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O'Donoghue L, Comer SP, Hiebner DW, Schoen I, von Kriegsheim A, Smolenski A. RhoGAP6 interacts with COPI to regulate protein transport. Biochem J 2023; 480:1109-1127. [PMID: 37409526 DOI: 10.1042/bcj20230013] [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: 01/16/2023] [Revised: 07/04/2023] [Accepted: 07/05/2023] [Indexed: 07/07/2023]
Abstract
RhoGAP6 is the most highly expressed GTPase-activating protein (GAP) in platelets specific for RhoA. Structurally RhoGAP6 contains a central catalytic GAP domain surrounded by large, disordered N- and C-termini of unknown function. Sequence analysis revealed three conserved consecutive overlapping di-tryptophan motifs close to the RhoGAP6 C-terminus which were predicted to bind to the mu homology domain (MHD) of δ-COP, a component of the COPI vesicle complex. We confirmed an endogenous interaction between RhoGAP6 and δ-COP in human platelets using GST-CD2AP which binds an N-terminal RhoGAP6 SH3 binding motif. Next, we confirmed that the MHD of δ-COP and the di-tryptophan motifs of RhoGAP6 mediate the interaction between both proteins. Each of the three di-tryptophan motifs appeared necessary for stable δ-COP binding. Proteomic analysis of other potential RhoGAP6 di-tryptophan motif binding partners indicated that the RhoGAP6/δ-COP interaction connects RhoGAP6 to the whole COPI complex. 14-3-3 was also established as a RhoGAP6 binding partner and its binding site was mapped to serine 37. We provide evidence of potential cross-regulation between 14-3-3 and δ-COP binding, however, neither δ-COP nor 14-3-3 binding to RhoGAP6 impacted RhoA activity. Instead, analysis of protein transport through the secretory pathway demonstrated that RhoGAP6/δ-COP binding increased protein transport to the plasma membrane, as did a catalytically inactive mutant of RhoGAP6. Overall, we have identified a novel interaction between RhoGAP6 and δ-COP which is mediated by conserved C-terminal di-tryptophan motifs, and which might control protein transport in platelets.
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Affiliation(s)
- Lorna O'Donoghue
- UCD School of Medicine, Conway Institute of Biomolecular and Biomedical Research, University College Dublin, Belfield Dublin 4, Ireland
- Irish Centre for Vascular Biology, Royal College of Surgeons in Ireland, 123 St Stephen's Green, Dublin D02 YN77, Ireland
| | - Shane P Comer
- UCD School of Medicine, Conway Institute of Biomolecular and Biomedical Research, University College Dublin, Belfield Dublin 4, Ireland
- Irish Centre for Vascular Biology, Royal College of Surgeons in Ireland, 123 St Stephen's Green, Dublin D02 YN77, Ireland
| | - Dishon W Hiebner
- Irish Centre for Vascular Biology, Royal College of Surgeons in Ireland, 123 St Stephen's Green, Dublin D02 YN77, Ireland
- UCD School of Chemical & Bioprocess Engineering, Engineering & Materials Science Centre, University College Dublin, Belfield Dublin 4, Ireland
| | - Ingmar Schoen
- Irish Centre for Vascular Biology, Royal College of Surgeons in Ireland, 123 St Stephen's Green, Dublin D02 YN77, Ireland
- School of Pharmacy and Biomolecular Sciences, Royal College of Surgeons in Ireland (RCSI), 123 St Stephen's Green, Dublin D02 YN77, Ireland
| | - Alex von Kriegsheim
- Edinburgh Cancer Research UK Centre, Institute of Genetics and Molecular Medicine, University of Edinburgh, Crewe Road South, Edinburgh EH4 2XR, U.K
| | - Albert Smolenski
- UCD School of Medicine, Conway Institute of Biomolecular and Biomedical Research, University College Dublin, Belfield Dublin 4, Ireland
- Irish Centre for Vascular Biology, Royal College of Surgeons in Ireland, 123 St Stephen's Green, Dublin D02 YN77, Ireland
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A current overview of RhoA, RhoB, and RhoC functions in vascular biology and pathology. Biochem Pharmacol 2022; 206:115321. [DOI: 10.1016/j.bcp.2022.115321] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/25/2022] [Revised: 10/17/2022] [Accepted: 10/18/2022] [Indexed: 11/24/2022]
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Inhibitory effects of Arhgap6 on cervical carcinoma cells. Tumour Biol 2015; 37:1411-25. [DOI: 10.1007/s13277-015-4502-z] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/07/2015] [Accepted: 11/24/2015] [Indexed: 12/12/2022] Open
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Mackenzie LS, Lymn JS, Hughes AD. Linking phospholipase C isoforms with differentiation function in human vascular smooth muscle cells. BIOCHIMICA ET BIOPHYSICA ACTA-MOLECULAR CELL RESEARCH 2013; 1833:3006-3012. [PMID: 23954266 DOI: 10.1016/j.bbamcr.2013.08.005] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/13/2013] [Revised: 07/23/2013] [Accepted: 08/06/2013] [Indexed: 12/23/2022]
Abstract
The phosphoinositol-phospholipase C (PLC) family of enzymes consists of a number of isoforms, each of which has different cellular functions. PLCγ1 is primarily linked to tyrosine kinase transduction pathways, whereas PLCδ1 has been associated with a number of regulatory proteins, including those controlling the cell cycle. Recent studies have shown a central role of PLC in cell organisation and in regulating a wide array of cellular responses. It is of importance to define the precise role of each isoform, and how this changes the functional outcome of the cell. Here we investigated differences in PLC isoform levels and activity in relation to differentiation of human and rat vascular smooth muscle cells. Using Western blotting and PLC activity assay, we show that PLCδ1 and PLCγ1 are the predominant isoforms in randomly cycling human vascular smooth muscle cells (HVSMCs). Growth arrest of HVSMCs for seven days of serum deprivation was consistently associated with increases in PLCδ1 and SM α-actin, whereas there were no changes in PLCγ1 immuno-reactivity. Organ culture of rat mesenteric arteries in serum free media (SFM), a model of de-differentiation, led to a loss of contractility as well as a loss of contractile proteins (SM α-actin and calponin) and PLCδ1, and no change in PLCγ1 immuno-reactivity. Taken together, these data indicate that PLCδ1 is the predominant PLC isoform in vascular smooth muscle, and confirm that PLCδ1 expression is affected by conditions that affect the cell cycle, differentiation status and contractile function.
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Affiliation(s)
- Louise S Mackenzie
- Department of Pharmacology, School of Life and Medical Sciences, University of Hertfordshire, College Lane, Hatfield AL10 9AB, UK; Department of Clinical Pharmacology, National Heart & Lung Institute, Imperial College London, QEQM Wing, St. Mary's Hospital, Paddington, London W2 1NY, UK.
| | - Joanne S Lymn
- Department of Clinical Pharmacology, National Heart & Lung Institute, Imperial College London, QEQM Wing, St. Mary's Hospital, Paddington, London W2 1NY, UK; Institute of Cell Signalling, The School of Health Sciences, The University of Nottingham, Queens Medical Centre, Nottingham NG7 2UH, UK
| | - Alun D Hughes
- Department of Clinical Pharmacology, National Heart & Lung Institute, Imperial College London, QEQM Wing, St. Mary's Hospital, Paddington, London W2 1NY, UK
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Hu JCC, Chan HC, Simmer SG, Seymen F, Richardson AS, Hu Y, Milkovich RN, Estrella NMRP, Yildirim M, Bayram M, Chen CF, Simmer JP. Amelogenesis imperfecta in two families with defined AMELX deletions in ARHGAP6. PLoS One 2012; 7:e52052. [PMID: 23251683 PMCID: PMC3522662 DOI: 10.1371/journal.pone.0052052] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/14/2012] [Accepted: 11/12/2012] [Indexed: 11/18/2022] Open
Abstract
Amelogenesis imperfecta (AI) is a group of inherited conditions featuring isolated enamel malformations. About 5% of AI cases show an X-linked pattern of inheritance, which are caused by mutations in AMELX. In humans there are two, non-allelic amelogenin genes: AMELX (Xp22.3) and AMELY (Yp11.2). About 90% of amelogenin expression is from AMELX, which is nested within intron 1 of the gene encoding Rho GTPase activating protein 6 (ARHGAP6). We recruited two AI families and determined that their disease-causing mutations were partial deletions in ARHGAP6 that completely deleted AMELX. Affected males in both families had a distinctive enamel phenotype resembling "snow-capped" teeth. The 96,240 bp deletion in family 1 was confined to intron 1 of ARHGAP6 (g.302534_398773del96240), but removed alternative ARHGAP6 promoters 1c and 1d. Analyses of developing teeth in mice showed that ARHGAP6 is not expressed from these promoters in ameloblasts. The 52,654 bp deletion in family 2 (g.363924_416577del52654insA) removed ARHGAP6 promoter 1d and exon 2, precluding normal expression of ARHGAP6. The male proband of family 2 had slightly thinner enamel with greater surface roughness, but exhibited the same pattern of enamel malformations characteristic of males in family 1, which themselves showed minor variations in their enamel phenotypes. We conclude that the enamel defects in both families were caused by amelogenin insufficiency, that deletion of AMELX results in males with a characteristic snow-capped enamel phenotype, and failed ARHGAP6 expression did not appreciably alter the severity of enamel defects when AMELX was absent.
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Affiliation(s)
- Jan C-C Hu
- Department of Biologic and Materials Sciences, University of Michigan School of Dentistry, Ann Arbor, Michigan, USA.
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Murakami R, Osanai T, Tomita H, Sasaki S, Maruyama A, Itoh K, Homma Y, Okumura K. p122 protein enhances intracellular calcium increase to acetylcholine: its possible role in the pathogenesis of coronary spastic angina. Arterioscler Thromb Vasc Biol 2010; 30:1968-75. [PMID: 20634475 DOI: 10.1161/atvbaha.110.203083] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/07/2023]
Abstract
OBJECTIVE Phospholipase C-δ1 activity is enhanced in patients with coronary artery spasm, and a p122 protein was recently cloned to potentiate phospholipase C-δ1 activity. To investigate the role of p122 in enhanced vasomotility, we examined p122 expression in the cultured skin fibroblasts obtained from patients with and without coronary spasm, intracellular Ca(2+) concentration ([Ca(2+)]i) [corrected] at baseline and after stimulation with acetylcholine in the cells transfected with p122, and promoter in genomic DNA. METHODS AND RESULTS [corrected] p122 protein and gene expression levels in patients with coronary spasm (n=11) were enhanced compared with levels in control subjects (n=9) (P<0.01 for both). [Ca(2+)](i) at baseline and the peak increase in [Ca(2+)](i) in response to acetylcholine were both 2 times higher in cells transfected with p122 than in those without p122. Conversely, knockdown of p122 resulted in diminished [Ca(2+)](i) response. In the p122 promoter analysis, the -228G/A and -1466C/T variants revealed the increase in luciferase activity. Although the -1466C/T variant was similar between 144 patients with coronary spasm and 148 controls, the -228G/A variant was more frequent in male patients than in male controls (P<0.05). CONCLUSIONS The p122 protein is upregulated in patients with coronary spasm, causing increased [Ca(2+)](i) to acetylcholine, and thereby seems to be related to enhanced coronary vasomotility.
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Affiliation(s)
- Reiichi Murakami
- Department of Cardiology, Hirosaki University Graduate School of Medicine, Hirosaki, Japan
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Identification of Rho GTPase Activating Protein 6 Isoform 1 Variant as a New Molecular Marker in Human Colorectal Tumors. Pathol Oncol Res 2009; 16:319-26. [DOI: 10.1007/s12253-009-9226-1] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/19/2009] [Accepted: 11/09/2009] [Indexed: 01/16/2023]
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Potet F, Petersen CI, Boutaud O, Shuai W, Stepanovic SZ, Balser JR, Kupershmidt S. Genetic screening in C. elegans identifies rho-GTPase activating protein 6 as novel HERG regulator. J Mol Cell Cardiol 2008; 46:257-67. [PMID: 19038263 DOI: 10.1016/j.yjmcc.2008.10.015] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/03/2008] [Revised: 09/17/2008] [Accepted: 10/10/2008] [Indexed: 10/21/2022]
Abstract
The human ether-a-go-go related gene (HERG) constitutes the pore forming subunit of I(Kr), a K(+) current involved in repolarization of the cardiac action potential. While mutations in HERG predispose patients to cardiac arrhythmias (Long QT syndrome; LQTS), altered function of HERG regulators are undoubtedly LQTS risk factors. We have combined RNA interference with behavioral screening in Caenorhabditis elegans to detect genes that influence function of the HERG homolog, UNC-103. One such gene encodes the worm ortholog of the rho-GTPase activating protein 6 (ARHGAP6). In addition to its GAP function, ARHGAP6 induces cytoskeletal rearrangements and activates phospholipase C (PLC). Here we show that I(Kr) recorded in cells co-expressing HERG and ARHGAP6 was decreased by 43% compared to HERG alone. Biochemical measurements of cell-surface associated HERG revealed that ARHGAP6 reduced membrane expression of HERG by 35%, which correlates well with the reduction in current. In an atrial myocyte cell line, suppression of endogenous ARHGAP6 by virally transduced shRNA led to a 53% enhancement of I(Kr). ARHGAP6 effects were maintained when we introduced a dominant negative rho-GTPase, or ARHGAP6 devoid of rhoGAP function, indicating ARHGAP6 regulation of HERG is independent of rho activation. However, ARHGAP6 lost effectiveness when PLC was inhibited. We further determined that ARHGAP6 effects are mediated by a consensus SH3 binding domain within the C-terminus of HERG, although stable ARHGAP6-HERG complexes were not observed. These data link a rhoGAP-activated PLC pathway to HERG membrane expression and implicate this family of proteins as candidate genes in disorders involving HERG.
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Affiliation(s)
- Franck Potet
- Department of Anesthesiology, Vanderbilt University, Nashville, TN 37232, USA
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