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Posttranslational Regulation of the Yeast PAH1 ‐encoded Phosphatidate Phosphatase
Author(s) -
SotoCardalda Anibal,
Carman George M.
Publication year - 2009
Publication title -
the faseb journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.709
H-Index - 277
eISSN - 1530-6860
pISSN - 0892-6638
DOI - 10.1096/fasebj.23.1_supplement.689.5
Subject(s) - phosphatidate , biochemistry , phosphatase , diacylglycerol kinase , ubiquitin , phosphatidylethanolamine , biology , ubiquitin ligase , alkaline phosphatase , dephosphorylation , enzyme , mutant , chemistry , microbiology and biotechnology , phosphatidylcholine , phospholipid , gene , membrane , protein kinase c
Phosphatidate (PA) phosphatase catalyzes the Mg 2+ ‐dependent dephosphorylation of PA to form diacylglycerol. This enzyme catalyzes the penultimate step in the synthesis of triacylglycerols and the phospholipids phosphatidylcholine and phosphatidylethanolamine via the Kennedy pathway. The analyses of pah1 mutants in yeast have shown that the PAH1 ‐encoded PA phosphatase plays a major role in controlling cellular levels of PA and triacylglycerol, the transcriptional regulation of phospholipid synthesis genes, and the growth of the nuclear/ER membrane. Triacylglycerols, which accumulate in the stationary phase of growth, are synthesized during the later stages of the exponential phase. The expression of PA phosphatase activity correlated with the synthesis of triacylglycerols during growth. However, as cells entered the stationary phase, the levels of the PA phosphatase protein disappeared. Immunoblot analysis of ubc1 and ubc4 mutants, which are defective in the ubiquitin‐conjugating enzymes that are induced in stationary phase, indicated that PA phosphatase is subjected to ubiquitination and proteolysis. That PA phosphatase is ubiquitinated is being examined through immunoblot analyses with anti‐ubiquitin antibodies and with antibodies directed against myc‐tagged ubiquitin bound to the PA phosphatase enzyme. Supported by NIH Grants GM 28140 and GM 75378.