The VPS4 gene is involved in protein transport out of a yeast pre-vacuolar endosome-like compartment.
Four yeast mutants were isolated in a screen for dominant-negative vacuolar protein-sorting mutants, secreting a carboxypeptidase Y-invertase hybrid protein. In addition to defects in the sorting/transport of soluble vacuolar hydrolases, the mutants accumulated a pre-vacuolar endosome-like compartment. The mutant alleles causing the defects were identified as the members of the VPS4 gene locus, each harbouring single-point mutations leading to amino-acid exchanges at positions 233 (E233Q), 211 (E211 K), and 178 (G178D). These mutations all reside within a 200 amino-acid-long ATPase module, common to members of the AAA-protein family. The VPS4 gene product shows homology to the yeast Sec18p (50% similarity and 25% identity), which is involved in several vesicle-mediated protein transport steps and homotypic membrane fusion events. Disruption of the VPS4 gene leads to a recessive vacuolar protein-sorting phenotype. About 40% of newly synthesized CPY is secreted as the Golgi-modified p2CPY precursor form. Transport of secretory proteins to the plasma membrane is normal as demonstrated by the secretion of invertase and alpha-factor. The alpha-factor, however, is secreted as a partially processed precursor, caused by defects in late Golgi function. The vps4 mutants also exhibit defects in fluid-phase endocytosis, as demonstrated by the accumulation of Lucifer Yellow in a pre-vacuolar endosome-like compartment. Based on the pleiotropic phenotype of the vps4 mutants and on the sequence homology to NSF/Sec18p, we propose that the VPS4 gene product is required for efficient transport out of the pre-vacuolar endosome-like compartment.
Finken-Eigen
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M
Biologisch-Medizinisches Forschungszentrum, Heinrich-Heine Universität Düsseldorf, Moorenstrasse 5, D-40225 Düsseldorf, Germany.
Röhricht
R A
RA
Köhrer
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K
D000251:Adenosine Triphosphatases; D000595:Amino Acid Sequence; D001692:Biological Transport; D002268:Carboxypeptidases / Q000235:genetics / Q000378:metabolism; D043402:Cathepsin A; D002451:Cell Compartmentation / Q000502:physiology*; D004705:Endocytosis / Q000235:genetics; D056827:Endosomal Sorting Complexes Required for Transport; D011992:Endosomes / Q000378:metabolism; D005656:Fungal Proteins / Q000235:genetics* / Q000378:metabolism*; D005799:Genes, Dominant; D005816:Genetic Complementation Test; D006026:Glycoside Hydrolases / Q000235:genetics / Q000378:metabolism; D006056:Golgi Apparatus / Q000235:genetics / Q000378:metabolism; D006867:Hydrolases / Q000378:metabolism; D008969:Molecular Sequence Data; D009154:Mutation; D016366:Open Reading Frames; D017354:Point Mutation; D011994:Recombinant Proteins / Q000235:genetics / Q000378:metabolism; D029701:Saccharomyces cerevisiae Proteins; D017386:Sequence Homology, Amino Acid; D014617:Vacuoles / Q000235:genetics / Q000378:metabolism*; D043324:beta-Fructofuranosidase
D056827:Endosomal Sorting Complexes Required for Transport; D005656:Fungal Proteins; D011994:Recombinant Proteins; D029701:Saccharomyces cerevisiae Proteins; C107528:VPS4 protein, S cerevisiae; D006867:Hydrolases; D006026:Glycoside Hydrolases; D043324:beta-Fructofuranosidase; D002268:Carboxypeptidases; D043402:Cathepsin A; D000251:Adenosine Triphosphatases