title: Yeast Ysl2p, homologous to Sec7 domain guanine nucleotide exchange factors, functions in endocytosis and maintenance of vacuole integrity and interacts with the Arf-Like small GTPase Arl1p.
abstract: We previously described the isolation of ysl2-1 due to its genetic interaction with Delta ypt51/vps21, a mutant with a deletion of the coding sequence for the yeast Rab5 homolog, which regulates endocytic traffic between early and late endosomes. Here we report that Ysl2p is a novel 186.8-kDa peripheral membrane protein homologous to members of the Sec7 family. We provide multiple genetic and biochemical evidence for an interaction between Ysl12p and the Arf-like protein Arl1p, consistent with a potential function as an Arf guanine nucleotide exchange factor (GEF). The temperature-sensitive alleles ysl2-307 and ysl2-316 are specifically defective in ligand-induced degradation of Ste2p and alpha-factor and exhibit vacuole fragmentation directly upon a shift to 37 degrees C. In living cells, green fluorescent protein (GFP)-Ysl2p colocalizes with endocytic elements that accumulate FM4-64. The GFP-Ysl2p staining is sensitive to a mutation in VPS27 resulting in the formation of an aberrant class E compartment, but it is not affected by a sec7 mutation. Consistent with the idea that Ysl2p and Arl1p have closely related functions, Delta arl1 cells are defective in endocytic transport and in vacuolar protein sorting.
authors.affiliation: Institute for Biochemistry, University of Stuttgart, D-70569 Stuttgart, Germany.
authors.forename: Alexandra
authors.initials: A
authors.lastname: Jochum
authors.forename: David
authors.initials: D
authors.lastname: Jackson
authors.forename: Heinz
authors.initials: H
authors.lastname: Schwarz
authors.forename: Rüdiger
authors.initials: R
authors.lastname: Pipkorn
authors.forename: Birgit
authors.initials: B
authors.lastname: Singer-Krüger
mesh_terms: D020727:ADP-Ribosylation Factors; D000595:Amino Acid Sequence; D001483:Base Sequence; D002268:Carboxypeptidases / Q000378:metabolism; D043402:Cathepsin A; D004705:Endocytosis; D011992:Endosomes / Q000378:metabolism; D005456:Fluorescent Dyes / Q000737:chemistry; D005656:Fungal Proteins / Q000378:metabolism; D020558:GTP Phosphohydrolases / Q000235:genetics / Q000378:metabolism*; D006026:Glycoside Hydrolases / Q000378:metabolism; D049452:Green Fluorescent Proteins; D020662:Guanine Nucleotide Exchange Factors / Q000378:metabolism*; D007425:Intracellular Membranes / Q000378:metabolism; D008164:Luminescent Proteins / Q000235:genetics / Q000378:metabolism; D008565:Membrane Proteins / Q000235:genetics / Q000378:metabolism*; D008969:Molecular Sequence Data; D009154:Mutation; D029363:Organic Anion Transporters, Sodium-Dependent / Q000235:genetics / Q000378:metabolism*; D011726:Pyridinium Compounds / Q000737:chemistry; D000644:Quaternary Ammonium Compounds / Q000737:chemistry; D017421:Sequence Analysis; D017386:Sequence Homology, Amino Acid; D060347:Sodium-Coupled Vitamin C Transporters; D027981:Symporters; D013696:Temperature; D014617:Vacuoles / Q000378:metabolism / Q000648:ultrastructure*; D043324:beta-Fructofuranosidase
chemical_list: C092350:FM 4-64; D005456:Fluorescent Dyes; D005656:Fungal Proteins; D020662:Guanine Nucleotide Exchange Factors; D008164:Luminescent Proteins; D008565:Membrane Proteins; D029363:Organic Anion Transporters, Sodium-Dependent; D011726:Pyridinium Compounds; D000644:Quaternary Ammonium Compounds; C066755:Sec7 guanine nucleotide exchange factors; D060347:Sodium-Coupled Vitamin C Transporters; D027981:Symporters; D049452:Green Fluorescent Proteins; D006026:Glycoside Hydrolases; D043324:beta-Fructofuranosidase; D002268:Carboxypeptidases; D043402:Cathepsin A; C097313:ADP-ribosylation factor related proteins; D020558:GTP Phosphohydrolases; D020727:ADP-Ribosylation Factors