its regulation of cellular morphology, migration, mitosis and other cellular behaviors to disease onset and progression. Understanding ARHGEF17 mechanisms of action will contribute to the design of therapeutic approaches targeting RhoGEF17, a potential drug target for the treatment of various endothelium-related diseases, Such as vascular inflammation, carcinogenesis and transendothelial metastasis of tumors.
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Affiliation(s)
- Zhuolin Wu
- Department of Neurosurgery, Tianjin Medical University General Hospital, Tianjin, China; Tianjin Neurological Institute, Key Laboratory of Post-Neuroinjury Neuro-Repair and Regeneration in Central Nervous System, Ministry of Education and Tianjin City, Tianjin Medical University General Hospital, Tianjin, China
| | - Quanlei Liu
- Department of Neurosurgery, Capital Medical University, Xuanwu Hospital, Beijing, China
| | - Yan Zhao
- Department of Neurosurgery, Tianjin Medical University General Hospital, Tianjin, China; Tianjin Neurological Institute, Key Laboratory of Post-Neuroinjury Neuro-Repair and Regeneration in Central Nervous System, Ministry of Education and Tianjin City, Tianjin Medical University General Hospital, Tianjin, China
| | | | - Wen Zheng
- Zhejiang University of Technology, Hangzhou, Zhejiang, China
| | - Zilin Zhao
- Department of Neurosurgery, Tianjin Medical University General Hospital, Tianjin, China; Tianjin Neurological Institute, Key Laboratory of Post-Neuroinjury Neuro-Repair and Regeneration in Central Nervous System, Ministry of Education and Tianjin City, Tianjin Medical University General Hospital, Tianjin, China
| | - Nai Zhang
- Department of Neurosurgery, Tianjin Medical University General Hospital, Tianjin, China
| | - Xinyu Yang
- Department of Neurosurgery, Tianjin Medical University General Hospital, Tianjin, China; Tianjin Neurological Institute, Key Laboratory of Post-Neuroinjury Neuro-Repair and Regeneration in Central Nervous System, Ministry of Education and Tianjin City, Tianjin Medical University General Hospital, Tianjin, China.
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3
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Moon SY, de Campos PS, Matte BF, Placone JK, Zanella VG, Martins MD, Lamers ML, Engler AJ. Cell contractility drives mechanical memory of oral squamous cell carcinoma. Mol Biol Cell 2023; 34:ar89. [PMID: 37342880 PMCID: PMC10398896 DOI: 10.1091/mbc.e22-07-0266] [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: 07/11/2022] [Revised: 06/06/2023] [Accepted: 06/15/2023] [Indexed: 06/23/2023] Open
Abstract
Matrix stiffening is ubiquitous in solid tumors and can direct epithelial-mesenchymal transition (EMT) and cancer cell migration. Stiffened niche can even cause poorly invasive oral squamous cell carcinoma (OSCC) cell lines to acquire a less adherent, more migratory phenotype, but mechanisms and durability of this acquired "mechanical memory" are unclear. Here, we observed that contractility and its downstream signals could underlie memory acquisition; invasive SSC25 cells overexpress myosin II (vs. noninvasive Cal27 cells) consistent with OSCC. However, prolonged exposure of Cal27 cells to a stiff niche or contractile agonists up-regulated myosin and EMT markers and enabled them to migrate as fast as SCC25 cells, which persisted even when the niche softened and indicated "memory" of their prior niche. Stiffness-mediated mesenchymal phenotype acquisition required AKT signaling and was also observed in patient samples, whereas phenotype recall on soft substrates required focal adhesion kinase (FAK) activity. Phenotype durability was further observed in transcriptomic differences between preconditioned Cal27 cells cultured without or with FAK or AKT antagonists, and such transcriptional differences corresponded to discrepant patient outcomes. These data suggest that mechanical memory, mediated by contractility via distinct kinase signaling, may be necessary for OSCC to disseminate.
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Affiliation(s)
- So Youn Moon
- Department of Bioengineering, University of California San Diego, La Jolla, CA 92093
- Sanford Consortium for Regenerative Medicine, La Jolla, CA 92037
| | | | | | - Jesse K. Placone
- Department of Bioengineering, University of California San Diego, La Jolla, CA 92093
- Department of Physics and Engineering, West Chester University of Pennsylvania, West Chester, PA 19383
| | - Virgı´lio G. Zanella
- Department of Oral Pathology, Federal University of Rio Grande do Sul
- Department of Head and Neck Surgery, Santa Rita Hospital, Santa Casa de Misericórdia de Porto, Alegre
| | | | - Marcelo Lazzaron Lamers
- Department of Oral Pathology, Federal University of Rio Grande do Sul
- Deparment of Morphological Sciences, Institute of Basic Health Sciences, Federal University of Rio Grande do Sul, Porto Alegre, RS 90035, Brazil
| | - Adam J. Engler
- Department of Bioengineering, University of California San Diego, La Jolla, CA 92093
- Sanford Consortium for Regenerative Medicine, La Jolla, CA 92037
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Abstract
Cell migration, a crucial step in numerous biological processes, is tightly regulated in space and time. Cells employ Rho GTPases, primarily Rho, Rac, and Cdc42, to regulate their motility. Like other small G proteins, Rho GTPases function as biomolecular switches in regulating cell migration by operating between GDP bound 'OFF' and GTP bound 'ON' states. Guanine nucleotide exchange factors (GEFs) catalyse the shuttling of GTPases from OFF to ON state. G protein-coupled receptors (GPCRs) are the largest family of cell surface receptors that are involved in many signalling phenomena including cell survival and cell migration events. In this review, we summarize signalling mechanisms, involving GPCRs, leading to the activation of RhoGEFs. GPCRs exhibit diverse GEF activation modes that include the interaction of heterotrimeric G protein subunits with different domains of GEFs, phosphorylation, protein-protein interaction, protein-lipid interaction, and/or a combination of these processes.
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Affiliation(s)
- Aishwarya Omble
- Division of Biochemical Sciences, CSIR-National Chemical Laboratory, Pune, India,Academy of Scientific and Innovative Research (AcSIR), Ghaziabad, India
| | - Kiran Kulkarni
- Division of Biochemical Sciences, CSIR-National Chemical Laboratory, Pune, India,Academy of Scientific and Innovative Research (AcSIR), Ghaziabad, India,CONTACT Kiran Kulkarni Academy of Scientific and Innovative Research (Acsir), Ghaziabad 201002, India
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5
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García-Jiménez I, Cervantes-Villagrana RD, Del-Río-Robles JE, Castillo-Kauil A, Beltrán-Navarro YM, García-Román J, Reyes-Cruz G, Vázquez-Prado J. Gβγ mediates activation of Rho guanine nucleotide exchange factor ARHGEF17 that promotes metastatic lung cancer progression. J Biol Chem 2021; 298:101440. [PMID: 34808208 PMCID: PMC8703085 DOI: 10.1016/j.jbc.2021.101440] [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: 04/17/2021] [Revised: 11/10/2021] [Accepted: 11/18/2021] [Indexed: 12/12/2022] Open
Abstract
Metastatic lung cancer is a major cause of death worldwide. Dissemination of cancer cells can be facilitated by various agonists within the tumor microenvironment, including by lysophosphatidic acid (LPA). We postulate that Rho guanine nucleotide exchange factors (RhoGEFs), which integrate signaling cues driving cell migration, are critical effectors in metastatic cancer. Specifically, we addressed the hypothetical role of ARHGEF17, a RhoGEF, as a potential effector of Gβγ in metastatic lung cancer cells responding to LPA. Here, we show that ARHGEF17, originally identified as a tumor endothelial marker, is involved in tumor growth and metastatic dissemination of lung cancer cells in an immunocompetent murine model. Gene expression–based analysis of lung cancer datasets showed that increased levels of ARHGEF17 correlated with reduced survival of patients with advanced-stage tumors. Cellular assays also revealed that this RhoGEF participates in the invasive and migratory responses elicited by Gi protein–coupled LPA receptors via the Gβγ subunit complex. We demonstrate that this signaling heterodimer promoted ARHGEF17 recruitment to the cell periphery and actin fibers. Moreover, Gβγ allosterically activates ARHGEF17 by the removal of inhibitory intramolecular restrictions. Taken together, our results indicate that ARHGEF17 may be a valid potential target in the treatment of metastatic lung cancer.
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6
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Lane BS, Heller B, Hollenberg MD, Wells CD. The RGS-RhoGEFs control the amplitude of YAP1 activation by serum. Sci Rep 2021; 11:2348. [PMID: 33504879 PMCID: PMC7841162 DOI: 10.1038/s41598-021-82027-4] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/10/2019] [Accepted: 01/14/2021] [Indexed: 12/16/2022] Open
Abstract
Actin-dependent mechanisms drive the nuclear translocation of Yap1 to enable its co-activation of transcription factors that induce pro-growth and survival programs. While Rho GTPases are necessary for the nuclear import of YAP1, the relevant Guanine Exchange Factors (GEFs) and GTPase Activating Proteins (GAPs) that connect this process to upstream signaling are not well defined. To this end, we measured the impact of expressing sixty-seven RhoGEFs and RhoGAPs on the YAP1 dependent activity of a TEAD element transcriptional reporter. Robust effects by all three members of the regulator of G-protein signaling (RGS) domain containing RhoGEFs (ArhGEF1, ArhGEF11 and ArhGEF12) prompted studies relating their known roles in serum signaling onto the regulation of Yap1. Under all conditions examined, ArhGEF12 preferentially mediated the activation of YAP1/TEAD by serum versus ArhGEF1 or ArhGEF11. Conversely, ArhGEF1 in multiple contexts inhibited both basal and serum elevated YAP1 activity through its GAP activity for Gα13. The sensitivity of such inhibition to cellular density and to low states of serum signaling supports that ArhGEF1 is a context dependent regulator of YAP1. Taken together, the relative activities of the RGS-RhoGEFs were found to dictate the degree to which serum signaling promotes YAP1 activity.
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Affiliation(s)
- Brandon S Lane
- Department of Biochemistry & Molecular Biology, Indiana University School of Medicine, Indianapolis, IN, 46202, USA
| | - Brigitte Heller
- Department of Biochemistry & Molecular Biology, Indiana University School of Medicine, Indianapolis, IN, 46202, USA
| | - Morley D Hollenberg
- Department of Physiology & Pharmacology, Cumming School of Medicine, University of Calgary, Calgary, AB, T2N 4N1, Canada
| | - Clark D Wells
- Department of Biochemistry & Molecular Biology, Indiana University School of Medicine, Indianapolis, IN, 46202, USA. .,Indiana University School of Medicine, John D. Van Nuys Medical Science Building. 635 Barnhill Dr., Rm. 4079A, Indianapolis, IN, USA.
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7
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Leukemia-Associated Rho Guanine Nucleotide Exchange Factor and Ras Homolog Family Member C Play a Role in Glioblastoma Cell Invasion and Resistance. THE AMERICAN JOURNAL OF PATHOLOGY 2020; 190:2165-2176. [PMID: 32693062 DOI: 10.1016/j.ajpath.2020.07.005] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/09/2020] [Revised: 06/16/2020] [Accepted: 07/07/2020] [Indexed: 11/23/2022]
Abstract
Glioblastoma (GBM) is the most common primary malignant brain cancer in adults. A hallmark of GBM is aggressive invasion of tumor cells into the surrounding normal brain. Both the current standard of care and targeted therapies have largely failed to specifically address this issue. Therefore, identifying key regulators of GBM cell migration and invasion is important. The leukemia-associated Rho guanine nucleotide exchange factor (LARG) has previously been implicated in cell invasion in other tumor types; however, its role in GBM pathobiology remains undefined. Herein, we report that the expression levels of LARG and ras homolog family members C (RhoC), and A (RhoA) increase with glial tumor grade and are highest in GBM. LARG and RhoC protein expression is more prominent in invading cells, whereas RhoA expression is largely restricted to cells in the tumor core. Knockdown of LARG by siRNA inhibits GBM cell migration in vitro and invasion ex vivo in organotypic brain slices. Moreover, siRNA-mediated silencing of RhoC suppresses GBM cell migration in vitro and invasion ex vivo, whereas depletion of RhoA enhances GBM cell migration and invasion, supporting a role for LARG and RhoC in GBM cell migration and invasion. Depletion of LARG increases the sensitivity of GBM cells to temozolomide treatment. Collectively, these results suggest that LARG and RhoC may represent unappreciated targets to inhibit glioma invasion.
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8
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Tutunea-Fatan E, Lee JC, Denker BM, Gunaratnam L. Heterotrimeric Gα 12/13 proteins in kidney injury and disease. Am J Physiol Renal Physiol 2020; 318:F660-F672. [PMID: 31984793 DOI: 10.1152/ajprenal.00453.2019] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/11/2023] Open
Abstract
Gα12 and Gα13 are ubiquitous members of the heterotrimeric guanine nucleotide-binding protein (G protein) family that play central and integrative roles in the regulation of signal transduction cascades within various cell types in the kidney. Gα12/Gα13 proteins enable the kidney to adapt to an ever-changing environment by transducing stimuli from cell surface receptors and accessory proteins to effector systems. Therefore, perturbations in Gα12/Gα13 levels or their activity can contribute to the pathogenesis of various renal diseases, including renal cancer. This review will highlight and discuss the complex and expanding roles of Gα12/Gα13 proteins on distinct renal pathologies, with emphasis on more recently reported findings. Deciphering how the different Gα12/Gα13 interaction networks participate in the onset and development of renal diseases may lead to the discovery of new therapeutic strategies.
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Affiliation(s)
- Elena Tutunea-Fatan
- Matthew Mailing Centre for Translational Transplant Studies, Lawson Health Research Institute, London, Ontario, Canada
| | - Jasper C Lee
- Department of Microbiology and Immunology, University of Western Ontario, London, Ontario, Canada
| | - Bradley M Denker
- Beth Israel Deaconess Medical Center and Department of Medicine, Harvard Medical School, Boston, Massachusetts
| | - Lakshman Gunaratnam
- Matthew Mailing Centre for Translational Transplant Studies, Lawson Health Research Institute, London, Ontario, Canada.,Department of Microbiology and Immunology, University of Western Ontario, London, Ontario, Canada.,Division of Nephrology, Department of Medicine, University of Western Ontario, London, Ontario, Canada
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9
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Diviani D, Raimondi F, Del Vescovo CD, Dreyer E, Reggi E, Osman H, Ruggieri L, Gonano C, Cavin S, Box CL, Lenoir M, Overduin M, Bellucci L, Seeber M, Fanelli F. Small-Molecule Protein-Protein Interaction Inhibitor of Oncogenic Rho Signaling. Cell Chem Biol 2016; 23:1135-1146. [PMID: 27593112 DOI: 10.1016/j.chembiol.2016.07.015] [Citation(s) in RCA: 26] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/28/2014] [Revised: 06/30/2016] [Accepted: 07/09/2016] [Indexed: 01/23/2023]
Abstract
Uncontrolled activation of Rho signaling by RhoGEFs, in particular AKAP13 (Lbc) and its close homologs, is implicated in a number of human tumors with poor prognosis and resistance to therapy. Structure predictions and alanine scanning mutagenesis of Lbc identified a circumscribed hot region for RhoA recognition and activation. Virtual screening targeting that region led to the discovery of an inhibitor of Lbc-RhoA interaction inside cells. By interacting with the DH domain, the compound inhibits the catalytic activity of Lbc, halts cellular responses to activation of oncogenic Lbc pathways, and reverses a number of prostate cancer cell phenotypes such as proliferation, migration, and invasiveness. This study provides insights into the structural determinants of Lbc-RhoA recognition. This is a successful example of structure-based discovery of a small protein-protein interaction inhibitor able to halt oncogenic Rho signaling in cancer cells with therapeutic implications.
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Affiliation(s)
- Dario Diviani
- Department of Pharmacology and Toxicology, Faculty of Biology and Medicine, University of Lausanne, Rue du Bugnon 27, 1005 Lausanne, Switzerland
| | - Francesco Raimondi
- Department of Life Sciences, University of Modena and Reggio Emilia, via Campi 103, 41125 Modena, Italy
| | - Cosmo D Del Vescovo
- Department of Pharmacology and Toxicology, Faculty of Biology and Medicine, University of Lausanne, Rue du Bugnon 27, 1005 Lausanne, Switzerland
| | - Elisa Dreyer
- Department of Pharmacology and Toxicology, Faculty of Biology and Medicine, University of Lausanne, Rue du Bugnon 27, 1005 Lausanne, Switzerland
| | - Erica Reggi
- Department of Pharmacology and Toxicology, Faculty of Biology and Medicine, University of Lausanne, Rue du Bugnon 27, 1005 Lausanne, Switzerland
| | - Halima Osman
- Department of Pharmacology and Toxicology, Faculty of Biology and Medicine, University of Lausanne, Rue du Bugnon 27, 1005 Lausanne, Switzerland
| | - Lucia Ruggieri
- Department of Pharmacology and Toxicology, Faculty of Biology and Medicine, University of Lausanne, Rue du Bugnon 27, 1005 Lausanne, Switzerland
| | - Cynthia Gonano
- Department of Pharmacology and Toxicology, Faculty of Biology and Medicine, University of Lausanne, Rue du Bugnon 27, 1005 Lausanne, Switzerland
| | - Sabrina Cavin
- Department of Pharmacology and Toxicology, Faculty of Biology and Medicine, University of Lausanne, Rue du Bugnon 27, 1005 Lausanne, Switzerland
| | - Clare L Box
- Institute of Cancer and Genomic Studies, University of Birmingham, Birmingham B15 2TT, UK
| | - Marc Lenoir
- Institute of Cancer and Genomic Studies, University of Birmingham, Birmingham B15 2TT, UK
| | - Michael Overduin
- Department of Biochemistry, University of Alberta, Edmonton, Alberta T6G 2H7, Canada
| | - Luca Bellucci
- Department of Life Sciences, University of Modena and Reggio Emilia, via Campi 103, 41125 Modena, Italy
| | - Michele Seeber
- Department of Life Sciences, University of Modena and Reggio Emilia, via Campi 103, 41125 Modena, Italy
| | - Francesca Fanelli
- Department of Life Sciences, University of Modena and Reggio Emilia, via Campi 103, 41125 Modena, Italy.
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10
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Helms MC, Grabocka E, Martz MK, Fischer CC, Suzuki N, Wedegaertner PB. Mitotic-dependent phosphorylation of leukemia-associated RhoGEF (LARG) by Cdk1. Cell Signal 2015; 28:43-52. [PMID: 26483157 DOI: 10.1016/j.cellsig.2015.10.004] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/08/2015] [Accepted: 10/15/2015] [Indexed: 01/14/2023]
Abstract
Rho GTPases are integral to the regulation of actin cytoskeleton-dependent processes, including mitosis. Rho and leukemia-associated Rho guanine-nucleotide exchange factor (LARG), also known as ARHGEF12, are involved in mitosis as well as diseases such as cancer and heart disease. Since LARG has a role in mitosis and diverse signaling functions beyond mitosis, it is important to understand the regulation of the protein through modifications such as phosphorylation. Here we report that LARG undergoes a mitotic-dependent and cyclin-dependent kinase 1 (Cdk1) inhibitor-sensitive phosphorylation. Additionally, LARG is phosphorylated at the onset of mitosis and dephosphorylated as cells exit mitosis, concomitant with Cdk1 activity. Furthermore, using an in vitro kinase assay, we show that LARG can be directly phosphorylated by Cdk1. Through expression of phosphonull mutants that contain non-phosphorylatable alanine mutations at potential Cdk1 S/TP sites, we demonstrate that LARG phosphorylation occurs in both termini. Using phosphospecific antibodies, we confirm that two sites, serine 190 and serine 1176, are phosphorylated during mitosis in a Cdk1-dependent manner. In addition, these phosphospecific antibodies show phosphorylated LARG at specific mitotic locations, namely the mitotic organizing centers and flanking the midbody. Lastly, RhoA activity assays reveal that phosphonull LARG is more active in cells than phosphomimetic LARG. Our data thus identifies LARG as a phosphoregulated RhoGEF during mitosis.
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Affiliation(s)
- Michelle C Helms
- Department of Biochemistry and Molecular Biology, Thomas Jefferson University, Philadelphia, PA, USA
| | - Elda Grabocka
- Department of Biochemistry and Molecular Biology, Thomas Jefferson University, Philadelphia, PA, USA
| | - Matthew K Martz
- Department of Biochemistry and Molecular Biology, Thomas Jefferson University, Philadelphia, PA, USA
| | - Christopher C Fischer
- Department of Biochemistry and Molecular Biology, Thomas Jefferson University, Philadelphia, PA, USA
| | - Nobuchika Suzuki
- Department of Signal Dynamics, University of Tokyo, Meguro, Tokyo, Japan
| | - Philip B Wedegaertner
- Department of Biochemistry and Molecular Biology, Thomas Jefferson University, Philadelphia, PA, USA.
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11
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Dunn HA, Ferguson SSG. PDZ Protein Regulation of G Protein–Coupled Receptor Trafficking and Signaling Pathways. Mol Pharmacol 2015; 88:624-39. [DOI: 10.1124/mol.115.098509] [Citation(s) in RCA: 82] [Impact Index Per Article: 9.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/18/2015] [Accepted: 03/25/2015] [Indexed: 01/03/2023] Open
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12
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RhoA/mDia-1/profilin-1 signaling targets microvascular endothelial dysfunction in diabetic retinopathy. Graefes Arch Clin Exp Ophthalmol 2015; 253:669-80. [PMID: 25791356 DOI: 10.1007/s00417-015-2985-3] [Citation(s) in RCA: 28] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/02/2014] [Revised: 02/21/2015] [Accepted: 03/02/2015] [Indexed: 12/20/2022] Open
Abstract
BACKGROUND Diabetic retinopathy (DR) is a major cause of blindness in the working-age populations of developed countries, and effective treatments and prevention measures have long been the foci of study. Patients with DR invariably demonstrate impairments of the retinal microvascular endothelium. Many observational and preclinical studies have shown that angiogenesis and apoptosis play crucial roles in the pathogenesis of DR. Increasing evidence suggests that in DR, the small guanosine-5'-triphosphate-binding protein RhoA activates its downstream targets mammalian Diaphanous homolog 1 (mDia-1) and profilin-1, thus affecting important cellular functions, including cell morphology, motility, secretion, proliferation, and gene expression. However, the specific underlying mechanism of disease remains unclear. CONCLUSION This review focuses on the RhoA/mDia-1/profilin-1 signaling pathway that specifically triggers endothelial dysfunction in diabetic patients. Recently, RhoA and profilin-1 signaling has attracted a great deal of attention in the context of diabetes-related research. However, the precise molecular mechanism by which the RhoA/mDia-1/profilin-1 pathway is involved in progression of microvascular endothelial dysfunction (MVED) during DR has not been determined. This review briefly describes each feature of the cascade before exploring the most recent findings on how the pathway may trigger endothelial dysfunction in DR. When the underlying mechanisms are understood, novel therapies seeking to restore the endothelial homeostasis comprised in DR will become possible.
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13
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Curcumin inhibits LPA-induced invasion by attenuating RhoA/ROCK/MMPs pathway in MCF7 breast cancer cells. Clin Exp Med 2015; 16:37-47. [PMID: 25596714 DOI: 10.1007/s10238-015-0336-7] [Citation(s) in RCA: 33] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/15/2014] [Accepted: 01/08/2015] [Indexed: 10/24/2022]
Abstract
Breast cancer generally shows poor prognosis because of its invasion and metastasis. Lysophosphatidic acid (LPA) induces and aggravates cancer invasion and metastasis by activating its downstream signal pathways. RhoA/ROCK/MMP signaling was found one of the LPA-induced pathways, which may be involved in invasion of breast cancer. Furthermore, we investigated whether this pathway was involved in curcumin's effect against LPA-induced invasion. LPA incubation was used to enhance invasion of MCF-7 breast cancer cells. RhoA expression was knocked-down by siRNA technique. MTT assay was used to evaluate the proliferation. Transwell assay was utilized to investigate the invasion ability of MCF-7 cells. Real-time PCR and Western blotting were used to assess the expressions of RhoA, ROCK1, ROCK2, MMP2 and MMP9 at both translational and transcriptional levels. The RhoA and ROCK activities were also evaluated. LPA incubation significantly boosted invasion rate of MCF-7. RhoA silencing by siRNA dramatically inhibited LPA-enhanced invasion. Concurrently, RhoA and ROCK activities and expression levels of RhoA, ROCK1, ROCK2, MMP2 and MMP9 were down-regulated by RhoA siRNA transfection. In order to avoid influence of cytotoxicity of curcumin, concentrations below 45 μmol/L were selected to further investigate the mechanism of curcumin's anti-invasion effect. Invasion of LPA-incubated MCF-7 cells was impaired by curcumin in a concentration-dependent manner. Concurrently, RhoA and ROCK activities and expression levels of RhoA, ROCK1, ROCK2, MMP2 and MMP9 were down-regulated by curcumin in a concentration-dependent manner. In conclusion, RhoA/ROCK/MMPs pathway activation is involved in LPA-induced invasion in MCF-7 cells; curcumin inhibited LPA-induced invasion in MCF-7 cells by attenuating RhoA/ROCK/MMPs pathway.
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14
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Liu Z, Hopkins MM, Zhang Z, Quisenberry CB, Fix LC, Galvan BM, Meier KE. Omega-3 fatty acids and other FFA4 agonists inhibit growth factor signaling in human prostate cancer cells. J Pharmacol Exp Ther 2014; 352:380-94. [PMID: 25491146 DOI: 10.1124/jpet.114.218974] [Citation(s) in RCA: 72] [Impact Index Per Article: 7.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022] Open
Abstract
Omega-3 fatty acids (n-3 FAs) are proposed to have many beneficial effects on human health. However, the mechanisms underlying their potential cancer preventative effects are unclear. G protein-coupled receptors (GPCRs) of the free fatty acid receptor (FFAR) family, FFA1/GPR40 and FFA4/GPR120, specifically bind n-3 FAs as agonist ligands. In this study, we examined the effects of n-3 FAs in human prostate cancer cell lines. Initial studies established that the long-chain n-3 FAs, eicosapentaenoic acid (EPA) and docosahexaenoic acid, inhibit proliferation of DU145 cells in response to lysophosphatidic acid (LPA), a mitogenic lipid mediator. When added alone to serum-starved DU145 cells, EPA transiently activates signaling events, including p70S6K phosphorylation. However, when added 15 minutes prior to LPA, EPA suppresses LPA-induced activating phosphorylations of ERK, FAK, and p70S6K, and expression of the matricellular protein CCN1. The rapid onset of the inhibitory action of EPA suggested involvement of a GPCR. Further studies showed that DU145 and PC-3 cells express mRNA and protein for both FFA4 and FFA1. TUG-891 (4-[(4-fluoro-4'-methyl[1,1'-biphenyl]-2-yl)methoxy]-benzenepropanoic acid), a selective agonist for FFA4, exerts inhibitory effects on LPA- and epidermal growth factor-induced proliferation and migration, similar to EPA, in DU145 and PC-3 cells. The effects of TUG-891 and EPA are readily reversible. The FFA1/FFA4 agonist GW9508 (4-[[(3-phenoxyphenyl)methyl]amino]-benzenepropranoic acid) likewise inhibits proliferation at doses that block FFA4. Knockdown of FFA4 expression prevents EPA- and TUG-891-induced inhibition of growth and migration. Together, these results indicate that activation of FFA4 initiates signaling events that can inhibit growth factor-induced signaling, providing a novel mechanism for suppression of cancer cell proliferation.
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Affiliation(s)
- Ze Liu
- Department of Pharmaceutical Sciences, College of Pharmacy, Washington State University, Spokane, Washington
| | - Mandi M Hopkins
- Department of Pharmaceutical Sciences, College of Pharmacy, Washington State University, Spokane, Washington
| | - Zhihong Zhang
- Department of Pharmaceutical Sciences, College of Pharmacy, Washington State University, Spokane, Washington
| | - Chrystal B Quisenberry
- Department of Pharmaceutical Sciences, College of Pharmacy, Washington State University, Spokane, Washington
| | - Louise C Fix
- Department of Pharmaceutical Sciences, College of Pharmacy, Washington State University, Spokane, Washington
| | - Brianna M Galvan
- Department of Pharmaceutical Sciences, College of Pharmacy, Washington State University, Spokane, Washington
| | - Kathryn E Meier
- Department of Pharmaceutical Sciences, College of Pharmacy, Washington State University, Spokane, Washington
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Goicoechea SM, Awadia S, Garcia-Mata R. I'm coming to GEF you: Regulation of RhoGEFs during cell migration. Cell Adh Migr 2014; 8:535-49. [PMID: 25482524 PMCID: PMC4594598 DOI: 10.4161/cam.28721] [Citation(s) in RCA: 70] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023] Open
Abstract
Cell migration is a highly regulated multistep process that requires the coordinated regulation of cell adhesion, protrusion, and contraction. These processes require numerous protein–protein interactions and the activation of specific signaling pathways. The Rho family of GTPases plays a key role in virtually every aspect of the cell migration cycle. The activation of Rho GTPases is mediated by a large and diverse family of proteins; the guanine nucleotide exchange factors (RhoGEFs). GEFs work immediately upstream of Rho proteins to provide a direct link between Rho activation and cell–surface receptors for various cytokines, growth factors, adhesion molecules, and G protein-coupled receptors. The regulated targeting and activation of RhoGEFs is essential to coordinate the migratory process. In this review, we summarize the recent advances in our understanding of the role of RhoGEFs in the regulation of cell migration.
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Key Words
- DH, Dbl-homology
- DHR, DOCK homology region
- DOCK, dedicator of cytokinesis
- ECM, extracellular matrix
- EGF, epidermal growth factor
- FA, focal adhesion
- FN, fibronectin
- GAP, GTPase activating protein
- GDI, guanine nucleotide dissociation inhibitor
- GEF, guanine nucleotide exchange factor
- GPCR, G protein-coupled receptor
- HGF, hepatocyte growth factor
- LPA, lysophosphatidic acid
- MII, myosin II
- PA, phosphatidic acid
- PDGF, platelet-derived growth factor
- PH, pleckstrin-homology
- PIP2, phosphatidylinositol 4, 5-bisphosphate
- PIP3, phosphatidylinositol (3, 4, 5)-trisphosphate.
- Rho GEFs
- Rho GTPases
- bFGF, basic fibroblast growth factor
- cell migration
- cell polarization
- focal adhesions
- guanine nucleotide exchange factors
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Affiliation(s)
- Silvia M Goicoechea
- a Department of Biological Sciences ; University of Toledo ; Toledo , OH USA
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16
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Patel M, Kawano T, Suzuki N, Hamakubo T, Karginov AV, Kozasa T. Gα13/PDZ-RhoGEF/RhoA signaling is essential for gastrin-releasing peptide receptor-mediated colon cancer cell migration. Mol Pharmacol 2014; 86:252-62. [PMID: 24958816 DOI: 10.1124/mol.114.093914] [Citation(s) in RCA: 30] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022] Open
Abstract
Gastrin-releasing peptide receptor (GRPR) is ectopically expressed in over 60% of colon cancers. GRPR expression has been correlated with increased colon cancer cell migration. However, the signaling pathway by which GRPR activation leads to increased cancer cell migration is not well understood. We set out to molecularly dissect the GRPR signaling pathways that control colon cancer cell migration through regulation of small GTPase RhoA. Our results show that GRP stimulation activates RhoA predominantly through G13 heterotrimeric G-protein signaling. We also demonstrate that postsynaptic density 95/disk-large/ZO-1 (PDZ)-RhoGEF (PRG), a member of regulator of G-protein signaling (RGS)-homology domain (RH) containing guanine nucleotide exchange factors (RH-RhoGEFs), is the predominant activator of RhoA downstream of GRPR. We found that PRG is required for GRP-stimulated colon cancer cell migration, through activation of RhoA-Rho-associated kinase (ROCK) signaling axis. In addition, PRG-RhoA-ROCK pathway also contributes to cyclo-oxygenase isoform 2 (Cox-2) expression. Increased Cox-2 expression is correlated with increased production of prostaglandin-E2 (PGE2), and Cox-2-PGE2 signaling contributes to total GRPR-mediated cancer cell migration. Our analysis reveals that PRG is overexpressed in colon cancer cell lines. Overall, our results have uncovered a key mechanism for GRPR-regulated colon cancer cell migration through the Gα13-PRG-RhoA-ROCK pathway.
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Affiliation(s)
- Maulik Patel
- Department of Pharmacology, University of Illinois at Chicago College of Medicine, Chicago, Illinois (M.P., A.V.K., T.Ko.); Department of Physiology and Biophysics, Virginia Commonwealth University School of Medicine, Richmond, Virginia (T. Ka.); and Research Center for Advanced Science and Technology, The University of Tokyo, Tokyo, Japan (N.S., T.H., T.Ko.)
| | - Takeharu Kawano
- Department of Pharmacology, University of Illinois at Chicago College of Medicine, Chicago, Illinois (M.P., A.V.K., T.Ko.); Department of Physiology and Biophysics, Virginia Commonwealth University School of Medicine, Richmond, Virginia (T. Ka.); and Research Center for Advanced Science and Technology, The University of Tokyo, Tokyo, Japan (N.S., T.H., T.Ko.)
| | - Nobuchika Suzuki
- Department of Pharmacology, University of Illinois at Chicago College of Medicine, Chicago, Illinois (M.P., A.V.K., T.Ko.); Department of Physiology and Biophysics, Virginia Commonwealth University School of Medicine, Richmond, Virginia (T. Ka.); and Research Center for Advanced Science and Technology, The University of Tokyo, Tokyo, Japan (N.S., T.H., T.Ko.)
| | - Takao Hamakubo
- Department of Pharmacology, University of Illinois at Chicago College of Medicine, Chicago, Illinois (M.P., A.V.K., T.Ko.); Department of Physiology and Biophysics, Virginia Commonwealth University School of Medicine, Richmond, Virginia (T. Ka.); and Research Center for Advanced Science and Technology, The University of Tokyo, Tokyo, Japan (N.S., T.H., T.Ko.)
| | - Andrei V Karginov
- Department of Pharmacology, University of Illinois at Chicago College of Medicine, Chicago, Illinois (M.P., A.V.K., T.Ko.); Department of Physiology and Biophysics, Virginia Commonwealth University School of Medicine, Richmond, Virginia (T. Ka.); and Research Center for Advanced Science and Technology, The University of Tokyo, Tokyo, Japan (N.S., T.H., T.Ko.)
| | - Tohru Kozasa
- Department of Pharmacology, University of Illinois at Chicago College of Medicine, Chicago, Illinois (M.P., A.V.K., T.Ko.); Department of Physiology and Biophysics, Virginia Commonwealth University School of Medicine, Richmond, Virginia (T. Ka.); and Research Center for Advanced Science and Technology, The University of Tokyo, Tokyo, Japan (N.S., T.H., T.Ko.).
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17
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Dynamics of Gαq-protein-p63RhoGEF interaction and its regulation by RGS2. Biochem J 2014; 458:131-40. [PMID: 24299002 DOI: 10.1042/bj20130782] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022]
Abstract
Some G-protein-coupled receptors regulate biological processes via Gα12/13- or Gαq/11-mediated stimulation of RhoGEFs (guanine-nucleotide-exchange factors). p63RhoGEF is known to be specifically activated by Gαq/11 and mediates a major part of the acute response of vascular smooth muscle cells to angiotensin II treatment. In order to gain information about the dynamics of receptor-mediated activation of p63RhoGEF, we developed a FRET-based assay to study interactions between Gαq-CFP and Venus-p63RhoGEF in single living cells. Upon activation of histaminergic H1 or muscarinic M3 receptors, a robust FRET signal occurred that allowed for the first time the analysis of the kinetics of this interaction in detail. On- and off-set kinetics of Gαq-p63RhoGEF interactions closely resembled the kinetics of Gαq activity. Analysis of the effect of RGS2 (regulator of G-protein signalling 2) on the dynamics of Gαq activity and their interaction with p63RhoGEF showed that RGS2 is able to accelerate both deactivation of Gαq proteins and dissociation of Gαq and p63RhoGEF to a similar extent. Furthermore, we were able to detect activation-dependent FRET between RGS2 and p63RhoGEF and observed a reduced p63RhoGEF-mediated downstream signalling in the presence of RGS2. In summary, these observations support the concept of a functional activation-dependent p63RhoGEF-Gαq-RGS2 complex.
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Gao J, Ma R, Wang W, Wang N, Sasaki R, Snyderman D, Wu J, Ruan K. Automated NMR fragment based screening identified a novel interface blocker to the LARG/RhoA complex. PLoS One 2014; 9:e88098. [PMID: 24505392 PMCID: PMC3914932 DOI: 10.1371/journal.pone.0088098] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/13/2013] [Accepted: 01/06/2014] [Indexed: 02/03/2023] Open
Abstract
The small GTPase cycles between the inactive GDP form and the activated GTP form, catalyzed by the upstream guanine exchange factors. The modulation of such process by small molecules has been proven to be a fruitful route for therapeutic intervention to prevent the over-activation of the small GTPase. The fragment based approach emerging in the past decade has demonstrated its paramount potential in the discovery of inhibitors targeting such novel and challenging protein-protein interactions. The details regarding the procedure of NMR fragment screening from scratch have been rarely disclosed comprehensively, thus restricts its wider applications. To achieve a consistent screening applicable to a number of targets, we developed a highly automated protocol to cover every aspect of NMR fragment screening as possible, including the construction of small but diverse libray, determination of the aqueous solubility by NMR, grouping compounds with mutual dispersity to a cocktail, and the automated processing and visualization of the ligand based screening spectra. We exemplified our streamlined screening in RhoA alone and the complex of the small GTPase RhoA and its upstream guanine exchange factor LARG. Two hits were confirmed from the primary screening in cocktail and secondary screening over individual hits for LARG/RhoA complex, while one of them was also identified from the screening for RhoA alone. HSQC titration of the two hits over RhoA and LARG alone, respectively, identified one compound binding to RhoA.GDP at a 0.11 mM affinity, and perturbed the residues at the switch II region of RhoA. This hit blocked the formation of the LARG/RhoA complex, validated by the native gel electrophoresis, and the titration of RhoA to ¹⁵N labeled LARG in the absence and presence the compound, respectively. It therefore provides us a starting point toward a more potent inhibitor to RhoA activation catalyzed by LARG.
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Affiliation(s)
- Jia Gao
- Hefei National Laboratory for Physical Sciences at the Microscale, School of Life Science, University of Science and Technology of China, Hefei, Anhui, China
| | - Rongsheng Ma
- Hefei National Laboratory for Physical Sciences at the Microscale, School of Life Science, University of Science and Technology of China, Hefei, Anhui, China
| | - Wei Wang
- Pfizer Worldwide Research and Development, San Diego, California, United States of America
| | - Na Wang
- Hefei National Laboratory for Physical Sciences at the Microscale, School of Life Science, University of Science and Technology of China, Hefei, Anhui, China
| | - Ryan Sasaki
- Advanced Chemistry Development Inc., Toronto, Ontario, Canada
| | - David Snyderman
- Advanced Chemistry Development Inc., Toronto, Ontario, Canada
| | - Jihui Wu
- Hefei National Laboratory for Physical Sciences at the Microscale, School of Life Science, University of Science and Technology of China, Hefei, Anhui, China
| | - Ke Ruan
- Hefei National Laboratory for Physical Sciences at the Microscale, School of Life Science, University of Science and Technology of China, Hefei, Anhui, China
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19
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Palomero T, Couronné L, Khiabanian H, Kim MY, Ambesi-Impiombato A, Perez-Garcia A, Carpenter Z, Abate F, Allegretta M, Haydu JE, Jiang X, Lossos IS, Nicolas C, Balbin M, Bastard C, Bhagat G, Piris MA, Campo E, Bernard OA, Rabadan R, Ferrando AA. Recurrent mutations in epigenetic regulators, RHOA and FYN kinase in peripheral T cell lymphomas. Nat Genet 2014; 46:166-70. [PMID: 24413734 PMCID: PMC3963408 DOI: 10.1038/ng.2873] [Citation(s) in RCA: 467] [Impact Index Per Article: 46.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/28/2013] [Accepted: 12/12/2013] [Indexed: 12/17/2022]
Abstract
Peripheral T cell lymphomas (PTCLs) are a heterogeneous and poorly understood group of non-Hodgkin lymphomas. Here we combined whole-exome sequencing of 12 tumor-normal DNA pairs, RNA sequencing analysis and targeted deep sequencing to identify new genetic alterations in PTCL transformation. These analyses identified highly recurrent epigenetic factor mutations in TET2, DNMT3A and IDH2 as well as a new highly prevalent RHOA mutation encoding a p.Gly17Val alteration present in 22 of 35 (67%) angioimmunoblastic T cell lymphoma (AITL) samples and in 8 of 44 (18%) PTCL, not otherwise specified (PTCL-NOS) samples. Mechanistically, the RHOA Gly17Val protein interferes with RHOA signaling in biochemical and cellular assays, an effect potentially mediated by the sequestration of activated guanine-exchange factor (GEF) proteins. In addition, we describe new and recurrent, albeit less frequent, genetic defects including mutations in FYN, ATM, B2M and CD58 implicating SRC signaling, impaired DNA damage response and escape from immune surveillance mechanisms in the pathogenesis of PTCL.
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Affiliation(s)
- Teresa Palomero
- 1] Institute for Cancer Genetics, Columbia University, New York, New York, USA. [2] Department of Pathology, Columbia University Medical Center, New York, New York, USA. [3]
| | - Lucile Couronné
- 1] Institute for Cancer Genetics, Columbia University, New York, New York, USA. [2]
| | - Hossein Khiabanian
- 1] Department of Systems Biology, Columbia University, New York, New York, USA. [2]
| | - Mi-Yeon Kim
- Institute for Cancer Genetics, Columbia University, New York, New York, USA
| | | | | | - Zachary Carpenter
- Department of Systems Biology, Columbia University, New York, New York, USA
| | - Francesco Abate
- 1] Department of Systems Biology, Columbia University, New York, New York, USA. [2] Department of Control and Computer Engineering, Politecnico di Torino, Torino, Italy
| | | | - J Erika Haydu
- Institute for Cancer Genetics, Columbia University, New York, New York, USA
| | - Xiaoyu Jiang
- Division of Hematology-Oncology, Sylvester Comprehensive Cancer Center, Miami, Florida, USA
| | - Izidore S Lossos
- 1] Division of Hematology-Oncology, Sylvester Comprehensive Cancer Center, Miami, Florida, USA. [2] Department of Molecular and Cellular Pharmacology, University of Miami, Miami, Florida, USA
| | - Concha Nicolas
- Hematology Service, Hospital Central de Asturias, Oviedo, Spain
| | - Milagros Balbin
- Molecular Oncology Laboratory, Instituto Universitario de Oncología del Principado de Asturias, Hospital Universitario Central de Asturias, Oviedo, Spain
| | - Christian Bastard
- INSERM U918, Rouen University, Centre Henri Becquerel, Rouen, France
| | - Govind Bhagat
- Department of Pathology, Columbia University Medical Center, New York, New York, USA
| | - Miguel A Piris
- 1] Pathology Department, Hospital Universitario Marqués de Valdecilla, Santander, Spain. [2] Instituto de Formacion e Investigacion Marques de Valdecilla-IFIMAV, Santander, Spain
| | - Elias Campo
- 1] Hematopathology Section, Department of Pathology, Hospital Clinic, Barcelona, Spain. [2] Institut d'Investigacions Biomèdiques August Pi i Sunyer, University of Barcelona, Barcelona, Spain
| | - Olivier A Bernard
- 1] INSERM U985, Villejuif, France. [2] Université Paris-Sud, Orsay, France. [3] Institut Gustave Roussy, Villejuif, France
| | - Raul Rabadan
- 1] Department of Systems Biology, Columbia University, New York, New York, USA. [2] Department of Biomedical Informatics, Columbia University, New York, New York, USA
| | - Adolfo A Ferrando
- 1] Institute for Cancer Genetics, Columbia University, New York, New York, USA. [2] Department of Pathology, Columbia University Medical Center, New York, New York, USA. [3] Department of Pediatrics, Columbia University Medical Center, New York, New York, USA
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Struckhoff AP, Rana MK, Kher SS, Burow ME, Hagan JL, Del Valle L, Worthylake RA. PDZ-RhoGEF is essential for CXCR4-driven breast tumor cell motility through spatial regulation of RhoA. J Cell Sci 2013; 126:4514-26. [PMID: 23868972 DOI: 10.1242/jcs.132381] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022] Open
Abstract
The CXCL12-CXCR4 chemokine signaling pathway is a well-established driver of cancer progression. One key process promoted by CXCR4 stimulation is tumor cell motility; however, the specific signaling pathways leading to migration remain poorly understood. Previously, we have shown that CXCL12 stimulation of migration depends on temporal regulation of RhoA. However, the specific RhoGEF that translates CXCR4 signaling into RhoA activity and cell motility is unknown. We screened the three regulator of G-protein signaling RhoGEFs (LSC, LARG and PRG) and found that PRG selectively regulated the migration and invasion of CXCR4-overexpressing breast tumor cells. Interestingly, we found that PDZ-RhoGEF (PRG) was required for spatial organization of F-actin structures in the center, but not periphery of the cells. The effects on the cytoskeleton were mirrored by the spatial effects on RhoA activity that were dependent upon PRG. Loss of PRG also enhanced adherens junctions in the epithelial-like MCF7-CXCR4 cell line, and inhibited directional persistence and polarity in the more mesenchymal MDA-MB-231 cell line. Thus, PRG is essential for CXCR4-driven tumor cell migration through spatial regulation of RhoA and the subsequent organization of the cytoskeletal structures that support motility. Furthermore, immunohistochemical analysis of human breast tumor tissues shows a significant increase of PRG expression in the invasive areas of the tumors, suggesting that this RhoGEF is associated with breast tumor invasion in vivo.
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Affiliation(s)
- Amanda P Struckhoff
- Stanley S. Scott Cancer Center, Louisiana State University Health, New Orleans, Louisiana, USA
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Distinctive G Protein-Dependent Signaling by Protease-Activated Receptor 2 (PAR2) in Smooth Muscle: Feedback Inhibition of RhoA by cAMP-Independent PKA. PLoS One 2013; 8:e66743. [PMID: 23825105 PMCID: PMC3688948 DOI: 10.1371/journal.pone.0066743] [Citation(s) in RCA: 36] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/25/2013] [Accepted: 05/10/2013] [Indexed: 11/18/2022] Open
Abstract
We examined expression of protease-activated receptors 2 (PAR2) and characterized their signaling pathways in rabbit gastric muscle cells. The PAR2 activating peptide SLIGRL (PAR2-AP) stimulated Gq, G13, Gi1, PI hydrolysis, and Rho kinase activity, and inhibited cAMP formation. Stimulation of PI hydrolysis was partly inhibited in cells expressing PAR2 siRNA, Gaq or Gai minigene and in cells treated with pertussis toxin, and augmented by expression of dominant negative regulator of G protein signaling (RGS4(N88S)). Stimulation of Rho kinase activity was abolished by PAR-2 or Ga13 siRNA, and by Ga13 minigene. PAR2-AP induced a biphasic contraction; initial contraction was selectively blocked by the inhibitor of PI hydrolysis (U73122) or MLC kinase (ML-9), whereas sustained contraction was selectively blocked by the Rho kinase inhibitor (Y27632). PAR2-AP induced phosphorylation of MLC20, MYPT1 but not CPI-17. PAR2-AP also caused a decrease in the association of NF-kB and PKA catalytic subunit: the effect of PAR2-AP was blocked by PAR2 siRNA or phosphorylation-deficient RhoA (RhoA(S188A)). PAR2-AP-induced degradation of IkBa and activation of NF-kB were abolished by the blockade of RhoA activity by Clostridium botulinum C3 exoenzyme suggesting RhoA-dependent activation of NF-kB. PAR2-AP-stimulated Rho kinase activity was significantly augmented by the inhibitors of PKA (myristoylated PKI), IKK2 (IKKIV) or NF-kB (MG132), and in cells expressing dominant negative mutants of IKK (IKK(K44A), IkBa (IkBa (S32A/S36A)) or RhoA(S188A), suggesting feedback inhibition of Rho kinase activity via PKA derived from NF-kB pathway. PAR2-AP induced phosphorylation of RhoA and the phosphorylation was attenuated in cells expressing phosphorylation-deficient RhoA(S188A). Our results identified signaling pathways activated by PAR2 to mediate smooth muscle contraction and a novel pathway for feedback inhibition of PAR2-stimulated RhoA. The pathway involves activation of the NF-kB to release catalytic subunit of PKA from its binding to IkBa and phosphorylation of RhoA at Ser188.
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Regulation of focal adhesion kinase activation, breast cancer cell motility, and amoeboid invasion by the RhoA guanine nucleotide exchange factor Net1. Mol Cell Biol 2013; 33:2773-86. [PMID: 23689132 DOI: 10.1128/mcb.00175-13] [Citation(s) in RCA: 46] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Net1 is a RhoA guanine nucleotide exchange factor (GEF) that is overexpressed in a subset of human cancers and contributes to cancer cell motility and invasion in vitro. However, the molecular mechanism accounting for its role in cell motility and invasion has not been described. In the present work, we show that expression of both Net1 isoforms in breast cancer cells is required for efficient cell motility. Although loss of Net1 isoform expression only partially blocks RhoA activation, it inhibits lysophosphatidic acid (LPA)-stimulated migration as efficiently as knockdown of RhoA itself. However, we demonstrate that the Net1A isoform predominantly controls myosin light-chain phosphorylation and is required for trailing edge retraction during migration. Net1A interacts with focal adhesion kinase (FAK), localizes to focal adhesions, and is necessary for FAK activation and focal adhesion maturation during cell spreading. Net1A expression is also required for efficient invasion through a Matrigel matrix. Analysis of invading cells demonstrates that Net1A is required for amoeboid invasion, and loss of Net1A expression causes cells to shift to a mesenchymal phenotype characterized by high β1-integrin activity and membrane type 1 matrix metalloproteinase (MT1-MMP) expression. These results demonstrate a previously unrecognized role for the Net1A isoform in controlling FAK activation during planar cell movement and amoeboid motility during extracellular matrix (ECM) invasion.
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Ritchie BJ, Smolski WC, Montgomery ER, Fisher ES, Choi TY, Olson CM, Foster LA, Meigs TE. Determinants at the N- and C-termini of Gα12 required for activation of Rho-mediated signaling. J Mol Signal 2013; 8:3. [PMID: 23531275 PMCID: PMC3636079 DOI: 10.1186/1750-2187-8-3] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/23/2013] [Accepted: 03/17/2013] [Indexed: 11/10/2022] Open
Abstract
BACKGROUND Heterotrimeric guanine nucleotide binding proteins of the G12/13 subfamily, which includes the α-subunits Gα12 and Gα13, stimulate the monomeric G protein RhoA through interaction with a distinct subset of Rho-specific guanine nucleotide exchange factors (RhoGEFs). The structural features that mediate interaction between Gα13 and RhoGEFs have been examined in crystallographic studies of the purified complex, whereas a Gα12:RhoGEF complex has not been reported. Several signaling responses and effector interactions appear unique to Gα12 or Gα13, despite their similarity in amino acid sequence. METHODS To comprehensively examine Gα12 for regions involved in RhoGEF interaction, we screened a panel of Gα12 cassette substitution mutants for binding to leukemia-associated RhoGEF (LARG) and for activation of serum response element mediated transcription. RESULTS We identified several cassette substitutions that disrupt Gα12 binding to LARG and the related p115RhoGEF. These Gα12 mutants also were impaired in activating serum response element mediated signaling, a Rho-dependent response. Most of these mutants matched corresponding regions of Gα13 reported to contact p115RhoGEF, but unexpectedly, several RhoGEF-uncoupling mutations were found within the N- and C-terminal regions of Gα12. Trypsin protection assays revealed several mutants in these regions as retaining conformational activation. In addition, charge substitutions near the Gα12 N-terminus selectively disrupted binding to LARG but not p115RhoGEF. CONCLUSIONS Several structural aspects of the Gα12:RhoGEF interface differ from the reported Gα13:RhoGEF complex, particularly determinants within the C-terminal α5 helix and structurally uncharacterized N-terminus of Gα12. Furthermore, key residues at the Gα12 N-terminus may confer selectivity for LARG as a downstream effector.
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Affiliation(s)
- Benjamin J Ritchie
- Department of Biology, University of North Carolina at Asheville, One University Heights, Asheville, NC 28804, USA.
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Siehler S. G12/13-dependent signaling of G-protein-coupled receptors: disease context and impact on drug discovery. Expert Opin Drug Discov 2013; 2:1591-604. [PMID: 23488903 DOI: 10.1517/17460441.2.12.1591] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/05/2022]
Abstract
G-protein-coupled receptors (GPCRs) transmit extracellular signals across the plasma membrane via intracellular activation of heterotrimeric G proteins. The signal transduction pathways of Gs, Gi and Gq protein families are widely studied, whereas signaling properties of G12 proteins are only emerging. Many GPCRs were found to couple to G12/13 proteins in addition to coupling to one or more other types of G proteins. G12/13 proteins couple GPCRs to activation of the small monomeric GTPase RhoA. Activation of RhoA modulates various downstream effector systems relevant to diseases such as hypertension, artherosclerosis, asthma and cancer. GPCR screening assays exist for Gs-, Gi- and Gq-linked pathways, whereas a drug-screening assay for the G12-Rho pathway was developed only recently. The review gives an overview of the present understanding of the G12/13-related biology of GPCRs.
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Affiliation(s)
- Sandra Siehler
- Novartis Institutes for BioMedical Research Basel, Center for Proteomic Chemistry, Novartis Pharma AG, WSJ-88.2.05, 4002 Basel, Switzerland +41 61 324 8946 ; +41 61 324 2870 ;
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Xiaolu D, Jing P, Fang H, Lifen Y, Liwen W, Ciliu Z, Fei Y. Role of p115RhoGEF in lipopolysaccharide-induced mouse brain microvascular endothelial barrier dysfunction. Brain Res 2011; 1387:1-7. [PMID: 21354111 DOI: 10.1016/j.brainres.2011.02.059] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/31/2010] [Revised: 02/15/2011] [Accepted: 02/18/2011] [Indexed: 12/24/2022]
Abstract
BACKGROUND In endothelial cells, exposure to lipopolysaccharide (LPS) results in barrier dysfunction through a complex signaling mechanism. The RhoA/Rho-kinase pathway plays a significant role in endothelial cell permeability. p115RhoGEF, a specific guanine nucleotide exchange factors (GEFs) activates RhoA, triggering RhoA-dependent cytoskeletal remodeling. However, little is known about the role of p115RhoGEF in LPS-induced brain endothelial barrier breakdown. We hypothesized that suppression of p115RhoGEF may inhibit activation of RhoA and prevent LPS-induced brain microvascular endothelial cell hyperpermeability. METHODS The cultured monolayer of bEnd.3 cells, an immortalized mouse brain endothelial cell line, was used in this study. bEnd.3 cells were pretreated with specific siRNA to knockdown p115RhoGEF or C3 transferase to inhibit RhoA activity, and then incubated with LPS (5μg/ml). The degree of RhoA activation was determined by a Rhotekin-based pull-down assay, and expression of p115RhoGEF, zonula occludens-1 (ZO-1), occludin and claudin-5 proteins were detected by Western blot analysis. The barrier function was measured by transendothelial electrical resistance (TEER). F-actin cytoskeleton was visualized by Rhodamine-phalloidin staining. RESULTS The expression level of p115RhoGEF protein was significantly increased in LPS-treated bEnd.3 cells. The activity of RhoA was enhanced after LPS stimulation and pretreatment with p115RhoGEF siRNA or exoenzyme C3 transferase reduced RhoA activation significantly as shown by the pull-down assay. Furthermore, depletion of p115RhoGEF partially prevented the LPS-induced decrease in TEER, stress fiber formation and tight junction proteins degradation. CONCLUSIONS These results suggest that p115RhoGEF is important for LPS signaling to RhoA and LPS-induced endothelial barrier dysfunction, providing new insight into the function of RhoGEFs in inflammation.
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Affiliation(s)
- Deng Xiaolu
- Department of Pediatrics, Xiangya Hospital, Central South University, Changsha 410008, China
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26
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Distribution of endogenous farnesyl pyrophosphate and four species of lysophosphatidic acid in rodent brain. Int J Mol Sci 2010; 11:3965-76. [PMID: 21152313 PMCID: PMC2996792 DOI: 10.3390/ijms11103965] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/24/2010] [Revised: 10/12/2010] [Accepted: 10/13/2010] [Indexed: 02/02/2023] Open
Abstract
Lysophosphatidic acid (LPA) is the umbrella term for lipid signaling molecules that share structural homology and activate the family of LPA receptors. Farnesyl Pyrophosphate (FPP) is commonly known as an intermediate in the synthesis of steroid hormones; however, its function as a signaling lipid is beginning to be explored. FPP was recently shown to an activator of the G-protein coupled receptor 92 (also known as LPA5) of the calcium channel TRPV3. The LPA receptors (including GPR92) are associated with the signal transduction of noxious stimuli, however, very little is known about the distribution of their signaling ligands (LPAs and FPP) in the brain. Here, using HPLC/MS/MS, we developed extraction and analytical methods for measuring levels of FPP and 4 species of LPA (palmitoyl, stearoyl, oleoyl and arachidonoyl-sn-glycerol-3 phosphate) in rodent brain. Relative distributions of each of the five compounds was significantly different across the brain suggesting divergent functionality for each as signaling molecules based on where and how much of each is being produced. Brainstem, midbrain, and thalamus contained the highest levels measured for each compound, though none in the same ratios while relatively small amounts were produced in cortex and cerebellum. These data provide a framework for investigations into functional relationships of these lipid ligands in specific brain areas, many of which are associated with the perception of pain.
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Medlin MD, Staus DP, Dubash AD, Taylor JM, Mack CP. Sphingosine 1-phosphate receptor 2 signals through leukemia-associated RhoGEF (LARG), to promote smooth muscle cell differentiation. Arterioscler Thromb Vasc Biol 2010; 30:1779-86. [PMID: 20702813 DOI: 10.1161/atvbaha.110.209395] [Citation(s) in RCA: 38] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/30/2023]
Abstract
OBJECTIVE The goals of this study were to identify the signaling pathway by which sphingosine 1-phosphate (S1P) activates RhoA in smooth muscle cells (SMC) and to evaluate the contribution of this pathway to the regulation of SMC phenotype. METHODS AND RESULTS Using a combination of receptor-specific agonists and antagonists we identified S1P receptor 2 (S1PR2) as the major S1P receptor subtype that regulates SMC differentiation marker gene expression. Based on the known coupling properties of S1PR2 and our demonstration that overexpression of Galpha(12) or Galpha(13) increased SMC-specific promoter activity, we next tested whether the effects of S1P in SMC were mediated by the regulator of G protein-signaling-Rho guanine exchange factors (RGS-RhoGEFs) (leukemia-associated RhoGEF [LARG], PDZ-RhoGEF [PRG], RhoGEF [p115]). Although each of the RGS-RhoGEFs enhanced actin polymerization, myocardin-related transcription factor-A nuclear localization, and SMC-specific promoter activity when overexpressed in 10T1/2 cells, LARG exhibited the most robust effect and was the only RGS-RhoGEF activated by S1P in SMC. Importantly, siRNA-mediated depletion of LARG significantly inhibited the activation of RhoA and SMC differentiation marker gene expression by S1P. Knockdown of LARG had no effect on SMC proliferation but promoted SMC migration as measured by scratch wound and transwell assays. CONCLUSIONS These data indicate that S1PR2-dependent activation of RhoA in SMC is mediated by LARG and that this signaling mechanism promotes the differentiated SMC phenotype.
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Affiliation(s)
- Matt D Medlin
- Department of Pathology, University of North Carolina, Chapel Hill, NC, USA
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28
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Bear MD, Li M, Liu Y, Giel-Moloney MA, Fanburg BL, Toksoz D. The Lbc Rho guanine nucleotide exchange factor α-catulin axis functions in serotonin-induced vascular smooth muscle cell mitogenesis and RhoA/ROCK activation. J Biol Chem 2010; 285:32919-32926. [PMID: 20696764 DOI: 10.1074/jbc.m109.062513] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Serotonin (5-hydroxytryptamine, 5-HT) is mitogenic for several cell types including pulmonary arterial smooth muscle cells (PASMC), and is associated with the abnormal vascular smooth muscle remodeling that occurs in pulmonary arterial hypertension. RhoA/Rho kinase (ROCK) function is required for 5-HT-induced PASMC mitogenesis, and 5-HT activates RhoA; however, the signaling steps are poorly defined. Rho guanine nucleotide exchange factors (Rho GEFs) transduce extracellular signals to Rho, and we found that 5-HT treatment of PASMC led to increased membrane-associated Lbc Rho GEF, suggesting modulation by 5-HT. Lbc knockdown by siRNA attenuated 5-HT-induced thymidine uptake in PASMC, indicating a role in PASMC mitogenesis. 5-HT triggered Rho-dependent serum response factor-mediated reporter activation in PASMC, and this was reduced by Lbc depletion. Lbc knockdown reduced 5-HT-induced RhoA/ROCK activation, but not p42/44 ERK MAP kinase activation, suggesting that Lbc is an intermediary between 5-HT and RhoA/ROCK, but not ERK. 5-HT stimulation of PASMC led to increased association between Lbc, RhoA, and the α-catulin scaffold. Furthermore, α-catulin knockdown attenuated 5-HT-induced PASMC thymidine uptake. 5-HT-induced PASMC mitogenesis was reduced by dominant-negative G(q) protein, suggesting cooperation with Lbc/α-catulin. These results for the first time define a Rho GEF involved in vascular smooth muscle cell growth and serotonin signaling, and suggest that Lbc Rho GEF family members play distinct roles. Thus, the Lbc/α-catulin axis participates in 5-HT-induced PASMC mitogenesis and RhoA/ROCK signaling, and may be an interventional target in diseases involving vascular smooth muscle remodeling.
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Affiliation(s)
- Michael D Bear
- From the Division of Pulmonary and Critical Care, Tupper Research Institute, Tufts Medical Center, Boston, Massachusetts 02111
| | - Min Li
- From the Division of Pulmonary and Critical Care, Tupper Research Institute, Tufts Medical Center, Boston, Massachusetts 02111
| | - Yinglin Liu
- From the Division of Pulmonary and Critical Care, Tupper Research Institute, Tufts Medical Center, Boston, Massachusetts 02111
| | - Maryann A Giel-Moloney
- Department of Physiology, Tufts University School of Medicine, Boston, Massachusetts 02111
| | - Barry L Fanburg
- From the Division of Pulmonary and Critical Care, Tupper Research Institute, Tufts Medical Center, Boston, Massachusetts 02111
| | - Deniz Toksoz
- From the Division of Pulmonary and Critical Care, Tupper Research Institute, Tufts Medical Center, Boston, Massachusetts 02111.
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Aittaleb M, Boguth CA, Tesmer JJG. Structure and function of heterotrimeric G protein-regulated Rho guanine nucleotide exchange factors. Mol Pharmacol 2009; 77:111-25. [PMID: 19880753 DOI: 10.1124/mol.109.061234] [Citation(s) in RCA: 115] [Impact Index Per Article: 7.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022] Open
Abstract
Activation of certain classes of G protein-coupled receptors (GPCRs) can lead to alterations in the actin cytoskeleton, gene transcription, cell transformation, and other processes that are known to be regulated by Rho family small-molecular-weight GTPases. Although these responses can occur indirectly via cross-talk from canonical heterotrimeric G protein cascades, it has recently been demonstrated that Dbl family Rho guanine nucleotide exchange factors (RhoGEFs) can serve as the direct downstream effectors of heterotrimeric G proteins. Heterotrimeric Galpha(12/13), Galpha(q), and Gbetagamma subunits are each now known to directly bind and regulate RhoGEFs. Atomic structures have recently been determined for several of these RhoGEFs and their G protein complexes, providing fresh insight into the molecular mechanisms of signal transduction between GPCRs and small molecular weight G proteins. This review covers what is currently known about the structure, function, and regulation of these recently recognized effectors of heterotrimeric G proteins.
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McCoy KL, Hepler JR. Regulators of G protein signaling proteins as central components of G protein-coupled receptor signaling complexes. PROGRESS IN MOLECULAR BIOLOGY AND TRANSLATIONAL SCIENCE 2009; 86:49-74. [PMID: 20374713 DOI: 10.1016/s1877-1173(09)86003-1] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
The regulators of G protein signaling (RGS) proteins bind directly to G protein alpha (Gα) subunits to regulate the signaling functions of Gα and their linked G protein-coupled receptors (GPCRs). Recent studies indicate that RGS proteins also interact with GPCRs, not just G proteins, to form preferred functional pairs. Interactions between GPCRs and RGS proteins may be direct or indirect (via a linker protein) and are dictated by the receptors, rather than the linked G proteins. Emerging models suggest that GPCRs serve as platforms for assembling an overlapping and distinct constellation of signaling proteins that perform receptor-specific signaling tasks. Compelling evidence now indicates that RGS proteins are central components of these GPCR signaling complexes. This review will outline recent discoveries of GPCR/RGS pairs as well as new data in support of the idea that GPCRs serve as platforms for the formation of multiprotein signaling complexes.
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Affiliation(s)
- Kelly L McCoy
- Department of Pharmacology, G205 Rollins Research Center, Emory University School of Medicine, Atlanta, Georgia 30322, USA
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31
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Xiao L, Eto M, Kazanietz MG. ROCK mediates phorbol ester-induced apoptosis in prostate cancer cells via p21Cip1 up-regulation and JNK. J Biol Chem 2009; 284:29365-75. [PMID: 19667069 DOI: 10.1074/jbc.m109.007971] [Citation(s) in RCA: 38] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023] Open
Abstract
It is established that androgen-dependent prostate cancer cells undergo apoptosis upon treatment with phorbol esters and related analogs, an effect primarily mediated by PKCdelta. Treatment of LNCaP prostate cancer cells with phorbol 12-myristate 13-acetate (PMA) causes a strong and sustained activation of RhoA and its downstream effector ROCK (Rho kinase) as well as the formation of stress fibers. These effects are impaired in cells subjected to PKCdelta RNA interference depletion. Functional studies revealed that expression of a dominant negative RhoA mutant or treatment with the ROCK inhibitor Y-27632 inhibits the apoptotic effect of PMA in LNCaP cells. Remarkably, the cytoskeleton inhibitors cytochalasin B and blebbistatin blocked not only PMA-induced apoptosis but also the activation of JNK, a mediator of the cell death effect by the phorbol ester. In addition, we found that up-regulation of the cell cycle inhibitor p21(Cip1) is required for PMA-induced apoptosis and that inhibitors of ROCK or the cytoskeleton organization prevent p21(Cip1) induction. Real time PCR analysis and reporter gene assay revealed that PMA induces p21(Cip1) transcriptionally in a ROCK- and cytoskeleton-dependent manner. p21(Cip1) promoter analysis revealed that PMA induction is dependent on Sp1 elements in the p21(Cip1) promoter but independent of p53. Taken together, our studies implicate ROCK-mediated up-regulation of p21(Cip1) and the cytoskeleton in PKCdelta-dependent apoptosis in prostate cancer cells.
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Affiliation(s)
- Liqing Xiao
- Department of Pharmacology, University of Pennsylvania School of Medicine, Philadelphia, Pennsylvania 19104-6160, USA
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32
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A conserved hydrophobic surface of the LARG pleckstrin homology domain is critical for RhoA activation in cells. Cell Signal 2009; 21:1569-78. [PMID: 19560536 DOI: 10.1016/j.cellsig.2009.06.003] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/26/2009] [Accepted: 06/16/2009] [Indexed: 01/23/2023]
Abstract
Leukemia associated Rho guanine nucleotide exchange factor (LARG) activates RhoA in response to signals received by specific classes of cell surface receptors. The catalytic core of LARG is a Dbl homology (DH) domain whose activity is modulated by an adjacent pleckstrin homology (PH) domain. In this study, we used a transcriptional assay and confocal microscopy to examine the roles of several novel structural features of the LARG DH/PH domains, including a conserved and exposed hydrophobic patch on the PH domain that mediates protein-protein interactions in crystal structures of LARG and its close homolog PDZ-RhoGEF. Mutation of the hydrophobic patch has no effect on nucleotide exchange activity in vitro, but abolished the ability of LARG to activate RhoA and to induce stress fiber formation in cultured cells. The activity of these mutants could be rescued by fusion with exogenous membrane-targeting domains. However, because membrane recruitment by activated G alpha(13) subunits was not sufficient to rescue activity of a hydrophobic patch mutant, the LARG PH domain cannot solely contribute to membrane targeting. Instead, it seems likely that the domain is involved in regulatory interactions with other proteins near the membrane surface. We also show that the hydrophobic patch of the PH domain is likely important for the activity of all Lbc subfamily RhoGEFs.
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33
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Hurst JH, Hooks SB. Regulator of G-protein signaling (RGS) proteins in cancer biology. Biochem Pharmacol 2009; 78:1289-97. [PMID: 19559677 DOI: 10.1016/j.bcp.2009.06.028] [Citation(s) in RCA: 125] [Impact Index Per Article: 8.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/28/2009] [Revised: 06/16/2009] [Accepted: 06/18/2009] [Indexed: 01/09/2023]
Abstract
The regulator of G-protein signaling (RGS) family is a diverse group of multifunctional proteins that regulate cellular signaling events downstream of G-protein coupled receptors (GPCRs). In recent years, GPCRs have been linked to the initiation and progression of multiple cancers; thus, regulators of GPCR signaling are also likely to be important to the pathophysiology of cancer. This review highlights recent studies detailing changes in RGS transcript expression during oncogenesis, single nucleotide polymorphisms in RGS proteins linked to lung and bladder cancers, and specific roles for RGS proteins in multiple cancer types.
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Affiliation(s)
- Jillian H Hurst
- Department of Pharmaceutical and Biomedical Sciences, College of Pharmacy, University of Georgia, Athens, GA 30602, USA
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Xie Y, Wolff DW, Wei T, Wang B, Deng C, Kirui JK, Jiang H, Qin J, Abel PW, Tu Y. Breast cancer migration and invasion depend on proteasome degradation of regulator of G-protein signaling 4. Cancer Res 2009; 69:5743-51. [PMID: 19549919 DOI: 10.1158/0008-5472.can-08-3564] [Citation(s) in RCA: 108] [Impact Index Per Article: 7.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
Aberrant signaling through G-protein coupled receptors promotes metastasis, the major cause of breast cancer death. We identified regulator of G-protein signaling 4 (RGS4) as a novel suppressor of breast cancer migration and invasion, important steps of metastatic cascades. By blocking signals initiated through G(i)-coupled receptors, such as protease-activated receptor 1 and CXC chemokine receptor 4, RGS4 disrupted Rac1-dependent lamellipodia formation, a key step involved in cancer migration and invasion. RGS4 has GTPase-activating protein (GAP) activity, which inhibits G-protein coupled receptor signaling by deactivating G-proteins. An RGS4 GAP-deficient mutant failed to inhibit migration and invasion of breast cancer cells in both in vitro assays and a mouse xenograft model. Interestingly, both established breast cancer cell lines and human breast cancer specimens showed that the highest levels of RGS4 protein were expressed in normal breast epithelia and that RGS4 down-regulation by proteasome degradation is an index of breast cancer invasiveness. Proteasome blockade increased endogenous RGS4 protein to levels that markedly inhibit breast cancer cell migration and invasion, which was reversed by an RGS4-targeted short hairpin RNA. Our findings point to the existence of a mechanism for posttranslational regulation of RGS4 function, which may have important implications for the acquisition of a metastatic phenotype by breast cancer cells. Preventing degradation of RGS4 protein should attenuate aberrant signal inputs from multiple G(i)-coupled receptors, thereby retarding the spread of breast cancer cells and making them targets for surgery, radiation, and immune treatment.
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Affiliation(s)
- Yan Xie
- Department of Pharmacology, Creighton University School of Medicine, Omaha, Nebraska 68178, USA
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35
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Hata K, Kaibuchi K, Inagaki S, Yamashita T. Unc5B associates with LARG to mediate the action of repulsive guidance molecule. ACTA ACUST UNITED AC 2009; 184:737-50. [PMID: 19273616 PMCID: PMC2686409 DOI: 10.1083/jcb.200807029] [Citation(s) in RCA: 74] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/03/2022]
Abstract
Neuronal axons are guided by attractive and repulsive cues in their local environment. Because the repulsive guidance molecule A (RGMa) was originally identified as an axon repellent in the visual system, diverse functions in the developing and adult central nervous system have been ascribed to it. RGMa binding to its receptor neogenin induces RhoA activation, leading to inhibitory/repulsive behavior and collapse of the neuronal growth cone. However, the precise mechanisms that regulate RhoA activation are poorly understood. In this study, we show that Unc5B, a member of the netrin receptor family, interacts with neogenin as a coreceptor for RGMa. Moreover, leukemia-associated guanine nucleotide exchange factor (LARG) associates with Unc5B to transduce the RhoA signal. Focal adhesion kinase (FAK) is involved in RGMa-induced tyrosine phosphorylation of LARG as well as RhoA activation. These findings uncover the molecular basis for diverse functions mediated by RGMa.
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Affiliation(s)
- Katsuhiko Hata
- Department of Molecular Neuroscience, Osaka University Graduate School of Medicine, Suita, Osaka 565-0871, Japan.
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36
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Wang D, Paria BC, Zhang Q, Karpurapu M, Li Q, Gerthoffer WT, Nakaoka Y, Rao GN. A role for Gab1/SHP2 in thrombin activation of PAK1: gene transfer of kinase-dead PAK1 inhibits injury-induced restenosis. Circ Res 2009; 104:1066-75. [PMID: 19359598 DOI: 10.1161/circresaha.109.196691] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
To understand the role of epidermal growth factor receptor (EGFR) transactivation in G protein-coupled receptor (GPCR) agonist-induced signaling events, we have studied the capacity of thrombin in the activation of Gab1-SHP2 in vascular smooth muscle cells (VSMCs). Thrombin activated both Gab1 and SHP2 in EGFR-dependent manner. Similarly, thrombin induced Rac1 and Cdc42 activation, and these responses were suppressed when either Gab1 or SHP2 stimulation is blocked. Thrombin also induced PAK1 activation in a time- and EGFR-Gab1-SHP2-Rac1/Cdc42-dependent manner. Inhibition of activation of EGFR, Gab1, SHP2, Rac1, Cdc42, or PAK1 by pharmacological or genetic approaches attenuated thrombin-induced VSMC stress fiber formation and motility. Thrombin activated RhoA in a time-dependent manner in VSMCs. LARG, a RhoA-specific GEF (guanine nucleotide exchange factor), was found to be associated with Gab1 and siRNA-mediated depletion of its levels suppressed RhoA, Rac1 and PAK1 activation. Dominant negative mutant-mediated interference of RhoA activation inhibited thrombin-induced Rac1 and PAK1 stimulation in VSMCs and their stress fiber formation and migration. Balloon injury induced PAK1 activity and interference with its activation led to attenuation of SMC migration from media to intima, resulting in reduced neointima formation and increased lumen size. Inhibition of thrombin signaling by recombinant hirudin also blocked balloon injury-induced EGFR tyrosine phosphorylation and PAK1 activity. These results show that thrombin-mediated PAK1 activation plays a crucial role in vascular wall remodeling and it could be a potential target for drug development against these vascular lesions.
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MESH Headings
- Angioplasty, Balloon/adverse effects
- Animals
- Carotid Artery Diseases/enzymology
- Carotid Artery Diseases/etiology
- Carotid Artery Diseases/genetics
- Carotid Artery Diseases/therapy
- Carotid Stenosis/enzymology
- Carotid Stenosis/etiology
- Carotid Stenosis/genetics
- Carotid Stenosis/prevention & control
- Cell Movement
- Cells, Cultured
- Disease Models, Animal
- ErbB Receptors/antagonists & inhibitors
- ErbB Receptors/metabolism
- Fibrinolytic Agents/pharmacology
- Gene Transfer Techniques
- Genetic Therapy/methods
- Guanine Nucleotide Exchange Factors/metabolism
- Hirudins/pharmacology
- Humans
- Muscle, Smooth, Vascular/drug effects
- Muscle, Smooth, Vascular/enzymology
- Muscle, Smooth, Vascular/pathology
- Mutation
- Phosphoproteins/genetics
- Phosphoproteins/metabolism
- Phosphorylation
- Protein Kinase Inhibitors/pharmacology
- Protein Tyrosine Phosphatase, Non-Receptor Type 11/genetics
- Protein Tyrosine Phosphatase, Non-Receptor Type 11/metabolism
- Quinazolines
- RNA Interference
- RNA, Small Interfering/metabolism
- Rats
- Rho Guanine Nucleotide Exchange Factors
- Stress Fibers/enzymology
- Thrombin/antagonists & inhibitors
- Thrombin/metabolism
- Time Factors
- Transfection
- Tyrphostins/pharmacology
- cdc42 GTP-Binding Protein/metabolism
- p21-Activated Kinases/genetics
- p21-Activated Kinases/metabolism
- rac1 GTP-Binding Protein/metabolism
- rhoA GTP-Binding Protein/metabolism
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Affiliation(s)
- Dong Wang
- Department of Physiology, University of Tennessee Health Science Center, 894 Union Ave., Memphis, TN 38163, USA
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37
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Abstract
G protein-coupled receptors (GPCRs) represent a large family of seven transmembrane receptors, which communicate extracellular signals into the cellular lumen. The human genome contains 720-800 GPCRs, and their diverse signal characteristics are determined by their specific tissue and subcellular expression profiles, as well as their coupling profile to the various G protein families (G(s), G(i), G(q), G(12)). The G protein coupling pattern links GPCR activation to the specific downstream effector pathways. G(12/13) signalling of GPCRs has been studied only recently in more detail, and involves activation of RhoGTPase nucleotide exchange factors (RhoGEFs). Four mammalian RhoGEFs regulated by G(12/13) proteins are known: p115-RhoGEF, PSD-95/Disc-large/ZO-1 homology-RhoGEF, leukemia-associated RhoGEF and lymphoid blast crisis-RhoGEF. These link GPCRs to activation of the small monomeric GTPase RhoA, and other downstream effectors. Misregulated G(12/13) signalling is involved in multiple pathophysiological conditions such as cancer, cardiovascular diseases, arterial and pulmonary hypertension, and bronchial asthma. Specific targeting of G(12/13) signalling-related diseases of GPCRs hence provides novel therapeutic approaches. Assays to quantitatively measure GPCR-mediated activation of G(12/13) are only emerging, and are required to understand the G(12/13)-linked pharmacology. The review gives an overview of G(12/13) signalling of GPCRs with a focus on RhoGEF proteins as the immediate mediators of G(12/13) activation.
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Affiliation(s)
- Sandra Siehler
- Novartis Institutes for BioMedical Research Basel, Center for Proteomic Chemistry, Novartis Pharma AG, Basel, Switzerland.
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38
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Suzuki N, Hajicek N, Kozasa T. Regulation and physiological functions of G12/13-mediated signaling pathways. Neurosignals 2009; 17:55-70. [PMID: 19212140 DOI: 10.1159/000186690] [Citation(s) in RCA: 75] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/10/2008] [Accepted: 10/10/2008] [Indexed: 12/12/2022] Open
Abstract
Accumulating data indicate that G12 subfamily (Galpha12/13)-mediated signaling pathways play pivotal roles in a variety of physiological processes, while aberrant regulation of this pathway has been identified in various human diseases. It has been demonstrated that Galpha12/13-mediated signals form networks with other signaling proteins at various levels, from cell surface receptors to transcription factors, to regulate cellular responses. Galpha12/13 have slow rates of nucleotide exchange and GTP hydrolysis, and specifically target RhoGEFs containing an amino-terminal RGS homology domain (RH-RhoGEFs), which uniquely function both as a GAP and an effector for Galpha12/13. In this review, we will focus on the mechanisms regulating the Galpha12/13 signaling system, particularly the Galpha12/13-RH-RhoGEF-Rho pathway, which can regulate a wide variety of cellular functions from migration to transformation.
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Affiliation(s)
- Nobuchika Suzuki
- Laboratory of Systems Biology and Medicine, Research Center for Advanced Science and Technology, The University of Tokyo, Tokyo, Japan.
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39
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Evelyn CR, Ferng T, Rojas RJ, Larsen MJ, Sondek J, Neubig RR. High-throughput screening for small-molecule inhibitors of LARG-stimulated RhoA nucleotide binding via a novel fluorescence polarization assay. ACTA ACUST UNITED AC 2009; 14:161-72. [PMID: 19196702 DOI: 10.1177/1087057108328761] [Citation(s) in RCA: 39] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/04/2023]
Abstract
Guanine nucleotide exchange factors (GEFs) stimulate guanine nucleotide exchange and the subsequent activation of Rho-family proteins in response to extracellular stimuli acting upon cytokine, tyrosine kinase, adhesion, integrin, and G-protein-coupled receptors (GPCRs). Upon Rho activation, several downstream events occur, such as morphological and cytoskeletal changes, motility, growth, survival, and gene transcription. The leukemia-associated RhoGEF (LARG) is a member of the regulators of G-protein signaling homology domain (RH) family of GEFs originally identified as a result of chromosomal translocation in acute myeloid leukemia. Using a novel fluorescence polarization guanine nucleotide-binding assay using BODIPY-Texas Red-GTPgammaS (BODIPY-TR-GTPgammaS), the authors performed a 10,000-compound high-throughput screen for inhibitors of LARG-stimulated RhoA nucleotide binding. Five compounds identified from the high-throughput screen were confirmed in a nonfluorescent radioactive guanine nucleotide-binding assay measuring LARG-stimulated [( 35)S] GTPgammaS binding to RhoA, thus ruling out nonspecific fluorescent effects. All 5 compounds selectively inhibited LARG-stimulated RhoA [( 35)S] GTPgammaS binding but had little to no effect on RhoA or Galpha( o) [(35)S] GTPgammaS binding. Therefore, these 5 compounds should serve as promising starting points for the development of small-molecule inhibitors of LARG-mediated nucleotide exchange as both pharmacological tools and therapeutics. In addition, the fluorescence polarization guanine nucleotide-binding assay described here should serve as a useful approach for both high-throughput screening and general biological applications.
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Affiliation(s)
- Chris R Evelyn
- Department of Pharmacology, University of Michigan Medical Center, Ann Arbor, Michigan 48109-0632, USA
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Dubash AD, Menold MM, Samson T, Boulter E, García-Mata R, Doughman R, Burridge K. Chapter 1 Focal Adhesions: New Angles on an Old Structure. INTERNATIONAL REVIEW OF CELL AND MOLECULAR BIOLOGY 2009; 277:1-65. [DOI: 10.1016/s1937-6448(09)77001-7] [Citation(s) in RCA: 66] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/04/2022]
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Ye X. Lysophospholipid signaling in the function and pathology of the reproductive system. Hum Reprod Update 2008; 14:519-36. [PMID: 18562325 DOI: 10.1093/humupd/dmn023] [Citation(s) in RCA: 94] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/31/2023] Open
Abstract
BACKGROUND Lysophosphatidic acid (LPA) and sphingosine-1-phosphate (S1P) are two prominent signaling lysophospholipids (LPs) exerting their functions through a group of G protein-coupled receptors (GPCRs). This review covers current knowledge of the LP signaling in the function and pathology of the reproductive system. METHODS PubMed was searched up to May 2008 for papers on lysophospholipids/LPA/S1P/LPC/SPC in combination with each part of the reproductive system, such as testis/ovary/uterus. RESULTS LPA and SIP are found in significant amounts in serum and other biological fluids. To date, 10 LP receptors have been identified, including LPA(1-5) and S1P(1-5). In vitro and in vivo studies from the past three decades have demonstrated or suggested the physiological functions of LP signaling in reproduction, such as spermatogenesis, male sexual function, ovarian function, fertilization, early embryo development, embryo spacing, implantation, decidualization, pregnancy maintenance and parturition, as well as pathological roles in ovary, cervix, mammary gland and prostate cancers. CONCLUSIONS Receptor knock-out and other studies indicate tissue-specific and receptor-specific functions of LP signaling in reproduction. More comprehensive studies are required to define mechanisms of LP signaling and explore the potential use as a therapeutic target.
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Affiliation(s)
- Xiaoqin Ye
- Department of Physiology and Pharmacology, College of Veterinary Medicine, University of Georgia, Athens, GA 30602, USA.
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Loberg RD, Tantivejkul K, Craig M, Neeley CK, Pienta KJ. PAR1-mediated RhoA activation facilitates CCL2-induced chemotaxis in PC-3 cells. J Cell Biochem 2007; 101:1292-300. [PMID: 17492768 DOI: 10.1002/jcb.21252] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Abstract
Patients with advanced prostate cancer often exhibit increased activation of the coagulation system. The key activator of the coagulation cascade is the serine protease thrombin which is capable of eliciting numerous cellular responses. We previously reported that the thrombin receptor PAR1 is overexpressed in prostate cancer. To investigate further the role of PAR1 in prostate cancer metastasis, we examined the effects of thrombin activation on cell adhesion and motility in PC-3 prostate cancer cells. Activation of PAR1-induced dynamic cytoskeletal reorganization and reduced PC-3 binding to collagen I, collagen IV, and laminin (P < 0.01) but not fibronectin. Expression of the cell surface integrin receptors did not change as assessed by flow cytometry. Immunofluorescence microscopy revealed that PAR1 stimulation caused reorganization of the focal adhesions, suggesting that PAR1 activation in PC-3 cells may be modulating cell adhesion through integrin function but not expression. Furthermore, RhoA was activated upon stimulation with thrombin with subsequent cell contraction, decreased cell adhesion, and induced migration towards monocyte chemoattractant protein 1 (MCP-1; CCL2). Thus, it appears that thrombin stimulation plays a role in prostate cancer metastasis by decreasing cell adhesion to the extracellular matrix and positioning the cell in a "ready state" for migration in response to a chemotactic signal. Further exploration is needed to determine whether PAR1 activation affects other signaling pathways involved in prostate cancer.
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Affiliation(s)
- Robert D Loberg
- Department of Urology, University of Michigan Comprehensive Cancer Center, Ann Arbor, Michigan 48109, USA.
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Evelyn CR, Wade SM, Wang Q, Wu M, Iñiguez-Lluhí JA, Merajver SD, Neubig RR. CCG-1423: a small-molecule inhibitor of RhoA transcriptional signaling. Mol Cancer Ther 2007; 6:2249-60. [PMID: 17699722 DOI: 10.1158/1535-7163.mct-06-0782] [Citation(s) in RCA: 161] [Impact Index Per Article: 9.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
Lysophosphatidic acid receptors stimulate a Galpha(12/13)/RhoA-dependent gene transcription program involving the serum response factor (SRF) and its coactivator and oncogene, megakaryoblastic leukemia 1 (MKL1). Inhibitors of this pathway could serve as useful biological probes and potential cancer therapeutic agents. Through a transcription-based high-throughput serum response element-luciferase screening assay, we identified two small-molecule inhibitors of this pathway. Mechanistic studies on the more potent CCG-1423 show that it acts downstream of Rho because it blocks SRE.L-driven transcription stimulated by Galpha(12)Q231L, Galpha(13)Q226L, RhoA-G14V, and RhoC-G14V. The ability of CCG-1423 to block transcription activated by MKL1, but not that induced by SRF-VP16 or GAL4-VP16, suggests a mechanism targeting MKL/SRF-dependent transcriptional activation that does not involve alterations in DNA binding. Consistent with its role as a Rho/SRF pathway inhibitor, CCG-1423 displays activity in several in vitro cancer cell functional assays. CCG-1423 potently (<1 mumol/L) inhibits lysophosphatidic acid-induced DNA synthesis in PC-3 prostate cancer cells, and whereas it inhibits the growth of RhoC-overexpressing melanoma lines (A375M2 and SK-Mel-147) at nanomolar concentrations, it is less active on related lines (A375 and SK-Mel-28) that express lower levels of Rho. Similarly, CCG-1423 selectively stimulates apoptosis of the metastasis-prone, RhoC-overexpressing melanoma cell line (A375M2) compared with the parental cell line (A375). CCG-1423 inhibited Rho-dependent invasion by PC-3 prostate cancer cells, whereas it did not affect the Galpha(i)-dependent invasion by the SKOV-3 ovarian cancer cell line. Thus, based on its profile, CCG-1423 is a promising lead compound for the development of novel pharmacologic tools to disrupt transcriptional responses of the Rho pathway in cancer.
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Affiliation(s)
- Chris R Evelyn
- Department of Pharmacology, University of Michigan Medical Center, 1301 MSRB III, Room 2220D, 1150 West Medical Center Drive, Ann Arbor, MI 48109-0632, USA
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Appert-Collin A, Cotecchia S, Nenniger-Tosato M, Pedrazzini T, Diviani D. The A-kinase anchoring protein (AKAP)-Lbc-signaling complex mediates alpha1 adrenergic receptor-induced cardiomyocyte hypertrophy. Proc Natl Acad Sci U S A 2007; 104:10140-5. [PMID: 17537920 PMCID: PMC1891209 DOI: 10.1073/pnas.0701099104] [Citation(s) in RCA: 79] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/18/2023] Open
Abstract
In response to various pathological stresses, the heart undergoes a pathological remodeling process that is associated with cardiomyocyte hypertrophy. Because cardiac hypertrophy can progress to heart failure, a major cause of lethality worldwide, the intracellular signaling pathways that control cardiomyocyte growth have been the subject of intensive investigation. It has been known for more than a decade that the small molecular weight GTPase RhoA is involved in the signaling pathways leading to cardiomyocyte hypertrophy. Although some of the hypertrophic pathways activated by RhoA have now been identified, the identity of the exchange factors that modulate its activity in cardiomyocytes is currently unknown. In this study, we show that AKAP-Lbc, an A-kinase anchoring protein (AKAP) with an intrinsic Rho-specific guanine nucleotide exchange factor activity, is critical for activating RhoA and transducing hypertrophic signals downstream of alpha1-adrenergic receptors (ARs). In particular, our results indicate that suppression of AKAP-Lbc expression by infecting rat neonatal ventricular cardiomyocytes with lentiviruses encoding AKAP-Lbc-specific short hairpin RNAs strongly reduces both alpha1-AR-mediated RhoA activation and hypertrophic responses. Interestingly, alpha1-ARs promote AKAP-Lbc activation via a pathway that requires the alpha subunit of the heterotrimeric G protein G12. These findings identify AKAP-Lbc as the first Rho-guanine nucleotide exchange factor (GEF) involved in the signaling pathways leading to cardiomyocytes hypertrophy.
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Affiliation(s)
- Aline Appert-Collin
- *Département de Pharmacologie et de Toxicologie, Faculté de Biologie et de Médecine, Université de Lausanne, 1005 Lausanne, Switzerland; and
| | - Susanna Cotecchia
- *Département de Pharmacologie et de Toxicologie, Faculté de Biologie et de Médecine, Université de Lausanne, 1005 Lausanne, Switzerland; and
| | - Monique Nenniger-Tosato
- *Département de Pharmacologie et de Toxicologie, Faculté de Biologie et de Médecine, Université de Lausanne, 1005 Lausanne, Switzerland; and
| | - Thierry Pedrazzini
- Department of Medicine, University of Lausanne Medical School, 1011 Lausanne, Switzerland
| | - Dario Diviani
- *Département de Pharmacologie et de Toxicologie, Faculté de Biologie et de Médecine, Université de Lausanne, 1005 Lausanne, Switzerland; and
- To whom correspondence should be addressed at:
Département de Pharmacologie et de Toxicologie, Rue du Bugnon 27, 1005 Lausanne, Switzerland. E-mail:
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Rusovici R, Ghaleb A, Shim H, Yang VW, Chris Yun C. Lysophosphatidic acid prevents apoptosis of Caco-2 colon cancer cells via activation of mitogen-activated protein kinase and phosphorylation of Bad. Biochim Biophys Acta Gen Subj 2007; 1770:1194-203. [PMID: 17544220 PMCID: PMC1989128 DOI: 10.1016/j.bbagen.2007.04.008] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/18/2006] [Revised: 04/17/2007] [Accepted: 04/24/2007] [Indexed: 01/24/2023]
Abstract
Lysophosphatidic acids (LPA) exert growth factor-like effects through specific G protein-coupled receptors. The presence of different LPA receptors often determines the specific signaling mechanisms and the physiological consequences of LPA in different environments. Among the four members of the LPA receptor family, LPA(2) has been shown to be overexpressed in colon cancer suggesting that the signaling by LPA(2) may potentiate growth and survival of tumor cells. In this study, we examined the effect of LPA on survival of colon cancer cells using Caco-2 cells as a cell model system. LPA rescued Caco-2 cells from apoptosis elicited by the chemotherapeutic drug, etoposide. This protection was accompanied by abrogation of etoposide-induced stimulation of caspase activity via a mechanism dependent on Erk and PI3K. In contrast, perturbation of cellular signaling mediated by the LPA(2) receptor by knockdown of a scaffold protein NHERF2 abrogated the protective effect of LPA. Etoposide decreased the expression of Bcl-2, which was reversed by LPA. Etoposide decreased the phosphorylation level of the proapoptotic protein Bad in an Erk-dependent manner, without changing Bad expression. We further show that LPA treatment resulted in delayed activation of Erk. These results indicate that LPA protects Caco-2 cells from apoptotic insult by a mechanism involving Erk, Bad, and Bcl-2.
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Affiliation(s)
- Raluca Rusovici
- Division of Digestive Diseases, Department of Medicine, Emory University School of Medicine, Atlanta, GA
| | - Amr Ghaleb
- Division of Digestive Diseases, Department of Medicine, Emory University School of Medicine, Atlanta, GA
| | - Hyunsuk Shim
- Winship Cancer Institute, Emory University School of Medicine, Atlanta, GA
| | - Vincent W. Yang
- Division of Digestive Diseases, Department of Medicine, Emory University School of Medicine, Atlanta, GA
- Winship Cancer Institute, Emory University School of Medicine, Atlanta, GA
| | - C. Chris Yun
- Division of Digestive Diseases, Department of Medicine, Emory University School of Medicine, Atlanta, GA
- Department of Physiology, Emory University School of Medicine, Atlanta, GA
- Corresponding author: Tel: 1-404-712-2865,
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Sternweis PC, Carter AM, Chen Z, Danesh SM, Hsiung YF, Singer WD. Regulation of Rho guanine nucleotide exchange factors by G proteins. ADVANCES IN PROTEIN CHEMISTRY 2007; 74:189-228. [PMID: 17854659 DOI: 10.1016/s0065-3233(07)74006-8] [Citation(s) in RCA: 50] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
Monomeric Rho GTPases regulate cellular dynamics through remodeling of the cytoskeleton, modulation of immediate signaling pathways, and longer-term regulation of gene transcription. One family of guanine nucleotide exchange factors for Rho proteins (RhoGEFs) provides a direct pathway for regulation of RhoA by cell surface receptors coupled to heterotrimeric G proteins. Some of these RhoGEFs also contain RGS domains that can attenuate signaling by the G(12) and G(13) proteins. The regulation provided by these RhoGEFs is defined by their selective regulation by specific G proteins, phosphorylation by kinases, and potential localization with signaling partners. Evidence of their physiological importance is derived from gene knockouts in Drosophila and mice. Current understanding of the basic regulatory mechanisms of these RhoGEFs is discussed. An overview of identified interactions with other signaling proteins suggests the growing spectrum of their involvement in numerous signaling pathways.
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Affiliation(s)
- Paul C Sternweis
- Department of Pharmacology, University of Texas Southwestern Medical Center, Dallas, Texas 75390, USA
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Zhang H, Wang D, Sun H, Hall RA, Chris Yun C. MAGI-3 regulates LPA-induced activation of Erk and RhoA. Cell Signal 2006; 19:261-8. [PMID: 16904289 PMCID: PMC1995035 DOI: 10.1016/j.cellsig.2006.06.008] [Citation(s) in RCA: 48] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/30/2006] [Accepted: 06/29/2006] [Indexed: 12/25/2022]
Abstract
Lysophosphatidic acids (LPA) exert multiple biological effects through specific G protein-coupled receptors. The LPA-activated receptor subtype LPA(2) contains a carboxyl-terminal motif that allows interaction with PDZ domain-containing proteins, such as NHERF2 and PDZ-RhoGEF. To identify additional interacting partners of LPA(2), the LPA(2) carboxyl-terminus was used to screen a proteomic array of PDZ domains. In addition to the previously identified NHERF2, several additional LPA(2)-interacting PDZ domains were found. These included MAGI-2, MAGI-3 and neurabin. In the present work, we demonstrate the specific interaction between LPA(2) and MAGI-3, and the effects of MAGI-3 in colon cancer cells using SW480 as a cell model. MAGI-3 specifically bound to LPA(2), but not to LPA(1) and LPA(3). This interaction was mediated via the fifth PDZ domain of MAGI-3 interacting with the carboxyl-terminal 4 amino acids of LPA(2), and mutational alteration of the carboxyl-terminal sequences of LPA(2) severely attenuated its ability to bind MAGI-3. LPA(2) also associated with MAGI-3 in cells as determined by co-affinity purification. Overexpression of MAGI-3 in SW480 cells showed no apparent effect on LPA-induced activation of Erk and Akt. In contrast, silencing of MAGI-3 expression by siRNA drastically inhibited LPA-induced Erk activation, suggesting that the lack of an effect by overexpression was due to the high endogenous MAGI-3 level in these cells. Previous studies have shown that the cellular signaling elicited by LPA results in activation of the small GTPase RhoA by Galpha(12/13) - as well as Galpha(q)-dependent pathways. Overexpression of MAGI-3 stimulated LPA-induced RhoA activation, whereas silencing of MAGI-3 by siRNA resulted in a small but statistically significant decrease in RhoA activation. These results demonstrate that MAGI-3 interacts directly with LPA(2) and regulates the ability of LPA(2) to activate Erk and RhoA.
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Affiliation(s)
- Huanchun Zhang
- Department of Medicine, Emory University School of Medicine, Atlanta, GA 30322, USA
| | - Dongsheng Wang
- Department of Medicine, Emory University School of Medicine, Atlanta, GA 30322, USA
| | - Hong Sun
- Department of Medicine, Emory University School of Medicine, Atlanta, GA 30322, USA
| | - Randy A. Hall
- Department of Pharmacology, Emory University School of Medicine, Atlanta, GA 30322, USA
| | - C. Chris Yun
- Department of Medicine, Emory University School of Medicine, Atlanta, GA 30322, USA
- Department of Physiology, Emory University School of Medicine, Atlanta, GA 30322, USA
- * Corresponding author. Department of Medicine, Emory University School of Medicine, Atlanta, GA 30322, USA. Tel.: +1 404 712 2865; fax: +1 404 727 5767. E-mail address: (C.C. Yun)
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Neitzel KL, Hepler JR. Cellular mechanisms that determine selective RGS protein regulation of G protein-coupled receptor signaling. Semin Cell Dev Biol 2006; 17:383-9. [PMID: 16647283 DOI: 10.1016/j.semcdb.2006.03.002] [Citation(s) in RCA: 63] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/06/2023]
Abstract
Regulators of G protein signaling (RGS proteins) bind directly to activated Galpha subunits to inhibit their signaling. However, recent findings show that RGS proteins selectively regulate signaling by certain G protein-coupled receptors (GPCRs) in cells, irrespective of the coupled G protein. New studies support an emerging model that suggests RGS proteins utilize both direct and indirect mechanisms to form stable functional pairs with preferred GPCRs to selectively modulate the signaling functions of those receptors and linked G proteins. Here, we discuss these findings and their implications for established models of GPCR signaling.
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Affiliation(s)
- Karen L Neitzel
- Department of Pharmacology, Emory University School of Medicine, G205 Rollins Research Center, 1510 Clifton Road, Atlanta, GA 30322, USA
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49
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Abstract
Regulators of G-protein signalling (RGS) proteins are a large and diverse family initially identified as GTPase activating proteins (GAPs) of heterotrimeric G-protein Galpha-subunits. At least some can also influence Galpha activity through either effector antagonism or by acting as guanine nucleotide dissociation inhibitors (GDIs). As our understanding of RGS protein structure and function has developed, so has the realisation that they play roles beyond G-protein regulation. Such diversity of function is enabled by the variety of RGS protein structure and their ability to interact with other cellular molecules including phospholipids, receptors, effectors and scaffolds. The activity, sub-cellular distribution and expression levels of RGS proteins are dynamically regulated, providing a layer of complexity that has yet to be fully elucidated.
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Affiliation(s)
- Gary B Willars
- Department of Cell Physiology and Pharmacology, University of Leicester, University Road, Leicester LE1 9HN, UK.
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50
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Jenkins RG, Su X, Su G, Scotton CJ, Camerer E, Laurent GJ, Davis GE, Chambers RC, Matthay MA, Sheppard D. Ligation of protease-activated receptor 1 enhances alpha(v)beta6 integrin-dependent TGF-beta activation and promotes acute lung injury. J Clin Invest 2006; 116:1606-14. [PMID: 16710477 PMCID: PMC1462943 DOI: 10.1172/jci27183] [Citation(s) in RCA: 242] [Impact Index Per Article: 13.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/20/2005] [Accepted: 04/11/2006] [Indexed: 01/03/2023] Open
Abstract
Activation of latent TGF-beta by the alpha(v)beta6 integrin is a critical step in the development of acute lung injury. However, the mechanism by which alpha(v)beta6-mediated TGF-beta activation is regulated has not been identified. We show that thrombin, and other agonists of protease-activated receptor 1 (PAR1), activate TGF-beta in an alpha(v)beta6 integrin-specific manner. This effect is PAR1 specific and is mediated by RhoA and Rho kinase. Intratracheal instillation of the PAR1-specific peptide TFLLRN increases lung edema during high-tidal-volume ventilation, and this effect is completely inhibited by a blocking antibody against the alpha(v)beta6 integrin. Instillation of TFLLRN during high-tidal-volume ventilation is associated with increased pulmonary TGF-beta activation; however, this is not observed in Itgb6-/- mice. Furthermore, Itgb6-/- mice are also protected from ventilator-induced lung edema. We also demonstrate that pulmonary edema and TGF-beta activity are similarly reduced in Par1-/- mice following bleomycin-induced lung injury. These results suggest that PAR1-mediated enhancement of alpha(v)beta6-dependent TGF-beta activation could be one mechanism by which activation of the coagulation cascade contributes to the development of acute lung injury, and they identify PAR1 and the alpha(v)beta6 integrin as potential therapeutic targets in this condition.
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Affiliation(s)
- R. Gisli Jenkins
- Lung Biology Center, UCSF, San Francisco, California, USA.
Centre for Respiratory Research, University College London, London, United Kingdom.
Cardiovascular Research Institute, UCSF, San Francisco, California, USA.
Department of Pathology and Laboratory Medicine, Texas A&M University System Health Science Center, College Station, Texas, USA
| | - Xiao Su
- Lung Biology Center, UCSF, San Francisco, California, USA.
Centre for Respiratory Research, University College London, London, United Kingdom.
Cardiovascular Research Institute, UCSF, San Francisco, California, USA.
Department of Pathology and Laboratory Medicine, Texas A&M University System Health Science Center, College Station, Texas, USA
| | - George Su
- Lung Biology Center, UCSF, San Francisco, California, USA.
Centre for Respiratory Research, University College London, London, United Kingdom.
Cardiovascular Research Institute, UCSF, San Francisco, California, USA.
Department of Pathology and Laboratory Medicine, Texas A&M University System Health Science Center, College Station, Texas, USA
| | - Christopher J. Scotton
- Lung Biology Center, UCSF, San Francisco, California, USA.
Centre for Respiratory Research, University College London, London, United Kingdom.
Cardiovascular Research Institute, UCSF, San Francisco, California, USA.
Department of Pathology and Laboratory Medicine, Texas A&M University System Health Science Center, College Station, Texas, USA
| | - Eric Camerer
- Lung Biology Center, UCSF, San Francisco, California, USA.
Centre for Respiratory Research, University College London, London, United Kingdom.
Cardiovascular Research Institute, UCSF, San Francisco, California, USA.
Department of Pathology and Laboratory Medicine, Texas A&M University System Health Science Center, College Station, Texas, USA
| | - Geoffrey J. Laurent
- Lung Biology Center, UCSF, San Francisco, California, USA.
Centre for Respiratory Research, University College London, London, United Kingdom.
Cardiovascular Research Institute, UCSF, San Francisco, California, USA.
Department of Pathology and Laboratory Medicine, Texas A&M University System Health Science Center, College Station, Texas, USA
| | - George E. Davis
- Lung Biology Center, UCSF, San Francisco, California, USA.
Centre for Respiratory Research, University College London, London, United Kingdom.
Cardiovascular Research Institute, UCSF, San Francisco, California, USA.
Department of Pathology and Laboratory Medicine, Texas A&M University System Health Science Center, College Station, Texas, USA
| | - Rachel C. Chambers
- Lung Biology Center, UCSF, San Francisco, California, USA.
Centre for Respiratory Research, University College London, London, United Kingdom.
Cardiovascular Research Institute, UCSF, San Francisco, California, USA.
Department of Pathology and Laboratory Medicine, Texas A&M University System Health Science Center, College Station, Texas, USA
| | - Michael A. Matthay
- Lung Biology Center, UCSF, San Francisco, California, USA.
Centre for Respiratory Research, University College London, London, United Kingdom.
Cardiovascular Research Institute, UCSF, San Francisco, California, USA.
Department of Pathology and Laboratory Medicine, Texas A&M University System Health Science Center, College Station, Texas, USA
| | - Dean Sheppard
- Lung Biology Center, UCSF, San Francisco, California, USA.
Centre for Respiratory Research, University College London, London, United Kingdom.
Cardiovascular Research Institute, UCSF, San Francisco, California, USA.
Department of Pathology and Laboratory Medicine, Texas A&M University System Health Science Center, College Station, Texas, USA
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