Acidification of the lysosome-like vacuole and the vacuolar H+-ATPase are deficient in two yeast mutants that fail to sort vacuolar proteins.

TitleAcidification of the lysosome-like vacuole and the vacuolar H+-ATPase are deficient in two yeast mutants that fail to sort vacuolar proteins.
Publication TypeJournal Article
Year of Publication1989
AuthorsRothman JH, Yamashiro CT, Raymond CK, Kane PM, Stevens TH
JournalJ Cell Biol
Volume109
Issue1
Pagination93-100
Date Published1989 Jul
ISSN0021-9525
KeywordsAdenosine Triphosphatases, Blotting, Western, Cell Compartmentation, Fungal Proteins, Hydrogen-Ion Concentration, Lysosomes, Mutation, Quinacrine, Saccharomyces cerevisiae, Vacuoles
Abstract

Organelle acidification plays a demonstrable role in intracellular protein processing, transport, and sorting in animal cells. We investigated the relationship between acidification and protein sorting in yeast by treating yeast cells with ammonium chloride and found that this lysosomotropic agent caused the mislocalization of a substantial fraction of the newly synthesized vacuolar (lysosomal) enzyme proteinase A (PrA) to the cell surface. We have also determined that a subset of the vpl mutants, which are deficient in sorting of vacuolar proteins (Rothman, J. H., and T. H. Stevens. 1986. Cell. 47:1041-1051; Rothman, J. H., I. Howald, and T. H. Stevens. EMBO [Eur. Mol. Biol. Organ.] J. In press), failed to accumulate the lysosomotropic fluorescent dye quinacrine within their vacuoles, mimicking the phenotype of wild-type cells treated with ammonium. The acidification defect of vpl3 and vpl6 mutants correlated with a marked deficiency in vacuolar ATPase activity, diminished levels of two immunoreactive subunits of the protontranslocating ATPase (H+-ATPase) in purified vacuolar membranes, and accumulation of the intracellular portion of PrA as the precursor species. Therefore, some of the VPL genes are required for the normal function of the yeast vacuolar H+-ATPase complex and may encode either subunits of the enzyme or components required for its assembly and targeting. Collectively, these findings implicate a critical role for acidification in vacuolar protein sorting and zymogen activation in yeast, and suggest that components of the yeast vacuolar acidification system may be identified by examining mutants defective in sorting of vacuolar proteins.

Alternate JournalJ. Cell Biol.
PubMed ID2526133
PubMed Central IDPMC2115461
Grant ListPHS 32448 / PH / PHPPO CDC HHS / United States