1
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Qiao L, Sinha S, Abd El-Hafeez AA, Lo IC, Midde KK, Ngo T, Aznar N, Lopez-Sanchez I, Gupta V, Farquhar MG, Rangamani P, Ghosh P. A circuit for secretion-coupled cellular autonomy in multicellular eukaryotic cells. Mol Syst Biol 2023; 19:e11127. [PMID: 36856068 PMCID: PMC10090951 DOI: 10.15252/msb.202211127] [Citation(s) in RCA: 9] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/18/2022] [Revised: 02/06/2023] [Accepted: 02/07/2023] [Indexed: 03/02/2023] Open
Abstract
Cancers represent complex autonomous systems, displaying self-sufficiency in growth signaling. Autonomous growth is fueled by a cancer cell's ability to "secrete-and-sense" growth factors (GFs): a poorly understood phenomenon. Using an integrated computational and experimental approach, here we dissect the impact of a feedback-coupled GTPase circuit within the secretory pathway that imparts secretion-coupled autonomy. The circuit is assembled when the Ras-superfamily monomeric GTPase Arf1, and the heterotrimeric GTPase Giαβγ and their corresponding GAPs and GEFs are coupled by GIV/Girdin, a protein that is known to fuel aggressive traits in diverse cancers. One forward and two key negative feedback loops within the circuit create closed-loop control, allow the two GTPases to coregulate each other, and convert the expected switch-like behavior of Arf1-dependent secretion into an unexpected dose-response alignment behavior of sensing and secretion. Such behavior translates into cell survival that is self-sustained by stimulus-proportionate secretion. Proteomic studies and protein-protein interaction network analyses pinpoint GFs (e.g., the epidermal GF) as key stimuli for such self-sustenance. Findings highlight how the enhanced coupling of two biological switches in cancer cells is critical for multiscale feedback control to achieve secretion-coupled autonomy of growth factors.
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Affiliation(s)
- Lingxia Qiao
- Department of Mechanical and Aerospace Engineering, Jacob's School of Engineering, University of California San Diego, La Jolla, CA, USA
| | - Saptarshi Sinha
- Department of Cellular and Molecular Medicine, School of Medicine, University of California San Diego, La Jolla, CA, USA
| | - Amer Ali Abd El-Hafeez
- Department of Cellular and Molecular Medicine, School of Medicine, University of California San Diego, La Jolla, CA, USA
| | - I-Chung Lo
- Department of Cellular and Molecular Medicine, School of Medicine, University of California San Diego, La Jolla, CA, USA
| | - Krishna K Midde
- Department of Cellular and Molecular Medicine, School of Medicine, University of California San Diego, La Jolla, CA, USA
| | - Tony Ngo
- Skaggs School of Pharmacy and Pharmaceutical Science, University of California San Diego, La Jolla, CA, USA
| | - Nicolas Aznar
- Department of Cellular and Molecular Medicine, School of Medicine, University of California San Diego, La Jolla, CA, USA
| | - Inmaculada Lopez-Sanchez
- Department of Cellular and Molecular Medicine, School of Medicine, University of California San Diego, La Jolla, CA, USA
| | - Vijay Gupta
- Department of Cellular and Molecular Medicine, School of Medicine, University of California San Diego, La Jolla, CA, USA
| | - Marilyn G Farquhar
- Department of Cellular and Molecular Medicine, School of Medicine, University of California San Diego, La Jolla, CA, USA
| | - Padmini Rangamani
- Department of Mechanical and Aerospace Engineering, Jacob's School of Engineering, University of California San Diego, La Jolla, CA, USA
| | - Pradipta Ghosh
- Department of Cellular and Molecular Medicine, School of Medicine, University of California San Diego, La Jolla, CA, USA.,Moores Comprehensive Cancer Center, University of California San Diego, La Jolla, CA, USA.,Department of Medicine, School of Medicine, University of California San Diego, La Jolla, CA, USA.,Veterans Affairs Medical Center, La Jolla, CA, USA
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2
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Regulation of DNA damage response by trimeric G-proteins. iScience 2023; 26:105973. [PMID: 36756378 PMCID: PMC9900518 DOI: 10.1016/j.isci.2023.105973] [Citation(s) in RCA: 5] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/10/2020] [Revised: 08/14/2022] [Accepted: 01/10/2023] [Indexed: 01/14/2023] Open
Abstract
Upon sensing DNA double-strand breaks (DSBs), eukaryotic cells either die or repair DSBs via one of the two competing pathways, i.e., non-homologous end-joining (NHEJ) or homologous recombination (HR). We show that cell fate after DSBs hinges on GIV/Girdin, a guanine nucleotide-exchange modulator of heterotrimeric Giα•βγ protein. GIV suppresses HR by binding and sequestering BRCA1, a key coordinator of multiple steps within the HR pathway, away from DSBs; it does so using a C-terminal motif that binds BRCA1's BRCT-modules via both phospho-dependent and -independent mechanisms. Using another non-overlapping C-terminal motif GIV binds and activates Gi and enhances the "free" Gβγ→PI-3-kinase→Akt pathway, which promotes survival and is known to suppress HR, favor NHEJ. Absence of GIV, or loss of either of its C-terminal motifs enhanced cell death upon genotoxic stress. Because GIV selectively binds other BRCT-containing proteins suggests that G-proteins may fine-tune sensing, repair, and survival after diverse types of DNA damage.
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3
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Abd El-hafeez AA, Sun N, Chakraborty A, Ear J, Roy S, Chamarthi P, Rajapakse N, Das S, Luker KE, Hazra TK, Luker GD, Ghosh P. Regulation of DNA damage response by trimeric G-protein Signaling.. [DOI: 10.1101/2021.07.21.452842] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 09/02/2023]
Abstract
AbstractUpon sensing DNA double-strand breaks (DSBs), eukaryotic cells either die or repair DSBs via one of two competing pathways, i.e., non-homologous end-joining (NHEJ) or homologous recombination (HR). We show that cell fate after DNA damage hinges on the guanine nucleotide-exchange modulator of heterotrimeric G-protein, Giα•βγ, GIV/Girdin. GIV suppresses HR by binding and sequestering BRCA1, a key coordinator of multiple steps within the HR pathway, away from DSBs; it does so using a C-terminal motif that binds BRCA1’s BRCT-modules via both phospho-dependent and -independent mechanisms. GIV promotes NHEJ, and binds and activates Gi and enhances the ‘free’ Gβγ→PI-3-kinase→Akt pathway, thus revealing the enigmatic origin of prosurvival Akt signals during dsDNA repair. Absence of GIV, or the loss of either of its two functions impaired DNA repair, and induced cell death when challenged with numerous cytotoxic agents. That GIV selectively binds few other BRCT-containing proteins suggests convergent signaling such that heterotrimeric G-proteins may finetune sensing, repair, and outcome after DNA damage.GRAPHIC ABSTRACTHIGHLIGHTSNon-receptor G protein modulator, GIV/Girdin binds BRCA1Binding occurs in both canonical and non-canonical modesGIV sequesters BRCA1 away from dsDNA breaks, suppresses HRActivation of Gi by GIV enhances Akt signals, favors NHEJIN BRIEFIn this work, the authors show that heterotrimeric G protein signaling that is triggered by non-receptor GEF, GIV/Girdin, in response to double-stranded DNA breaks is critical for decisive signaling events which favor non-homologous end-joining (NHEJ) and inhibit homologous recombination (HR).
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Landin Malt A, Hogan AK, Smith CD, Madani MS, Lu X. Wnts regulate planar cell polarity via heterotrimeric G protein and PI3K signaling. J Cell Biol 2021; 219:152025. [PMID: 32805026 PMCID: PMC7659710 DOI: 10.1083/jcb.201912071] [Citation(s) in RCA: 16] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/12/2019] [Revised: 04/15/2020] [Accepted: 07/13/2020] [Indexed: 12/16/2022] Open
Abstract
In the mammalian cochlea, the planar cell polarity (PCP) pathway aligns hair cell orientation along the plane of the sensory epithelium. Concurrently, multiple cell intrinsic planar polarity (referred to as iPCP) modules mediate planar polarization of the hair cell apical cytoskeleton, including the kinocilium and the V-shaped hair bundle essential for mechanotransduction. How PCP and iPCP are coordinated during development and the roles of Wnt ligands in this process remain unresolved. Here we show that genetic blockade of Wnt secretion in the cochlear epithelium resulted in a shortened cochlear duct and misoriented and misshapen hair bundles. Mechanistically, Wnts stimulate Gi activity by regulating the localization of Daple, a guanine nucleotide exchange factor (GEF) for Gαi. In turn, the Gβγ complex signals through phosphoinositide 3-kinase (PI3K) to regulate kinocilium positioning and asymmetric localizations of a subset of core PCP proteins, thereby coordinating PCP and iPCP. Thus, our results identify a putative Wnt/heterotrimeric G protein/PI3K pathway for PCP regulation.
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Affiliation(s)
- Andre Landin Malt
- Department of Cell Biology, University of Virginia Health System, Charlottesville, VA
| | - Arielle K Hogan
- Department of Cell Biology, University of Virginia Health System, Charlottesville, VA
| | - Connor D Smith
- Department of Cell Biology, University of Virginia Health System, Charlottesville, VA
| | - Maxwell S Madani
- Department of Cell Biology, University of Virginia Health System, Charlottesville, VA
| | - Xiaowei Lu
- Department of Cell Biology, University of Virginia Health System, Charlottesville, VA
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5
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Qiao L, Sinha S, El-hafeez AAA, Lo I, Midde KK, Ngo T, Aznar N, Lopez-sanchez I, Gupta V, Farquhar MG, Rangamani P, Ghosh P. A Circuit for Secretion-coupled Cellular Autonomy in Multicellular Eukaryotes.. [DOI: 10.1101/2021.03.18.436048] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 09/02/2023]
Abstract
ABSTRACTCancers represent complex autonomous systems, displaying self-sufficiency in growth signaling. Autonomous growth is fueled by a cancer cell’s ability to ‘secrete-and-sense’ growth factors: a poorly understood phenomenon. Using an integrated systems and experimental approach, here we dissect the impact of a feedback-coupled GTPase circuit within the secretory pathway that imparts secretion-coupled autonomy. The circuit is assembled when the Ras-superfamily monomeric GTPase Arf1, and the heterotrimeric GTPase Giαβγ and their corresponding GAPs and GEFs are coupled by GIV/Girdin, a protein that is known to fuel aggressive traits in diverse cancers. One forward and two key negative feedback loops within the circuit create closed-loop control (CLC), allow the two GTPases to coregulate each other, and convert the expected switch-like behavior of Arf1-dependent secretion into an unexpected dose response alignment behavior of sensing and secretion. Such behavior translates into cell survival that is self-sustained by stimulus-proportionate secretion. Proteomic studies and protein-protein interaction network analyses pinpoint growth factors (e.g., the epidermal growth factor; EGF) as a key stimuli for such self-sustenance. Findings highlight how enhanced coupling of two biological switches in cancer cells is critical for multiscale feedback control to achieve secretion-coupled autonomy of growth factors.SYNOPSIS IMAGESTANDFIRST TEXTThis work defines the inner workings of a Golgi-localized molecular circuitry comprised of coupled GTPases, which empowers cells to achieve self-sufficiency in growth factor signaling by creating a secrete-and-sense autocrine loop.HIGHLIGHTS/MAIN FINDINGSModeling and experimental approaches were used to dissect a coupled GTPase circuit.Coupling enables closed loop feedback and mutual control of GTPases.Coupling generates dose response alignment behavior of sensing and secretion of growth factors.Coupling is critical for multiscale feedback control to achieve secretion-coupled autonomy.
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6
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Receptor tyrosine kinases activate heterotrimeric G proteins via phosphorylation within the interdomain cleft of Gαi. Proc Natl Acad Sci U S A 2020; 117:28763-28774. [PMID: 33139573 DOI: 10.1073/pnas.2004699117] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/19/2023] Open
Abstract
The molecular mechanisms by which receptor tyrosine kinases (RTKs) and heterotrimeric G proteins, two major signaling hubs in eukaryotes, independently relay signals across the plasma membrane have been extensively characterized. How these hubs cross-talk has been a long-standing question, but answers remain elusive. Using linear ion-trap mass spectrometry in combination with biochemical, cellular, and computational approaches, we unravel a mechanism of activation of heterotrimeric G proteins by RTKs and chart the key steps that mediate such activation. Upon growth factor stimulation, the guanine-nucleotide exchange modulator dissociates Gαi•βγ trimers, scaffolds monomeric Gαi with RTKs, and facilitates the phosphorylation on two tyrosines located within the interdomain cleft of Gαi. Phosphorylation triggers the activation of Gαi and inhibits second messengers (cAMP). Tumor-associated mutants reveal how constitutive activation of this pathway impacts cell's decision to "go" vs. "grow." These insights define a tyrosine-based G protein signaling paradigm and reveal its importance in eukaryotes.
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7
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Aznar N, Ear J, Dunkel Y, Sun N, Satterfield K, He F, Kalogriopoulos NA, Lopez-Sanchez I, Ghassemian M, Sahoo D, Kufareva I, Ghosh P. Convergence of Wnt, growth factor, and heterotrimeric G protein signals on the guanine nucleotide exchange factor Daple. Sci Signal 2018; 11:11/519/eaao4220. [PMID: 29487190 DOI: 10.1126/scisignal.aao4220] [Citation(s) in RCA: 21] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
Cellular proliferation, differentiation, and morphogenesis are shaped by multiple signaling cascades, and their dysregulation plays an integral role in cancer progression. Three cascades that contribute to oncogenic potential are those mediated by Wnt proteins and the receptor Frizzled (FZD), growth factor receptor tyrosine kinases (RTKs), and heterotrimeric G proteins and associated GPCRs. Daple is a guanine nucleotide exchange factor (GEF) for the G protein Gαi Daple also binds to FZD and the Wnt/FZD mediator Dishevelled (Dvl), and it enhances β-catenin-independent Wnt signaling in response to Wnt5a-FZD7 signaling. We identified Daple as a substrate of multiple RTKs and non-RTKs and, hence, as a point of convergence for the three cascades. We found that phosphorylation near the Dvl-binding motif in Daple by both RTKs and non-RTKs caused Daple/Dvl complex dissociation and augmented the ability of Daple to bind to and activate Gαi, which potentiated β-catenin-independent Wnt signals and stimulated epithelial-mesenchymal transition (EMT) similarly to Wnt5a/FZD7 signaling. Although Daple acts as a tumor suppressor in the healthy colon, the concurrent increased abundance of Daple and epidermal growth factor receptor (EGFR) in colorectal tumors was associated with poor patient prognosis. Thus, the Daple-dependent activation of Gαi and the Daple-dependent enhancement of β-catenin-independent Wnt signals are not only stimulated by Wnt5a/FZD7 to suppress tumorigenesis but also hijacked by growth factor-activated RTKs to enhance tumor progression. These findings identify a cross-talk paradigm among growth factor RTKs, heterotrimeric G proteins, and the Wnt/FZD pathway in cancer.
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Affiliation(s)
- Nicolas Aznar
- Department of Medicine, University of California, San Diego, La Jolla, CA 92093, USA.
| | - Jason Ear
- Department of Medicine, University of California, San Diego, La Jolla, CA 92093, USA
| | - Ying Dunkel
- Department of Medicine, University of California, San Diego, La Jolla, CA 92093, USA
| | - Nina Sun
- Department of Medicine, University of California, San Diego, La Jolla, CA 92093, USA
| | - Kendall Satterfield
- Department of Medicine, University of California, San Diego, La Jolla, CA 92093, USA
| | - Fang He
- Department of Medicine, University of California, San Diego, La Jolla, CA 92093, USA
| | | | | | - Majid Ghassemian
- Department of Chemistry and Biochemistry, University of California, San Diego, La Jolla, CA 92093, USA
| | - Debashis Sahoo
- Skaggs School of Pharmacy and Pharmaceutical Sciences, University of California, San Diego, La Jolla, CA 92093, USA.,Department of Computer Science and Engineering, Jacobs School of Engineering, University of California, San Diego, La Jolla, CA 92093, USA
| | - Irina Kufareva
- Department of Pediatrics, 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 Cancer Center, University of California, San Diego, La Jolla, CA 92093, USA
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8
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Hudson BD. Using Biosensors to Study Free Fatty Acid Receptor Pharmacology and Function. Handb Exp Pharmacol 2016; 236:79-100. [PMID: 27757763 DOI: 10.1007/164_2016_58] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/22/2023]
Abstract
The free fatty acid (FFA) family of G protein coupled receptors (GPCRs) has generated significant interest for exploiting its members as potential drug targets. However, unravelling the complex pharmacology of this family of receptors has proven challenging. In recent years the use of biosensor technologies capable of assessing biological functions in living cells, and in real time, has greatly enhanced our ability to study GPCR pharmacology and function. These include genetically encoded sensors that change the intensity or wavelength of light emitted from a bioluminescent or fluorescent protein in response to a stimulus, as well as non-genetically encoded sensors able to measure more global cellular changes, such as mass redistribution within a cell. This chapter will examine how these sensors can be used to study GPCRs, and in particular how they are helping uncover the pharmacology of the FFA family of receptors.
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Affiliation(s)
- Brian D Hudson
- Centre for Translational Pharmacology, Institute of Molecular, Cell and Systems Biology, University of Glasgow, Glasgow, G12 8QQ, UK.
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9
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Aznar N, Midde KK, Dunkel Y, Lopez-Sanchez I, Pavlova Y, Marivin A, Barbazán J, Murray F, Nitsche U, Janssen KP, Willert K, Goel A, Abal M, Garcia-Marcos M, Ghosh P. Daple is a novel non-receptor GEF required for trimeric G protein activation in Wnt signaling. eLife 2015; 4:e07091. [PMID: 26126266 PMCID: PMC4484057 DOI: 10.7554/elife.07091] [Citation(s) in RCA: 90] [Impact Index Per Article: 10.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/19/2015] [Accepted: 06/01/2015] [Indexed: 12/17/2022] Open
Abstract
Wnt signaling is essential for tissue homeostasis and its dysregulation causes cancer. Wnt ligands trigger signaling by activating Frizzled receptors (FZDRs), which belong to the G-protein coupled receptor superfamily. However, the mechanisms of G protein activation in Wnt signaling remain controversial. In this study, we demonstrate that FZDRs activate G proteins and trigger non-canonical Wnt signaling via the Dishevelled-binding protein, Daple. Daple contains a Gα-binding and activating (GBA) motif, which activates Gαi proteins and an adjacent domain that directly binds FZDRs, thereby linking Wnt stimulation to G protein activation. This triggers non-canonical Wnt responses, that is, suppresses the β-catenin/TCF/LEF pathway and tumorigenesis, but enhances PI3K-Akt and Rac1 signals and tumor cell invasiveness. In colorectal cancers, Daple is suppressed during adenoma-to-carcinoma transformation and expressed later in metastasized tumor cells. Thus, Daple activates Gαi and enhances non-canonical Wnt signaling by FZDRs, and its dysregulation can impact both tumor initiation and progression to metastasis.
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Affiliation(s)
- Nicolas Aznar
- Department of Medicine, University of California, San Diego, San Diego, United States
| | - Krishna K Midde
- 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
| | | | - Yelena Pavlova
- Department of Medicine, University of California, San Diego, San Diego, United States
| | - Arthur Marivin
- Department of Biochemistry, Boston University School of Medicine, Boston, United States
| | - Jorge Barbazán
- Translational Medical Oncology Laboratory, Health Research Institute of Santiago, Servizo Galego de Saúde, Santiago de Compostela, Spain
| | - Fiona Murray
- Department of Medicine, University of California, San Diego, San Diego, United States
| | - Ulrich Nitsche
- Department of Surgery, Klinikum rechts der Isar, Technische Universität München, Munich, Germany
| | - Klaus-Peter Janssen
- Department of Surgery, Klinikum rechts der Isar, Technische Universität München, Munich, Germany
| | - Karl Willert
- Sanford Consortium for Regenerative Medicine, University of California, San Diego, La Jolla, California, United States
| | - Ajay Goel
- Division of Gastroenterology, Department of Internal Medicine and Charles A Sammons Cancer Center and Baylor Research Institute, Baylor University Medical Center, Dallas, Texas, United States
| | - Miguel Abal
- Translational Medical Oncology Laboratory, Health Research Institute of Santiago, Servizo Galego de Saúde, Santiago de Compostela, Spain
| | - Mikel Garcia-Marcos
- Department of Biochemistry, Boston University School of Medicine, Boston, United States
| | - Pradipta Ghosh
- Department of Medicine, University of California, San Diego, San Diego, United States
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10
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Lo IC, Gupta V, Midde KK, Taupin V, Lopez-Sanchez I, Kufareva I, Abagyan R, Randazzo PA, Farquhar MG, Ghosh P. Activation of Gαi at the Golgi by GIV/Girdin imposes finiteness in Arf1 signaling. Dev Cell 2015; 33:189-203. [PMID: 25865347 DOI: 10.1016/j.devcel.2015.02.009] [Citation(s) in RCA: 36] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/07/2014] [Revised: 11/25/2014] [Accepted: 02/09/2015] [Indexed: 01/22/2023]
Abstract
A long-held tenet of heterotrimeric G protein signal transduction is that it is triggered by G protein-coupled receptors (GPCRs) at the PM. Here, we demonstrate that Gi is activated in the Golgi by GIV/Girdin, a non-receptor guanine-nucleotide exchange factor (GEF). GIV-dependent activation of Gi at the Golgi maintains the finiteness of the cyclical activation of ADP-ribosylation factor 1 (Arf1), a fundamental step in vesicle traffic in all eukaryotes. Several interactions with other major components of Golgi trafficking-e.g., active Arf1, its regulator, ArfGAP2/3, and the adaptor protein β-COP-enable GIV to coordinately regulate Arf1 signaling. When the GIV-Gαi pathway is selectively inhibited, levels of GTP-bound Arf1 are elevated and protein transport along the secretory pathway is delayed. These findings define a paradigm in non-canonical G protein signaling at the Golgi, which places GIV-GEF at the crossroads between signals gated by the trimeric G proteins and the Arf family of monomeric GTPases.
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Affiliation(s)
- I-Chung Lo
- Departments of Cellular and Molecular Medicine, University of California, San Diego, La Jolla, CA 92093, USA
| | - Vijay Gupta
- Departments of Cellular and Molecular Medicine, University of California, San Diego, La Jolla, CA 92093, USA
| | - Krishna K Midde
- Department of Medicine, University of California, San Diego, La Jolla, CA 92093, USA
| | - Vanessa Taupin
- Departments of Cellular and Molecular Medicine, University of California, San Diego, La Jolla, CA 92093, USA
| | | | - Irina Kufareva
- Skaggs School of Pharmacy and Pharmaceutical Sciences, University of California, San Diego, La Jolla, CA 92093, USA
| | - Ruben Abagyan
- Skaggs School of Pharmacy and Pharmaceutical Sciences, University of California, San Diego, La Jolla, CA 92093, USA
| | - Paul A Randazzo
- Laboratory of Cellular and Molecular Biology, Center for Cancer Research, National Cancer Institute, Bethesda, MD 20892, USA
| | - Marilyn G Farquhar
- Departments of Cellular and Molecular Medicine, 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.
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11
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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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12
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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: 48] [Impact Index Per Article: 4.8] [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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GIV/Girdin is a central hub for profibrogenic signalling networks during liver fibrosis. Nat Commun 2014; 5:4451. [PMID: 25043713 PMCID: PMC4107319 DOI: 10.1038/ncomms5451] [Citation(s) in RCA: 75] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/02/2014] [Accepted: 06/18/2014] [Indexed: 01/18/2023] Open
Abstract
Progressive liver fibrosis is characterized by the deposition of collagen by activated hepatic stellate cells (HSCs). Activation of HSCs is a multiple receptor-driven process in which profibrotic signals are enhanced, and anti-fibrotic pathways are suppressed. Here we report the discovery of a novel signaling platform comprised of G protein subunit, Gαi and GIV, its guanine exchange factor (GEF), which serves as a central hub within the fibrogenic signalling network initiated by diverse classes of receptors. GIV is expressed in the liver after fibrogenic injury and is required for HSC activation. Once expressed, GIV enhances the profibrotic (PI3K-Akt-FoxO1 and TGFβ-SMAD) and inhibits the anti-fibrotic (cAMP-PKA-pCREB) pathways to skew the signalling network in favor of fibrosis, all via activation of Gαi. We also provide evidence that GIV may serve as a biomarker for progression of fibrosis after liver injury and a therapeutic target for arresting and/or reversing HSC activation during liver fibrosis.
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Wang H, Misaki T, Taupin V, Eguchi A, Ghosh P, Farquhar MG. GIV/girdin links vascular endothelial growth factor signaling to Akt survival signaling in podocytes independent of nephrin. J Am Soc Nephrol 2014; 26:314-27. [PMID: 25012178 DOI: 10.1681/asn.2013090985] [Citation(s) in RCA: 39] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022] Open
Abstract
Podocytes are critically involved in the maintenance of the glomerular filtration barrier and are key targets of injury in many glomerular diseases. Chronic injury leads to progressive loss of podocytes, glomerulosclerosis, and renal failure. Thus, it is essential to maintain podocyte survival and avoid apoptosis after acute glomerular injury. In normal glomeruli, podocyte survival is mediated via nephrin-dependent Akt signaling. In several glomerular diseases, nephrin expression decreases and podocyte survival correlates with increased vascular endothelial growth factor (VEGF) signaling. How VEGF signaling contributes to podocyte survival and prevents apoptosis remains unknown. We show here that Gα-interacting, vesicle-associated protein (GIV)/girdin mediates VEGF receptor 2 (VEGFR2) signaling and compensates for nephrin loss. In puromycin aminonucleoside nephrosis (PAN), GIV expression increased, GIV was phosphorylated by VEGFR2, and p-GIV bound and activated Gαi3 and enhanced downstream Akt2, mammalian target of rapamycin complex 1 (mTORC1), and mammalian target of rapamycin complex-2 (mTORC2) signaling. In GIV-depleted podocytes, VEGF-induced Akt activation was abolished, apoptosis was triggered, and cell migration was impaired. These effects were reversed by introducing GIV but not a GIV mutant that cannot activate Gαi3. Our data indicate that after PAN injury, VEGF promotes podocyte survival by triggering assembly of an activated VEGFR2/GIV/Gαi3 signaling complex and enhancing downstream PI3K/Akt survival signaling. Because of its important role in promoting podocyte survival, GIV may represent a novel target for therapeutic intervention in the nephrotic syndrome and other proteinuric diseases.
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Affiliation(s)
- Honghui Wang
- Departments of Cellular and Molecular Medicine and
| | - Taro Misaki
- Departments of Cellular and Molecular Medicine and
| | | | - Akiko Eguchi
- Medicine, University of California, San Diego, La Jolla, California
| | - Pradipta Ghosh
- Medicine, University of California, San Diego, La Jolla, California
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Jenkins L, Alvarez-Curto E, Campbell K, de Munnik S, Canals M, Schlyer S, Milligan G. Agonist activation of the G protein-coupled receptor GPR35 involves transmembrane domain III and is transduced via Gα₁₃ and β-arrestin-2. Br J Pharmacol 2011; 162:733-48. [PMID: 20958291 DOI: 10.1111/j.1476-5381.2010.01082.x] [Citation(s) in RCA: 53] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022] Open
Abstract
BACKGROUND AND PURPOSE GPR35 is a poorly characterized G protein-coupled receptor at which kynurenic acid has been suggested to be the endogenous ligand. We wished to test this and develop assays appropriate for the study of this receptor. EXPERIMENTAL APPROACH Human and rat orthologues of GPR35 were engineered and expressed and assays developed to assess interaction with β-arrestin-2, activation of Gα₁₃ and agonist-induced internalization. KEY RESULTS GPR35-β-arrestin-2 interaction assays confirmed that both the endogenous tryptophan metabolite kynurenic acid and the synthetic ligand zaprinast had agonist action at each orthologue. Zaprinast was substantially more potent than kynurenic acid at each and both agonists displayed substantially greater potency at rat GPR35. Two novel thiazolidinediones also displayed agonism and displayed similar potency at each GPR35 orthologue. The three ligand classes acted orthosterically with respect to each other, suggesting overlapping binding sites and, consistent with this, mutation to alanine of the conserved arginine at position 3.36 or tyrosine 3.32 in transmembrane domain III abolished β-arrestin-2 recruitment in response to each ligand at each orthologue. CONCLUSIONS AND IMPLICATIONS These studies indicate that β-arrestin-2 interaction assays are highly appropriate to explore the pharmacology of GPR35 and that Gα₁₃ activation is an alternative avenue of signal generation from GPR35. Arginine and tyrosine residues in transmembrane domain III are integral to agonist recognition and function of this receptor. The potency of kynurenic acid at human GPR35 is sufficiently low, however, to question whether it is likely to be the true endogenous ligand for this receptor.
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Affiliation(s)
- Laura Jenkins
- Molecular Pharmacology Group, Neuroscience and Molecular Pharmacology, Faculty of Biomedical and Life Sciences, University of Glasgow, Glasgow, UK
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Replication methods and tools in high-throughput cultivation processes - recognizing potential variations of growth and product formation by on-line monitoring. BMC Biotechnol 2010; 10:22. [PMID: 20233443 PMCID: PMC2847957 DOI: 10.1186/1472-6750-10-22] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/31/2009] [Accepted: 03/16/2010] [Indexed: 11/17/2022] Open
Abstract
Background High-throughput cultivations in microtiter plates are the method of choice to express proteins from recombinant clone libraries. Such processes typically include several steps, whereby some of them are linked by replication steps: transformation, plating, colony picking, preculture, main culture and induction. In this study, the effects of conventional replication methods and replication tools (8-channel pipette, 96-pin replicators: steel replicator with fixed or spring-loaded pins, plastic replicator with fixed pins) on growth kinetics of Escherichia coli SCS1 pQE-30 pSE111 were observed. Growth was monitored with the BioLector, an on-line monitoring technique for microtiter plates. Furthermore, the influence of these effects on product formation of Escherichia coli pRhotHi-2-EcFbFP was investigated. Finally, a high-throughput cultivation process was simulated with Corynebacterium glutamicum pEKEx2-phoD-GFP, beginning at the colony picking step. Results Applying different replication tools and methods for one single strain resulted in high time differences of growth of the slowest and fastest growing culture. The shortest time difference (0.3 h) was evaluated for the 96 cultures that were transferred with an 8-channel pipette from a thawed and mixed cryoculture and the longest time difference (6.9 h) for cultures that were transferred with a steel replicator with fixed pins from a frozen cryoculture. The on-line monitoring of a simulated high-throughput cultivation process revealed strong variances in growth kinetics and a twofold difference in product formation. Another experiment showed that varying growth kinetics, caused by varying initial biomass concentrations (OD600 of 0.0125 to 0.2) led to strongly varying product formation upon induction at a defined point of time. Conclusions To improve the reproducibility of high-throughput cultivation processes and the comparability between different applied cultures, it is strongly recommended to use automated or manual liquid handling stations or, alternatively, multi-channel pipettes. Because of their higher transfer volume and hence precision in comparison to pin replicators, they reduce the variance of initial biomass concentrations. With respect to the results obtained, other methods to increase the comparability between parallel cultivations by compensating differences in biomass concentrations are required, such as using autoinduction media, fed-batch operation of precultures or on-line monitoring in microtiter plates combined with automated liquid handling.
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Cavero I, Kaplan HR. Drug discovery paradigms: past, present, future - a centennial symposium of the American Society for Pharmacology and Experimental Therapeutics. Expert Opin Drug Discov 2008; 3:1145-54. [PMID: 23506185 DOI: 10.1517/17460441.3.9.1145] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/05/2022]
Abstract
BACKGROUND The American Society for Pharmacology and Experimental Therapeutics (ASPET) celebrated its centennial during the April 2008 Experimental Biology meeting held in San Diego, CA, USA. OBJECTIVES This report summarizes a centennial symposium on past, present and future paradigms in drug discovery. The John Langley (1905) concept of 'receptive substances' initiated a cascade of cardinal discoveries for pharmacology. During the following 100 years, receptors achieved the status of well-defined multifunctional cellular proteins mediating all drug effects. The G-protein-coupled receptors (GPCRs) were discussed in relation to multiple targets they represent for clinically used or new medicines. The development of inbred and transgenic animal strains is a fundamental twentieth century achievement for biological research activities. Progress in treating CNS disorders still awaits breakthrough treatments. Drug development remains a risky and expensive venture; improvements are expected from emerging biomarker and translational medicine technologies. Future clinical research has to document the benefits that new medications provide to concerned stakeholders. CONCLUSIONS We wish ASPET a new century of great achievements and acknowledge the dedication of several generations of colleagues, many of whom are our 'unsung heroes'. They have left us a precious heritage to be pursued with passion in the quest for better medicines.
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Affiliation(s)
- Icilio Cavero
- Via dei Bacchettoni 19B, 55100 LUCCA, Italy +39 05 83 48 75 20 ; +39 05 83 48 75 20 ;
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