title: The Arf6 GTPase-activating proteins ARAP2 and ACAP1 define distinct endosomal compartments that regulate integrin α5β1 traffic.
abstract: Arf6 and the Arf6 GTPase-activating protein (GAP) ACAP1 are established regulators of integrin traffic important to cell adhesion and migration. However, the function of Arf6 with ACAP1 cannot explain the range of Arf6 effects on integrin-based structures. We propose that Arf6 has different functions determined, in part, by the associated Arf GAP. We tested this idea by comparing the Arf6 GAPs ARAP2 and ACAP1. We found that ARAP2 and ACAP1 had opposing effects on apparent integrin β1 internalization. ARAP2 knockdown slowed, whereas ACAP1 knockdown accelerated, integrin β1 internalization. Integrin β1 association with adaptor protein containing a pleckstrin homology (PH) domain, phosphotyrosine-binding (PTB) domain, and leucine zipper motif (APPL)-positive endosomes and EEA1-positive endosomes was affected by ARAP2 knockdown and depended on ARAP2 GAP activity. ARAP2 formed a complex with APPL1 and colocalized with Arf6 and APPL in a compartment distinct from the Arf6/ACAP1 tubular recycling endosome. In addition, although ACAP1 and ARAP2 each colocalized with Arf6, they did not colocalize with each other and had opposing effects on focal adhesions (FAs). ARAP2 overexpression promoted large FAs, but ACAP1 overexpression reduced FAs. Taken together, the data support a model in which Arf6 has at least two sites of opposing action defined by distinct Arf6 GAPs.
authors.affiliation: Laboratory of Cellular and Molecular Biology, NCI, National Institutes of Health, Bethesda, Maryland 20892.
authors.forename: Pei-Wen
authors.initials: PW
authors.lastname: Chen
authors.affiliation: Laboratory of Cellular and Molecular Biology, NCI, National Institutes of Health, Bethesda, Maryland 20892.
authors.forename: Ruibai
authors.initials: R
authors.lastname: Luo
authors.affiliation: Laboratory of Cellular and Molecular Biology, NCI, National Institutes of Health, Bethesda, Maryland 20892.
authors.forename: Xiaoying
authors.initials: X
authors.lastname: Jian
authors.affiliation: Laboratory of Cellular and Molecular Biology, NCI, National Institutes of Health, Bethesda, Maryland 20892. Electronic address: randazzp@mail.nih.gov.
authors.forename: Paul A
authors.initials: PA
authors.lastname: Randazzo
mesh_terms: D000089982:ADP-Ribosylation Factor 6; D020727:ADP-Ribosylation Factors / Q000378:metabolism; D048868:Adaptor Proteins, Signal Transducing / Q000378:metabolism; D002352:Carrier Proteins / Q000502:physiology*; D004705:Endocytosis; D011992:Endosomes / Q000378:metabolism*; D066246:ErbB Receptors / Q000378:metabolism; D022001:Focal Adhesions / Q000378:metabolism; D020690:GTPase-Activating Proteins / Q000502:physiology*; D006367:HeLa Cells; D006801:Humans; D021381:Protein Transport; D019030:Receptors, Vitronectin / Q000378:metabolism*; D014168:Transferrin / Q000378:metabolism; D033921:Vesicular Transport Proteins / Q000378:metabolism
chemical_list: C507017:ACAP1 protein, human; D000089982:ADP-Ribosylation Factor 6; C464801:APPL1 protein, human; C446514:ARAP2 protein, human; D048868:Adaptor Proteins, Signal Transducing; D002352:Carrier Proteins; D020690:GTPase-Activating Proteins; D019030:Receptors, Vitronectin; D014168:Transferrin; D033921:Vesicular Transport Proteins; C093846:early endosome antigen 1; C094340:integrin alphavbeta1; C512478:EGFR protein, human; D066246:ErbB Receptors; D020727:ADP-Ribosylation Factors; C000715348:ARF6 protein, human
keywords: ACAP1; ADP Ribosylation Factor (ARF); APPL; ARAP2; Endosome; GTPase-activating Protein (GAP); Integrin; Membrane Trafficking