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Bph1p, the Saccharomyces cerevisiae Homologue of CHS1/Beige, Functions in Cell Wall Formation and Protein Sorting
Author(s) -
Shiflett Shelly L.,
Vaughn Michael B,
Huynh Dinh,
Kaplan Jerry,
Ward Diane McVey
Publication year - 2004
Publication title -
traffic
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.677
H-Index - 130
eISSN - 1600-0854
pISSN - 1398-9219
DOI - 10.1111/j.1600-0854.2004.00213.x
Subject(s) - biology , saccharomyces cerevisiae , secretion , biochemistry , microbiology and biotechnology , vacuole , yeast , cytoplasm
Mutations in the Chediak–Higashi syndrome gene ( CHS1 ) and its murine homologue Beige result in the formation of enlarged lysosomes. BPH1 (Beige Protein Homologue 1) encodes the Saccharomyces cerevisiae homologue of CHS1/Beige. BPH1 is not essential and the encoded protein was found to be both cytosolic and peripherally bound to a membrane. Neither disruption nor overexpression of BPH1 affected vacuole morphology as assessed by fluorescence microscopy. The δ bph1 strain showed an impaired growth on defined synthetic media containing potassium acetate buffered below pH 4.25, increased sensitivity to calcofluor white, and increased agglutination in response to low pH. A library screen identified VPS9 , FLO1 , FLO9 , BTS1 and OKP1 as high copy suppressors of the growth defect of δ bph1 on both low pH potassium acetate and calcofluor white. The δ bph1 strain demonstrated a mild defect in sorting vacuolar components, including increased secretion of carboxypeptidase Y and missorting of alkaline phosphatase. Overexpression of VPS9 , BTS1 and OKP1 suppressed the carboxypeptidase Y secretion defect of δ bph1 . Overexpression of BPH1 was found to suppress the calcofluor white sensitivity of a class E VPS deletion strain, δ vta1 . Together, these data suggest that Bph1p associates with a membrane and is involved in protein sorting and cell wall formation.