Affinage

ARHGAP21

Rho GTPase-activating protein 21 · UniProt Q5T5U3

Length
1958 aa
Mass
217.5 kDa
Annotated
2026-06-09
24 papers in source corpus 15 papers cited in narrative 15 extracted findings
Cross-family judge vs UniProt: Affinage preferred faithfulness: 6/6 claims corpus-supported (100%)

Mechanistic narrative

Synthesis pass · prose summary of the discoveries below

ARHGAP21 is a large multifunctional Rho-family GTPase-activating protein that couples membrane and adhesion signaling to actin cytoskeletal remodeling, vesicular trafficking, and tissue morphogenesis (PMID:17347647, PMID:23235160). It is recruited to the Golgi by GTP-bound ARF1 through a bipartite Arf-binding domain comprising a PH domain and an adjacent C-terminal alpha helix, both of which engage the ARF1 switch regions (PMID:17347647). At its catalytic core it inactivates Cdc42, and also RhoA and RhoC, thereby controlling actin dynamics in contexts ranging from dynein-dependent retrograde transport of Shiga toxin to the Golgi and surface delivery of influenza neuraminidase (PMID:19692570, PMID:22318733), to cell-cell junction stability and HGF-induced epithelial-mesenchymal transition, where it additionally binds alpha-tubulin to promote its acetylation (PMID:23200924, PMID:23235160). Its GAP activity is dynamically restrained by direct binding of beta-arrestin 1 across the GAP domain following angiotensin II receptor stimulation, gating RhoA-driven stress fiber formation (PMID:21173159), and the same beta-arrestin1/ARHGAP21/Cdc42 scaffold operates downstream of membrane-associated PTEN to orient the mitotic spindle during 3D glandular morphogenesis (PMID:28749339). ARHGAP21 further acts as a scaffold for FAK and PKCzeta signaling to suppress cell migration (PMID:19268501, PMID:18662671), stabilizes filamin A by recruiting HSP90alpha through its PDZ domain to block FLNA ubiquitination (PMID:41957357), and is regulated by SUMO2/3 modification at lysine K1443 (PMID:22922005). Through RhoC inactivation it controls hematopoietic progenitor adhesion, mobilization, and erythroid commitment (PMID:29212046).

Mechanistic history

Synthesis pass · year-by-year structured walk · 14 steps
  1. 2007 High

    Established the structural basis for how ARHGAP21 is targeted to the Golgi, answering how an Arf GTPase localizes a RhoGAP to a membrane compartment.

    Evidence X-ray crystallography of the ARF1(GTP)-ArfBD complex with site-directed mutagenesis and Golgi recruitment assays

    PMID:17347647

    Open questions at the time
    • Does not define which Rho GTPase is regulated at the Golgi
    • Does not address regulation of the GAP catalytic domain
  2. 2008 Medium

    Identified ARHGAP21 as a scaffold associating with PKCzeta and FAK that relocalizes upon cardiac mechanical stress, linking it to phospho-dependent signaling assemblies.

    Evidence Co-transfection, pulldown, Co-IP and immunofluorescence in cardiac tissue from sham and SHR rats

    PMID:18662671

    Open questions at the time
    • Does not establish a catalytic or GTPase-dependent role in this context
    • Functional consequence of relocalization not tested
  3. 2009 Medium

    Demonstrated that ARHGAP21 negatively regulates FAK signaling and migration via Cdc42 in glioblastoma, connecting its GAP activity to invasive behavior.

    Evidence shRNAi knockdown with FAK pulldown, phosphorylation, Cdc42 activity, and migration assays

    PMID:19268501

    Open questions at the time
    • Direct GAP-on-Cdc42 catalysis not separated from scaffolding
    • Single lab, single tumor type
  4. 2009 Medium

    Showed ARHGAP21-controlled Cdc42 inactivation is required for dynein-dependent retrograde transport to the Golgi, placing it in a trafficking pathway.

    Evidence siRNA, constitutively active Cdc42, Cdc42-GTP pulldown, and Shiga toxin trafficking microscopy

    PMID:19692570

    Open questions at the time
    • Link to ARF1-dependent Golgi recruitment not directly tested
    • Mechanism connecting Cdc42 to dynein unresolved
  5. 2010 High

    Defined a direct regulatory mechanism: beta-arrestin1 binding across the GAP domain inhibits ARHGAP21 GAP activity downstream of a GPCR, timing RhoA activation.

    Evidence Yeast two-hybrid, peptide array, in vitro binding, truncation, Co-IP, and cell-permeant peptide inhibitor following angiotensin II stimulation

    PMID:21173159

    Open questions at the time
    • Structural basis of GAP-domain occlusion not solved
    • Generalizability to other GPCRs unknown
  6. 2012 Medium

    Broadened the substrate repertoire to RhoA and RhoC and tied ARHGAP21 to proliferation/migration balance in prostate cancer.

    Evidence shRNA with RhoA/RhoC GTPase activity assays and proliferation/migration assays in PC3 cells

    PMID:23200924

    Open questions at the time
    • Relative contribution of each GTPase to phenotype not dissected
    • No in vivo validation
  7. 2012 Medium

    Connected ARHGAP21 to cell-cell adhesion and EMT, showing it localizes to junctions, inactivates Cdc42 there, and binds alpha-tubulin to drive its acetylation.

    Evidence Co-IP, immunofluorescence during adhesion, Cdc42 activity assay, shRNA, alpha-tubulin acetylation assay

    PMID:23235160

    Open questions at the time
    • Mechanism linking alpha-tubulin binding to acetylation unknown
    • Junctional recruitment signal not defined
  8. 2012 Medium

    Established ARHGAP21 as a post-translationally SUMOylated protein, mapping a defined modification site.

    Evidence Co-IP, in vitro SUMOylation, MS, and immunofluorescence mapping SUMO2/3 to K1443

    PMID:22922005

    Open questions at the time
    • Functional consequence of SUMOylation on GAP activity not determined
    • Conditions inducing modification unclear
  9. 2012 Medium

    Showed ARHGAP21-mediated Cdc42 control gates surface delivery of a viral glycoprotein and restricts influenza replication, extending its trafficking role to host-pathogen interactions.

    Evidence shRNA, constitutively active/dominant-negative Cdc42, surface NA quantification, viral replication assay

    PMID:22318733

    Open questions at the time
    • Compartment of action not pinpointed
    • Direct GAP catalysis vs scaffolding not separated
  10. 2015 Medium

    Implicated ARHGAP21 in regulated secretion, linking its actin control to insulin exocytosis machinery in beta cells.

    Evidence Antisense knockdown with F-actin quantification, insulin secretion, pERK1/2 Western, and RT-PCR in MIN6 cells/islets

    PMID:25744409

    Open questions at the time
    • Which Rho GTPase mediates the actin effect not specified
    • pERK1/2 link mechanistically undefined
  11. 2017 High

    Integrated ARHGAP21 into a PTEN-driven scaffold controlling Cdc42-dependent spindle orientation and epithelial architecture.

    Evidence siRNA, Co-IP, Cdc42 activity, 3D morphogenesis, spindle orientation, and PTEN C2 domain mutant rescue

    PMID:28749339

    Open questions at the time
    • How membrane-bound PTEN recruits the complex structurally unknown
    • Direct PTEN-ARHGAP21 vs beta-arrestin1-bridged contact not resolved
  12. 2017 Medium

    Demonstrated an in vivo physiological role via RhoC inactivation in hematopoiesis using a loss-of-function mouse.

    Evidence Arhgap21 haploinsufficient mice, RhoC-GTP pulldown, colony formation, transplantation, and human CMP/MEP knockdown

    PMID:29212046

    Open questions at the time
    • Cell-intrinsic vs niche contributions not fully separated
    • Mechanism downstream of RhoC in erythroid commitment unclear
  13. 2024 Medium

    Showed the ortholog's contact-site enrichment depends on afadin and E-cadherin, defining how ARHGAP21 is recruited to junctions during morphogenesis.

    Evidence Null mutants, RNAi, localization, and genetic epistasis of PAC-1/ARHGAP21, AFD-1, and E-cadherin in C. elegans

    PMID:38556137

    Open questions at the time
    • Conservation of afadin-dependent recruitment in mammals not tested
    • Direct vs indirect afadin interaction not defined
  14. 2026 Medium

    Revealed a GAP-independent function: ARHGAP21 stabilizes filamin A by recruiting HSP90alpha to block FLNA ubiquitination, controlling actin remodeling and metastasis.

    Evidence Co-IP, PDZ domain mapping, ubiquitination assay, FLNA-overexpression rescue, and migration/invasion assays in HCC

    PMID:41957357

    Open questions at the time
    • How HSP90alpha recruitment inhibits the relevant E3 ligase unknown
    • Interplay with GAP activity not dissected

Open questions

Synthesis pass · forward-looking unresolved questions
  • How ARHGAP21's distinct activities — ARF1-dependent Golgi GAP function, beta-arrestin/PTEN-gated scaffolding, tubulin acetylation, and FLNA stabilization — are coordinated within a single protein and which dominate in a given cell type remains unresolved.
  • No integrated structure-function map across domains
  • Regulation linking SUMOylation, beta-arrestin binding, and substrate selectivity unknown
  • Direct disease-causing mutation not established in the corpus

Mechanism profile

Synthesis pass · controlled-vocabulary classification · explore literature graph →
Molecular activity
GO:0098772 molecular function regulator activity 4 GO:0008092 cytoskeletal protein binding 3 GO:0060090 molecular adaptor activity 3
Localization
GO:0005634 nucleus 2 GO:0005794 Golgi apparatus 2 GO:0005829 cytosol 2 GO:0005886 plasma membrane 2
Pathway
R-HSA-1266738 Developmental Biology 3 R-HSA-162582 Signal Transduction 2 R-HSA-5653656 Vesicle-mediated transport 2
Partners
ARF1ARRB1CDC42FLNAHSP90AA1PRKCZPTENPTK2
Complex memberships
beta-arrestin1/ARHGAP21/Cdc42 scaffold

Evidence

Reading pass · 15 per-paper findings extracted from the source corpus
Year Finding Method Journal Conf PMIDs
2007 Crystal structure of ARF1(GTP)-bound form in complex with the Arf-binding domain (ArfBD) of ARHGAP21 at 2.1 Å resolution showed that ArfBD comprises a PH domain adjoining a C-terminal alpha helix, and that ARF1 interacts with both motifs through its switch regions, triggering structural rearrangement of the PH domain. Site-directed mutagenesis confirmed both the PH domain and helical motif are essential for ARF1 binding and Golgi recruitment of ARHGAP21. X-ray crystallography (2.1 Å) + site-directed mutagenesis + Golgi recruitment assay The EMBO journal High 17347647
2010 β-arrestin 1 directly binds to ARHGAP21 in a region that transects the RhoA effector GAP domain, inhibiting its GAP function. This interaction is dynamically increased following angiotensin II stimulation of the type 1A receptor, and the complex modulates the temporal activation of RhoA leading to stress fiber formation. A cell-permeant peptide disrupting the β-arrestin 1/ARHGAP21 complex resulted in more active ARHGAP21, less efficient RhoA signaling, and attenuated stress fiber formation. Yeast two-hybrid screening, peptide array, in vitro binding, truncation analyses, co-immunoprecipitation, cell-permeant peptide inhibitor assay Molecular and cellular biology High 21173159
2009 ARHGAP21 is expressed in nuclear and perinuclear regions of glioblastoma cell lines and interacts with the C-terminal region of FAK. ARHGAP21 depletion by shRNAi increases FAK phosphorylation and downstream signaling activation, increases Cdc42 activity, MMP-2 production, and cell migration, indicating ARHGAP21 negatively regulates FAK signaling and cell migration. shRNAi knockdown, pulldown assay (FAK C-terminal region), phosphorylation assays, cell migration assay Biochimica et biophysica acta Medium 19268501
2008 ARHGAP21 associates with PKCzeta and FAK in cardiac tissue and is redistributed to Z-lines and costameres after pressure overload. Co-transfection studies showed ARHGAP21 associates with PKCzeta-GST and endogenous FAK; pulldown assay confirmed ARHGAP21 binds the C-terminal region of FAK. ARHGAP21 binds to PKCzeta phosphorylated on Thr410 in sham and SHR rats, and to FAK phosphorylated on Tyr925 only in SHR. Co-transfection, pulldown assay, co-immunoprecipitation, immunofluorescence localization Biochemical and biophysical research communications Medium 18662671
2009 Constitutively active Cdc42 or knockdown of the Cdc42-specific GAP ARHGAP21 inhibited retrograde transport of Shiga toxin to the Golgi apparatus. Shiga toxin addition greatly decreases levels of active Cdc42-GTP in an ARHGAP21-dependent manner, demonstrating that ARHGAP21 and Cdc42-based signaling regulates dynein-dependent retrograde transport. siRNA knockdown, constitutively active Cdc42 expression, Cdc42-GTP pull-down activity assay, fluorescence microscopy of toxin trafficking Molecular biology of the cell Medium 19692570
2012 ARHGAP21 presents GAP activity for RhoA and RhoC in PC3 prostate cancer cells (not just Cdc42), and its depletion results in decreased proliferation and increased migration. ARHGAP21 is localized in the nucleus and cytoplasm of prostate cancer cell lines. shRNA knockdown, RhoA/RhoC GTPase activity assay, cell proliferation and migration assays, subcellular fractionation/immunofluorescence Biochimica et biophysica acta Medium 23200924
2012 ARHGAP21 is transiently redistributed to cell-cell junctions 4 hours after initiation of cell-cell adhesion, where it interacts with Cdc42 and decreases Cdc42 activity. ARHGAP21 also interacts with α-tubulin and is essential for α-tubulin acetylation during epithelial-mesenchymal transition (EMT). Cells lacking ARHGAP21 show weaker cell-cell adhesions, increased migration, and diminished HGF-induced EMT. Co-immunoprecipitation, immunofluorescence (localization during adhesion), Cdc42 activity assay, shRNA knockdown, α-tubulin acetylation assay The Journal of biological chemistry Medium 23235160
2012 ARHGAP21 is post-translationally modified by SUMO2/3; co-immunoprecipitation and in vitro SUMOylation mapped the SUMOylation site to lysine K1443. A 250 kDa modified form of ARHGAP21 is differentially expressed among cell lines and human primary cells. ARHGAP21 co-localizes with SUMO2/3 in cytoplasm and membrane compartments. Co-immunoprecipitation, in vitro SUMOylation assay, mass spectrometry, immunofluorescence FEBS letters Medium 22922005
2012 ARHGAP21 regulates Cdc42 activity to control transport of influenza virus neuraminidase (NA) to the cell surface. Depletion of ARHGAP21 or expression of constitutively active Cdc42 promoted NA transport to plasma membranes, while overexpression of ARHGAP21 or shRNA targeting Cdc42 decreased cell surface NA. Silencing ARHGAP21 increased influenza A virus replication. shRNA knockdown, constitutively active/dominant-negative mutant expression, surface NA quantification, viral replication assay The Journal of biological chemistry Medium 22318733
2017 PTEN controls 3D glandular morphogenesis through a membrane-associated β-arrestin1/ARHGAP21/Cdc42 scaffolding complex. PTEN knockdown impairs β-arrestin1 membrane localization and β-arrestin1-ARHGAP21 interactions, reducing Cdc42 activation and disrupting mitotic spindle orientation. Silencing of ARHGAP21 enhanced Cdc42 activation and rescued aberrant morphogenic processes of PTEN-deficient cultures. A membrane-binding defective mutant of PTEN C2 domain abrogated these rescue properties. siRNA knockdown, co-immunoprecipitation, Cdc42 activity assay, 3D morphogenesis assay, mitotic spindle orientation analysis, domain mutant rescue eLife High 28749339
2017 Arhgap21 haploinsufficiency in mice leads to enhanced RhoC activity in bone marrow cells, impaired hematopoietic progenitor adhesion, enhanced mobilization of LSK and myeloid progenitors, and reduced erythroid commitment. ARHGAP21 knockdown in human CMP and MEP cells recapitulated decreased erythroid commitment, indicating Arhgap21 functions in hematopoiesis at least partially through RhoC inactivation. Haploinsufficient mouse model, RhoC-GTP pull-down assay, in vitro colony formation, in vivo transplantation, human primary cell knockdown Stem cell research Medium 29212046
2015 ARHGAP21 co-localizes with actin in MIN6 beta cells and with insulin in neonatal pancreatic islets. Antisense-mediated knockdown of ARHGAP21 reduces F-actin polymerization, increases basal insulin secretion (but not GSIS), increases pERK1/2, and upregulates VAMP2 and SNAP25 gene expression, indicating ARHGAP21 regulates insulin secretion via actin rearrangement and pERK1/2 signaling. Antisense oligonucleotide knockdown, phalloidin staining (F-actin quantification), insulin secretion assay, Western blot (pERK1/2), RT-PCR, immunofluorescence Life sciences Medium 25744409
2024 In C. elegans, PAC-1/ARHGAP21 is enriched at cell contact sites in a manner dependent on afadin (AFD-1), and genetic interactions indicate afd-1 and pac-1 regulate epidermal morphogenesis through parallel mechanisms. E-cadherin is required for polarized distribution of AFD-1, which in turn promotes PAC-1/ARHGAP21 enrichment at cell contacts. Null mutation (genetic), RNAi, fluorescence localization, genetic epistasis analysis Developmental biology Medium 38556137
2026 ARHGAP21 directly binds to filamin A (FLNA) via its PDZ domain interacting with the 1-1200 aa fragment of FLNA. ARHGAP21 also directly binds and recruits HSP90α to stabilize FLNA by inhibiting its ubiquitination and degradation. Overexpression of FLNA reversed the actin cytoskeleton remodeling-related suppression of tumor metastasis caused by ARHGAP21 knockdown in HCC cells. Co-immunoprecipitation, domain mapping (PDZ domain deletion/mutation), ubiquitination assay, rescue by FLNA overexpression, in vitro and in vivo migration/invasion assays Cell death discovery Medium 41957357
2023 ARHGAP21 knockdown in NSCLC cells significantly decreased ubiquitination of β-catenin, upregulated N-cadherin, and activated the WNT signaling pathway by affecting expression of APC, GSK3β, and Axin, promoting cell migration and metastasis in vivo. siRNA knockdown, Western blot (β-catenin ubiquitination, pathway components), Transwell/wound healing migration assay, nude mouse tail-vein metastasis model Nan fang yi ke da xue xue bao Low 37712268

Source papers

Stage 0 corpus · 24 papers · ranked by NIH iCite citations
Year Title Journal Citations PMID
2007 Structural basis for ARF1-mediated recruitment of ARHGAP21 to Golgi membranes. The EMBO journal 90 17347647
2012 Transport of influenza virus neuraminidase (NA) to host cell surface is regulated by ARHGAP21 and Cdc42 proteins. The Journal of biological chemistry 65 22318733
2012 ARHGAP21 is a RhoGAP for RhoA and RhoC with a role in proliferation and migration of prostate adenocarcinoma cells. Biochimica et biophysica acta 57 23200924
2010 β-Arrestin 1 inhibits the GTPase-activating protein function of ARHGAP21, promoting activation of RhoA following angiotensin II type 1A receptor stimulation. Molecular and cellular biology 56 21173159
2012 ARHGAP21 protein, a new partner of α-tubulin involved in cell-cell adhesion formation and essential for epithelial-mesenchymal transition. The Journal of biological chemistry 46 23235160
2015 Genetic association of ARHGAP21 gene variant with mandibular prognathism. Journal of dental research 44 25691070
2009 ARHGAP21 modulates FAK activity and impairs glioblastoma cell migration. Biochimica et biophysica acta 44 19268501
2009 Retrograde Shiga toxin trafficking is regulated by ARHGAP21 and Cdc42. Molecular biology of the cell 37 19692570
2018 ARHGAP21 as a master regulator of multiple cellular processes. Journal of cellular physiology 21 29856495
2017 Hematopoietic defects in response to reduced Arhgap21. Stem cell research 19 29212046
2008 ARHGAP21 associates with FAK and PKCzeta and is redistributed after cardiac pressure overload. Biochemical and biophysical research communications 18 18662671
2017 PTEN controls glandular morphogenesis through a juxtamembrane β-Arrestin1/ARHGAP21 scaffolding complex. eLife 16 28749339
2018 Whole body ARHGAP21 reduction improves glucose homeostasis in high-fat diet obese mice. Journal of cellular physiology 10 29574752
2012 Post-translational modification of the RhoGTPase activating protein 21, ARHGAP21, by SUMO2/3. FEBS letters 10 22922005
2019 Whole-Body ARHGAP21-Deficiency Improves Energetic Homeostasis in Lean and Obese Mice. Frontiers in endocrinology 9 31191459
2019 ARHGAP21 deficiency impairs hepatic lipid metabolism and improves insulin signaling in lean and obese mice. Canadian journal of physiology and pharmacology 8 31247150
2024 C. elegans Afadin is required for epidermal morphogenesis and functionally interfaces with the cadherin-catenin complex and RhoGAP PAC-1/ARHGAP21. Developmental biology 7 38556137
2015 ARHGAP21 prevents abnormal insulin release through actin rearrangement in pancreatic islets from neonatal mice. Life sciences 5 25744409
2023 ARHGAP21 Is Involved in the Carcinogenic Mechanism of Cholangiocarcinoma: A Study Based on Bioinformatic Analyses and Experimental Validation. Medicina (Kaunas, Lithuania) 4 36676763
2020 ARHGAP21 Acts as an Inhibitor of the Glucose-Stimulated Insulin Secretion Process. Frontiers in endocrinology 4 33324349
2021 Arhgap21 Deficiency Results in Increase of Osteoblastic Lineage Cells in the Murine Bone Marrow Microenvironment. Frontiers in cell and developmental biology 2 34917608
2023 C. elegans Afadin is required for epidermal morphogenesis and functionally interfaces with the cadherin-catenin complex and RhoGAP PAC-1/ARHGAP21. bioRxiv : the preprint server for biology 1 37546884
2026 ARHGAP21 enhances metastasis in hepatocellular carcinoma by inhibiting ubiquitination of filamin A. Cell death discovery 0 41957357
2023 [ARHGAP21 inhibits epithelial-mesenchymal transition by inactivating the WNT signaling pathway in non-small cell lung cancer]. Nan fang yi ke da xue xue bao = Journal of Southern Medical University 0 37712268

Missed literature

Know a paper Affinage missed for ARHGAP21? Flag it for the maintainers and the community.

No submissions yet.