title: Syt1p promotes activation of Arl1p at the late Golgi to recruit Imh1p.
abstract: In yeast, Arl3p recruits Arl1p GTPase to regulate Golgi function and structure. However, the molecular mechanism involved in regulating activation of Arl1p at the Golgi is unknown. Here, we show that Syt1p promoted activation of Arl1p and recruitment of a golgin protein, Imh1p, to the Golgi. Deletion of SYT1 resulted in the majority of Arl1p being distributed diffusely throughout the cytosol. Overexpression of Syt1p increased Arl1p-GTP production in vivo and the Syt1-Sec7 domain promoted nucleotide exchange on Arl1p in vitro. Syt1p function required the N-terminal region, Sec7 and PH domains. Arl1p, but not Arl3p, interacted with Syt1p. Localization of Syt1p to the Golgi did not require Arl3p. Unlike arl1Δ or arl3Δ mutants, syt1Δ did not show defects in Gas1p transport, cell wall integrity or vacuolar structure. These findings reveal that activation of Arl1p is regulated in part by Syt1p, and imply that Arl1p activation, by using more than one GEF, exerts distinct biological activities at the Golgi compartment.
authors.affiliation: Institute of Molecular Medicine, College of Medicine, National Taiwan University, and Department of Medical Research, National Taiwan University Hospital, Taipei 100, Taiwan.
authors.forename: Kuan-Yu
authors.initials: KY
authors.lastname: Chen
authors.forename: Pei-Chin
authors.initials: PC
authors.lastname: Tsai
authors.forename: Jia-Wei
authors.initials: JW
authors.lastname: Hsu
authors.forename: Hsin-Chia
authors.initials: HC
authors.lastname: Hsu
authors.forename: Chiung-Ying
authors.initials: CY
authors.lastname: Fang
authors.forename: Lin-Chun
authors.initials: LC
authors.lastname: Chang
authors.forename: Yueh-Tso
authors.initials: YT
authors.lastname: Tsai
authors.forename: Chia-Jung
authors.initials: CJ
authors.lastname: Yu
authors.forename: Fang-Jen S
authors.initials: FJ
authors.lastname: Lee
mesh_terms: D001692:Biological Transport / Q000235:genetics / Q000502:physiology; D002473:Cell Wall / Q000235:genetics / Q000378:metabolism; D004591:Electrophoresis, Polyacrylamide Gel; D019084:Fluorescent Antibody Technique, Indirect; D006056:Golgi Apparatus / Q000378:metabolism*; D020662:Guanine Nucleotide Exchange Factors / Q000235:genetics / Q000378:metabolism*; D008562:Membrane Glycoproteins / Q000378:metabolism; D020559:Monomeric GTP-Binding Proteins / Q000235:genetics / Q000378:metabolism*; D012441:Saccharomyces cerevisiae / Q000235:genetics / Q000378:metabolism*; D029701:Saccharomyces cerevisiae Proteins / Q000235:genetics / Q000378:metabolism*; D020798:Two-Hybrid System Techniques; D033921:Vesicular Transport Proteins / Q000235:genetics / Q000378:metabolism*
chemical_list: C066709:GAS1 protein, S cerevisiae; D020662:Guanine Nucleotide Exchange Factors; C117417:IMH1 protein, S cerevisiae; D008562:Membrane Glycoproteins; C121631:SYT1 protein, S cerevisiae; D029701:Saccharomyces cerevisiae Proteins; D033921:Vesicular Transport Proteins; C487039:ARL1 protein, S cerevisiae; D020559:Monomeric GTP-Binding Proteins