Characterization of GAPCenA, a GTPase activating protein for Rab6, part of which associates with the centrosome

• Published in: The EMBO journal Vol. 18; no. 7; pp. 1772 - 1782
• Main Authors: Cuif, Marie-Hélène, Possmayer, Franziska, Zander, Hilke, Bordes, Nicole, Jollivet, Florence, Couedel-Courteille, Anne, Janoueix-Lerosey, Isabelle, Langsley, Gordon, Bornens, Michel, Goud, Bruno
• Format: Journal Article
• Language: English
• Published: Chichester, UK John Wiley & Sons, Ltd 01.04.1999; Blackwell Publishing Ltd
• Subjects: Amino Acid Sequence; Animals; Base Sequence; Carrier Proteins - metabolism; centrosome; Centrosome - metabolism; Cloning, Molecular; DNA Primers - genetics; Enzyme Activation; Fungal Proteins - genetics; Golgi apparatus; GTP Phosphohydrolases - metabolism; GTPase activating protein; GTPase-Activating Proteins; HeLa Cells; Humans; Microtubule-Associated Proteins - genetics; Microtubule-Associated Proteins - metabolism; mitosis; Molecular Sequence Data; Proteins - genetics; Proteins - metabolism; rab GTP-Binding Proteins; Rab6; ras GTPase-Activating Proteins; ras Proteins - metabolism; Recombinant Proteins - genetics; Recombinant Proteins - metabolism; Saccharomyces cerevisiae; Saccharomyces cerevisiae - genetics; Schizosaccharomyces - genetics; Schizosaccharomyces pombe; Sequence Homology, Amino Acid; Subcellular Fractions - metabolism; Tubulin - metabolism
• ISSN: 0261-4189; 1460-2075; 1460-2075
• DOI: 10.1093/emboj/18.7.1772

The Rab6 GTPase regulates intracellular transport at the level of the Golgi apparatus, probably in a retrograde direction. Here, we report the identification and characterization of a novel human Rab6‐interacting protein named human GAPCenA (for ‘GAP and centrosome‐associated’). Primary sequence analysis indicates that GAPCenA displays similarities, within a central 200 amino acids domain, to both the yeast Rab GTPase activating proteins (GAPs) and to the spindle checkpoint proteins Saccharomyces cerevisiae Bub2p and Schizosaccharomyces pombe Cdc16p. We demonstrate that GAPCenA is indeed a GAP, specifically active in vitro on Rab6 and, to a lesser extent, on Rab4 and Rab2 proteins. Immunofluorescence and cell fractionation experiments showed that GAPCenA is mainly cytosolic but that a minor pool is associated with the centrosome. Moreover, GAPCenA was found to form complexes with cytosolic γ‐tubulin and to play a role in microtubule nucleation. Therefore, GAPCenA may be involved in the coordination of microtubule and Golgi dynamics during the cell cycle.