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Garcia-Marcos M. Heterotrimeric G protein signaling without GPCRs: The Gα-binding-and-activating (GBA) motif. J Biol Chem 2024; 300:105756. [PMID: 38364891 PMCID: PMC10943482 DOI: 10.1016/j.jbc.2024.105756] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/28/2023] [Revised: 01/30/2024] [Accepted: 02/02/2024] [Indexed: 02/18/2024] Open
Abstract
Heterotrimeric G proteins (Gαβγ) are molecular switches that relay signals from 7-transmembrane receptors located at the cell surface to the cytoplasm. The function of these receptors is so intimately linked to heterotrimeric G proteins that they are named G protein-coupled receptors (GPCRs), showcasing the interdependent nature of this archetypical receptor-transducer axis of transmembrane signaling in eukaryotes. It is generally assumed that activation of heterotrimeric G protein signaling occurs exclusively by the action of GPCRs, but this idea has been challenged by the discovery of alternative mechanisms by which G proteins can propagate signals in the cell. This review will focus on a general principle of G protein signaling that operates without the direct involvement of GPCRs. The mechanism of G protein signaling reviewed here is mediated by a class of G protein regulators defined by containing an evolutionarily conserved sequence named the Gα-binding-and-activating (GBA) motif. Using the best characterized proteins with a GBA motif as examples, Gα-interacting vesicle-associated protein (GIV)/Girdin and dishevelled-associating protein with a high frequency of leucine residues (DAPLE), this review will cover (i) the mechanisms by which extracellular cues not relayed by GPCRs promote the coupling of GBA motif-containing regulators with G proteins, (ii) the structural and molecular basis for how GBA motifs interact with Gα subunits to facilitate signaling, (iii) the relevance of this mechanism in different cellular and pathological processes, including cancer and birth defects, and (iv) strategies to manipulate GBA-G protein coupling for experimental therapeutics purposes, including the development of rationally engineered proteins and chemical probes.
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Affiliation(s)
- Mikel Garcia-Marcos
- Department of Biochemistry & Cell Biology, Chobanian & Avedisian School of Medicine, Boston University, Boston, Massachusetts, USA; Department of Biology, College of Arts & Sciences, Boston University, Boston, Massachusetts, USA.
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2
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Wei Q, Gao F, Gao L, Gao H, Zhang J, Bao R, Zhang H, Wang J, Shen Q, Gu M. Construction of chrysophanol loaded nanoparticles with N-octyl-O-sulfate chitosan for enhanced nephroprotective effect. Eur J Pharm Sci 2024; 193:106685. [PMID: 38154506 DOI: 10.1016/j.ejps.2023.106685] [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: 11/01/2023] [Revised: 12/26/2023] [Accepted: 12/26/2023] [Indexed: 12/30/2023]
Abstract
Natural occurring anthraquinone like chrysophanol has been studied because of its anti-diabetic, anti-tumor, anti-inflammatory, hepatoprotective and neuroprotective properties. Nonetheless, its poor water solubility and unstable nature are big concerns in achieving efficient delivery and associated pharmacokinetic and pharmacodynamic effects. Herein, this study sought to solve the above-mentioned problem through development of chrysophanol-loaded nanoparticles to enhance the bioavailability of chrysophanol and to evaluate its anti-renal fibrosis effect in rats. After synthesis of a safe N-octyl-O-sulfate chitosan, we used it to prepare chrysophanol-loaded nanoparticles through dialysis technique before we performed and physical characterization. Also, we tested the stability of the nanoparticles for 21 days at 4 °C and room temperature (25 °C) and evaluated their pharmacokinetics and anti-renal fibrosis effect in rat model of chronic kidney disease (CKD). In terms of results, the nano-preparation demonstrated an acceptable narrow size distribution, wherein the encapsulation rate, size, polydispersed index (PDI) and electrokinetic potential at room temperature were respectively 83.41±0.89 %, 364.88±13.62 nm, 0.192±0.015 and 23.78±1.39 mV. During 21 days of storage, we observed that size of particles and electrokinetic potential altered slightly but the difference was statistically insignificant (p > 0.05). Also, in vitro release studies showed that the formulation reached 84.74 % at 24 h. Chrysophanol nanoparticles showed a 2.57-fold increase in bioavailability compared to unformulated chrysophanol. More importantly, chrysophanol nanoparticles demonstrated certain renal internalization properties and anti-renal fibrosis effects, which could ultimately result in reduced blood-urea nitrogen (BUN), kidney-injury molecule-1 (KIM-1) and serum creatinine (SCr) levels in model rats. In conclusion, the prepared chrysophanol-loaded nanoparticles potentially increased bioavailability and enhanced nephroprotective effects of chrysophanol.
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Affiliation(s)
- Qingxue Wei
- Department of Nephrology, Changshu Hospital Affiliated to Nanjing University of Chinese Medicine, 6 Huanghe Road, Changshu, Jiangsu 215500, China
| | - Fuping Gao
- Department of Pathology, Gaochun People's Hospital, Nanjing, Jiangsu 211300, China
| | - Leiping Gao
- Department of Nephrology, Changshu Hospital Affiliated to Nanjing University of Chinese Medicine, 6 Huanghe Road, Changshu, Jiangsu 215500, China
| | - Hong Gao
- PharmaMax Pharmaceuticals, Ltd., No.1 Nanbatang Road, China Medical City, Taizhou, Jiangsu 225300, China
| | - Jian Zhang
- Department of Orthopedics, Taicang Affiliated Hospital of Soochow University, No.58 Changsheng South Road, Taicang, Jiangsu 215499, China
| | - Rui Bao
- Department of Pharmaceutics, School of Pharmacy, Jiangsu University, Zhenjiang, Jiangsu 212013, China
| | - Hang Zhang
- Department of Nephrology, Changshu Hospital Affiliated to Nanjing University of Chinese Medicine, 6 Huanghe Road, Changshu, Jiangsu 215500, China
| | - Jiapeng Wang
- Department of Pharmaceutics, School of Pharmacy, Jiangsu University, Zhenjiang, Jiangsu 212013, China
| | - Qiusheng Shen
- Department of Cardiology, Changshu Hospital affiliated to Nanjing University of Chinese Medicine, 6 Huanghe Road, Changshu, Jiangsu 215500, China.
| | - Mingjia Gu
- Department of Nephrology, Changshu Hospital Affiliated to Nanjing University of Chinese Medicine, 6 Huanghe Road, Changshu, Jiangsu 215500, China.
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3
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Chantaravisoot N, Wongkongkathep P, Kalpongnukul N, Pacharakullanon N, Kaewsapsak P, Ariyachet C, Loo JA, Tamanoi F, Pisitkun T. mTORC2 interactome and localization determine aggressiveness of high-grade glioma cells through association with gelsolin. Sci Rep 2023; 13:7037. [PMID: 37120454 PMCID: PMC10148843 DOI: 10.1038/s41598-023-33872-y] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/20/2022] [Accepted: 04/20/2023] [Indexed: 05/01/2023] Open
Abstract
mTOR complex 2 (mTORC2) has been implicated as a key regulator of glioblastoma cell migration. However, the roles of mTORC2 in the migrational control process have not been entirely elucidated. Here, we elaborate that active mTORC2 is crucial for GBM cell motility. Inhibition of mTORC2 impaired cell movement and negatively affected microfilament and microtubule functions. We also aimed to characterize important players involved in the regulation of cell migration and other mTORC2-mediated cellular processes in GBM cells. Therefore, we quantitatively characterized the alteration of the mTORC2 interactome under selective conditions using affinity purification-mass spectrometry in glioblastoma. We demonstrated that changes in cell migration ability specifically altered mTORC2-associated proteins. GSN was identified as one of the most dynamic proteins. The mTORC2-GSN linkage was mostly highlighted in high-grade glioma cells, connecting functional mTORC2 to multiple proteins responsible for directional cell movement in GBM. Loss of GSN disconnected mTORC2 from numerous cytoskeletal proteins and affected the membrane localization of mTORC2. In addition, we reported 86 stable mTORC2-interacting proteins involved in diverse molecular functions, predominantly cytoskeletal remodeling, in GBM. Our findings might help expand future opportunities for predicting the highly migratory phenotype of brain cancers in clinical investigations.
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Affiliation(s)
- Naphat Chantaravisoot
- Department of Biochemistry, Faculty of Medicine, Chulalongkorn University, 1873 Rama IV Pathumwan, Bangkok, 10330, Thailand.
- Center of Excellence in Systems Biology, Faculty of Medicine, Chulalongkorn University, Bangkok, 10330, Thailand.
| | - Piriya Wongkongkathep
- Center of Excellence in Systems Biology, Faculty of Medicine, Chulalongkorn University, Bangkok, 10330, Thailand
- Research Affairs, Faculty of Medicine, Chulalongkorn University, Bangkok, 10330, Thailand
| | - Nuttiya Kalpongnukul
- Center of Excellence in Systems Biology, Faculty of Medicine, Chulalongkorn University, Bangkok, 10330, Thailand
| | - Narawit Pacharakullanon
- Department of Biochemistry, Faculty of Medicine, Chulalongkorn University, 1873 Rama IV Pathumwan, Bangkok, 10330, Thailand
| | - Pornchai Kaewsapsak
- Department of Biochemistry, Faculty of Medicine, Chulalongkorn University, 1873 Rama IV Pathumwan, Bangkok, 10330, Thailand
- Research Unit of Systems Microbiology, Faculty of Medicine, Chulalongkorn University, Bangkok, 10330, Thailand
| | - Chaiyaboot Ariyachet
- Department of Biochemistry, Faculty of Medicine, Chulalongkorn University, 1873 Rama IV Pathumwan, Bangkok, 10330, Thailand
- Center of Excellence in Hepatitis and Liver Cancer, Faculty of Medicine, Chulalongkorn University, Bangkok, 10330, Thailand
| | - Joseph A Loo
- Department of Chemistry and Biochemistry, University of California, Los Angeles, CA, 90095, USA
- UCLA/DOE Institute of Genomics and Proteomics, University of California, Los Angeles, CA, 90095, USA
- Department of Biological Chemistry, University of California, Los Angeles, CA, 90095, USA
| | - Fuyuhiko Tamanoi
- Department of Microbiology, Immunology and Molecular Genetics, University of California, Los Angeles, CA, 90095, USA
- Institute for Integrated Cell-Material Sciences, Institute for Advanced Study, Kyoto University, Kyoto, 606-8501, Japan
| | - Trairak Pisitkun
- Center of Excellence in Systems Biology, Faculty of Medicine, Chulalongkorn University, Bangkok, 10330, Thailand.
- Research Affairs, Faculty of Medicine, Chulalongkorn University, Bangkok, 10330, Thailand.
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Wang H, Yuan YC, Chang C, Izumi T, Wang HH, Yang JK. The signaling protein GIV/Girdin mediates the Nephrin-dependent insulin secretion of pancreatic islet β cells in response to high glucose. J Biol Chem 2023; 299:103045. [PMID: 36822326 PMCID: PMC10040812 DOI: 10.1016/j.jbc.2023.103045] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/04/2022] [Revised: 02/10/2023] [Accepted: 02/12/2023] [Indexed: 02/23/2023] Open
Abstract
Glucose-stimulated insulin secretion of pancreatic β cells is essential in maintaining glucose homeostasis. Recent evidence suggests that the Nephrin-mediated intercellular junction between β cells is implicated in the regulation of insulin secretion. However, the underlying mechanisms are only partially characterized. Herein we report that GIV is a signaling mediator coordinating glucose-stimulated Nephrin phosphorylation and endocytosis with insulin secretion. We demonstrate that GIV is expressed in mouse islets and cultured β cells. The loss of function study suggests that GIV is essential for the second phase of glucose-stimulated insulin secretion. Next, we demonstrate that GIV mediates the high glucose-stimulated tyrosine phosphorylation of GIV and Nephrin by recruiting Src kinase, which leads to the endocytosis of Nephrin. Subsequently, the glucose-induced GIV/Nephrin/Src signaling events trigger downstream Akt phosphorylation, which activates Rac1-mediated cytoskeleton reorganization, allowing insulin secretory granules to access the plasma membrane for the second-phase secretion. Finally, we found that GIV is downregulated in the islets isolated from diabetic mice, and rescue of GIV ameliorates the β-cell dysfunction to restore the glucose-stimulated insulin secretion. We conclude that the GIV/Nephrin/Akt signaling axis is vital to regulate glucose-stimulated insulin secretion. This mechanism might be further targeted for therapeutic intervention of diabetic mellitus.
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Affiliation(s)
- Hao Wang
- Beijing Key Laboratory of Diabetes Research and Care, Beijing Diabetes Institute, Beijing Tongren Hospital, Capital Medical University, Beijing, China.
| | - Ying-Chao Yuan
- Beijing Key Laboratory of Diabetes Research and Care, Beijing Diabetes Institute, Beijing Tongren Hospital, Capital Medical University, Beijing, China
| | - Cong Chang
- College of Biology, Hunan University, Changsha, Hunan, China; Hunan Food and Drug Vocational College, Changsha, Hunan, China
| | - Tetsuro Izumi
- Laboratory of Molecular Endocrinology and Metabolism, Department of Molecular Medicine, Institute for Molecular and Cellular Regulation, Gunma University, Maebashi, Gunma, Japan
| | - Hong-Hui Wang
- College of Biology, Hunan University, Changsha, Hunan, China.
| | - Jin-Kui Yang
- Beijing Key Laboratory of Diabetes Research and Care, Beijing Diabetes Institute, Beijing Tongren Hospital, Capital Medical University, Beijing, China.
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5
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Lin L, Tian E, Ren J, Wu Z, Deng J, Yang J. Traditional Chinese Medicine in Treating Primary Podocytosis: From Fundamental Science to Clinical Research. Front Pharmacol 2022; 13:932739. [PMID: 36003509 PMCID: PMC9393213 DOI: 10.3389/fphar.2022.932739] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/30/2022] [Accepted: 06/23/2022] [Indexed: 11/30/2022] Open
Abstract
Podocytes form a key component of the glomerular filtration barrier. Damage to podocytes is referred to as “podocyte disease.” There are many causes of podocyte injury, including primary injury, secondary injury, and gene mutations. Primary podocytosis mostly manifests as nephrotic syndrome. At present, first-line treatment is based on glucocorticoid administration combined with immunosuppressive therapy, but some patients still progress to end-stage renal disease. In Asia, especially in China, traditional Chinese medicine (TCM) still plays an important role in the treatment of kidney diseases. This study summarizes the potential mechanism of TCM and its active components in protecting podocytes, such as repairing podocyte injury, inhibiting podocyte proliferation, reducing podocyte apoptosis and excretion, maintaining podocyte skeleton structure, and upregulating podocyte-related protein expression. At the same time, the clinical efficacy of TCM in the treatment of primary podocytosis (including idiopathic membranous nephropathy, minimal change disease, and focal segmental glomerulosclerosis) is summarized to support the development of new treatment strategies for primary podocytosis.
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Affiliation(s)
- Lirong Lin
- Department of Nephrology, The Third Affiliated Hospital of Chongqing Medical University (General Hospital), Chongqing, China
| | - En Tian
- Department of Nephrology, The Third Affiliated Hospital of Chongqing Medical University (General Hospital), Chongqing, China
| | - Jiangwen Ren
- Department of Nephrology, Rheumatism and Immunology, Jiulongpo District People’s Hospital of Chongqing, Chongqing, China
| | - Zhifeng Wu
- Department of Nephrology, The Third Affiliated Hospital of Chongqing Medical University (General Hospital), Chongqing, China
| | | | - Jurong Yang
- Department of Nephrology, The Third Affiliated Hospital of Chongqing Medical University (General Hospital), Chongqing, China
- *Correspondence: Jurong Yang,
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6
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Muehlig AK, Gies S, Huber TB, Braun F. Collapsing Focal Segmental Glomerulosclerosis in Viral Infections. Front Immunol 2022; 12:800074. [PMID: 35095882 PMCID: PMC8792967 DOI: 10.3389/fimmu.2021.800074] [Citation(s) in RCA: 15] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/22/2021] [Accepted: 12/20/2021] [Indexed: 01/10/2023] Open
Abstract
Collapsing glomerulopathy represents a special variant of the proteinuric kidney disease focal segmental glomerulosclerosis (FSGS). Histologically, the collapsing form of FSGS (cFSGS) is characterized by segmental or global condensation and obliteration of glomerular capillaries, the appearance of hyperplastic and hypertrophic podocytes and severe tubulointerstitial damage. Clinically, cFSGS patients present with acute kidney injury, nephrotic-range proteinuria and are at a high risk of rapid progression to irreversible kidney failure. cFSGS can be attributed to numerous etiologies, namely, viral infections like HIV, cytomegalovirus, Epstein-Barr-Virus, and parvovirus B19 and also drugs and severe ischemia. Risk variants of the APOL1 gene, predominantly found in people of African descent, increase the risk of developing cFSGS. Patients infected with the new Corona-Virus SARS-CoV-2 display an increased rate of acute kidney injury (AKI) in severe cases of COVID-19. Besides hemodynamic instability, cytokine mediated injury and direct viral entry and infection of renal epithelial cells contributing to AKI, there are emerging reports of cFSGS associated with SARS-CoV-2 infection in patients of mainly African ethnicity. The pathogenesis of cFSGS is proposed to be linked with direct viral infection of podocytes, as described for HIV-associated glomerulopathy. Nevertheless, there is growing evidence that the systemic inflammatory cascade, activated in acute viral infections like COVID-19, is a major contributor to the impairment of basic cellular functions in podocytes. This mini review will summarize the current knowledge on cFSGS associated with viral infections with a special focus on the influence of systemic immune responses and potential mechanisms propagating the development of cFSGS.
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Affiliation(s)
- Anne K Muehlig
- III. Department of Medicine, University Medical Center Hamburg-Eppendorf, Hamburg, Germany.,University Children's Hospital, University Medical Center Hamburg-Eppendorf, Hamburg, Germany.,University Children's Research@Kinder-UKE, University Medical Center Hamburg-Eppendorf, Hamburg, Germany
| | - Sydney Gies
- III. Department of Medicine, University Medical Center Hamburg-Eppendorf, Hamburg, Germany
| | - Tobias B Huber
- III. Department of Medicine, University Medical Center Hamburg-Eppendorf, Hamburg, Germany
| | - Fabian Braun
- III. Department of Medicine, University Medical Center Hamburg-Eppendorf, Hamburg, Germany
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7
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Wang X, Wei Z, Lan T, He Y, Cheng B, Li R, Chen H, Li F, Liu G, Jiang B, Lin Y, Lu M, Meng Z. CCDC88A/GIV promotes HBV replication and progeny secretion via enhancing endosomal trafficking and blocking autophagic degradation. Autophagy 2021; 18:357-374. [PMID: 34190023 PMCID: PMC8942511 DOI: 10.1080/15548627.2021.1934271] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/18/2023] Open
Abstract
Hepatitis B virus (HBV) particles are thought to be secreted from hepatocytes through multivesicular bodies (MVBs); however, the cellular trafficking mechanisms prior to this process remain elusive. It has been reported that CCDC88A/GIV expression, which is involved in multiple aspects of vesicular trafficking, changes dynamically at different phases of chronic HBV infection. In this study, we focused on the role of CCDC88A/GIV in HBV replication. In the liver tissues of chronically HBV-infected patients, HBV infection significantly enhanced CCDC88A/GIV expression, and increased endoplasmic reticulum (ER) stress and autophagosome formation without changing endosome formation. Additionally, colocalization of SHBsAg with early endosomes (~30.2%) far exceeded that with autophagosomes (~3.2%). In hepatoma cells, CCDC88A/GIV and its downstream proteins, DNM2 (dynamin 2; a CCDC88A/GIV effector), CLTC and RAB5A significantly enhanced HBV replication and endosome formation but inhibited autophagosome formation. Blocking endocytosis disrupted HBsAg trafficking to endosomes and caused its accumulation in the ER lumen, which triggered ER stress to initiate the unfolded protein response (UPR). Therefore, HBsAg trafficking into autophagosomes was increased, and the lysosomal activity and maturation, which was inhibited by HBV infection, were restored. Meanwhile, core particles were prevented from entering MVBs. CCDC88A/GIV and its other effector, GNAI3, decreased autophagic flux by enhancing the insulin-induced AKT-MTOR pathway, thereby inhibiting HBV antigens autophagic degradation. In conclusion, CCDC88A/GIV enhanced HBV replication by increasing endosomal trafficking and reducing autophagic degradation of HBV antigens, suggesting that CCDC88A/GIV-mediated endosomal trafficking plays an important role in HBV replication and progeny secretion.Abbreviations: ACTB: actin beta; AO: acridine orange; ATF6: activating transcription factor 6; CCDC88A/GIV: coiled-coil domain containing 88A; CLTC: clathrin heavy chain; CQ: chloroquine; DAPI: 4ʹ,6-diamidino-2-phenylindole; DNM2: dynamin 2; ER: endoplasmic reticulum; ERN1: endoplasmic reticulum to nucleus signaling 1; EIF2A: eukaryotic translation initiation factor 2A; FBS: fetal bovine serum; GNAI3: G protein subunit alpha i3; HBV: hepatitis B virus; HBV RIs: HBV replication intermediates; HBcAg: HBV core protein; HBsAg: HBV surface antigen; MAP1LC3B/LC3B: microtubule associated protein 1 light chain 3 beta; MVBs: multivesicular bodies; MTOR: mechanistic target of rapamycin kinase; PDI: protein disulfide isomerase; PHH: primary human hepatocyte; pSM2: a HBV replication-competent plasmid; HSPA5/BIP: heat shock protein family A (Hsp70) member 5; SQSTM1/p62: sequestosome 1; siRNA: small interfering RNA; SEM: standard error of the mean; UPR: unfolded protein response
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Affiliation(s)
- Xueyu Wang
- Institute of Biomedical Research, Hubei Clinical Research Center for Precise Diagnosis and Treatment of Liver Cancer, Taihe Hospital, Hubei University of Medicine, Shiyan, Hubei province, China.,Institute of Virology, University Hospital Essen, University of Duisburg-Essen, Essen, Germany
| | - Zhiqiang Wei
- Institute of Biomedical Research, Hubei Clinical Research Center for Precise Diagnosis and Treatment of Liver Cancer, Taihe Hospital, Hubei University of Medicine, Shiyan, Hubei province, China.,Institute of Virology, University Hospital Essen, University of Duisburg-Essen, Essen, Germany
| | - Tingyu Lan
- Institute of Biomedical Research, Hubei Clinical Research Center for Precise Diagnosis and Treatment of Liver Cancer, Taihe Hospital, Hubei University of Medicine, Shiyan, Hubei province, China.,Department of Infectious Diseases, Taihe Hospital, Hubei University of Medicine, Shiyan, Hubei province, China
| | - Yulin He
- Institute of Biomedical Research, Hubei Clinical Research Center for Precise Diagnosis and Treatment of Liver Cancer, Taihe Hospital, Hubei University of Medicine, Shiyan, Hubei province, China
| | - Bin Cheng
- Institute of Biomedical Research, Hubei Clinical Research Center for Precise Diagnosis and Treatment of Liver Cancer, Taihe Hospital, Hubei University of Medicine, Shiyan, Hubei province, China
| | - Ruimin Li
- Institute of Biomedical Research, Hubei Clinical Research Center for Precise Diagnosis and Treatment of Liver Cancer, Taihe Hospital, Hubei University of Medicine, Shiyan, Hubei province, China
| | - Hongxia Chen
- Institute of Biomedical Research, Hubei Clinical Research Center for Precise Diagnosis and Treatment of Liver Cancer, Taihe Hospital, Hubei University of Medicine, Shiyan, Hubei province, China
| | - Fahong Li
- Institute of Virology, University Hospital Essen, University of Duisburg-Essen, Essen, Germany.,Department of Infectious Diseases,Huashan Hospital, Fudan University, Shanghai, China
| | - Guohua Liu
- Institute of Biomedical Research, Hubei Clinical Research Center for Precise Diagnosis and Treatment of Liver Cancer, Taihe Hospital, Hubei University of Medicine, Shiyan, Hubei province, China
| | - Bin Jiang
- Institute of Biomedical Research, Hubei Clinical Research Center for Precise Diagnosis and Treatment of Liver Cancer, Taihe Hospital, Hubei University of Medicine, Shiyan, Hubei province, China.,Department of Hepatobiliary Pancreatic Surgery, Taihe Hospital, Hubei University of Medicine, Shiyan, Hubei province, China
| | - Yong Lin
- Institute of Virology, University Hospital Essen, University of Duisburg-Essen, Essen, Germany.,The Key Laboratory of Molecular Biology of Infectious Diseases Designated by the Chinese Ministry of Education, Institute for Viral Hepatitis, Department of Infectious Diseases, The Second Affiliated Hospital, Chongqing Medical University, Chongqing, China
| | - Mengji Lu
- Institute of Virology, University Hospital Essen, University of Duisburg-Essen, Essen, Germany
| | - Zhongji Meng
- Institute of Biomedical Research, Hubei Clinical Research Center for Precise Diagnosis and Treatment of Liver Cancer, Taihe Hospital, Hubei University of Medicine, Shiyan, Hubei province, China.,Department of Infectious Diseases, Taihe Hospital, Hubei University of Medicine, Shiyan, Hubei province, China.,Hubei Key Laboratory of Embryonic Stem Cell Research, Taihe Hospital, Hubei University of Medicine, Shiyan, Hubei province, China
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8
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Łukasik P, Załuski M, Gutowska I. Cyclin-Dependent Kinases (CDK) and Their Role in Diseases Development-Review. Int J Mol Sci 2021; 22:ijms22062935. [PMID: 33805800 PMCID: PMC7998717 DOI: 10.3390/ijms22062935] [Citation(s) in RCA: 79] [Impact Index Per Article: 26.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/09/2021] [Revised: 03/07/2021] [Accepted: 03/09/2021] [Indexed: 12/13/2022] Open
Abstract
Cyclin-dependent kinases (CDKs) are involved in many crucial processes, such as cell cycle and transcription, as well as communication, metabolism, and apoptosis. The kinases are organized in a pathway to ensure that, during cell division, each cell accurately replicates its DNA, and ensure its segregation equally between the two daughter cells. Deregulation of any of the stages of the cell cycle or transcription leads to apoptosis but, if uncorrected, can result in a series of diseases, such as cancer, neurodegenerative diseases (Alzheimer’s or Parkinson’s disease), and stroke. This review presents the current state of knowledge about the characteristics of cyclin-dependent kinases as potential pharmacological targets.
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Affiliation(s)
- Paweł Łukasik
- Department of Medical Chemistry, Pomeranian Medical University in Szczecin, Powstancow Wlkp. 72 Av., 70-111 Szczecin, Poland;
| | - Michał Załuski
- Department of Pharmaceutical Chemistry, Pomeranian Medical University in Szczecin, Powstancow Wlkp. 72 Av., 70-111 Szczecin, Poland;
| | - Izabela Gutowska
- Department of Medical Chemistry, Pomeranian Medical University in Szczecin, Powstancow Wlkp. 72 Av., 70-111 Szczecin, Poland;
- Correspondence:
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9
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Stolerman LM, Ghosh P, Rangamani P. Stability Analysis of a Signaling Circuit with Dual Species of GTPase Switches. Bull Math Biol 2021; 83:34. [PMID: 33609194 PMCID: PMC8378325 DOI: 10.1007/s11538-021-00864-w] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/31/2020] [Accepted: 01/25/2021] [Indexed: 10/22/2022]
Abstract
GTPases are molecular switches that regulate a wide range of cellular processes, such as organelle biogenesis, position, shape, function, vesicular transport between organelles, and signal transduction. These hydrolase enzymes operate by toggling between an active ("ON") guanosine triphosphate (GTP)-bound state and an inactive ("OFF") guanosine diphosphate (GDP)-bound state; such a toggle is regulated by GEFs (guanine nucleotide exchange factors) and GAPs (GTPase activating proteins). Here we propose a model for a network motif between monomeric (m) and trimeric (t) GTPases assembled exclusively in eukaryotic cells of multicellular organisms. We develop a system of ordinary differential equations in which these two classes of GTPases are interlinked conditional to their ON/OFF states within a motif through coupling and feedback loops. We provide explicit formulae for the steady states of the system and perform classical local stability analysis to systematically investigate the role of the different connections between the GTPase switches. Interestingly, a coupling of the active mGTPase to the GEF of the tGTPase was sufficient to provide two locally stable states: one where both active/inactive forms of the mGTPase can be interpreted as having low concentrations and the other where both m- and tGTPase have high concentrations. Moreover, when a feedback loop from the GEF of the tGTPase to the GAP of the mGTPase was added to the coupled system, two other locally stable states emerged. In both states the tGTPase is inactivated and active tGTPase concentrations are low. Finally, the addition of a second feedback loop, from the active tGTPase to the GAP of the mGTPase, gives rise to a family of steady states that can be parametrized by a range of inactive tGTPase concentrations. Our findings reveal that the coupling of these two different GTPase motifs can dramatically change their steady-state behaviors and shed light on how such coupling may impact signaling mechanisms in eukaryotic cells.
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Affiliation(s)
- Lucas M Stolerman
- Department of Mechanical and Aerospace Engineering, University of California, San Diego, La Jolla, CA, 92093, USA
| | - Pradipta Ghosh
- Department of Medicine, University of California, San Diego, La Jolla, CA, 92093, USA.
- Department of Cellular and Molecular Medicine, University of California, San Diego, La Jolla, CA, 92093, USA.
- Moores Comprehensive Cancer Center, University of California, San Diego, La Jolla, CA, 92093, USA.
| | - Padmini Rangamani
- Department of Mechanical and Aerospace Engineering, University of California, San Diego, La Jolla, CA, 92093, USA.
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10
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Getz M, Rangamani P, Ghosh P. Regulating cellular cyclic adenosine monophosphate: "Sources," "sinks," and now, "tunable valves". WILEY INTERDISCIPLINARY REVIEWS-SYSTEMS BIOLOGY AND MEDICINE 2020; 12:e1490. [PMID: 32323924 DOI: 10.1002/wsbm.1490] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/01/2019] [Revised: 01/31/2020] [Accepted: 03/31/2020] [Indexed: 12/16/2022]
Abstract
A number of hormones and growth factors stimulate target cells via the second messenger pathways, which in turn regulate cellular phenotypes. Cyclic adenosine monophosphate (cAMP) is a ubiquitous second messenger that facilitates numerous signal transduction pathways; its production in cells is tightly balanced by ligand-stimulated receptors that activate adenylate cyclases (ACs), that is, "source" and by phosphodiesterases (PDEs) that hydrolyze it, that is, "sinks." Because it regulates various cellular functions, including cell growth and differentiation, gene transcription and protein expression, the cAMP signaling pathway has been exploited for the treatment of numerous human diseases. Reduction in cAMP is achieved by blocking "sources"; however, elevation in cAMP is achieved by either stimulating "source" or blocking "sinks." Here we discuss an alternative paradigm for the regulation of cellular cAMP via GIV/Girdin, the prototypical member of a family of modulators of trimeric GTPases, Guanine nucleotide Exchange Modulators (GEMs). Cells upregulate or downregulate cellular levels of GIV-GEM, which modulates cellular cAMP via spatiotemporal mechanisms distinct from the two most often targeted classes of cAMP modulators, "sources" and "sinks." A network-based compartmental model for the paradigm of GEM-facilitated cAMP signaling has recently revealed that GEMs such as GIV serve much like a "tunable valve" that cells may employ to finetune cellular levels of cAMP. Because dysregulated signaling via GIV and other GEMs has been implicated in multiple disease states, GEMs constitute a hitherto untapped class of targets that could be exploited for modulating aberrant cAMP signaling in disease states. This article is categorized under: Models of Systems Properties and Processes > Mechanistic Models Biological Mechanisms > Cell Signaling.
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Affiliation(s)
- Michael Getz
- Chemical Engineering Graduate Program, University of California San Diego, La Jolla, California, USA
| | - Padmini Rangamani
- Department of Mechanical and Aerospace Engineering, University of California San Diego, La Jolla, California, USA
| | - Pradipta Ghosh
- Department of Medicine, University of California San Diego, La Jolla, California, USA
- Department of Cellular and Molecular Medicine, University of California San Diego, La Jolla, California, USA
- Moores Comprehensive Cancer Center, University of California San Diego, La Jolla, California, USA
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11
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Urinary Exosomal MicroRNA Signatures in Nephrotic, Biopsy-Proven Diabetic Nephropathy. J Clin Med 2020; 9:jcm9041220. [PMID: 32340338 PMCID: PMC7231152 DOI: 10.3390/jcm9041220] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/05/2020] [Revised: 04/18/2020] [Accepted: 04/21/2020] [Indexed: 12/16/2022] Open
Abstract
Diabetic kidney disease (DKD) is the leading cause of chronic kidney disease (CKD). Elucidating the mechanisms underlying proteinuria in DKD is crucial because it is a common problem in DKD-related mortality and morbidity. MicroRNAs (miRs) associated with DKD have been detected in experimental diabetes models and in patients with both diabetes and CKD. Here, we aimed to investigate pathologic miRs in diabetic nephropathy (DN) by prospectively following six nephrotic, biopsy-proven isolated DN patients (enrolled between August 2015 and July 2017) for one year. The urinary exosomes were isolated at the time of the biopsy and the contained miRs were analyzed by next-generation sequencing. The results were compared to the control group, composed of age-, gender-, and CKD stage-matched patients with proteinuric CKD who did not present diabetes. Among the 72 identified miRs, we investigated eight (miR-188-5p, miR-150-3p, miR-760, miR-3677-3p, miR-548ah-3p, miR-548p, miR-320e, and miR-23c) exhibiting the strongest upregulation (13–15 fold) and two (miR-133a-3p and miR-153-3p) with the strongest downregulation (7–9 fold). The functional analysis of these miRs showed that they were involved in known and novel pathways of DN, supporting their pathologic roles. The bioinformatics-based prediction of the target genes of these miRs will inspire future research on the mechanisms underlying DN pathogenesis.
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12
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Mao H, Jiang C, Xu L, Chen D, Liu H, Xu Y, Ma K, Wang M. Ginsenoside protects against AKI via activation of HIF‑1α and VEGF‑A in the kidney‑brain axis. Int J Mol Med 2020; 45:939-946. [PMID: 31985021 DOI: 10.3892/ijmm.2020.4466] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/17/2019] [Accepted: 11/29/2019] [Indexed: 11/06/2022] Open
Abstract
Acute kidney injury (AKI) is characterized by abrupt kidney dysfunction. It results in remote organ dysfunction, including the brain. The underlying mechanism of the kidney‑brain axis in AKI and effective protective approaches remain unknown. The present study aimed to investigate the potential protective effect of ginsenoside (GS) on AKI induced by glycerol in rats. Kidney function was initially assessed by blood urea nitrogen (BUN) and creatinine (Cre) tests, and was identified to be severely impaired following glycerol treatment, based on significant increases in BUN and Cre levels observed. Severe extensive necrosis of the majority of the renal tubules was observed by hematoxylin and eosin staining, additionally confirming that glycerol induced AKI. GS was identified to ameliorate the impairment of kidney function in the context of AKI. Further investigation of the mechanism revealed that GS may induce protection against oxidative stress via a kidney‑brain axis. Furthermore, GS improved the activation of hypoxia‑inducible factor 1α (HIF‑1α) and vascular endothelial growth factor A (VEGF‑A) in the hypothalamus response to AKI, and in the kidney tissues. The protective effect of GS in AKI may be associated with the interaction between the kidney and the brain. Taken together, these results suggested that GS was involved in the protective effects against AKI by decreasing oxidative damage to the kidney and brain, and by upregulating HIF‑1α and VEGF‑A levels in the kidney‑brain axis.
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Affiliation(s)
- Huizheng Mao
- College of Basic Medical Sciences, Dalian Medical University, Dalian, Liaoning 116044, P.R. China
| | - Chunling Jiang
- College of Basic Medical Sciences, Dalian Medical University, Dalian, Liaoning 116044, P.R. China
| | - Leilei Xu
- Second Affiliated Hospital, Dalian Medical University, Dalian, Liaoning 116044, P.R. China
| | - Dapeng Chen
- Laboratory Animal Center, Dalian Medical University, Dalian, Liaoning 116044, P.R. China
| | - Hui Liu
- College of Medical Laboratory, Dalian Medical University, Dalian, Liaoning 116044, P.R. China
| | - Yuefei Xu
- College of Basic Medical Sciences, Dalian Medical University, Dalian, Liaoning 116044, P.R. China
| | - Keli Ma
- College of Basic Medical Sciences, Dalian Medical University, Dalian, Liaoning 116044, P.R. China
| | - Min Wang
- Department of Physiology, College of Medicine, Jiaxing University, Jiaxing, Zhejiang 314001, P.R. China
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13
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tRNA-derived fragments (tRFs) contribute to podocyte differentiation. Biochem Biophys Res Commun 2019; 521:1-8. [PMID: 31629473 DOI: 10.1016/j.bbrc.2019.09.009] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/09/2019] [Revised: 09/01/2019] [Accepted: 09/04/2019] [Indexed: 11/21/2022]
Abstract
Loss of glomerular podocytes is the crucial event in the progression of chronic kidney disease (CKD). tRNA-derived fragments (tRFs), a newfangled branch of small non-coding RNA (sncRNA), recently reported to play a vital part in several diseases. In present study, we aimed to detect and reveal the role of tRFs in podocyte differentiation. The expression levels of tRFs between undifferentiated and differentiated podocytes were sequenced by illumina nextseq 500, and further verified by quantitative RT-PCR. 69 upregulated and 70 downregulated tRFs in total were singled out (Fold change > 2, P < 0.05). Gene ontology (GO) analysis indicated they are involved in the biological processes of transcription, DNA-templated, positive regulation of transcription from RNA polymerase II promoter, angiogenesis, cell adhesion. Besides, KEGG analysis suggested that these differentially tRFs are associated with PI3K-Akt signaling pathway, Rap1 signaling pathway, Ras signaling pathway, MAPK signaling pathway, and Wnt signaling pathway. Therefore, the differentially tRFs might regulate the differentiation of podocyte and the process of CKD. The functions and mechanisms of tRFs in podocytes are needed to be further explored.
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14
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Yuan YP, Zhao H, Peng LQ, Li ZF, Liu S, Yuan CY, Mwamunyi MJ, Pearce D, Yao LJ. The SGK3-triggered ubiquitin-proteasome degradation of podocalyxin (PC) and ezrin in podocytes was associated with the stability of the PC/ezrin complex. Cell Death Dis 2018; 9:1114. [PMID: 30385740 PMCID: PMC6212497 DOI: 10.1038/s41419-018-1161-1] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/20/2018] [Revised: 09/27/2018] [Accepted: 10/18/2018] [Indexed: 12/28/2022]
Abstract
Podocyte damage is commonly accompanied by destabilization of the podocalyxin (PC)/ezrin complex. Serum- and glucocorticoid-inducible kinase 3 (SGK3) plays a role in the maintenance of podocyte function, but the details of this role are poorly understood. Herein we demonstrated that SGK3 and its downstream target protein neural precursor cell expressed developmentally downregulated protein 4 subtype 2 (Nedd4-2) triggered PC and ezrin interaction. In adriamycin (ADR)-induced nephritic mice, and after puromycin aminonucleoside (PAN)-induced podocyte damage in vitro, PC and ezrin protein expression levels decreased significantly, while Nedd4-2 activity increased. Moreover, PAN treatment increased PC and ezrin ubiquitination and decreased PC/ezrin interaction in cultured mouse podocytes. The downregulation of SGK3 activity in mouse podocytes resulted in decreased PC and ezrin protein expression and increased the ubiquitin-proteasome degradation of PC and ezrin. Furthermore, upregulation of SGK3 activity mostly reversed the PAN-induced decrease in PC and ezrin protein expression. Overexpression of Nedd4-2 led to decreased ezrin protein expression via the upregulation of ezrin ubiquitination. In contrast, Nedd4-2 knockdown resulted in increased ezrin protein expression but decreased ezrin ubiquitination. In PC-transfected human embryonic kidney (HEK293T) cells, SGK3 activity downregulation and Nedd4-2 overexpression resulted in decreased PC/ezrin interaction. These results suggested that SGK3 triggers the ubiquitin-proteasome degradation of PC and ezrin, while the SGK3/Nedd4-2 signaling pathway regulates ezrin, but not PC, ubiquitination. Thus SGK3 helps to regulate podocyte function by maintaining the stability of the PC/ezrin complex.
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Affiliation(s)
- Ya-Pei Yuan
- Department of Nephrology, Union Hospital, Tongji Medical College, Huazhong University of Science and Technology, 430022, Wuhan, China
| | - Hong Zhao
- Department of Trauma Surgery, Tongji Hospital, Tongji Medical College, Huazhong University of Science and Technology, 430030, Wuhan, China
| | - Li-Qin Peng
- Department of Nephrology, Union Hospital, Tongji Medical College, Huazhong University of Science and Technology, 430022, Wuhan, China.,Department of Rheumatology, Sun Yat-sen Memorial Hospital, Sun Yat-sen University, 510120, Guangzhou, China
| | - Zi-Fang Li
- Department of Nephrology, Union Hospital, Tongji Medical College, Huazhong University of Science and Technology, 430022, Wuhan, China
| | - Song Liu
- Department of Nephrology, Union Hospital, Tongji Medical College, Huazhong University of Science and Technology, 430022, Wuhan, China
| | - Cheng-Yan Yuan
- Department of Nephrology, Union Hospital, Tongji Medical College, Huazhong University of Science and Technology, 430022, Wuhan, China
| | - Mercy-Julian Mwamunyi
- Department of Nephrology, Union Hospital, Tongji Medical College, Huazhong University of Science and Technology, 430022, Wuhan, China
| | - David Pearce
- Department of Medicine, University of California, San Francisco, CA, 94107-2140, USA.,Department of Molecular and Cellular Pharmacology, University of California, San Francisco, CA, 94107-2140, USA
| | - Li-Jun Yao
- Department of Nephrology, Union Hospital, Tongji Medical College, Huazhong University of Science and Technology, 430022, Wuhan, China.
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15
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Saygı Hİ, Güngör ZB, Kalay F, Seçkin İ. In glomerular cells of puromycin aminonucleoside nephrosis rats both phosphorylated and total STAT3 levels increased during proteinuria. Acta Histochem 2018; 120:595-603. [PMID: 30054017 DOI: 10.1016/j.acthis.2018.07.005] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/17/2018] [Revised: 07/18/2018] [Accepted: 07/20/2018] [Indexed: 01/05/2023]
Abstract
Recent studies showed that JAK/STAT pathway plays role in glomerular damages. The fact that STAT3 could be activated also by oxidative stress make Puromycin Aminonucleoside (PAN) Nephrosis model very appropriate for examination of STAT3 expression changes in glomerular pathology. Along with a control group, three PAN groups sacrificed on different days were formed by the i.p. injection of PAN for 5 consecutive days. Throughout the experiment, 24-hour-urines were collected on specific days and proteinuria levels were monitored. At the end of the experiments, tissue specimens were stained immunohistochemically for both total and phosphorylated STAT3 and evaluated subjectively. They were also examined ultrastructurally in transmission electron microscope. The proteinuria levels did not increase significantly on 5th day but showed a dramatic increase on 10th and 15th days. On 20th and 25th days, urinary protein levels gradually decreased. Ultrastructural examinations showed glomerular damages such as significant decrease in slit pore number, a significant gradual increase in glomerular basement membrane thickness and podocyte hypertrophy on 5th and 15th days; besides significant increase in mesangial matrix. The first significant increases in phosphorylated and total STAT3 levels occurred in 5th day and 15th day groups respectively. These increases diminished in 25th day group. Regarding all the findings, it was deduced that STAT3 is one of the active factors in glomerular pathologies.
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Affiliation(s)
- Halil İbrahim Saygı
- İstanbul University, Cerrahpaşa Medical Faculty, Histology and Embryology Department, Turkey.
| | - Zeynep Banu Güngör
- İstanbul University, Cerrahpaşa Medical Faculty, Biochemistry Department, Turkey
| | - Fatma Kalay
- İstanbul University, Cerrahpaşa Medical Faculty, Biochemistry Department, Turkey
| | - İsmail Seçkin
- İstanbul University, Cerrahpaşa Medical Faculty, Histology and Embryology Department, Turkey
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16
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Abstract
Purpose of review Glomerular filtration occurs in specialized, microscopic organelles. Each glomerulus contains unique cells and these cooperate to maintain normal filtration. Phenomenal adaptation is required for the glomerulus to respond to variable mechanical loads and this adaptation requires efficient communication between the resident cells. This review will focus on the latest discoveries related to signalling events that mediate the crosstalk between glomerular cells, and detail how disease processes can influence normal regulation. Recent findings New data indicate that the crosstalk between glomerular cells involves an increasing number of secreted signalling ligands that act in an autocrine or paracrine fashion. Furthermore, extended roles for some of the classical signalling molecules have been described and there is emerging evidence of therapeutic strategies to manipulate cellular crosstalk. The glomerular extracellular matrix harbours many of these signalling ligands, acting as a reservoir and presenting ligands to cell surface receptors. Signals can also be transferred between cells by extracellular vesicles and this is an emerging concept in cellular crosstalk. Summary Recent discoveries are building our understanding about glomerular cell crosstalk, and this review focuses on growth factors and signalling peptides, methods of delivery to target cells, and the potential for developing new therapies for glomerular disease.
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17
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Ghosh P, Aznar N, Swanson L, Lo IC, Lopez-Sanchez I, Ear J, Rohena C, Kalogriopoulos N, Joosen L, Dunkel Y, Sun N, Nguyen P, Bhandari D. Biochemical, Biophysical and Cellular Techniques to Study the Guanine Nucleotide Exchange Factor, GIV/Girdin. CURRENT PROTOCOLS IN CHEMICAL BIOLOGY 2016; 8:265-298. [PMID: 27925669 PMCID: PMC5154557 DOI: 10.1002/cpch.13] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
Abstract
Canonical signal transduction via heterotrimeric G proteins is spatiotemporally restricted, i.e., triggered exclusively at the plasma membrane, only by agonist activation of G protein-coupled receptors via a finite process that is terminated within a few hundred milliseconds. Recently, a rapidly emerging paradigm has revealed a noncanonical pathway for activation of heterotrimeric G proteins via the nonreceptor guanidine-nucleotide exchange factor, GIV/Girdin. Biochemical, biophysical, and functional studies evaluating this pathway have unraveled its unique properties and distinctive spatiotemporal features. As in the case of any new pathway/paradigm, these studies first required an in-depth optimization of tools/techniques and protocols, governed by rationale and fundamentals unique to the pathway, and more specifically to the large multimodular GIV protein. Here we provide the most up-to-date overview of protocols that have generated most of what we know today about noncanonical G protein activation by GIV and its relevance in health and disease. © 2016 by John Wiley & Sons, Inc.
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Affiliation(s)
- Pradipta Ghosh
- Department of Cellular and Molecular Medicine, University of California at San Diego, La Jolla, CA 92093-0651
- Department of Medicine, University of California at San Diego, La Jolla, CA 92093-0651
| | - Nicolas Aznar
- Department of Medicine, University of California at San Diego, La Jolla, CA 92093-0651
| | - Lee Swanson
- Department of Medicine, University of California at San Diego, La Jolla, CA 92093-0651
| | - I-Chung Lo
- Department of Cellular and Molecular Medicine, University of California at San Diego, La Jolla, CA 92093-0651
| | | | - Jason Ear
- Department of Medicine, University of California at San Diego, La Jolla, CA 92093-0651
| | - Cristina Rohena
- Department of Medicine, University of California at San Diego, La Jolla, CA 92093-0651
| | | | - Linda Joosen
- Department of Medicine, University of California at San Diego, La Jolla, CA 92093-0651
| | - Ying Dunkel
- Department of Medicine, University of California at San Diego, La Jolla, CA 92093-0651
| | - Nina Sun
- Department of Medicine, University of California at San Diego, La Jolla, CA 92093-0651
| | - Peter Nguyen
- Department of Chemistry and Biochemistry, California State University Long Beach, Long Beach, CA 90840-9507
| | - Deepali Bhandari
- Department of Chemistry and Biochemistry, California State University Long Beach, Long Beach, CA 90840-9507
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18
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Parag-Sharma K, Leyme A, DiGiacomo V, Marivin A, Broselid S, Garcia-Marcos M. Membrane Recruitment of the Non-receptor Protein GIV/Girdin (Gα-interacting, Vesicle-associated Protein/Girdin) Is Sufficient for Activating Heterotrimeric G Protein Signaling. J Biol Chem 2016; 291:27098-27111. [PMID: 27864364 DOI: 10.1074/jbc.m116.764431] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/22/2016] [Revised: 11/17/2016] [Indexed: 11/06/2022] Open
Abstract
GIV (aka Girdin) is a guanine nucleotide exchange factor that activates heterotrimeric G protein signaling downstream of RTKs and integrins, thereby serving as a platform for signaling cascade cross-talk. GIV is recruited to the cytoplasmic tail of receptors upon stimulation, but the mechanism of activation of its G protein regulatory function is not well understood. Here we used assays in humanized yeast models and G protein activity biosensors in mammalian cells to investigate the role of GIV subcellular compartmentalization in regulating its ability to promote G protein signaling. We found that in unstimulated cells GIV does not co-fractionate with its substrate G protein Gαi3 on cell membranes and that constitutive membrane anchoring of GIV in yeast cells or rapid membrane translocation in mammalian cells via chemically induced dimerization leads to robust G protein activation. We show that membrane recruitment of the GIV "Gα binding and activating" motif alone is sufficient for G protein activation and that it does not require phosphomodification. Furthermore, we engineered a synthetic protein to show that recruitment of the GIV "Gα binding and activating" motif to membranes via association with active RTKs, instead of via chemically induced dimerization, is also sufficient for G protein activation. These results reveal that recruitment of GIV to membranes in close proximity to its substrate G protein is a major mechanism responsible for the activation of its G protein regulatory function.
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Affiliation(s)
- Kshitij Parag-Sharma
- From the Department of Biochemistry, Boston University School of Medicine, Boston, Massachusetts 02118
| | - Anthony Leyme
- From the Department of Biochemistry, Boston University School of Medicine, Boston, Massachusetts 02118
| | - Vincent DiGiacomo
- From the Department of Biochemistry, Boston University School of Medicine, Boston, Massachusetts 02118
| | - Arthur Marivin
- From the Department of Biochemistry, Boston University School of Medicine, Boston, Massachusetts 02118
| | - Stefan Broselid
- From the Department of Biochemistry, Boston University School of Medicine, Boston, Massachusetts 02118
| | - Mikel Garcia-Marcos
- From the Department of Biochemistry, Boston University School of Medicine, Boston, Massachusetts 02118
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19
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Aznar N, Patel A, Rohena CC, Dunkel Y, Joosen LP, Taupin V, Kufareva I, Farquhar MG, Ghosh P. AMP-activated protein kinase fortifies epithelial tight junctions during energetic stress via its effector GIV/Girdin. eLife 2016; 5. [PMID: 27813479 PMCID: PMC5119889 DOI: 10.7554/elife.20795] [Citation(s) in RCA: 37] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/21/2016] [Accepted: 11/03/2016] [Indexed: 02/06/2023] Open
Abstract
Loss of epithelial polarity impacts organ development and function; it is also oncogenic. AMPK, a key sensor of metabolic stress stabilizes cell-cell junctions and maintains epithelial polarity; its activation by Metformin protects the epithelial barrier against stress and suppresses tumorigenesis. How AMPK protects the epithelium remains unknown. Here, we identify GIV/Girdin as a novel effector of AMPK, whose phosphorylation at a single site is both necessary and sufficient for strengthening mammalian epithelial tight junctions and preserving cell polarity and barrier function in the face of energetic stress. Expression of an oncogenic mutant of GIV (cataloged in TCGA) that cannot be phosphorylated by AMPK increased anchorage-independent growth of tumor cells and helped these cells to evade the tumor-suppressive action of Metformin. This work defines a fundamental homeostatic mechanism by which the AMPK-GIV axis reinforces cell junctions against stress-induced collapse and also provides mechanistic insight into the tumor-suppressive action of Metformin.
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Affiliation(s)
- Nicolas Aznar
- Department of Medicine, University of California, San Diego, San Diego, United States
| | - Arjun Patel
- Department of Medicine, University of California, San Diego, San Diego, United States
| | - Cristina C Rohena
- Department of Medicine, University of California, San Diego, San Diego, United States
| | - Ying Dunkel
- Department of Medicine, University of California, San Diego, San Diego, United States
| | - Linda P Joosen
- Department of Medicine, University of California, San Diego, San Diego, United States
| | - Vanessa Taupin
- Department of Cellular and Molecular Medicine, University of California, San Diego, San Diego, United States
| | - Irina Kufareva
- Skaggs School of Pharmacy and Pharmaceutical Sciences, University of California, San Diego, San Diego, United States
| | - Marilyn G Farquhar
- Department of Cellular and Molecular Medicine, University of California, San Diego, San Diego, United States
| | - Pradipta Ghosh
- Department of Medicine, University of California, San Diego, San Diego, United States.,Department of Cellular and Molecular Medicine, University of California, San Diego, San Diego, United States.,Moores Cancer Center, University of California, San Diego, San Diego, United States
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20
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Turner RJ, Eikmans M, Bajema IM, Bruijn JA, Baelde HJ. Stability and Species Specificity of Renal VEGF-A Splicing Patterns in Kidney Disease. PLoS One 2016; 11:e0162166. [PMID: 27598902 PMCID: PMC5012578 DOI: 10.1371/journal.pone.0162166] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/01/2015] [Accepted: 07/08/2016] [Indexed: 12/29/2022] Open
Abstract
Vascular endothelial growth factor A (VEGF-A) is essential for maintaining the glomerular filtration barrier. Absolute renal levels of VEGF-A change in patients with diabetic nephropathy and inflammatory kidney diseases, but whether changes in the renal splicing patterns of VEGF-A play a role remains unclear. In this study, we investigated mRNA splicing patterns of pro-angiogenic isoforms of VEGF-A in glomeruli and whole kidney samples from human patients with kidney disease and from mouse models of kidney disease. Kidney biopsies were obtained from patients with acute rejection following kidney transplantation, patients with diabetic nephropathy, and control subjects. In addition, kidney samples were obtained from mice with lupus nephritis, mice with diabetes mellitus, and control mice. The relative expression of each VEGF-A splice variant was measured using RT-PCR followed by quantitative fragment analysis. The pattern of renal VEGF-A splice variants was unchanged in diabetic nephropathy and lupus nephritis and was stable throughout disease progression in acute transplant rejection and diabetic nephropathy; these results suggest renal VEGF-A splicing stability during kidney disease. The splicing patterns were species-specific; in the control human kidney samples, VEGF-A 121 was the dominant isoform, whereas VEGF-A 164 was the dominant isoform measured in the mouse kidney samples.
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Affiliation(s)
- R. J. Turner
- Department of Pathology, Leiden University Medical Center, Leiden, the Netherlands
- * E-mail:
| | - M. Eikmans
- Department of Immunohematology and Blood Transfusion, Leiden University Medical Center, Leiden, the Netherlands
| | - I. M. Bajema
- Department of Pathology, Leiden University Medical Center, Leiden, the Netherlands
| | - J. A. Bruijn
- Department of Pathology, Leiden University Medical Center, Leiden, the Netherlands
| | - H. J. Baelde
- Department of Pathology, Leiden University Medical Center, Leiden, the Netherlands
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21
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Gong W, Yu J, Wang Q, Li S, Song J, Jia Z, Huang S, Zhang A. Estrogen-related receptor (ERR) γ protects against puromycin aminonucleoside-induced podocyte apoptosis by targeting PI3K/Akt signaling. Int J Biochem Cell Biol 2016; 78:75-86. [PMID: 27417234 DOI: 10.1016/j.biocel.2016.07.005] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/26/2015] [Revised: 07/06/2016] [Accepted: 07/08/2016] [Indexed: 12/21/2022]
Abstract
Accumulating evidence has shown that podocyte apoptosis is of vital importance for the development of glomerulosclerosis and progressive loss of renal function. However, the molecular mechanisms leading to podocyte apoptosis are still elusive. In this study, we investigated the role of estrogen-related receptor (ERR) γ in podocyte apoptosis, as well as the underlying mechanisms. Treatment of PAN caused a dose- and time-dependent podocyte apoptosis in line with a significant downregulation of ERRγ. Interestingly, the occurrence of ERRγ downregulation appeared earlier than the onset of cell apoptosis, suggesting a potential that ERRγ reduction triggered apoptotic response in podocyte. To test this hypothesis, ERRγ siRNA was administered to the podocytes. Strikingly, ERRγ silencing resulted in a significant cell apoptosis accompanied with increased injury markers of B7-1 and cathepsin L and decreased podocyte protein nephrin. In contrast, overexpression of ERRγ remarkably attenuated PAN-induced cell apoptosis. Moreover, ERRγ overexpression stimulated PI3K/Akt signaling pathway evidenced by increased expression of PI3K subunits p85α and p110α and phosphorylated Akt. Importantly, a specific PI3K inhibitor LY294002 entirely reversed the anti-apoptotic effect of ERRγ following PAN treatment. Finally, we observed a striking downregulation of ERRγ in PAN-treated rat kidneys, suggesting that our cell model replicated the in vivo condition. Taken together, these data highly suggested that ERRγ played a novel role in modulating podocyte apoptosis by targeting PI3K/Akt signaling pathway.
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Affiliation(s)
- Wei Gong
- Department of Nephrology, Nanjing Children's Hospital Affiliated to Nanjing Medical University, Nanjing 210008, China; State Key Laboratory of Reproductive Medicine, Nanjing Medical University, Nanjing 210029, China; Jiangsu Key Laboratory of Pediatrics, Nanjing Medical University, Nanjing 210029, China
| | - Jing Yu
- Department of Nephrology, Nanjing Children's Hospital Affiliated to Nanjing Medical University, Nanjing 210008, China; State Key Laboratory of Reproductive Medicine, Nanjing Medical University, Nanjing 210029, China; Jiangsu Key Laboratory of Pediatrics, Nanjing Medical University, Nanjing 210029, China
| | - Qilei Wang
- Department of Nephrology, Nanjing Children's Hospital Affiliated to Nanjing Medical University, Nanjing 210008, China; Jiangsu Key Laboratory of Pediatrics, Nanjing Medical University, Nanjing 210029, China
| | - Shuzhen Li
- Department of Nephrology, Nanjing Children's Hospital Affiliated to Nanjing Medical University, Nanjing 210008, China; Nanjing Key Laboratory of Pediatrics, Nanjing 210008, China
| | - Jiayu Song
- Department of Nephrology, Nanjing Children's Hospital Affiliated to Nanjing Medical University, Nanjing 210008, China; State Key Laboratory of Reproductive Medicine, Nanjing Medical University, Nanjing 210029, China; Jiangsu Key Laboratory of Pediatrics, Nanjing Medical University, Nanjing 210029, China
| | - Zhanjun Jia
- Department of Nephrology, Nanjing Children's Hospital Affiliated to Nanjing Medical University, Nanjing 210008, China; Jiangsu Key Laboratory of Pediatrics, Nanjing Medical University, Nanjing 210029, China; Nanjing Key Laboratory of Pediatrics, Nanjing 210008, China
| | - Songming Huang
- Department of Nephrology, Nanjing Children's Hospital Affiliated to Nanjing Medical University, Nanjing 210008, China; Jiangsu Key Laboratory of Pediatrics, Nanjing Medical University, Nanjing 210029, China; Nanjing Key Laboratory of Pediatrics, Nanjing 210008, China
| | - Aihua Zhang
- Department of Nephrology, Nanjing Children's Hospital Affiliated to Nanjing Medical University, Nanjing 210008, China; State Key Laboratory of Reproductive Medicine, Nanjing Medical University, Nanjing 210029, China; Jiangsu Key Laboratory of Pediatrics, Nanjing Medical University, Nanjing 210029, China; Nanjing Key Laboratory of Pediatrics, Nanjing 210008, China.
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22
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Ying C, Zhou X, Chang Z, Ling H, Cheng X, Li W. Blood glucose fluctuation accelerates renal injury involved to inhibit the AKT signaling pathway in diabetic rats. Endocrine 2016; 53:81-96. [PMID: 26860515 DOI: 10.1007/s12020-016-0867-z] [Citation(s) in RCA: 33] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/24/2015] [Accepted: 01/12/2016] [Indexed: 12/20/2022]
Abstract
Blood glucose fluctuation is associated with diabetic nephropathy. However, the mechanism by which blood glucose fluctuation accelerates renal injury is not fully understood. The aim of the present study was to assess the effects of blood glucose fluctuation on diabetic nephropathy in rats and investigate its underlying mechanism. Diabetes in the rats was induced by a high sugar, high-fat diet, and a single dose of STZ (35 mg/kg)-injected intraperitoneally. Unstable blood sugar models were induced by subcutaneous insulin injection and intravenous glucose injection alternately. Body weight, glycosylated hemoglobin A1c (HbAlc), blood urea nitrogen (BUN), serum creatinine (Scr), and Creatinine clearance (Ccr) were assessed. T-SOD activity and MDA level were measured by assay kit. Change in renal tissue ultrastructure was observed by light microscopy and electron microscopy. Phosphorylated ser/thr protein kinase (p-AKT) (phosphor-Ser473), phosphorylated glycogen synthase kinase-3 beta (p-GSK-3β) (phosphor-Ser9), Bcl-2-associated X protein (BAX), B cell lymphoma/leukemia 2 (BCL-2), and cleaved-cysteinyl aspartate-specific proteinase-3 (caspase-3) levels were detected by immunohistochemistry and Western blot. We observed that BUN and Scr were increased in diabetic rats, and Ccr was decreased. Furthermore, blood glucose fluctuations could exacerbate the Ccr changes. Renal tissue ultrastructure was also seriously injured by glucose variability in diabetic rats. In addition, glucose fluctuation increased the oxidative stress of renal tissue. Moreover, fluctuating blood glucose decreased p-AKT level and BCL-2, and increased p-GSK-3β, BAX, cleaved-caspase-3 levels, and ratio of BAX/BCL-2 in the kidneys of diabetic rats. In conclusion, these results suggest that blood glucose fluctuation accelerated renal injury is due, at least in part to its oxidative stress promoting and inhibiting the AKT signaling pathway in diabetic rats.
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Affiliation(s)
- Changjiang Ying
- Department of Endocrinology, The First Affiliated Hospital of Soochow University, 188 Shizi Street, Suzhou, 215006, Jiangsu, People's Republic of China
- Department of Endocrinology, Affiliated Hospital of Xuzhou Medical College, Xuzhou, 221002, Jiangsu, People's Republic of China
| | - Xiaoyan Zhou
- Laboratory of Morphology, Xuzhou Medical College, Xuzhou, 221004, Jiangsu, People's Republic of China
| | - Zhenzhen Chang
- Department of Endocrinology, Affiliated Hospital of Xuzhou Medical College, Xuzhou, 221002, Jiangsu, People's Republic of China
| | - Hongwei Ling
- Department of Endocrinology, Affiliated Hospital of Xuzhou Medical College, Xuzhou, 221002, Jiangsu, People's Republic of China
| | - Xingbo Cheng
- Department of Endocrinology, The First Affiliated Hospital of Soochow University, 188 Shizi Street, Suzhou, 215006, Jiangsu, People's Republic of China.
| | - Wei Li
- Department of Endocrinology, Affiliated Hospital of Xuzhou Medical College, Xuzhou, 221002, Jiangsu, People's Republic of China.
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23
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Podocyte directed therapy of nephrotic syndrome-can we bring the inside out? Pediatr Nephrol 2016; 31:393-405. [PMID: 25939817 DOI: 10.1007/s00467-015-3116-4] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/19/2014] [Revised: 04/08/2015] [Accepted: 04/09/2015] [Indexed: 12/15/2022]
Abstract
Several of the drugs currently used for the treatment of glomerular diseases are prescribed for their immunotherapeutic or anti-inflammatory properties, based on the current understanding that glomerular diseases are mediated by immune responses. In recent years our understanding of podocytic signalling pathways and the crucial role of genetic predispositions in the pathology of glomerular diseases has broadened. Delineation of those signalling pathways supports the hypothesis that several of the medications and immunosuppressive agents used to treat glomerular diseases directly target glomerular podocytes. Several central downstream signalling pathways merge into regulatory pathways of the podocytic actin cytoskeleton and its connection to the slit diaphragm. The slit diaphragm and the cytoskeleton of the foot process represent a functional unit. A breakdown of the cytoskeletal backbone of the foot processes leads to internalization of slit diaphragm molecules, and internalization of slit diaphragm components in turn negatively affects cytoskeletal signalling pathways. Podocytes display a remarkable ability to recover from complete effacement and to re-form interdigitating foot processes and intact slit diaphragms after pharmacological intervention. This ability indicates an active inside-out signalling machinery which stabilizes integrin complex formations and triggers the recycling of slit diaphragm molecules from intracellular compartments to the cell surface. In this review we summarize current evidence from patient studies and model organisms on the direct impact of immunosuppressive and supportive drugs on podocyte signalling pathways. We highlight new therapeutic targets that may open novel opportunities to enhance and stabilize inside-out pathways in podocytes.
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24
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Aznar N, Kalogriopoulos N, Midde KK, Ghosh P. Heterotrimeric G protein signaling via GIV/Girdin: Breaking the rules of engagement, space, and time. Bioessays 2016; 38:379-93. [PMID: 26879989 DOI: 10.1002/bies.201500133] [Citation(s) in RCA: 39] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023]
Abstract
Canonical signal transduction via heterotrimeric G proteins is spatially and temporally restricted, that is, triggered exclusively at the plasma membrane (PM), only by agonist activation of G protein-coupled receptors (GPCRs) via a process that completes within a few hundred milliseconds. Recently, a rapidly emerging paradigm has revealed a non-canonical pathway for activation of heterotrimeric G proteins by the non-receptor guanidine-nucleotide exchange factor (GEF), GIV/Girdin. This pathway has distinctive temporal and spatial features and an unusual profile of receptor engagement: diverse classes of receptors, not just GPCRs can engage with GIV to trigger such activation. Such activation is spatially and temporally unrestricted, that is, can occur both at the PM and on internal membranes discontinuous with the PM, and can continue for prolonged periods of time. Here, we provide the most complete up-to-date review of the molecular mechanisms that govern the unique spatiotemporal aspects of non-canonical G protein activation by GIV and the relevance of this new paradigm in health and disease.
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Affiliation(s)
- Nicolas Aznar
- Department of Medicine, University of California at San Diego, La Jolla, CA, USA
| | | | - Krishna K Midde
- Department of Medicine, University of California at San Diego, La Jolla, CA, USA
| | - Pradipta Ghosh
- Department of Medicine, University of California at San Diego, La Jolla, CA, USA.,Department of Cell and Molecular Medicine, University of California at San Diego, La Jolla, CA, USA
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25
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Ghosh P. The untapped potential of tyrosine-based G protein signaling. Pharmacol Res 2016; 105:99-107. [PMID: 26808081 DOI: 10.1016/j.phrs.2016.01.017] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/13/2016] [Revised: 01/14/2016] [Accepted: 01/15/2016] [Indexed: 01/14/2023]
Abstract
Tyrosine-based and trimeric G protein-based signaling are the two most widely studied and distinct mechanisms for signal transduction in eukaryotes. How each of them relay signals across the plasma membrane independently of each other has been extensively characterized; however, an understanding of how they work together remained obscure. Recently, a rapidly emerging paradigm has revealed that tyrosine based signals are relayed via G proteins, and that the cross-talk between the two hubs are more robustly and sophisticatedly integrated than was previously imagined. More importantly, by straddling the two signaling hubs that are most frequently targeted for their therapeutic significance, the tyrosine-based G-protein signaling pathway has its own growing list of pathophysiologic importance, both as therapeutic target in a variety of disease states, and by paving the way for personalized medicine. The fundamental principles of this emerging paradigm and its pharmacologic potential are discussed.
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Affiliation(s)
- Pradipta Ghosh
- Department of Medicine and Department of Cell and Molecular Medicine, University of California at San Diego, La Jolla, CA 92093-0651, United States.
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26
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Coleman BD, Marivin A, Parag-Sharma K, DiGiacomo V, Kim S, Pepper JS, Casler J, Nguyen LT, Koelle MR, Garcia-Marcos M. Evolutionary Conservation of a GPCR-Independent Mechanism of Trimeric G Protein Activation. Mol Biol Evol 2015; 33:820-37. [PMID: 26659249 PMCID: PMC4760084 DOI: 10.1093/molbev/msv336] [Citation(s) in RCA: 29] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022] Open
Abstract
Trimeric G protein signaling is a fundamental mechanism of cellular communication in eukaryotes. The core of this mechanism consists of activation of G proteins by the guanine-nucleotide exchange factor (GEF) activity of G protein coupled receptors. However, the duration and amplitude of G protein-mediated signaling are controlled by a complex network of accessory proteins that appeared and diversified during evolution. Among them, nonreceptor proteins with GEF activity are the least characterized. We recently found that proteins of the ccdc88 family possess a Gα-binding and activating (GBA) motif that confers GEF activity and regulates mammalian cell behavior. A sequence similarity-based search revealed that ccdc88 genes are highly conserved across metazoa but the GBA motif is absent in most invertebrates. This prompted us to investigate whether the GBA motif is present in other nonreceptor proteins in invertebrates. An unbiased bioinformatics search in Caenorhabditis elegans identified GBAS-1 (GBA and SPK domain containing-1) as a GBA motif-containing protein with homologs only in closely related worm species. We demonstrate that GBAS-1 has GEF activity for the nematode G protein GOA-1 and that the two proteins are coexpressed in many cells of living worms. Furthermore, we show that GBAS-1 can activate mammalian Gα-subunits and provide structural insights into the evolutionarily conserved determinants of the GBA–G protein interface. These results demonstrate that the GBA motif is a functional GEF module conserved among highly divergent proteins across evolution, indicating that the GBA-Gα binding mode is strongly constrained under selective pressure to mediate receptor-independent G protein activation in metazoans.
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Affiliation(s)
| | - Arthur Marivin
- Department of Biochemistry, Boston University School of Medicine
| | | | | | - Seongseop Kim
- Department of Molecular Biophysics and Biochemistry, Yale University School of Medicine
| | - Judy S Pepper
- Department of Molecular Biophysics and Biochemistry, Yale University School of Medicine
| | - Jason Casler
- Department of Biochemistry, Boston University School of Medicine
| | - Lien T Nguyen
- Department of Biochemistry, Boston University School of Medicine
| | - Michael R Koelle
- Department of Molecular Biophysics and Biochemistry, Yale University School of Medicine
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27
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Lopez-Sanchez I, Kalogriopoulos N, Lo IC, Kabir F, Midde KK, Wang H, Ghosh P. Focal adhesions are foci for tyrosine-based signal transduction via GIV/Girdin and G proteins. Mol Biol Cell 2015; 26:4313-24. [PMID: 26446841 PMCID: PMC4666128 DOI: 10.1091/mbc.e15-07-0496] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/21/2015] [Accepted: 09/28/2015] [Indexed: 12/14/2022] Open
Abstract
GIV is a guanine-nucleotide exchange factor and a bona fide metastasis-related protein. It is found, unexpectedly, that focal adhesions are the major foci for GIV-dependent signaling and that GIV modulates integrin-FAK signaling via activation of G proteins. It is also shown how this phenomenon is altered during cancer progression. GIV/Girdin is a multimodular signal transducer and a bona fide metastasis-related protein. As a guanidine exchange factor (GEF), GIV modulates signals initiated by growth factors (chemical signals) by activating the G protein Gαi. Here we report that mechanical signals triggered by the extracellular matrix (ECM) also converge on GIV-GEF via β1 integrins and that focal adhesions (FAs) serve as the major hubs for mechanochemical signaling via GIV. GIV interacts with focal adhesion kinase (FAK) and ligand-activated β1 integrins. Phosphorylation of GIV by FAK enhances PI3K-Akt signaling, the integrity of FAs, increases cell–ECM adhesion, and triggers ECM-induced cell motility. Activation of Gαi by GIV-GEF further potentiates FAK-GIV-PI3K-Akt signaling at the FAs. Spatially restricted signaling via tyrosine phosphorylated GIV at the FAs is enhanced during cancer metastasis. Thus GIV-GEF serves as a unifying platform for integration and amplification of adhesion (mechanical) and growth factor (chemical) signals during cancer progression.
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Affiliation(s)
- Inmaculada Lopez-Sanchez
- Department of Medicine, University of California, San Diego, School of Medicine, La Jolla, CA 92093
| | - Nicholas Kalogriopoulos
- Department of Medicine, University of California, San Diego, School of Medicine, La Jolla, CA 92093
| | - I-Chung Lo
- Department of Cellular and Molecular Medicine, University of California, San Diego, School of Medicine, La Jolla, CA 92093
| | - Firooz Kabir
- Department of Medicine, University of California, San Diego, School of Medicine, La Jolla, CA 92093
| | - Krishna K Midde
- Department of Medicine, University of California, San Diego, School of Medicine, La Jolla, CA 92093
| | - Honghui Wang
- Department of Cellular and Molecular Medicine, University of California, San Diego, School of Medicine, La Jolla, CA 92093
| | - Pradipta Ghosh
- Department of Medicine, University of California, San Diego, School of Medicine, La Jolla, CA 92093 Department of Cellular and Molecular Medicine, University of California, San Diego, School of Medicine, La Jolla, CA 92093
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28
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Akt-dependent Girdin phosphorylation regulates repair processes after acute myocardial infarction. J Mol Cell Cardiol 2015; 88:55-63. [PMID: 26393439 DOI: 10.1016/j.yjmcc.2015.09.012] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/13/2015] [Revised: 09/18/2015] [Accepted: 09/18/2015] [Indexed: 12/15/2022]
Abstract
Myocardial infarction is a leading cause of death, and cardiac rupture following myocardial infarction leads to extremely poor prognostic feature. A large body of evidence suggests that Akt is involved in several cardiac diseases. We previously reported that Akt-mediated Girdin phosphorylation is essential for angiogenesis and neointima formation. The role of Girdin expression and phosphorylation in myocardial infarction, however, is not understood. Therefore, we employed Girdin-deficient mice and Girdin S1416A knock-in (Girdin(SA/SA)) mice, replacing the Akt phosphorylation site with alanine, to address this question. We found that Girdin was expressed and phosphorylated in cardiac fibroblasts in vitro and that its phosphorylation was crucial for the proliferation and migration of cardiac fibroblasts. In vivo, Girdin was localized in non-cardiomyocyte interstitial cells and phosphorylated in α-smooth muscle actin-positive cells, which are likely to be cardiac myofibroblasts. In an acute myocardial infarction model, Girdin(SA/SA) suppressed the accumulation and proliferation of cardiac myofibroblasts in the infarcted area. Furthermore, lower collagen deposition in Girdin(SA/SA) mice impaired cardiac repair and resulted in increased mortality attributed to cardiac rupture. These findings suggest an important role of Girdin phosphorylation at serine 1416 in cardiac repair after acute myocardial infarction and provide insights into the complex mechanism of cardiac rupture through the Akt/Girdin-mediated regulation of cardiac myofibroblasts.
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29
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Park F. Accessory proteins for heterotrimeric G-proteins in the kidney. Front Physiol 2015; 6:219. [PMID: 26300785 PMCID: PMC4528294 DOI: 10.3389/fphys.2015.00219] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/11/2015] [Accepted: 07/20/2015] [Indexed: 11/17/2022] Open
Abstract
Heterotrimeric G-proteins play a fundamentally important role in regulating signal transduction pathways in the kidney. Accessory proteins are being identified as direct binding partners for heterotrimeric G-protein α or βγ subunits to promote more diverse mechanisms by which G-protein signaling is controlled. In some instances, accessory proteins can modulate the signaling magnitude, localization, and duration following the activation of cell membrane-associated receptors. Alternatively, accessory proteins complexed with their G-protein α or βγ subunits can promote non-canonical models of signaling activity within the cell. In this review, we will highlight the expression profile, localization and functional importance of these newly identified accessory proteins to control the function of select G-protein subunits under normal and various disease conditions observed in the kidney.
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Affiliation(s)
- Frank Park
- Department of Pharmaceutical Sciences, College of Pharmacy, University of Tennessee Health Science Center Memphis, TN, USA
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30
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Ghosh P. Heterotrimeric G proteins as emerging targets for network based therapy in cancer: End of a long futile campaign striking heads of a Hydra. Aging (Albany NY) 2015; 7:469-74. [PMID: 26224586 PMCID: PMC4543036 DOI: 10.18632/aging.100781] [Citation(s) in RCA: 31] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/05/2015] [Accepted: 07/15/2015] [Indexed: 01/17/2023]
Abstract
Most common diseases, e.g., cancer are driven by not one, but multiple cell surface receptors that trigger and sustain a pathologic signaling network. The largest fraction of therapeutic agents that target individual receptors/pathways eventually fail due to the emergence of compensatory mechanisms that reestablish the pathologic network. Recently, a rapidly emerging paradigm has revealed GIV/Girdin as a central platform for receptor cross-talk which integrates signals downstream of a myriad of cell surface receptors, and modulates several key pathways within downstream signaling network, all via non-canonical activation of trimeric G proteins. Unlike canonical signal transduction via G proteins, which is spatially and temporally restricted, the temporal and spatial features of non-canonical activation of G protein via GIV is unusually unrestricted. Consequently, the GIV●G protein interface serves as a central hub allowing for control over several pathways within the pathologic signaling network, all at once. The relevance of this new paradigm in cancer and other disease states and the pros and cons of targeting the GIV●G protein interface are discussed.
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Affiliation(s)
- Pradipta Ghosh
- Department of Medicine, University of California at San Diego, La Jolla, CA 92093, USA
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31
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Abstract
Environmental cues are transmitted to the interior of the cell via a complex network of signaling hubs. Receptor tyrosine kinases (RTKs) and trimeric G proteins are 2 such major signaling hubs in eukaryotes. Canonical signal transduction via trimeric G proteins is spatially and temporally restricted, i.e., triggered exclusively at the plasma membrane (PM) by agonist activation of G-protein-coupled receptors (GPCRs) via a process that completes within a few hundred milliseconds. Recently, a rapidly emerging paradigm has revealed a non-canonical pathway for activation of trimeric G proteins by the non-receptor GEF, GIV/Girdin, that has distinctive temporal and spatial features. Such activation can be triggered by multiple growth factor RTKs, can occur at the PM and on internal membranes discontinuous with the PM, and can continue for prolonged periods of time. The molecular mechanisms that govern such non-canonical G protein activation and the relevance of this new paradigm in health and disease is discussed.
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Affiliation(s)
- Pradipta Ghosh
- a Department of Medicine ; University of California at San Diego ; La Jolla , CA USA
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32
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From Glomerular Endothelium to Podocyte Pathobiology in Preeclampsia: a Paradigm Shift. Curr Hypertens Rep 2015; 17:54. [DOI: 10.1007/s11906-015-0566-9] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/15/2023]
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33
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SV2B is essential for the integrity of the glomerular filtration barrier. J Transl Med 2015; 95:534-45. [PMID: 25730372 DOI: 10.1038/labinvest.2015.39] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/08/2014] [Revised: 12/12/2014] [Accepted: 12/17/2014] [Indexed: 11/09/2022] Open
Abstract
The glomerular visceral epithelial cell (podocyte) is characterized as a specialized structure of the interdigitating foot processes, covering the outer side of the glomerular basement membrane (GBM). The neighboring foot processes are connected by a slit diaphragm, which is a key structure regulating the barrier function of the glomerular capillary wall to prevent proteinuria. We have previously reported that synaptic vesicle protein 2 B (SV2B) is expressed in the podocyte and that the expression is clearly decreased in nephrotic models. However, the precise function of SV2B in the podocyte is unclear. To investigate the role of SV2B in maintaining the podocyte function and to better understand the function of the neuron-like vesicle expressing SV2B in the podocyte, we analyzed them with SV2B knockout (KO) mice. An increase in the amount of proteinuria, effacement of the foot process of the podocyte, and alterations of the GBM were detected in SV2B KO mice. It was also found that the expression of CD2AP, nephrin, and NEPH1, the functional molecules of the slit diaphragm, and laminin, a critical component of the GBM, is clearly altered in SV2B KO mice. Synaptotagmin and neurexin, which have a role in the synaptic vesicle docking in neurons, are downregulated in the kidney cortex of SV2B KO mice. We have previously reported that neurexin interacts with CD2AP, and the present study shows that SV2B interacts with CD2AP. These findings suggest that the SV2B-neurexin complex is involved in the formation and maintenance of the slit diaphragm. In addition, SV2B is densely expressed close to the cell surface in the presumptive podocyte in the early stage of glomerulogenesis. These results suggest that SV2B has an essential role in the formation and maintenance of the glomerular capillary wall.
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34
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Therapeutic effects of cell-permeant peptides that activate G proteins downstream of growth factors. Proc Natl Acad Sci U S A 2015; 112:E2602-10. [PMID: 25926659 DOI: 10.1073/pnas.1505543112] [Citation(s) in RCA: 31] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
In eukaryotes, receptor tyrosine kinases (RTKs) and trimeric G proteins are two major signaling hubs. Signal transduction via trimeric G proteins has long been believed to be triggered exclusively by G protein-coupled receptors (GPCRs). This paradigm has recently been challenged by several studies on a multimodular signal transducer, Gα-Interacting Vesicle associated protein (GIV/Girdin). We recently demonstrated that GIV's C terminus (CT) serves as a platform for dynamic association of ligand-activated RTKs with Gαi, and for noncanonical transactivation of G proteins. However, exogenous manipulation of this platform has remained beyond reach. Here we developed cell-permeable GIV-CT peptides by fusing a TAT-peptide transduction domain (TAT-PTD) to the minimal modular elements of GIV that are necessary and sufficient for activation of Gi downstream of RTKs, and used them to engineer signaling networks and alter cell behavior. In the presence of an intact GEF motif, TAT-GIV-CT peptides enhanced diverse processes in which GIV's GEF function has previously been implicated, e.g., 2D cell migration after scratch-wounding, invasion of cancer cells, and finally, myofibroblast activation and collagen production. Furthermore, topical application of TAT-GIV-CT peptides enhanced the complex, multireceptor-driven process of wound repair in mice in a GEF-dependent manner. Thus, TAT-GIV peptides provide a novel and versatile tool to manipulate Gαi activation downstream of growth factors in a diverse array of pathophysiologic conditions.
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35
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Midde KK, Aznar N, Laederich MB, Ma GS, Kunkel MT, Newton AC, Ghosh P. Multimodular biosensors reveal a novel platform for activation of G proteins by growth factor receptors. Proc Natl Acad Sci U S A 2015; 112:E937-46. [PMID: 25713130 PMCID: PMC4352799 DOI: 10.1073/pnas.1420140112] [Citation(s) in RCA: 39] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022] Open
Abstract
Environmental cues are transmitted to the interior of the cell via a complex network of signaling hubs. Receptor tyrosine kinases (RTKs) and trimeric G proteins are two such major signaling hubs in eukaryotes. Conventionally, canonical signal transduction via trimeric G proteins is thought to be triggered exclusively by G protein-coupled receptors. Here we used molecular engineering to develop modular fluorescent biosensors that exploit the remarkable specificity of bimolecular recognition, i.e., of both G proteins and RTKs, and reveal the workings of a novel platform for activation of G proteins by RTKs in single living cells. Comprised of the unique modular makeup of guanidine exchange factor Gα-interacting vesicle-associated protein (GIV)/girdin, a guanidine exchange factor that links G proteins to a variety of RTKs, these biosensors provide direct evidence that RTK-GIV-Gαi ternary complexes are formed in living cells and that Gαi is transactivated within minutes after growth factor stimulation at the plasma membrane. Thus, GIV-derived biosensors provide a versatile strategy for visualizing, monitoring, and manipulating the dynamic association of Gαi with RTKs for noncanonical transactivation of G proteins in cells and illuminate a fundamental signaling event regulated by GIV during diverse cellular processes and pathophysiologic states.
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Affiliation(s)
| | | | | | | | | | | | - Pradipta Ghosh
- Departments of Medicine and Pharmacology and Moores Cancer Center, University of California, San Diego, La Jolla, CA 92093
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36
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Abstract
Heterotrimeric G proteins play a crucial role in regulating signal processing to maintain normal cellular homeostasis, and subtle perturbations in its activity can potentially lead to the pathogenesis of renal disorders or diseases. Cell-surface receptors and accessory proteins, which normally modify and organize the coupling of individual G protein subunits, contribute to the regulation of heterotrimeric G protein activity and their convergence and/or divergence of downstream signaling initiated by effector systems. Activators of G protein signaling (AGS) are a family of accessory proteins that intervene at multiple distinct points during the activation-inactivation cycle of G proteins, even in the absence of receptor stimulation. Perturbations in the expression of individual AGS proteins have been reported to modulate signal transduction pathways in a wide array of diseases and disorders within the brain, heart, immune system, and more recently, the kidney. This review will provide an overview of the expression profile, localization, and putative biologic role of the AGS family in the context of normal and diseased states of the kidney.
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Affiliation(s)
- Frank Park
- Department of Pharmaceutical Sciences, College of Pharmacy, University of Tennessee Health Science Center, Memphis, Tennessee
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37
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Garcia-Marcos M, Ghosh P, Farquhar MG. GIV/Girdin transmits signals from multiple receptors by triggering trimeric G protein activation. J Biol Chem 2015; 290:6697-704. [PMID: 25605737 DOI: 10.1074/jbc.r114.613414] [Citation(s) in RCA: 70] [Impact Index Per Article: 7.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022] Open
Abstract
Activation of trimeric G proteins has been traditionally viewed as the exclusive job of G protein-coupled receptors (GPCRs). This view has been challenged by the discovery of non-receptor activators of trimeric G proteins. Among them, GIV (a.k.a. Girdin) is the first for which a guanine nucleotide exchange factor (GEF) activity has been unequivocally associated with a well defined motif. Here we discuss how GIV assembles alternative signaling pathways by sensing cues from various classes of surface receptors and relaying them via G protein activation. We also describe the dysregulation of this mechanism in disease and how its targeting holds promise for novel therapeutics.
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Affiliation(s)
- Mikel Garcia-Marcos
- From the Department of Biochemistry, Boston University School of Medicine, Boston, Massachusetts 02118 and
| | | | - Marilyn G Farquhar
- Cellular and Molecular Medicine, University of California, San Diego, La Jolla, California 92093-0651
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Bai X, Geng J, Li X, Yang F, Tian J. VEGF-A inhibition ameliorates podocyte apoptosis via repression of activating protein 1 in diabetes. Am J Nephrol 2015; 40:523-34. [PMID: 25572464 DOI: 10.1159/000369942] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/28/2014] [Accepted: 11/12/2014] [Indexed: 12/14/2022]
Abstract
BACKGROUND/AIMS Vascular endothelial growth factor-A (VEGF-A) upregulation and podocyte apoptosis have been documented in diabetes. This study was designed to investigate whether inhibiting VEGF-A could ameliorate podocyte apoptosis in diabetes and the underlying mechanisms. METHODS In vitro, small interfering RNAs (siRNAs) of VEGF-A and activator protein 1 (AP-1, c-fos and c-jun), bevacizumab (VEGF-A inhibitor) and SP600125 (AP-1 inhibitor) were added to high glucose (30 mM) induced podocytes. Luciferase reporter assay was used to investigate whether AP-1 was a direct target of VEGF-A. In vivo, bevacizumab and SP600125 were administered to 12-week-old streptozotocin-induced male Sprague Dawley rats. The level of VEGF-A, c-fos, c-jun and bcl-2 were examined using immunostaining and Western blot analysis. Podocyte apoptosis was detected using the terminal deoxynucleotidyl transferase-mediated uridine 5'-triphosphate-biotin nick end labeling (TUNEL) assay, electron microscopy and flow cytometry. RESULTS Silencing VEGF-A or AP-1 upregulated bcl-2 and ameliorated podocyte apoptosis. Silencing VEGF-A decreased the level of c-fos and c-jun and bevacizumab and SP600125 treatment attenuated podocyte apoptosis. Luciferase reporter activity of VEGF-A-3'-UTR constructs was significantly provoked when stimulated with TGF-β1. In diabetic rat kidneys, VEGF-A co-localized with bcl-2 in podocytes. With bevacizumab and SP600125 treatment, the level of VEGF-A and AP-1 decreased while bcl-2 increased. Podocyte apoptotic rate was reduced with condensed podocyte nuclei less frequently observed. The urine albumin excretion rate (UAER) and albumin/creatinine were improved. CONCLUSION This study demonstrates VEGF-A inhibition ameliorates podocyte apoptosis by regulating AP-1 and bcl-2 signaling. AP-1 is a direct target of VEGF-A and a novel player in podocyte apoptosis.
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Affiliation(s)
- Xiaoyan Bai
- Division of Nephrology, Nanfang Hospital, Southern Medical University, National Clinical Medical Research Center for Kidney Disease, National Key Lab for Organ Failure Research, Guangdong Provincial Institute of Nephrology, Guangzhou, Guangdong, PR China
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Localization and expression profile of Group I and II Activators of G-protein Signaling in the kidney. J Mol Histol 2014; 46:123-36. [PMID: 25533045 DOI: 10.1007/s10735-014-9605-0] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/21/2014] [Accepted: 12/15/2014] [Indexed: 10/24/2022]
Abstract
Activators of G-protein Signaling (AGS) are a family of accessory proteins that were discovered as modulators of heterotrimeric G-protein subunits. The primary aim of the present study was to localize Group I and II AGS proteins and determine the renal expression profile using immunohistochemistry and quantitative RT-PCR, respectively, during normal and injured states of the kidney. Group I AGS1 was found to be predominantly localized to the proximal tubule, Group II AGS3 and AGS5 were exclusively localized to the distal tubular segments, and Group II AGS6 was ubiquitously expressed in every nephron segment of the rodent kidney. In rat kidneys following ischemia-reperfusion injury (IRI), Group I AGS1 mRNA was dramatically increased after 24 h by fivefold (P < 0.05), whereas Group II AGS3 and AGS4 mRNA was significantly decreased at the same time point (P < 0.05). No significant change in the transcript levels were detected at other time points for any of the AGS genes between control and IRI groups. In polycystic diseased kidneys, mRNA levels for AGS3, AGS4 and AGS6 was significantly increased (P < 0.05) by 75-80 % in PCK rat kidneys. The identification of Group I and II AGS mRNA and protein in the kidney may provide insight into the potential mechanism of action during normal and varying states of renal disease or injury.
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Lin C, Ear J, Midde K, Lopez-Sanchez I, Aznar N, Garcia-Marcos M, Kufareva I, Abagyan R, Ghosh P. Structural basis for activation of trimeric Gi proteins by multiple growth factor receptors via GIV/Girdin. Mol Biol Cell 2014; 25:3654-71. [PMID: 25187647 PMCID: PMC4230624 DOI: 10.1091/mbc.e14-05-0978] [Citation(s) in RCA: 50] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/07/2023] Open
Abstract
GIV, a guanidine exchange factor for trimeric Gi, contains a unique domain that functions like a SH2 domain. GIV's SH2-like domain binds autophosphorylated RTKs. Binding of GIV's SH2 to RTKs enables the receptors to activate trimeric Gi. Inhibition of GIV:RTK interaction abolishes GIV-dependent Akt enhancement downstream of RTKs. A long-standing issue in the field of signal transduction is to understand the cross-talk between receptor tyrosine kinases (RTKs) and heterotrimeric G proteins, two major and distinct signaling hubs that control eukaryotic cell behavior. Although stimulation of many RTKs leads to activation of trimeric G proteins, the molecular mechanisms behind this phenomenon remain elusive. We discovered a unifying mechanism that allows GIV/Girdin, a bona fide metastasis-related protein and a guanine-nucleotide exchange factor (GEF) for Gαi, to serve as a direct platform for multiple RTKs to activate Gαi proteins. Using a combination of homology modeling, protein–protein interaction, and kinase assays, we demonstrate that a stretch of ∼110 amino acids within GIV C-terminus displays structural plasticity that allows folding into a SH2-like domain in the presence of phosphotyrosine ligands. Using protein–protein interaction assays, we demonstrated that both SH2 and GEF domains of GIV are required for the formation of a ligand-activated ternary complex between GIV, Gαi, and growth factor receptors and for activation of Gαi after growth factor stimulation. Expression of a SH2-deficient GIV mutant (Arg 1745→Leu) that cannot bind RTKs impaired all previously demonstrated functions of GIV—Akt enhancement, actin remodeling, and cell migration. The mechanistic and structural insights gained here shed light on the long-standing questions surrounding RTK/G protein cross-talk, set a novel paradigm, and characterize a unique pharmacological target for uncoupling GIV-dependent signaling downstream of multiple oncogenic RTKs.
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Affiliation(s)
- Changsheng Lin
- Department of Medicine, University of California, San Diego, School of Medicine, CA 92093
| | - Jason Ear
- Department of Medicine, University of California, San Diego, School of Medicine, CA 92093
| | - Krishna Midde
- Department of Medicine, University of California, San Diego, School of Medicine, CA 92093
| | | | - Nicolas Aznar
- Department of Medicine, University of California, San Diego, School of Medicine, CA 92093
| | - Mikel Garcia-Marcos
- Department of Cellular and Molecular Medicine, University of California, San Diego, School of Medicine, CA 92093
| | - Irina Kufareva
- Skaggs School of Pharmacy and Pharmaceutical Sciences, University of California, San Diego, La Jolla, CA 92093
| | - Ruben Abagyan
- Skaggs School of Pharmacy and Pharmaceutical Sciences, University of California, San Diego, La Jolla, CA 92093
| | - Pradipta Ghosh
- Department of Medicine, University of California, San Diego, School of Medicine, CA 92093
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