title: ARL4D recruits cytohesin-2/ARNO to modulate actin remodeling.
abstract: ARL4D is a developmentally regulated member of the ADP-ribosylation factor/ARF-like protein (ARF/ARL) family of Ras-related GTPases. Although the primary structure of ARL4D is very similar to that of other ARF/ARL molecules, its function remains unclear. Cytohesin-2/ARF nucleotide-binding-site opener (ARNO) is a guanine nucleotide-exchange factor (GEF) for ARF, and, at the plasma membrane, it can activate ARF6 to regulate actin reorganization and membrane ruffling. We show here that ARL4D interacts with the C-terminal pleckstrin homology (PH) and polybasic c domains of cytohesin-2/ARNO in a GTP-dependent manner. Localization of ARL4D at the plasma membrane is GTP- and N-terminal myristoylation-dependent. ARL4D(Q80L), a putative active form of ARL4D, induced accumulation of cytohesin-2/ARNO at the plasma membrane. Consistent with a known action of cytohesin-2/ARNO, ARL4D(Q80L) increased GTP-bound ARF6 and induced disassembly of actin stress fibers. Expression of inactive cytohesin-2/ARNO(E156K) or small interfering RNA knockdown of cytohesin-2/ARNO blocked ARL4D-mediated disassembly of actin stress fibers. Similar to the results with cytohesin-2/ARNO or ARF6, reduction of ARL4D suppressed cell migration activity. Furthermore, ARL4D-induced translocation of cytohesin-2/ARNO did not require phosphoinositide 3-kinase activation. Together, these data demonstrate that ARL4D acts as a novel upstream regulator of cytohesin-2/ARNO to promote ARF6 activation and modulate actin remodeling.
authors.affiliation: Institute of Molecular Medicine, College of Medicine, National Taiwan University, Taipei 100, Taiwan.
authors.forename: Chun-Chun
authors.initials: CC
authors.lastname: Li
authors.forename: Tsai-Chen
authors.initials: TC
authors.lastname: Chiang
authors.forename: Tsung-Sheng
authors.initials: TS
authors.lastname: Wu
authors.forename: Gustavo
authors.initials: G
authors.lastname: Pacheco-Rodriguez
authors.forename: Joel
authors.initials: J
authors.lastname: Moss
authors.forename: Fang-Jen S
authors.initials: FJ
authors.lastname: Lee
mesh_terms: D020727:ADP-Ribosylation Factors / Q000235:genetics / Q000378:metabolism*; D000199:Actins / Q000378:metabolism*; D000818:Animals; D002384:Catalysis; D002460:Cell Line; D002462:Cell Membrane / Q000378:metabolism; D002465:Cell Movement; D002522:Chlorocebus aethiops; D020690:GTPase-Activating Proteins / Q000378:metabolism*; D006160:Guanosine Triphosphate / Q000378:metabolism; D006801:Humans; D008565:Membrane Proteins / Q000235:genetics / Q000378:metabolism*; D009154:Mutation / Q000235:genetics; D019869:Phosphatidylinositol 3-Kinases / Q000378:metabolism; D011485:Protein Binding; D021381:Protein Transport; D051057:Proto-Oncogene Proteins c-akt / Q000378:metabolism; D015398:Signal Transduction; D014157:Transcription Factors / Q000378:metabolism