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| Figure 1. Schematic representation of ARHGAP21 protein. Domain positions were based on National Center for Biotechnology Information (NCBI) (https://www.ncbi.nlm.nih.gov/gene/57584). |
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Description | RhoGAPs are usually large proteins with additional domains other than the RhoGAP domain (Tcherkezian and Lamarche-Vane 2007). ARHGAP21 is composed of 1958 amino acids and has a predicted molecular weight of 217 kDa. In addition to the RhoGAP domain, ARHGAP21 comprises a PH (pleckstrin homology) and a PDZ domain (Figure 1). Although PH domains can bind to phosphatidylinositol lipids within biological membranes (Harlan et al. 1994; Saito et al. 2001), the ARHGAP21 PH domain has been demonstrated to not bind to lipids (Dubois et al. 2005). ARHGAP21 has been described to be SUMOylated in lysine K1443 by SUMO2/3. This post-translational modification may possibly explain the higher weight found by mass spectrometry (250 kDa) in contrast with the predicted weight (Bigarella et al. 2009). |
Expression | ARHGAP21 gene was widely expressed in a panel of different human tissues. Higher ARHGAP21 gene expression was observed in brain, heart, skeletal muscle, and placenta (Basseres et al. 2002). Results from FANTOM5 project also showed an increased ARHGAP21 gene expression in tissues of the human nervous system, such as cerebellum, diencephalon and hippocampus (Expression Atlas data bank). |
Localisation | ARHGAP21 has been shown to localize in the nuclei and cytoplasm of different cell types, such as adenocarcinoma PC3 and LNCAP cells and in glioblastoma T98G cells (Bigarella et al. 2009; Lazarini et al. 2013). In epithelial Caco-2 and JEG-3 cells, ARHGAP21 was detected at the cell-cell junctions and at the nucleus and perinuclear region (Sousa et al. 2005). Breast adenocarcinoma MCF-7 cells and HeLa cells presented ARHGAP21 localization in Golgi complex and in vesicular cytoplasmic structures (Dubois et al. 2005). In cardiomyocytes, ARHGAP21 was relocated from the nucleus to Z-lines and costameres after pressure overload (Borges et al. 2008). |
Function | ARHGAP21 acts as a RhoGAP for RHOA, RHOC andCDC42, but not for RAC1 (Dubois et al. 2005; Sousa et al. 2005; Lazarini et al. 2013). Such as occurs with other RhoGAP proteins, the ARHGAP21 RhoGAP activity has not been tested for most Rho GTPases. However, several ARHGAP21 partners have been described, suggesting that ARHGAP21 functions as a scaffold, linking Rho GTPases to other signaling pathways. ARHGAP21 has been shown to interact with ARF1, ARF6 (Dubois et al. 2005), catenin alpha (Sousa et al. 2005), PTK2 (FAK), PRKCZ (PKC zeta) (Borges et al. 2008), arrestin beta (Anthony et al. 2011), tubulin alpha (Barcellos et al. 2013), PRICKLE1 (Zhang et al. 2016). The functions of ARHGAP21 have been investigated in several types of cells. ARHGAP21 plays a role in cell proliferation (Lazarini et al. 2013; Luo et al. 2016), migration (Bigarella et al. 2009; Lazarini et al. 2013), vesicle traffic (Dubois et al. 2005), cell adhesions (Sousa et al. 2005; Barcellos et al. 2013; Zhang et al. 2016) and insulin secretion (Ferreira et al. 2015). |
Homology | ARHGAP21 shares homology with other members of the RhoGAP protein family (Tcherkezian and Lamarche-Vane 2007). ARHGAP21 also presents high homology among different species (Table 1). Table 1. Comparative identity of human ARHGAP21 with other species % Identity for: Homo sapiens ARHGAP21 | Symbol | Protein | DNA | vs. P. troglodytes | ARHGAP21 | 99.5 | 99.5 | vs. M. mulatta | ARHGAP21 | 98.2 | 98.0 | vs. C. lupus | ARHGAP21 | 87.1 | 85.6 | vs. B. taurus | ARHGAP21 | 87.3 | 85.0 | vs. M. musculus | Arhgap21 | 87.3 | 84.0 | vs. R. norvegicus | Arhgap21 | 86.9 | 83.3 | vs. G. gallus | ARHGAP21 | 74.9 | 75.1 | vs. X. tropicalis | arhgap21 | 65.1 | 67.4 | vs. D. rerio | arhgap21 | 57.9 | 59.5 |
(Source: http://www.ncbi.nlm.nih.gov/homologene) |
Note | The role of ARHGAP21 has been evaluated in different types of human cancers, mostly using knockdown or overexpression assays in cancer cell lines. |
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Entity | Head and neck squamous cell carcinoma (HNSCC) |
Note | ARHGAP21 was identified as a differentially expressed gene in hypopharyngeal carcinoma, using Differential Display analysis. The increased ARHGAP21 expression in tumor tissues compared to normal matched tissues was further confirmed with additional techniques, such as reverse Northern hybridization. Immunohistochemistry analysis revealed a weak cytoplasmic ARHGAP21 staining in neoplastic cells of (HNSCC), whereas no staining was detected in normal uvula epithelium (Carles et al. 2006). However, studies on ARHGAP21 functions in HNSCC have not been published to date. |
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Entity | Glioblastoma multiforme |
Note | ARHGAP21 functions were investigated in glioblastoma cell lines. In T98G and U138MG cells, both N-terminal and C-terminal portions of ARHGAP21 interacted with Focal Adhesion Kinase (FAK). Confocal micrographs showed that this interaction possibly occurs in the perinuclear region. FAK phosphorylation in Tyr397 and in Tyr925 was higher in T98G cells silenced for ARHGAP21, in comparison with control cells. Phosphorylation of Scr and p130CAS, two downstream FAK effectors, was also increased. T98G cells silenced for ARHGAP21 displayed morphological changes, which resembled epithelial mesenchymal transition. These cells also presented higher Cdc42 activity and increased rate of migration and MMP-2 secretion, indicating a possible tumor suppressor role in glioblastoma cells (Bigarella et al. 2009). |
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Entity | Prostate adenocarcinoma |
Note | ARHGAP21 function was investigated in prostate adenocarcinoma cells (Barcellos et al. 2013; Lazarini et al. 2013). However, ARHGAP21 expression in primary cells and impact in patient prognosis remains unknown. ARHGAP21 has been shown to inactivate RhoA and RhoC, though not Cdc42, in PC3 cells (human prostate adenocarcinoma cell line). PC3 cells with ARHGAP21 overexpression presented a round morphology, with increased protrusions and decreased adhesion in the tissue culture plastic plate. A similar phenotype was observed after p190 RhoGAP overexpression. ARHGAP21 silencing decreased PC3 cell proliferation, whereas increased random migration speed in fibronectin coated plates. In addition, microarray assays revealed a number of genes with altered expression in PC3 cells silenced for ARHGAP21, such as genes involved in the endothelin-1 signaling pathway (Lazarini et al. 2013). In DU145 cells, another model of prostate adenocarcinoma, ARHGAP21 interacted with tubulin alpha and was relocated from the perinuclear region to the front of the polarized cells after initiation of migration. DU145 cells silenced for ARHGAP21 also presented increased migration rate. However, stimulation with HGF had no effect upon the migration and scattering of the cells silenced for ARHGAP21. A decreased effect of HGF treatment was also observed in epithelial-mesenchymal transition (EMT) markers of DU145 cells silenced for ARHGAP21, in comparison to control cells (Barcellos et al. 2013). |
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Entity | Ovarian Cancer |
Note | ARHGAP21 expression was reported to be reduced in cancer ovarian tissues compared to adjacent non-tumorous tissue, using quantitative PCR analysis. Reduced ARHGAP21 expression correlated with poor survival of patients. In contrast, lentiviral overexpression ARHGAP21 in A2780 and HO-8910 ovarian cancer cell lines led to decreased proliferation. When A2780 cells overexpressing ARHGAP21 were subcutaneously injected into Nude mice, a decreased tumor volume was observed. ARHGAP21 overexpression also induced G0/G1 phase cell cycle arrest and apoptosis, whereas decreased the adhesion on fibronectin, migration and invasiveness of A2780 and HO-8910 cells (Luo et al. 2016). |
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Note | ARHGAP21 has shown a role in lateral signaling of MDA-MB-231 breast cancer cell line. Prickle (Pk) is a core planar cell polarity (PCP) component (Gray et al. 2011) and Pk1 has been demonstrated to interact with ARHGAP21, using affinity purification and mass spectrometry assay in MDA-MB-231 cells. The RhoGAP ARHGAP23 was identified as another Pk1 interactor. Separate knockdown of ARHGAP21 or ARHGAP23 induced no significant effect on the migration of MDA-MB-231 stimulated with active conditioned media (ACM) derived from fibroblast L cells. However, combinatorial silencing of both ARHGAPs inhibited ACM-induced migration. Pk1, ARHGAP21 and ARHGAP23 localized at non-protrusive membranes that are lateral to active protrusions. Concomitant ARHGAP21/23 silencing also induced a round morphology and diffuse protrusive activity. In addition, MDA-MB-231 silenced for ARHGAP21/23 presented increased RhoA activity and subsequent increase of myosin light chain 2 and focal adhesion activities, as well as alteration in mechanical properties of cell membrane. According to this study, the Pk1-ARHGAP21/23 complex confines protrusive activity of MDA-MB-231 cells through the regulation of RhoA activity (Zhang et al. 2016). |
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β-Arrestin 1 inhibits the GTPase-activating protein function of ARHGAP21, promoting activation of RhoA following angiotensin II type 1A receptor stimulation |
Anthony DF, Sin YY, Vadrevu S, Advant N, Day JP, Byrne AM, Lynch MJ, Milligan G, Houslay MD, Baillie GS |
Mol Cell Biol 2011 Mar;31(5):1066-75 |
PMID 21173159 |
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ARHGAP21 protein, a new partner of α-tubulin involved in cell-cell adhesion formation and essential for epithelial-mesenchymal transition |
Barcellos KS, Bigarella CL, Wagner MV, Vieira KP, Lazarini M, Langford PR, Machado-Neto JA, Call SG, Staley DM, Chung JY, Hansen MD, Saad ST |
J Biol Chem 2013 Jan 25;288(4):2179-89 |
PMID 23235160 |
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ARHGAP10, a novel human gene coding for a potentially cytoskeletal Rho-GTPase activating protein |
Bassères DS, Tizzei EV, Duarte AA, Costa FF, Saad ST |
Biochem Biophys Res Commun 2002 Jun 14;294(3):579-85 |
PMID 12056806 |
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ARHGAP21 modulates FAK activity and impairs glioblastoma cell migration |
Bigarella CL, Borges L, Costa FF, Saad ST |
Biochim Biophys Acta 2009 May;1793(5):806-16 |
PMID 19268501 |
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ARHGAP21 associates with FAK and PKCzeta and is redistributed after cardiac pressure overload |
Borges L, Bigarella CL, Baratti MO, Crosara-Alberto DP, Joazeiro PP, Franchini KG, Costa FF, Saad ST |
Biochem Biophys Res Commun 2008 Oct 3;374(4):641-6 |
PMID 18662671 |
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Head and neck squamous cell carcinoma transcriptome analysis by comprehensive validated differential display |
Carles A, Millon R, Cromer A, Ganguli G, Lemaire F, Young J, Wasylyk C, Muller D, Schultz I, Rabouel Y, Dembélé D, Zhao C, Marchal P, Ducray C, Bracco L, Abecassis J, Poch O, Wasylyk B |
Oncogene 2006 Mar 16;25(12):1821-31 |
PMID 16261155 |
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Golgi-localized GAP for Cdc42 functions downstream of ARF1 to control Arp2/3 complex and F-actin dynamics |
Dubois T, Paléotti O, Mironov AA, Fraisier V, Stradal TE, De Matteis MA, Franco M, Chavrier P |
Nat Cell Biol 2005 Apr;7(4):353-64 |
PMID 15793564 |
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ARHGAP21 prevents abnormal insulin release through actin rearrangement in pancreatic islets from neonatal mice |
Ferreira SM, Santos GJ, Rezende LF, Gonçalves LM, Santos-Silva JC, Bigarella CL, Carneiro EM, Saad ST, Boschero AC, Barbosa-Sampaio HC |
Life Sci 2015 Apr 15;127:53-8 |
PMID 25744409 |
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Planar cell polarity: coordinating morphogenetic cell behaviors with embryonic polarity |
Gray RS, Roszko I, Solnica-Krezel L |
Dev Cell 2011 Jul 19;21(1):120-33 |
PMID 21763613 |
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Pleckstrin homology domains bind to phosphatidylinositol-4,5-bisphosphate |
Harlan JE, Hajduk PJ, Yoon HS, Fesik SW |
Nature 1994 Sep 8;371(6493):168-70 |
PMID 8072546 |
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ARHGAP21 is a RhoGAP for RhoA and RhoC with a role in proliferation and migration of prostate adenocarcinoma cells |
Lazarini M, Traina F, Machado-Neto JA, Barcellos KS, Moreira YB, Brandão MM, Verjovski-Almeida S, Ridley AJ, Saad ST |
Biochim Biophys Acta 2013 Feb;1832(2):365-74 |
PMID 23200924 |
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ARHGAP10, downregulated in ovarian cancer, suppresses tumorigenicity of ovarian cancer cells |
Luo N, Guo J, Chen L, Yang W, Qu X, Cheng Z |
Cell Death Dis 2016 Mar 24;7:e2157 |
PMID 27010858 |
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Interaction between the Btk PH domain and phosphatidylinositol-3,4,5-trisphosphate directly regulates Btk |
Saito K, Scharenberg AM, Kinet JP |
J Biol Chem 2001 May 11;276(19):16201-6 |
PMID 11279148 |
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ARHGAP10 is necessary for alpha-catenin recruitment at adherens junctions and for Listeria invasion |
Sousa S, Cabanes D, Archambaud C, Colland F, Lemichez E, Popoff M, Boisson-Dupuis S, Gouin E, Lecuit M, Legrain P, Cossart P |
Nat Cell Biol 2005 Oct;7(10):954-60 |
PMID 16184169 |
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Current knowledge of the large RhoGAP family of proteins |
Tcherkezian J, Lamarche-Vane N |
Biol Cell 2007 Feb;99(2):67-86 |
PMID 17222083 |
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A lateral signalling pathway coordinates shape volatility during cell migration |
Zhang L, Luga V, Armitage SK, Musiol M, Won A, Yip CM, Plotnikov SV, Wrana JL |
Nat Commun 2016 May 26;7:11714 |
PMID 27226243 |
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