(679.2) Interaction Sites of the Nem1-Spo7/Pah1 Phosphatase Cascade in Yeast Lipid Synthesis

Poster Board Number: A463

Ruta Jog (Rutgers University), Mona Mirheydari (Rutgers University), Gil-Soo Han (Rutgers University), George Carman (Rutgers University)

In the yeast Saccharomyces cerevisiae, Pah1 phosphatidate (PA) phosphatase catalyzes the dephosphorylation of PA to produce the diacylglycerol used to synthesize triacylglycerol that is stored in lipid droplets. Pah1 is inactive as a phosphorylated form in the cytosol and becomes active as a dephosphorylated form on the nuclear/ER membrane following its recruitment and dephosphorylation by the Nem1-Spo7 protein phosphatase complex. Spo7, the regulatory subunit in this protein phosphatase complex, is required for stability and function of the catalytic subunit Nem1. In this work, we examined regions of Spo7 that are involved with the interaction with Nem1 for Nem1-Spo7 complex formation and interaction with Pah1. By deletion analyses and site-directed mutagenesis, we found that the Spo7 C-terminal residues 240-259 are important for Nem1-Spo7/Pah1 phosphatase function as indicated by a dramatic reduction in triacylglycerol synthesis and lipid droplet formation, along with a temperature-sensitive phenotype. We are currently investigating whether this sequence is required for physical interaction with Nem1 or Pah1.

Supported by NIH grant GM136128