Linked Life Data

7738102

Source:http://linkedlifedata.com/resource/pubmed/id/7738102

Statements in which the resource exists as a subject.
PredicateObject
rdf:type
lifeskim:mentions
pubmed:dateCreated
1995-6-8
pubmed:abstractText
The budding yeast Pichia pastoris responds to methanolic media by synthesizing high levels of cytosolic enzymes (e.g. formate dehydrogenase) and peroxisomal enzymes (e.g. alcohol oxidase), which are necessary to assimilate this carbon source. Major alterations in cellular metabolism are initiated upon a shift in carbon source to ethanol or glucose. These alterations require the synthesis of new proteins and the rapid degradation of those enzymes no longer needed for methanol utilization. In this study, we have measured cytosolic and peroxisomal enzyme activities and examined the fate of morphologically distinct peroxisomes to assess the degradative response of this yeast during nutrient adaptation. Utilizing biochemical, morphological and genetic approaches, we have shown that there exist in P. pastoris at least two pathways for the sequestration of peroxisomes into the vacuole for degradation. The ethanol-induced pathway is independent of protein synthesis and includes an intermediate stage in which individual peroxisomes are sequestered into autophagosomes by wrapping membranes, which then fuse with the vacuole. This process is analogous to macroautophagy. The glucose-induced pathway invokes the engulfment of clusters of peroxisomes by finger-like protrusions of the vacuole by a process analogous to microautophagy. Unlike ethanol adaptation, glucose stimulated the degradation of formate dehydrogenase as well. Peroxisomes remained outside the vacuoles of glucose-adapted cycloheximide-treated normal cells, suggesting that protein synthesis is required for peroxisome entry into the yeast vacuole. Two complementary mutants (gsa1 and gsa2) that are unable to degrade peroxisomes or formate dehydrogenase during glucose adaptation were isolated. The mutated gene products appear to function in one or more events upstream of degradation within the vacuole, since ethanol-induced peroxisome degradation proceeded normally in these mutants and peroxisomes were found outside the vacuoles of glucose-adapted gsa2 cells. Mutants lacking vacuolar proteinases A and B were unable to degrade alcohol oxidase or formate dehydrogenase during ethanol or glucose adaptation. Peroxisomes were found to accumulate within the vacuoles of these proteinase mutants during adaptation. Combined, the results suggest that there exist in Pichia pastoris two independent pathways for the sequestration of peroxisomes into the vacuole, the site of degradation.
pubmed:grant
pubmed:language
eng
pubmed:journal
pubmed:citationSubset
IM
pubmed:chemical
pubmed:status
MEDLINE
pubmed:month
Jan
pubmed:issn
0021-9533
pubmed:author
pubmed:issnType
Print
pubmed:volume
108 ( Pt 1)
pubmed:geneSymbol
gsa2
pubmed:owner
NLM
pubmed:authorsComplete
Y
pubmed:pagination
25-35
pubmed:dateRevised
2007-11-14
pubmed:meshHeading
pubmed:year
1995
pubmed:articleTitle
Divergent modes of autophagy in the methylotrophic yeast Pichia pastoris.
pubmed:affiliation
University of Florida College of Medicine, Department of Anatomy and Cell Biology, Gainesville 32610-0235, USA.
pubmed:publicationType
Journal Article, Comparative Study, Research Support, U.S. Gov't, P.H.S.