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Traffic. 2012 Mar;13(3):468-82. doi: 10.1111/j.1600-0854.2011.01314.x. Epub 2012 Jan 8.

Regulation of membrane protein degradation by starvation-response pathways.

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1
Department of Biology, University of Utah, 257 South 1400 East, Salt Lake City, UT 84112-9202, USA.

Abstract

The multivesicular body (MVB) pathway delivers membrane proteins to the lumen of the vacuole/lysosome for degradation. The resulting amino acids are transported to the cytoplasm for reuse in protein synthesis. Our study shows that this amino acid recycling system plays an essential role in the adaptation of cells to starvation conditions. Cells respond to amino acid starvation by upregulating both endocytosis and the MVB pathway, thereby providing amino acids through increased protein turnover. Our data suggest that increased Rsp5-dependent ubiquitination of membrane proteins and a drop in Ist1 levels, a negative regulator of endosomal sorting complex required for transport (ESCRT) activity, cause this response. Furthermore, we found that target of rapamycin complex 1 (TORC1) and a second, unknown nutrient-sensing system are responsible for the starvation-induced protein turnover. Together, the data indicate that protein synthesis and turnover are linked by a common regulatory system that ensures adaptation and survival under nutrient-stress conditions.

PMID:
22118530
PMCID:
PMC3276697
DOI:
10.1111/j.1600-0854.2011.01314.x
[Indexed for MEDLINE]
Free PMC Article
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