Overexpression of MID2 suppresses the profilin-deficient phenotype of yeast cells.
Profilin-deficient Saccharomyces cerevisiae cells show abnormal growth, actin localization, chitin deposition, bud formation and cytokinesis. Previous studies have also revealed a synthetic lethality between pfy1 and late secretory mutants, suggesting a role for profilin in intracellular transport. In this work, we document further the secretion defect associated with the pfy1delta mutant. Electron microscopic observations reveal an accumulation of glycoproteins in the bud and in the mother cell. The MATa, pfy1delta cells mate as well as wild-type cells, while the mating efficiency of MAT alpha, pfy1delta cells is reduced. Pulse-chase experiments demonstrate an accumulation of the 19 kDa alpha-factor precursor and delayed secretion of the mature alpha-factor. The TGN protein Kex2p is the principal enzyme responsible for the endoproteolytic cleavage of the alpha-factor precursor. An immunofluorescence detection of Kex2p shows an altered localization in pfy1delta cells. Instead of a discrete punctate distribution, the enzyme is dispersed throughout the cytoplasm. A high-copy-number plasmid containing MID2, which encodes a potential transmembrane protein involved in cell cycle control, suppresses the abnormal growth, actin distribution, alpha-factor maturation and the accumulation of intracellular membranous structures in pfy1delta cells.
Pavillon Charles-Eugène Marchand, Laval University, Ste-Foy, Québec, Canada.
N
N
Marcoux
Y
Y
Bourbonnais
P M
PM
Charest
D
D
Pallotta
D002135:Calcium-Binding Proteins / Q000235:genetics* / Q000378:metabolism; D018797:Cell Cycle Proteins / Q000235:genetics*; D018628:Gene Dosage; D016153:Genes, Suppressor; D006023:Glycoproteins / Q000378:metabolism; D006026:Glycoside Hydrolases / Q000378:metabolism; D047908:Intracellular Signaling Peptides and Proteins; D000072235:Mating Factor; D008562:Membrane Glycoproteins; D008565:Membrane Proteins / Q000235:genetics* / Q000378:metabolism; D010455:Peptides / Q000235:genetics / Q000378:metabolism; D010641:Phenotype; D051304:Profilins; D043484:Proprotein Convertases; D012441:Saccharomyces cerevisiae / Q000502:physiology* / Q000648:ultrastructure; D029701:Saccharomyces cerevisiae Proteins; D013381:Subtilisins / Q000378:metabolism; D043324:beta-Fructofuranosidase
C086662:CDC3 protein, S cerevisiae; D002135:Calcium-Binding Proteins; D018797:Cell Cycle Proteins; D006023:Glycoproteins; D047908:Intracellular Signaling Peptides and Proteins; C091625:MID2 protein, S cerevisiae; D008562:Membrane Glycoproteins; D008565:Membrane Proteins; D010455:Peptides; D051304:Profilins; D029701:Saccharomyces cerevisiae Proteins; D000072235:Mating Factor; D006026:Glycoside Hydrolases; D043324:beta-Fructofuranosidase; D043484:Proprotein Convertases; D013381:Subtilisins; C058751:KEX2 protein, S cerevisiae