Mol. Cell. Biol., 01 1996, 442-456, Vol 16, No. 1
G Muller, E Gross, S Wied and W Bandlow
Transfer of spheroplasts from the yeast Saccharomyces cerevisiae to glucose
leads to the activation of an endogenous (glycosyl)-
phosphatidylinositol-specific phospholipase C ([G]PI-PLC), which cleaves
the anchor of at least one glycosyl-phosphatidylinositol (GPI)- anchored
protein, the cyclic AMP (cAMP)-binding ectoprotein Gce1p (G. Muller and W.
Bandlow, J. Cell Biol. 122:325-336, 1993). Analyses of the turnover of two
constituents of the anchor, myo-inositol and ethanolamine, relative to the
protein label as well as separation of the two differently processed
versions of Gce1p by isoelectric focusing in spheroplasts demonstrate the
glucose-induced conversion of amphiphilic Gce1p first into a lipolytically
cleaved hydrophilic intermediate, which is then processed into another
hydrophilic version lacking both myo-inositol and ethanolamine. When
incubated with unlabeled spheroplasts, the lipolytically cleaved
intermediate prepared in vitro is converted into the version lacking all
anchor constituents, whereby the anchor glycan is apparently removed as a
whole. The secondary cleavage ensues independently of the carbon source,
attributing the key role in glucose-induced anchor processing to the
endogenous (G)PI-PLC. The secondary processing of the lipolytically cleaved
intermediate of Gce1p at the plasma membrane is correlated with the
emergence of a covalently linked high-molecular-weight form of a
cAMP-binding protein at the cell wall. This protein lacks anchor
components, and its protein moiety appears to be identical with double-
processed Gce1p detectable at the plasma membrane in spheroplasts. The data
suggest that glucose-induced double processing of GPI anchors represents
part of a mechanism of regulated cell wall expression of proteins in yeast
cells.
Copyright © 1996, American Society for Microbiology
Glucose-induced sequential processing of a glycosyl- phosphatidylinositol-anchored ectoprotein in Saccharomyces cerevisiae
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