title: Novel Golgi to vacuole delivery pathway in yeast: identification of a sorting determinant and required transport component.
abstract: More than 40 vacuolar protein sorting (vps) mutants have been identified which secrete proenzyme forms of soluble vacuolar hydrolases to the cell surface. A subset of these mutants has been found to show selective defects in the sorting of two vacuolar membrane proteins. Under non-permissive conditions, vps45tsf (SEC1 homolog) and pep12/vps6tsf (endosomal t-SNARE) mutants efficiently sort alkaline phosphatase (ALP) to the vacuole while multiple soluble vacuolar proteins and the membrane protein carboxypeptidase yscS (CPS) are no longer delivered to the vacuole. Vacuolar localization of ALP in these mutants does not require transport to the plasma membrane followed by endocytic uptake, as double mutants of pep12tsf and vps45tsf with sec1 and end3 sort and mature ALP at the non-permissive temperature. Given the demonstrated role of t-SNAREs such as Pep12p in transport vesicle recognition, our results indicate that ALP and CPS are packaged into distinct transport intermediates. Consistent with ALP following an alternative route to the vacuole, isolation of a vps41tsf mutant revealed that at non-permissive temperature ALP is mislocalized while vacuolar delivery of CPS and CPY is maintained. A series of domain-swapping experiments was used to define the sorting signal that directs selective packaging and transport of ALP. Our data demonstrate that the amino-terminal 16 amino acid portion of the ALP cytoplasmic tail domain contains a vacuolar sorting signal which is responsible for the active recognition, packaging and transport of ALP from the Golgi to the vacuole via a novel delivery pathway.
authors.affiliation: Division of Cellular and Molecular Medicine and Howard Hughes Medical Institute, University of California at San Diego, School of Medicine, La Jolla 92093-0668, USA.
authors.forename: C R
authors.initials: CR
authors.lastname: Cowles
authors.forename: W B
authors.initials: WB
authors.lastname: Snyder
authors.forename: C G
authors.initials: CG
authors.lastname: Burd
authors.forename: S D
authors.initials: SD
authors.lastname: Emr
mesh_terms: D000469:Alkaline Phosphatase / Q000235:genetics / Q000378:metabolism; D000595:Amino Acid Sequence; D001692:Biological Transport; D002268:Carboxypeptidases / Q000235:genetics / Q000378:metabolism; D002352:Carrier Proteins / Q000235:genetics / Q000378:metabolism*; D043402:Cathepsin A; D002451:Cell Compartmentation; D005656:Fungal Proteins / Q000235:genetics / Q000378:metabolism; D006056:Golgi Apparatus / Q000502:physiology*; D008565:Membrane Proteins / Q000235:genetics / Q000378:metabolism; D008954:Models, Biological; D008969:Molecular Sequence Data; D009687:Nuclear Proteins; D050765:Qa-SNARE Proteins; D016601:RNA-Binding Proteins / Q000235:genetics / Q000378:metabolism*; D011993:Recombinant Fusion Proteins / Q000378:metabolism; D012441:Saccharomyces cerevisiae / Q000502:physiology* / Q000648:ultrastructure; D029701:Saccharomyces cerevisiae Proteins; D014617:Vacuoles / Q000502:physiology*; D033921:Vesicular Transport Proteins
chemical_list: D002352:Carrier Proteins; D005656:Fungal Proteins; D008565:Membrane Proteins; C077734:NPL3 protein, S cerevisiae; D009687:Nuclear Proteins; C081224:PEP12 protein, S cerevisiae; D050765:Qa-SNARE Proteins; D016601:RNA-Binding Proteins; D011993:Recombinant Fusion Proteins; D029701:Saccharomyces cerevisiae Proteins; C083878:VPS41 protein, S cerevisiae; C092934:VPS45 protein, S cerevisiae; D033921:Vesicular Transport Proteins; D000469:Alkaline Phosphatase; D002268:Carboxypeptidases; D043402:Cathepsin A