Glucose-6-P control of glycogen synthase phosphorylation in yeast

Dongqing Huang, Wayne A. Wilson, Peter J. Roach

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Abstract

The SNF1 gene encodes a protein kinase necessary for expression of glucose-repressible genes and for the synthesis of the storage polysaccharide glycogen. From a genetic screen, we have found that mutation of the PFK2 gene, which encodes the β-subunit of 6-phosphofructo-1-kinase, restores glycogen accumulation in snf1 cells. Loss of PFK2 causes elevated levels of metabolites such as glucose-6-P, hyperaccumulation of glycogen, and activation of glycogen synthase, whereas glucose-6-P is reduced in snf1 cells. Other mutations that increase glucose-6-P, deletion of PFK1, which codes for the α-subunit of 6-phosphofructo-1-kinase, or of PG11, the phosphoglucoisomerase gene, had similar effects on glycogen metabolism as did pfk2 mutants. We propose that elevated glucose-6-P mediates the effects of these mutations on glycogen storage. Glycogen synthase kinase activity was reduced in extracts from pfk2 cells but was restored to that of wild type if the extract was gel-filtered to remove small molecules. Also, added glucose- 6-P inhibited the glycogen synthase kinase activity in extracts from wild- type cells, half-maximally at ~2 mM. We suggest that glucose-6-P controls glycogen synthase activity by two separate mechanisms. First, glucose-6-P is a direct activator of glycogen synthase, and second, it controls the phosphorylation state of glycogen synthase by inhibiting a glycogen synthase kinase.

Original languageEnglish (US)
Pages (from-to)22495-22501
Number of pages7
JournalJournal of Biological Chemistry
Volume272
Issue number36
DOIs
StatePublished - Sep 5 1997

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ASJC Scopus subject areas

  • Biochemistry
  • Molecular Biology
  • Cell Biology

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