title: Competition between the golgin Imh1p and the GAP Gcs1p stabilizes activated Arl1p at the late-Golgi.
abstract: Golgins play diverse roles in regulating the structure and function of the Golgi. The yeast golgin Imh1p is targeted to the trans-Golgi network (TGN) through interaction of its GRIP domain with GTP-bound Arl1p. Recycling of Arl1p and Imh1p to the cytosol requires the hydrolysis of GTP bound to Arl1p; however, the point at which GTP hydrolysis occurs remains unknown. Here, we report that self-interaction of Imh1p plays a role in modulating spatial inactivation of Arl1p. Deletion of IMH1 in yeast decreases the amount of the GTP-bound Arl1p and results in less Arl1p residing on the TGN. Biochemically, purified Imh1p competes with Gcs1p, an Arl1p GTPase-activating protein (GAP), for binding to Arl1p, thus interfering with the GAP activity of Gcs1p toward Arl1p. Furthermore, we demonstrate that the self-interaction of Imh1p attenuates the Gcs1p-dependent GTP hydrolysis of Arl1p. Thus, we propose that the golgin Imh1p serves as a feedback regulator to modulate the GTP hydrolysis of Arl1p.
authors: Institute of Molecular Medicine, College of Medicine, National Taiwan University and Department of Medical Research, National Taiwan University Hospital, Taipei 100, Taiwan.
authors: Kuan-Yu
authors: KY
authors: Chen
authors: Pei-Chin
authors: PC
authors: Tsai
authors: Ya-Wen
authors: YW
authors: Liu
authors: Fang-Jen S
authors: FJ
authors: Lee
mesh_terms: D001667:Binding, Competitive; D004268:DNA-Binding Proteins / Q000378:metabolism*; D004789:Enzyme Activation; D020690:GTPase-Activating Proteins / Q000378:metabolism*; D017353:Gene Deletion; D055786:Gene Knockout Techniques; D006056:Golgi Apparatus / Q000201:enzymology*; D006160:Guanosine Triphosphate / Q000378:metabolism; D006868:Hydrolysis; D008954:Models, Biological; D020559:Monomeric GTP-Binding Proteins / Q000737:chemistry / Q000378:metabolism; D011485:Protein Binding; D055503:Protein Multimerization; D055550:Protein Stability; D017434:Protein Structure, Tertiary; D021381:Protein Transport; D012441:Saccharomyces cerevisiae / Q000166:cytology* / Q000201:enzymology* / Q000378:metabolism; D029701:Saccharomyces cerevisiae Proteins / Q000737:chemistry / Q000378:metabolism*; D013329:Structure-Activity Relationship; D033921:Vesicular Transport Proteins / Q000737:chemistry / Q000378:metabolism*; D021601:trans-Golgi Network / Q000378:metabolism
chemical_list: D004268:DNA-Binding Proteins; C089147:GCS1 protein, S cerevisiae; D020690:GTPase-Activating Proteins; C117417:IMH1 protein, S cerevisiae; D029701:Saccharomyces cerevisiae Proteins; D033921:Vesicular Transport Proteins; D006160:Guanosine Triphosphate; C487039:ARL1 protein, S cerevisiae; D020559:Monomeric GTP-Binding Proteins