Involvement of protein N-glycosyl chain glucosylation and processing in the biosynthesis of cell wall beta-1,6-glucan of Saccharomyces cerevisiae.
beta-1,6-Glucan plays a key structural role in the yeast cell wall. Of the genes involved in its biosynthesis, the activity of Cwh41p is known, i.e., the glucosidase I enzyme of protein N-chain glucose processing. We therefore examined the effects of N-chain glucosylation and processing mutants on beta-1,6-glucan biosynthesis and show that incomplete N-chain glucose processing results in a loss of beta-1,6-glucan, demonstrating a relationship between N-chain glucosylation/processing and beta-1,6-glucan biosynthesis. To explore the involvement of other N-chain-dependent events with beta-1,6-glucan synthesis, we investigated the Saccharomyces cerevisiae KRE5 and CNE1 genes, which encode homologs of the "quality control" components UDP-Glc:glycoprotein glucosyltransferase and calnexin, respectively. We show that the essential activity of Kre5p is separate from its possible role as a UDP-Glc:glycoprotein glucosyltransferase. We also observe a approximately 30% decrease in beta-1,6-glucan upon disruption of the CNE1 gene, a phenotype that is additive with other beta-1,6-glucan synthetic mutants. Analysis of the cell wall anchorage of the mannoprotein alpha-agglutinin suggests the existence of two beta-1,6-glucan biosynthetic pathways, one N-chain dependent, the other involving protein glycosylphosphatidylinositol modification.
Shahinian
S
S
Department of Biology, McGill University, Montréal, Québec, Canada, H3A 1B1.
Dijkgraaf
G J
GJ
Sdicu
A M
AM
Thomas
D Y
DY
Jakob
C A
CA
Aebi
M
M
Bussey
H
H
D037281:Calnexin; D002473:Cell Wall / Q000201:enzymology / Q000235:genetics / Q000378:metabolism; D005656:Fungal Proteins / Q000235:genetics / Q000502:physiology; D005936:Glucans / Q000096:biosynthesis* / Q000235:genetics; D005947:Glucose / Q000235:genetics / Q000378:metabolism*; D006023:Glycoproteins / Q000235:genetics / Q000502:physiology; D006031:Glycosylation; D000072235:Mating Factor; D008565:Membrane Proteins; D016297:Mutagenesis, Site-Directed; D010455:Peptides / Q000378:metabolism; D010675:Pheromones / Q000378:metabolism; D011499:Protein Processing, Post-Translational; D012441:Saccharomyces cerevisiae / Q000201:enzymology / Q000235:genetics / Q000378:metabolism*; D029701:Saccharomyces cerevisiae Proteins; D047071:beta-Glucans
C080582:CNE1 protein, S cerevisiae; D005656:Fungal Proteins; D005936:Glucans; D006023:Glycoproteins; C064198:KRE5 protein, S cerevisiae; D008565:Membrane Proteins; D010455:Peptides; D010675:Pheromones; D029701:Saccharomyces cerevisiae Proteins; D047071:beta-Glucans; D037281:Calnexin; C064197:beta-1,6-glucan; D000072235:Mating Factor; D005947:Glucose