title: The arf6 GAP centaurin alpha-1 is a neuronal actin-binding protein which also functions via GAP-independent activity to regulate the actin cytoskeleton.
abstract: Centaurin alpha-1 is a high-affinity PtdIns(3,4,5)P3-binding protein enriched in brain. Sequence analysis indicates centaurin alpha-1 contains two pleckstrin homology domains, ankyrin repeats and an Arf GAP homology domain, placing it in the AZAP family of phosphoinositide-regulated Arf GAPs. Other members of this family are involved in actin cytoskeletal and focal adhesion organization. Recently, it was reported that centaurin alpha-1 expression diminishes cortical actin and decreases Arf6GTP levels consistent with it functioning as an Arf6 GAP in vivo. In the current report, we show that centaurin alpha-1 binds Arfs in vitro and colocalizes with Arf6 and Arf5 in vivo, further supporting an interaction with Arfs. Centaurin alpha-1 expression produces dramatic effects on the actin cytoskeleton, decreasing stress fibers, diminishing cortical actin, and enhancing membrane ruffles and filopodia. Expression of centaurin alpha-1 also enhances cell spreading and disrupts focal adhesion protein localization. The effects of centaurin alpha-1 on stress fibers and cell spreading are reminiscent of those of Arf6GTP. Consistent with this, we show that many of the centaurin alpha-1-induced effects on the actin cytoskeleton and actin-dependent activities do not require GAP activity. Thus, centaurin alpha-1 likely functions via both GAP-dependent and GAP-independent mechanisms to regulate the actin cytoskeleton. Furthermore, we demonstrate that in vitro, centaurin alpha-1 binds F-actin directly, with actin binding activity localized to the PtdIns(3,4,5)P3-binding PH domain. Our data suggest that centaurin alpha-1 may be a component of the neuronal PI 3-kinase cascade that leads to regulation of the neuronal actin cytoskeleton.
authors.affiliation: Department of Neurobiology and Cell Biology, University of Alabama at Birmingham, Birmingham, AL 35294, USA.
authors.forename: Erin
authors.initials: E
authors.lastname: Thacker
authors.forename: Brian
authors.initials: B
authors.lastname: Kearns
authors.forename: Carlene
authors.initials: C
authors.lastname: Chapman
authors.forename: Jennifer
authors.initials: J
authors.lastname: Hammond
authors.forename: Audrey
authors.initials: A
authors.lastname: Howell
authors.forename: Anne
authors.initials: A
authors.lastname: Theibert
mesh_terms: D016475:3T3 Cells; D000089982:ADP-Ribosylation Factor 6; D020727:ADP-Ribosylation Factors / Q000378:metabolism / Q000502:physiology*; D000199:Actins / Q000378:metabolism*; D048868:Adaptor Proteins, Signal Transducing; D000595:Amino Acid Sequence; D000818:Animals; D002352:Carrier Proteins / Q000235:genetics / Q000502:physiology*; D002448:Cell Adhesion / Q000502:physiology; D003599:Cytoskeleton / Q000378:metabolism*; D022001:Focal Adhesions / Q000502:physiology; D020690:GTPase-Activating Proteins / Q000378:metabolism / Q000502:physiology*; D015870:Gene Expression; D006367:HeLa Cells; D006801:Humans; D051379:Mice; D008840:Microfilament Proteins / Q000502:physiology*; D008969:Molecular Sequence Data; D009419:Nerve Tissue Proteins / Q000235:genetics / Q000378:metabolism / Q000502:physiology*; D011485:Protein Binding; D017386:Sequence Homology, Amino Acid; D013997:Time Factors
chemical_list: C100956:ADAP1 protein, human; D000089982:ADP-Ribosylation Factor 6; D000199:Actins; C491062:Adap1 protein, rat; D048868:Adaptor Proteins, Signal Transducing; D002352:Carrier Proteins; D020690:GTPase-Activating Proteins; D008840:Microfilament Proteins; D009419:Nerve Tissue Proteins; D020727:ADP-Ribosylation Factors; C000715348:ARF6 protein, human; C000715727:Arf6 protein, mouse; C000715349:Arf6 protein, rat