ARAP2 effects on the actin cytoskeleton are dependent on Arf6-specific GTPase-activating-protein activity and binding to RhoA-GTP.
ARAP2 is a protein that contains both ArfGAP and RhoGAP domains. We found that it is a phosphatidylinositol (3,4,5)-trisphosphate-dependent Arf6 GAP that binds RhoA-GTP but lacks RhoGAP activity. In agreement with the hypothesis that ARAP2 mediates effects of RhoA, endogenous ARAP2 associated with focal adhesions (FAs) and reduction of ARAP2 expression, by RNAi, resulted in fewer FAs and actin stress fibers (SFs). In cells with reduced levels of endogenous ARAP2, FAs and SFs could be restored with wild-type recombinant ARAP2 but not mutants lacking ArfGAP or Rho-binding activity. Constitutively active Arf6 also caused a loss of SFs. The Rho effector ROKalpha was ineffective in restoring FAs. Conversely, overexpression of ARAP2 did not restore SFs in cells treated with a ROK inhibitor but induced punctate accumulations of paxillin. We conclude that ARAP2 is an Arf6GAP that functions downstream of RhoA to regulate focal adhesion dynamics.
Yoon
Hye-Young
HY
Laboratory of Cellular Oncology, Center for Cancer Research, National Cancer Institute, Department of Health and Human Services, Building 37, Bethesda, MD 20892, USA.
Miura
Koichi
K
Cuthbert
E Jebb
EJ
Davis
Kathryn Kay
KK
Ahvazi
Bijan
B
Casanova
James E
JE
Randazzo
Paul A
PA
D020823:ADP-Ribosylation Factor 1 / Q000378:metabolism; D000089982:ADP-Ribosylation Factor 6; D020727:ADP-Ribosylation Factors / Q000378:metabolism*; D000199:Actins / Q000378:metabolism*; D002352:Carrier Proteins / Q000235:genetics / Q000502:physiology*; D002460:Cell Line; D003599:Cytoskeleton / Q000378:metabolism*; D022001:Focal Adhesions; D020690:GTPase-Activating Proteins / Q000235:genetics / Q000502:physiology*; D006801:Humans; D008958:Models, Molecular; D009154:Mutation; D018129:Phosphatidylinositol Phosphates / Q000502:physiology; D011485:Protein Binding; D017434:Protein Structure, Tertiary; D021381:Protein Transport; D022502:Stress Fibers / Q000502:physiology; D020742:rhoA GTP-Binding Protein / Q000378:metabolism*
D000089982:ADP-Ribosylation Factor 6; C446514:ARAP2 protein, human; D000199:Actins; D002352:Carrier Proteins; D020690:GTPase-Activating Proteins; D018129:Phosphatidylinositol Phosphates; C060974:phosphatidylinositol 3,4,5-triphosphate; D020823:ADP-Ribosylation Factor 1; D020727:ADP-Ribosylation Factors; C000715348:ARF6 protein, human; D020742:rhoA GTP-Binding Protein