1
|
GPR125 (ADGRA3) is an autocleavable adhesion GPCR that traffics with Dlg1 to the basolateral membrane and regulates epithelial apico-basal polarity. J Biol Chem 2022; 298:102475. [PMID: 36089063 PMCID: PMC9539791 DOI: 10.1016/j.jbc.2022.102475] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/31/2022] [Revised: 08/30/2022] [Accepted: 09/02/2022] [Indexed: 01/12/2023] Open
Abstract
The adhesion family of G protein–coupled receptors (GPCRs) is defined by an N-terminal large extracellular region that contains various adhesion-related domains and a highly-conserved GPCR-autoproteolysis-inducing (GAIN) domain, the latter of which is located immediately before a canonical seven-transmembrane domain. These receptors are expressed widely and involved in various functions including development, angiogenesis, synapse formation, and tumorigenesis. GPR125 (ADGRA3), an orphan adhesion GPCR, has been shown to modulate planar cell polarity in gastrulating zebrafish, but its biochemical properties and role in mammalian cells have remained largely unknown. Here, we show that human GPR125 likely undergoes cis-autoproteolysis when expressed in canine kidney epithelial MDCK cells and human embryonic kidney HEK293 cells. The cleavage appears to occur at an atypical GPCR proteolysis site within the GAIN domain during an early stage of receptor biosynthesis. The products, i.e., the N-terminal and C-terminal fragments, seem to remain associated after self-proteolysis, as observed in other adhesion GPCRs. Furthermore, in polarized MDCK cells, GPR125 is exclusively recruited to the basolateral domain of the plasma membrane. The recruitment likely requires the C-terminal PDZ-domain–binding motif of GPR125 and its interaction with the cell polarity protein Dlg1. Knockdown of GPR125 as well as that of Dlg1 results in formation of aberrant cysts with multiple lumens in Matrigel 3D culture of MDCK cells. Consistent with the multilumen phenotype, mitotic spindles are incorrectly oriented during cystogenesis in GPR125-KO MDCK cells. Thus, the basolateral protein GPR125, an autocleavable adhesion GPCR, appears to play a crucial role in apicobasal polarization in epithelial cells.
Collapse
|
2
|
Zeng H, Castillo-Cabrera J, Manser M, Lu B, Yang Z, Strande V, Begue D, Zamponi R, Qiu S, Sigoillot F, Wang Q, Lindeman A, Reece-Hoyes JS, Russ C, Bonenfant D, Jiang X, Wang Y, Cong F. Genome-wide CRISPR screening reveals genetic modifiers of mutant EGFR dependence in human NSCLC. eLife 2019; 8:50223. [PMID: 31741433 PMCID: PMC6927754 DOI: 10.7554/elife.50223] [Citation(s) in RCA: 26] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/16/2019] [Accepted: 11/04/2019] [Indexed: 12/24/2022] Open
Abstract
EGFR-mutant NSCLCs frequently respond to EGFR tyrosine kinase inhibitors (TKIs). However, the responses are not durable, and the magnitude of tumor regression is variable, suggesting the existence of genetic modifiers of EGFR dependency. Here, we applied a genome-wide CRISPR-Cas9 screening to identify genetic determinants of EGFR TKI sensitivity and uncovered putative candidates. We show that knockout of RIC8A, essential for G-alpha protein activation, enhanced EGFR TKI-induced cell death. Mechanistically, we demonstrate that RIC8A is a positive regulator of YAP signaling, activation of which rescued the EGFR TKI sensitizing phenotype resulting from RIC8A knockout. We also show that knockout of ARIH2, or other components in the Cullin-5 E3 complex, conferred resistance to EGFR inhibition, in part by promoting nascent protein synthesis through METAP2. Together, these data uncover a spectrum of previously unidentified regulators of EGFR TKI sensitivity in EGFR-mutant human NSCLC, providing insights into the heterogeneity of EGFR TKI treatment responses. Cancer is caused by cells growing and dividing uncontrollably as a result of mutations in certain genes. Many human lung cancers have a mutation in the gene that makes the protein EGFR. In healthy cells, EGFR allows a cell to respond to chemical signals that encourage healthy growth. In cancer, the altered EGFR is always on, which allows the cell to rapidly grow without any control, resulting in cancer. One approach to treating these cancers is with drugs that block the activity of mutant EGFR. Although these drugs have been very successful, they do not always succeed in completely treating the cancer. This is because over time the cancer cells can become resistant to the drug and start forming new tumors. One way that this can happen is if random mutations lead to changes in other proteins that make the drug less effective or stop it from accessing the EGFR proteins. However, it is unclear how other proteins in cancer cells affect the response to these EGFR inhibiting drugs. Now, Zeng et al. have used gene editing to systematically remove every protein from human lung cancer cells grown in the laboratory to see how this affects resistance to EGFR inhibitor treatment. This revealed that a number of different proteins could change how cancer cells responded to the drug. For instance, cells lacking the protein RIC8A were more sensitive to EGFR inhibitors and less likely to develop resistance. This is because loss of RIC8A turns down a key cell survival pathway in cancer cells. Whereas, cancer cells lacking the ARIH2 protein were able to produce more proteins that are needed for cancer cell growth, which resulted in them having increased resistance to EGFR inhibitors. The proteins identified in this study could be used to develop new drugs that improve the effectiveness of EGFR inhibitors. Understanding how cancer cells respond to EGFR inhibitor treatment could help determine how likely a patient is to develop resistance to these drugs.
Collapse
Affiliation(s)
- Hao Zeng
- Chemical Biology and Therapeutics, Novartis Institutes for Biomedical Research, Cambridge, United States
| | - Johnny Castillo-Cabrera
- Chemical Biology and Therapeutics, Novartis Institutes for Biomedical Research, Cambridge, United States
| | - Mika Manser
- Oncology Disease Area, Novartis Institutes for Biomedical Research, Cambridge, United States
| | - Bo Lu
- Chemical Biology and Therapeutics, Novartis Institutes for Biomedical Research, Cambridge, United States
| | - Zinger Yang
- Chemical Biology and Therapeutics, Novartis Institutes for Biomedical Research, Cambridge, United States
| | - Vaik Strande
- Analytical Sciences and Imaging, Novartis Institutes for Biomedical Research, Basel, Switzerland
| | - Damien Begue
- Analytical Sciences and Imaging, Novartis Institutes for Biomedical Research, Basel, Switzerland
| | - Raffaella Zamponi
- Chemical Biology and Therapeutics, Novartis Institutes for Biomedical Research, Cambridge, United States
| | - Shumei Qiu
- Oncology Disease Area, Novartis Institutes for Biomedical Research, Cambridge, United States
| | - Frederic Sigoillot
- Chemical Biology and Therapeutics, Novartis Institutes for Biomedical Research, Cambridge, United States
| | - Qiong Wang
- Chemical Biology and Therapeutics, Novartis Institutes for Biomedical Research, Cambridge, United States
| | - Alicia Lindeman
- Chemical Biology and Therapeutics, Novartis Institutes for Biomedical Research, Cambridge, United States
| | - John S Reece-Hoyes
- Chemical Biology and Therapeutics, Novartis Institutes for Biomedical Research, Cambridge, United States
| | - Carsten Russ
- Chemical Biology and Therapeutics, Novartis Institutes for Biomedical Research, Cambridge, United States
| | - Debora Bonenfant
- Analytical Sciences and Imaging, Novartis Institutes for Biomedical Research, Basel, Switzerland
| | - Xiaomo Jiang
- Chemical Biology and Therapeutics, Novartis Institutes for Biomedical Research, Cambridge, United States
| | - Youzhen Wang
- Oncology Disease Area, Novartis Institutes for Biomedical Research, Cambridge, United States
| | - Feng Cong
- Chemical Biology and Therapeutics, Novartis Institutes for Biomedical Research, Cambridge, United States
| |
Collapse
|
3
|
Takayanagi H, Hayase J, Kamakura S, Miyano K, Chishiki K, Yuzawa S, Sumimoto H. Intramolecular interaction in LGN, an adaptor protein that regulates mitotic spindle orientation. J Biol Chem 2019; 294:19655-19666. [PMID: 31732560 DOI: 10.1074/jbc.ra119.011457] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/11/2019] [Revised: 11/07/2019] [Indexed: 12/11/2022] Open
Abstract
Proper mitotic spindle orientation requires that astral microtubules are connected to the cell cortex by the microtubule-binding protein NuMA, which is recruited from the cytoplasm. Cortical recruitment of NuMA is at least partially mediated via direct binding to the adaptor protein LGN. LGN normally adopts a closed conformation via an intramolecular interaction between its N-terminal NuMA-binding domain and its C-terminal region that contains four GoLoco (GL) motifs, each capable of binding to the membrane-anchored Gαi subunit of heterotrimeric G protein. Here we show that the intramolecular association with the N-terminal domain in LGN involves GL3, GL4, and a region between GL2 and GL3, whereas GL1 and GL2 do not play a major role. This conformation renders GL1 but not the other GL motifs in a state easily accessible to Gαi To interact with full-length LGN in a closed state, NuMA requires the presence of Gαi; both NuMA and Gαi are essential for cortical recruitment of LGN in mitotic cells. In contrast, mInsc, a protein that competes with NuMA for binding to LGN and regulates mitotic spindle orientation in asymmetric cell division, efficiently binds to full-length LGN without Gαi and induces its conformational change, enhancing its association with Gαi In nonpolarized symmetrically dividing HeLa cells, disruption of the LGN-NuMA interaction by ectopic expression of mInsc results in a loss of cortical localization of NuMA during metaphase and anaphase and promotes mitotic spindle misorientation and a delayed anaphase progression. These findings highlight a specific role for LGN-mediated cell cortex recruitment of NuMA.
Collapse
Affiliation(s)
- Hiroki Takayanagi
- Department of Biochemistry, Kyushu University Graduate School of Medical Sciences, Fukuoka 812-8582, Japan
| | - Junya Hayase
- Department of Biochemistry, Kyushu University Graduate School of Medical Sciences, Fukuoka 812-8582, Japan
| | - Sachiko Kamakura
- Department of Biochemistry, Kyushu University Graduate School of Medical Sciences, Fukuoka 812-8582, Japan
| | - Kei Miyano
- Department of Biochemistry, Kyushu University Graduate School of Medical Sciences, Fukuoka 812-8582, Japan
| | - Kanako Chishiki
- Department of Biochemistry, Kyushu University Graduate School of Medical Sciences, Fukuoka 812-8582, Japan
| | - Satoru Yuzawa
- Department of Biochemistry, Kyushu University Graduate School of Medical Sciences, Fukuoka 812-8582, Japan
| | - Hideki Sumimoto
- Department of Biochemistry, Kyushu University Graduate School of Medical Sciences, Fukuoka 812-8582, Japan
| |
Collapse
|
4
|
Pergolizzi B, Bozzaro S, Bracco E. G-Protein Dependent Signal Transduction and Ubiquitination in Dictyostelium. Int J Mol Sci 2017; 18:ijms18102180. [PMID: 29048338 PMCID: PMC5666861 DOI: 10.3390/ijms18102180] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/14/2017] [Revised: 10/12/2017] [Accepted: 10/16/2017] [Indexed: 12/20/2022] Open
Abstract
Signal transduction through G-protein-coupled receptors (GPCRs) is central for the regulation of virtually all cellular functions, and it has been widely implicated in human diseases. These receptors activate a common molecular switch that is represented by the heterotrimeric G-protein generating a number of second messengers (cAMP, cGMP, DAG, IP3, Ca2+ etc.), leading to a plethora of diverse cellular responses. Spatiotemporal regulation of signals generated by a given GPCR is crucial for proper signalling and is accomplished by a series of biochemical modifications. Over the past few years, it has become evident that many signalling proteins also undergo ubiquitination, a posttranslational modification that typically leads to protein degradation, but also mediates processes such as protein-protein interaction and protein subcellular localization. The social amoeba Dictyostelium discoideum has proven to be an excellent model to investigate signal transduction triggered by GPCR activation, as cAMP signalling via GPCR is a major regulator of chemotaxis, cell differentiation, and multicellular morphogenesis. Ubiquitin ligases have been recently involved in these processes. In the present review, we will summarize the most significant pathways activated upon GPCRs stimulation and discuss the role played by ubiquitination in Dictyostelium cells.
Collapse
Affiliation(s)
- Barbara Pergolizzi
- Department of Clinical and Biological Sciences, University of Turin, AOUS. Luigi, 10043 Orbassano TO, Italy.
| | - Salvatore Bozzaro
- Department of Clinical and Biological Sciences, University of Turin, AOUS. Luigi, 10043 Orbassano TO, Italy.
| | - Enrico Bracco
- Department of Oncology, University of Turin, AOU S. Luigi, 10043 Orbassano TO, Italy.
| |
Collapse
|
5
|
Chishiki K, Kamakura S, Hayase J, Sumimoto H. Ric-8A, an activator protein of Gαi, controls mammalian epithelial cell polarity for tight junction assembly and cystogenesis. Genes Cells 2017; 22:293-309. [PMID: 28185378 DOI: 10.1111/gtc.12477] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/09/2017] [Accepted: 01/11/2017] [Indexed: 01/04/2023]
Abstract
Correct cyst morphogenesis of epithelial cells requires apical-basal polarization, which is partly regulated by mitotic spindle orientation, a process dependent on the heterotrimeric G protein subunit Gαi and its binding protein LGN. Here, we show that in three-dimensional culture of mammalian epithelial Madin-Darby canine kidney (MDCK) cells, the Gαi-activating protein Ric-8A is crucial for orientation of the mitotic spindle and formation of normal cysts that comprise a single layer of polarized cells with their apical surfaces lining an inner lumen. Consistent with the involvement of LGN, cystogenesis can be well organized by ADP-ribosylated Gαi, retaining the ability to interact with LGN, but not by the interaction-defective mutant protein Gαi2 (N150I). In monolayer culture of MDCK cells, functional tight junction (TJ) assembly, a process associated with epithelial cell polarization, is significantly delayed in Ric-8A-depleted cells as well as in Gαi-depleted cells in a mitosis-independent manner. Ric-8A knockdown results in a delayed cortical delivery of Gαi and the apical membrane protein gp135, and an increased formation of intercellular lumens surrounded by membranes rich in Gαi3 and gp135. TJ development also involves LGN and its related protein AGS3. Thus, Ric-8A regulates mammalian epithelial cell polarity for TJ assembly and cystogenesis probably in concert with Gαi and LGN/AGS3.
Collapse
Affiliation(s)
- Kanako Chishiki
- Department of Biochemistry, Kyushu University Graduate School of Medical Sciences, Fukuoka, 812-8582, Japan
| | - Sachiko Kamakura
- Department of Biochemistry, Kyushu University Graduate School of Medical Sciences, Fukuoka, 812-8582, Japan
| | - Junya Hayase
- Department of Biochemistry, Kyushu University Graduate School of Medical Sciences, Fukuoka, 812-8582, Japan
| | - Hideki Sumimoto
- Department of Biochemistry, Kyushu University Graduate School of Medical Sciences, Fukuoka, 812-8582, Japan
| |
Collapse
|
6
|
Chishiki K, Kamakura S, Hayase J, Yuzawa S, Sumimoto H. Ric-8A-mediated stabilization of the trimeric G protein subunit Gαi is inhibited by pertussis toxin-catalyzed ADP-ribosylation. Biochem Biophys Res Commun 2017; 483:941-945. [PMID: 28082199 DOI: 10.1016/j.bbrc.2017.01.036] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/24/2016] [Accepted: 01/09/2017] [Indexed: 11/26/2022]
Abstract
The heterotrimeric G protein subunit Gαi can be activated by G protein-coupled receptors and the cytosolic protein Ric-8A, the latter of which is also known to prevent ubiquitin-dependent degradation of Gαi. Here we show that the amounts of the three Gαi-related proteins Gαi1, Gαi2, and Gαi3, but not that of Gαq, are rapidly decreased by cell treatment with pertussis toxin (PTX). The decrease appears to be due to ADP-ribosylation of Gαi, because PTX treatment does not affect the amount of a mutant Gαi2 carrying alanine substitution for Cys352, the residue that is ADP-ribosylated by the toxin. The presence of endogenous and exogenous Ric-8A increases Gαi stability as shown in cells treated with the protein synthesis inhibitor cycloheximide; however, Ric-8A fails to efficiently stabilize ADP-ribosylated Gαi. The failure agrees with the inability of Ric-8A to bind to ADP-ribosylated Gαi both in vitro and in vivo. Thus PTX appears to exert its pathological effects at least in part by converting Gαi to an unstable ADP-ribosylated form, in addition to the well-known inability of ADP-ribosylated Gαi to transduce signals triggered by G protein-coupled receptors.
Collapse
Affiliation(s)
- Kanako Chishiki
- Department of Biochemistry, Kyushu University Graduate School of Medical Sciences, Fukuoka 812-8582, Japan
| | - Sachiko Kamakura
- Department of Biochemistry, Kyushu University Graduate School of Medical Sciences, Fukuoka 812-8582, Japan
| | - Junya Hayase
- Department of Biochemistry, Kyushu University Graduate School of Medical Sciences, Fukuoka 812-8582, Japan
| | - Satoru Yuzawa
- Department of Biochemistry, Kyushu University Graduate School of Medical Sciences, Fukuoka 812-8582, Japan
| | - Hideki Sumimoto
- Department of Biochemistry, Kyushu University Graduate School of Medical Sciences, Fukuoka 812-8582, Japan.
| |
Collapse
|
7
|
Kant R, Zeng B, Thomas CJ, Bothner B, Sprang SR. Ric-8A, a G protein chaperone with nucleotide exchange activity induces long-range secondary structure changes in Gα. eLife 2016; 5. [PMID: 28008853 PMCID: PMC5182059 DOI: 10.7554/elife.19238] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/29/2016] [Accepted: 11/22/2016] [Indexed: 11/24/2022] Open
Abstract
Cytosolic Ric-8A has guanine nucleotide exchange factor (GEF) activity and is a chaperone for several classes of heterotrimeric G protein α subunits in vertebrates. Using Hydrogen-Deuterium Exchange-Mass Spectrometry (HDX-MS) we show that Ric-8A disrupts the secondary structure of the Gα Ras-like domain that girds the guanine nucleotide-binding site, and destabilizes the interface between the Gαi1 Ras and helical domains, allowing domain separation and nucleotide release. These changes are largely reversed upon binding GTP and dissociation of Ric-8A. HDX-MS identifies a potential Gα interaction site in Ric-8A. Alanine scanning reveals residues crucial for GEF activity within that sequence. HDX confirms that, like G protein-coupled receptors (GPCRs), Ric-8A binds the C-terminus of Gα. In contrast to GPCRs, Ric-8A interacts with Switches I and II of Gα and possibly at the Gα domain interface. These extensive interactions provide both allosteric and direct catalysis of GDP unbinding and release and GTP binding. DOI:http://dx.doi.org/10.7554/eLife.19238.001
Collapse
Affiliation(s)
- Ravi Kant
- Department of Chemistry and Biochemistry, Montana State University, Bozeman, United States
| | - Baisen Zeng
- Center for Biomolecular Structure and Dynamics, The University of Montana, Missoula, United States
| | - Celestine J Thomas
- Center for Biomolecular Structure and Dynamics, The University of Montana, Missoula, United States
| | - Brian Bothner
- Department of Chemistry and Biochemistry, Montana State University, Bozeman, United States
| | - Stephen R Sprang
- Center for Biomolecular Structure and Dynamics, The University of Montana, Missoula, United States
| |
Collapse
|
8
|
Torres M. Chapter Two - Heterotrimeric G Protein Ubiquitination as a Regulator of G Protein Signaling. PROGRESS IN MOLECULAR BIOLOGY AND TRANSLATIONAL SCIENCE 2016; 141:57-83. [PMID: 27378755 DOI: 10.1016/bs.pmbts.2016.03.001] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
Abstract
Ubiquitin-mediated regulation of G proteins has been known for over 20 years as a result of discoveries made independently in yeast and vertebrate model systems for pheromone and photoreception, respectively. Since that time, several details underlying the cause and effect of G protein ubiquitination have been determined-including the initiating signals, responsible enzymes, trafficking pathways, and their effects on protein structure, function, interactions, and cell signaling. The collective body of evidence suggests that Gα subunits are the primary targets of ubiquitination. However, longstanding and recent results suggest that Gβ and Gγ subunits are also ubiquitinated, in some cases impacting cell polarization-a process essential for chemotaxis and polarized cell growth. More recently, evidence from mass spectrometry (MS)-based proteomics coupled with advances in PTM bioinformatics have revealed that protein families representing G protein subunits contain several structural hotspots for ubiquitination-most of which have not been investigated for a functional role in signal transduction. Taken together, our knowledge and understanding of heterotrimeric G protein ubiquitination as a regulator of G protein signaling-despite 20 years of research-is still emerging.
Collapse
Affiliation(s)
- M Torres
- Georgia Institute of Technology, School of Biology, Atlanta, GA, United States.
| |
Collapse
|
9
|
Abstract
The G12 family of heterotrimeric G proteins is defined by their α-subunits,
Gα12 and Gα13. These α-subunits
regulate cellular homeostasis, cell migration, and oncogenesis in a
context-specific manner primarily through their interactions with distinct
proteins partners that include diverse effector molecules and scaffold proteins.
With a focus on identifying any other novel regulatory protein(s) that can
directly interact with Gα13, we subjected Gα13
to tandem affinity purification-coupled mass spectrometric analysis. Our results
from such analysis indicate that Gα13 potently interacts with
mammalian Ric-8A. Our mass spectrometric analysis data also indicates that
Ric-8A, which was tandem affinity purified along with Gα13, is
phosphorylated at Ser-436, Thr-441, Thr-443 and Tyr-435. Using a serial deletion
approach, we have defined that the C-terminus of Gα13 containing
the guanine-ring interaction site is essential and sufficient for its
interaction with Ric-8A. Evaluation of Gα13-specific signaling
pathways in SKOV3 or HeyA8 ovarian cancer cell lines indicate that Ric-8A
potentiates Gα13-mediated activation of RhoA, Cdc42, and the
downstream p38MAPK. We also establish that the tyrosine phosphorylation of
Ric-8A, thus far unidentified, is potently stimulated by Gα13.
Our results also indicate that the stimulation of tyrosine-phosphorylation of
Ric-8A by Gα13 is partially sensitive to inhibitors of
Src-family of kinases, namely PP2 and SI. Furthermore, we demonstrate that
Gα13 promotes the translocation of Ric-8A to plasma membrane
and this translocation is attenuated by the Src-inhibitors, SI1 and PP2. Thus,
our results demonstrate for the first time that Gα13 stimulates
the tyrosine phosphorylation of Ric-8A and Gα13-mediated
tyrosine-phosphorylation plays a critical role in the translocation of Ric-8A to
plasma membrane.
Collapse
|
10
|
Structural basis of cofactor-mediated stabilization and substrate recognition of the α-tubulin acetyltransferase αTAT1. Biochem J 2015; 467:103-13. [PMID: 25602620 DOI: 10.1042/bj20141193] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
The functions of microtubules are controlled in part by tubulin post-translational modification including acetylation of Lys⁴⁰ in α-tubulin. αTAT1 (α-tubulin acetyltransferase 1), an enzyme evolutionarily conserved among eukaryotes, has recently been identified as the major α-tubulin Lys⁴⁰ acetyltransferase, in which AcCoA (acetyl-CoA) serves as an acetyl group donor. The regulation and substrate recognition of this enzyme, however, have not been fully understood. In the present study, we show that AcCoA and CoA each form a stable complex with human αTAT1 to maintain the protein integrity both in vivo and in vitro. The invariant residues Arg¹³² and Ser¹⁶⁰ in αTAT1 participate in the stable interaction not only with AcCoA but also with CoA, which is supported by analysis of the present crystal structures of the αTAT1 catalytic domain in complex with CoA. Alanine substitution for Arg¹³² or Ser¹⁶⁰ leads to a drastic misfolding of the isolated αTAT1 catalytic domain in the absence of CoA and AcCoA but not in the presence of excess amounts of either cofactor. A mutant αTAT1 carrying the R132A or S160A substitution is degraded much faster than the wild-type protein when expressed in mammalian Madin-Darby canine kidney cells. Furthermore, alanine-scanning experiments using Lys⁴⁰-containing peptides reveal that α-tubulin Ser³⁸ is crucial for substrate recognition of αTAT1, whereas Asp³⁹, Ile⁴², the glycine stretch (amino acid residues 43-45) and Asp⁴⁶ are also involved. The requirement for substrate selection is totally different from that in various histone acetyltransferases, which appears to be consistent with the inability of αTAT1 to acetylate histones.
Collapse
|
11
|
Hwang IY, Park C, Harrison K, Boularan C, Galés C, Kehrl JH. An essential role for RGS protein/Gαi2 interactions in B lymphocyte-directed cell migration and trafficking. THE JOURNAL OF IMMUNOLOGY 2015; 194:2128-39. [PMID: 25617475 DOI: 10.4049/jimmunol.1401952] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/14/2023]
Abstract
Chemokines engage B lymphocyte surface receptors, triggering heterotrimeric G protein Gαi subunit guanine nucleotide exchange. RGS proteins limit the duration that Gαi subunits remain GTP bound, and the loss of an individual RGS protein typically enhances chemokine receptor signaling. In this study, we show that B cells carrying a Gαi2 (G184S/G184S) mutation that disables all RGS protein/Gαi2 interactions exhibit an unexpectedly severe reduction in chemokine receptor signaling. The Gαi2 (G184S/G184S) B cells have markedly elevated basal calcium levels, but poor chemokine-induced increases, enhanced nonspecific migration, but extremely poor chemotaxis. In striking contrast, the Gαi2 (G184S/G184S) B cells exhibited enhanced sensitivity to sphingosine 1-phosphate (S1P). S1P elicited heightened intracellular calcium responses and enhanced S1P-triggered cell migration. Mice with the Gαi2 (G184S/G184S) mutation displayed excessive numbers of germinal center-like structures; abnormal serum Ig profiles; and aberrant B lymphocyte trafficking. These findings establish an essential role for RGS proteins in B cell chemoattractant signaling and for the proper position of B lymphocytes in lymphoid organs.
Collapse
Affiliation(s)
- Il-Young Hwang
- Laboratory of Immunoregulation, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Bethesda, MD 20892; and
| | - Chung Park
- Laboratory of Immunoregulation, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Bethesda, MD 20892; and
| | - Kathleen Harrison
- Laboratory of Immunoregulation, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Bethesda, MD 20892; and
| | - Cedric Boularan
- Laboratory of Immunoregulation, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Bethesda, MD 20892; and INSERM U1048, Institut des Maladies Métaboliques et Cardiovasculaires, 31432 Toulouse Cedex 4, France
| | - Céline Galés
- INSERM U1048, Institut des Maladies Métaboliques et Cardiovasculaires, 31432 Toulouse Cedex 4, France
| | - John H Kehrl
- Laboratory of Immunoregulation, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Bethesda, MD 20892; and
| |
Collapse
|
12
|
The guanine nucleotide exchange factor Ric-8A induces domain separation and Ras domain plasticity in Gαi1. Proc Natl Acad Sci U S A 2015; 112:1404-9. [PMID: 25605908 DOI: 10.1073/pnas.1423878112] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023] Open
Abstract
Heterotrimeric G proteins are activated by exchange of GDP for GTP at the G protein alpha subunit (Gα), most notably by G protein-coupled transmembrane receptors. Ric-8A is a soluble cytoplasmic protein essential for embryonic development that acts as both a guanine nucleotide exchange factor (GEF) and a chaperone for Gα subunits of the i, q, and 12/13 classes. Previous studies demonstrated that Ric-8A stabilizes a dynamically disordered state of nucleotide-free Gα as the catalytic intermediate for nucleotide exchange, but no information was obtained on the structures involved or the magnitude of the structural fluctuations. In the present study, site-directed spin labeling (SDSL) together with double electron-electron resonance (DEER) spectroscopy is used to provide global distance constraints that identify discrete members of a conformational ensemble in the Gαi1:Ric-8A complex and the magnitude of structural differences between them. In the complex, the helical and Ras-like nucleotide-binding domains of Gαi1 pivot apart to occupy multiple resolved states with displacements as large as 25 Å. The domain displacement appears to be distinct from that observed in Gαs upon binding of Gs to the β2 adrenergic receptor. Moreover, the Ras-like domain exhibits structural plasticity within and around the nucleotide-binding cavity, and the switch I and switch II regions, which are known to adopt different conformations in the GDP- and GTP-bound states of Gα, undergo structural rearrangements. Collectively, the data show that Ric-8A induces a conformationally heterogeneous state of Gαi and provide insight into the mechanism of action of a nonreceptor Gα GEF.
Collapse
|
13
|
Papasergi MM, Patel BR, Tall GG. The G protein α chaperone Ric-8 as a potential therapeutic target. Mol Pharmacol 2014; 87:52-63. [PMID: 25319541 DOI: 10.1124/mol.114.094664] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023] Open
Abstract
Resistance to inhibitors of cholinesterase (Ric-8)A and Ric-8B are essential genes that encode positive regulators of heterotrimeric G protein α subunits. Controversy persists surrounding the precise way(s) that Ric-8 proteins affect G protein biology and signaling. Ric-8 proteins chaperone nucleotide-free Gα-subunit states during biosynthetic protein folding prior to G protein heterotrimer assembly. In organisms spanning the evolutionary window of Ric-8 expression, experimental perturbation of Ric-8 genes results in reduced functional abundances of G proteins because G protein α subunits are misfolded and degraded rapidly. Ric-8 proteins also act as Gα-subunit guanine nucleotide exchange factors (GEFs) in vitro. However, Ric-8 GEF activity could strictly be an in vitro phenomenon stemming from the ability of Ric-8 to induce partial Gα unfolding, thereby enhancing GDP release. Ric-8 GEF activity clearly differs from the GEF activity of G protein-coupled receptors (GPCRs). G protein βγ is inhibitory to Ric-8 action but obligate for receptors. It remains an open question whether Ric-8 has dual functions in cells and regulates G proteins as both a molecular chaperone and GEF. Clearly, Ric-8 has a profound influence on heterotrimeric G protein function. For this reason, we propose that Ric-8 proteins are as yet untested therapeutic targets in which pharmacological inhibition of the Ric-8/Gα protein-protein interface could serve to attenuate the effects of disease-causing G proteins (constitutively active mutants) and/or GPCR signaling. This minireview will chronicle the understanding of Ric-8 function, provide a comparative discussion of the Ric-8 molecular chaperoning and GEF activities, and support the case for why Ric-8 proteins should be considered potential targets for development of new therapies.
Collapse
Affiliation(s)
- Makaía M Papasergi
- Department of Pharmacology and Physiology, University of Rochester Medical Center, Rochester, New York
| | - Bharti R Patel
- Department of Pharmacology and Physiology, University of Rochester Medical Center, Rochester, New York
| | - Gregory G Tall
- Department of Pharmacology and Physiology, University of Rochester Medical Center, Rochester, New York
| |
Collapse
|
14
|
A Ric8/synembryn homolog promotes Gpa1 and Gpa2 activation to respectively regulate cyclic AMP and pheromone signaling in Cryptococcus neoformans. EUKARYOTIC CELL 2014; 13:1290-9. [PMID: 25084863 DOI: 10.1128/ec.00109-14] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
The G protein α subunits Gpa1, Gpa2, and Gpa3 mediate signal transduction and are important in the growth and virulence of Cryptococcus neoformans. To understand how Gpa1 functions without a conventional Gβ subunit, we characterized a resistance to inhibitors of cholinesterase 8 (Ric8) homolog from C. neoformans, which shares amino acid sequence homology with other Ric8 proteins that exhibit guanine nucleotide exchange factor (GEF) activity toward Gα. We found that the ric8 mutant was reduced in capsule size and melanin formation, which could be suppressed by cyclic AMP (cAMP) supplementation or by introducing the activated GPA1(Q284L) allele. Consistent with the fact that Ric8 participates in cAMP signaling to regulate virulence, the ric8 mutant was attenuated in virulence toward mice. Interestingly, disruption of RIC8 also resulted in opposing effects on pheromone signaling, as the ric8 mutant showed reduced mating but an enhanced ability to induce the pheromone response in the mating partner. To identify Ric8 functional mechanisms, we examined the interactions between Ric8 and the three Gα proteins. Ric8 interacted with Gpa1 and Gpa2, but not Gpa3. The presence of Gpa1(Q284L) negatively affected its interaction with Ric8, whereas the activated Gpa2(Q203L) allele abolished the interaction. Collectively, these findings suggest that Ric8 functions as a GEF to facilitate the activation of Gpa1-cAMP signaling and to promote Gpa2, affecting mating efficiency. Our study highlights the distinct and conserved characteristics associated with G protein signaling and contributes to our overall understanding of how G protein α subunits function with or without a canonical Gβ partner in C. neoformans.
Collapse
|
15
|
Sánchez-Fernández G, Cabezudo S, García-Hoz C, Benincá C, Aragay AM, Mayor F, Ribas C. Gαq signalling: the new and the old. Cell Signal 2014; 26:833-48. [PMID: 24440667 DOI: 10.1016/j.cellsig.2014.01.010] [Citation(s) in RCA: 68] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/09/2013] [Accepted: 01/09/2014] [Indexed: 01/25/2023]
Abstract
In the last few years the interactome of Gαq has expanded considerably, contributing to improve our understanding of the cellular and physiological events controlled by this G alpha subunit. The availability of high-resolution crystal structures has led the identification of an effector-binding region within the surface of Gαq that is able to recognise a variety of effector proteins. Consequently, it has been possible to ascribe different Gαq functions to specific cellular players and to identify important processes that are triggered independently of the canonical activation of phospholipase Cβ (PLCβ), the first identified Gαq effector. Novel effectors include p63RhoGEF, that provides a link between G protein-coupled receptors and RhoA activation, phosphatidylinositol 3-kinase (PI3K), implicated in the regulation of the Akt pathway, or the cold-activated TRPM8 channel, which is directly inhibited upon Gαq binding. Recently, the activation of ERK5 MAPK by Gq-coupled receptors has also been described as a novel PLCβ-independent signalling axis that relies upon the interaction between this G protein and two novel effectors (PKCζ and MEK5). Additionally, the association of Gαq with different regulatory proteins can modulate its effector coupling ability and, therefore, its signalling potential. Regulators include accessory proteins that facilitate effector activation or, alternatively, inhibitory proteins that downregulate effector binding or promote signal termination. Moreover, Gαq is known to interact with several components of the cytoskeleton as well as with important organisers of membrane microdomains, which suggests that efficient signalling complexes might be confined to specific subcellular environments. Overall, the complex interaction network of Gαq underlies an ever-expanding functional diversity that puts forward this G alpha subunit as a major player in the control of physiological functions and in the development of different pathological situations.
Collapse
Affiliation(s)
- Guzmán Sánchez-Fernández
- Departamento de Biología Molecular and Centro de Biologia Molecular "Severo Ochoa", CSIC-UAM, Universidad Autónoma de Madrid, Spain; Instituto de Investigación Sanitaria La Princesa, Madrid, Spain
| | - Sofía Cabezudo
- Departamento de Biología Molecular and Centro de Biologia Molecular "Severo Ochoa", CSIC-UAM, Universidad Autónoma de Madrid, Spain; Instituto de Investigación Sanitaria La Princesa, Madrid, Spain
| | - Carlota García-Hoz
- Departamento de Biología Molecular and Centro de Biologia Molecular "Severo Ochoa", CSIC-UAM, Universidad Autónoma de Madrid, Spain; Instituto de Investigación Sanitaria La Princesa, Madrid, Spain
| | | | - Anna M Aragay
- Department of Cell Biology, Molecular Biology Institute of Barcelona, Spain
| | - Federico Mayor
- Departamento de Biología Molecular and Centro de Biologia Molecular "Severo Ochoa", CSIC-UAM, Universidad Autónoma de Madrid, Spain; Instituto de Investigación Sanitaria La Princesa, Madrid, Spain
| | - Catalina Ribas
- Departamento de Biología Molecular and Centro de Biologia Molecular "Severo Ochoa", CSIC-UAM, Universidad Autónoma de Madrid, Spain; Instituto de Investigación Sanitaria La Princesa, Madrid, Spain.
| |
Collapse
|