title: ADP ribosylation factor-like protein 2 (Arl2) regulates the interaction of tubulin-folding cofactor D with native tubulin.
abstract: The ADP ribosylation factor-like proteins (Arls) are a family of small monomeric G proteins of unknown function. Here, we show that Arl2 interacts with the tubulin-specific chaperone protein known as cofactor D. Cofactors C, D, and E assemble the alpha/beta- tubulin heterodimer and also interact with native tubulin, stimulating it to hydrolyze GTP and thus acting together as a beta-tubulin GTPase activating protein (GAP). We find that Arl2 downregulates the tubulin GAP activity of C, D, and E, and inhibits the binding of D to native tubulin in vitro. We also find that overexpression of cofactors D or E in cultured cells results in the destruction of the tubulin heterodimer and of microtubules. Arl2 specifically prevents destruction of tubulin and microtubules by cofactor D, but not by cofactor E. We generated mutant forms of Arl2 based on the known properties of classical Ras-family mutations. Experiments using these altered forms of Arl2 in vitro and in vivo demonstrate that it is GDP-bound Arl2 that interacts with cofactor D, thereby averting tubulin and microtubule destruction. These data establish a role for Arl2 in modulating the interaction of tubulin-folding cofactors with native tubulin in vivo.
authors.affiliation: Department of Biochemistry, New York University Medical Center, New York, New York 10016, USA.
authors.forename: A
authors.initials: A
authors.lastname: Bhamidipati
authors.forename: S A
authors.initials: SA
authors.lastname: Lewis
authors.forename: N J
authors.initials: NJ
authors.lastname: Cowan
mesh_terms: D005656:Fungal Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D019204:GTP-Binding Proteins / Q000235:genetics* / Q000378:metabolism; D020690:GTPase-Activating Proteins / Q000378:metabolism; D015870:Gene Expression / Q000502:physiology; D017930:Genes, Reporter; D049452:Green Fluorescent Proteins; D006367:HeLa Cells; D006801:Humans; D007202:Indicators and Reagents / Q000378:metabolism; D008164:Luminescent Proteins / Q000235:genetics / Q000378:metabolism; D008869:Microtubule-Associated Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D008870:Microtubules / Q000737:chemistry / Q000378:metabolism*; D008969:Molecular Sequence Data; D016296:Mutagenesis / Q000502:physiology; D010641:Phenotype; D017510:Protein Folding; D012441:Saccharomyces cerevisiae; D029702:Schizosaccharomyces pombe Proteins; D017386:Sequence Homology, Amino Acid; D014162:Transfection; D014404:Tubulin / Q000737:chemistry / Q000378:metabolism*
chemical_list: C110653:Alp1 protein, S pombe; D005656:Fungal Proteins; D020690:GTPase-Activating Proteins; D007202:Indicators and Reagents; D008164:Luminescent Proteins; D008869:Microtubule-Associated Proteins; D029702:Schizosaccharomyces pombe Proteins; D014404:Tubulin; D049452:Green Fluorescent Proteins; C410130:ARL2 protein, human; D019204:GTP-Binding Proteins