Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: EC:3.1.3.16 (calcineurin)
 17,112 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The Nem1-Spo7 protein phosphatase plays a role in lipid synthesis by controlling the membrane localization of Pah1, the diacylglycerol-producing phosphatidate (PA) phosphatase that is crucial for the synthesis of triacylglycerol in the yeast Saccharomyces cerevisiae By dephosphorylating Pah1, Nem1-Spo7 facilitates its translocation to the nuclear/endoplasmic reticulum membrane for catalytic activity. Like its substrate Pah1, Nem1-Spo7 is phosphorylated in the cell, but the specific protein kinases involved remain to be identified. In this study, we demonstrate that the Nem1-Spo7 complex is phosphorylated by protein kinase A (PKA), which is associated with active cell growth, metabolic activity, and membrane phospholipid synthesis. In vitro phosphorylation of purified Nem1-Spo7 and of their synthetic peptides revealed that both subunits of the phosphatase complex are PKA substrates. Using phosphoamino acid and phosphopeptide-mapping analyses coupled with site-directed mutagenesis, we identified Ser-140 and Ser-210 of Nem1 and Ser-28 of Spo7 as PKA-targeted phosphorylation sites. Immunodetection of the phosphatase complex from the cell with anti-PKA substrate antibody confirmed the in vivo phosphorylations of Nem1 and Spo7 on the serine residues. Lipid-labeling analysis of cells bearing phosphorylation-deficient alleles of NEM1 and SPO7 indicated that the PKA phosphorylation of the phosphatase complex stimulates phospholipid synthesis and attenuates the synthesis of triacylglycerol. This work advances the understanding of how PKA-mediated posttranslational modifications of Nem1 and Spo7 regulate lipid synthesis in yeast.
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PMID:Protein kinase A phosphorylates the Nem1-Spo7 protein phosphatase complex that regulates the phosphorylation state of the phosphatidate phosphatase Pah1 in yeast. 3020 7

The Nem1-Spo7 complex in the yeast Saccharomyces cerevisiae is a protein phosphatase required for the nuclear/endoplasmic reticulum membrane localization of Pah1, a phosphatidate phosphatase that produces diacylglycerol for triacylglycerol synthesis at the expense of phospholipid synthesis. In a previous study, we showed that the protein phosphatase is subject to phosphorylation by protein kinase A (PKA). Here, we demonstrate that Nem1-Spo7 is regulated through its phosphorylation by protein kinase C (PKC), which plays multiple roles, including the regulation of lipid synthesis and cell wall integrity. Phosphorylation analyses of Nem1-Spo7 and its synthetic peptides indicate that both subunits of the complex are bona fide PKC substrates. Site-directed mutagenesis of NEM1 and SPO7, coupled with phosphopeptide mapping and immunoblotting with a phosphoserine-specific PKC substrate antibody, revealed that Ser-201 in Nem1 and Ser-22/Ser-28 in Spo7 are major PKC target sites of phosphorylation. Activity analysis of mutant Nem1-Spo7 complexes indicates that the PKC phosphorylation of Nem1 exerts a stimulatory effect, but the phosphorylation of Spo7 has no effect. Lipid-labeling analysis of cells expressing the phosphorylation-deficient alleles of NEM1 and SPO7 indicates that the stimulation of the Nem1-Spo7 activity has the effect of increasing triacylglycerol synthesis. Prephosphorylation of Nem1-Spo7 by PKC inhibits the PKA phosphorylation of Nem1, whereas prephosphorylation of the phosphatase complex by PKA inhibits the PKC phosphorylation of Spo7. Collectively, this work advances the understanding of the Nem1-Spo7 regulation by phosphorylation and its impact on lipid synthesis.
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PMID:Protein kinase C mediates the phosphorylation of the Nem1-Spo7 protein phosphatase complex in yeast. 3150 Dec 44