MassIVE MSV000095027

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Septin-associated protein kinase Hsl1 phosphorylates Pah1 to inhibit phosphatidate phosphatase activity and regulate lipid synthesis in Saccharomyces cerevisiae

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Description

In Saccharomyces cerevisiae, Pah1 phosphatidate (PA) phosphatase, which catalyzes the Mg2+-dependent dephosphorylation of PA to produce diacylglycerol, plays a key role in utilizing PA for the synthesis of membrane phospholipids or the neutral lipid triacylglycerol. Low activity favors phospholipid synthesis, whereas high activity favors triacylglycerol synthesis. Pah1 function is controlled by its subcellular location as regulated by phosphorylation and dephosphorylation. Multiple protein kinases phosphorylate Pah1 for its inactivation in the cytosol; Pah1 is activated via recruitment and dephosphorylation by the protein phosphatase Nem1-Spo7 at the nuclear/endoplasmic reticulum membrane where the PA phosphatase reaction occurs. Additionally, phosphorylation inhibits PA phosphatase activity and stabilizes Pah1 abundance, while dephosphorylation stimulates activity and destabilizes the enzyme abundance. Many of the protein kinases that phosphorylate Pah1 have yet to be characterized and their sites of phosphorylation defined. Here, we established Pah1 as a bona fide substrate of septin-associated Hsl1, a protein kinase involved in mitotic morphogenesis checkpoint signaling. Using Pah1 as substrate, Hsl1 activity was dependent on reaction time and the amounts of protein kinase, Pah1, and ATP. The phosphorylation occurred on Ser-748 and Ser-773, which together caused a 5-fold reduction in PA phosphatase catalytic efficiency. Analysis of cells expressing phosphorylation-deficient S748A and S773A mutant forms of Pah1 indicated that the Hsl1-mediated phosphorylation of Pah1 promoted membrane phospholipid synthesis at the expense of triacylglycerol, and ensured the dependence of Pah1 function on the Nem1-Spo7 protein phosphatase. This work advances understanding of how Hsl1 facilitates membrane phospholipid synthesis through the phosphorylation-mediated regulation of Pah1. [doi:10.25345/C5QB9VH4W] [dataset license: CC0 1.0 Universal (CC0 1.0)]

Keywords: Pah1, phosphatidate phosphatase, Hsl1, protein kinase, phospholipid, triacylglycerol, yeast

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Principal Investigators:
(in alphabetical order) 		George M. Carman, Rutgers, USA
Submitting User: haiyanzheng
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