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Identification of Lipin-1β Phosphorylation Sites by Interaction with 14-3-3β Proteins

Presenters Name: 
Dana Wang
Co Presenters Name: 
Primary Research Mentor: 
Thurl Harris
Secondary Research Mentor: 
Mitch Granade
2:00 - 3:15
Time of Presentation: 
2019 - 2:00pm to 3:15pm
Newcomb Hall Ballroom
Presentation Type: 
Presentations Academic Category: 
Grant Program Recipient: 
Not a Recipient

Obesity is a growing epidemic that increases the risk of chronic diseases in children and adults. Biologically, obesity is the excessive accumulation of triacylglycerol (TAG), a storage lipid that constitutes most of human body fat. Lipin is a phosphatidate phosphatase (PAP) enzyme involved in regulating the biosynthesis of triacylglycerol. Lipin’s PAP activity and subcellular localization is regulated by phosphorylation, as well as by lipin’s interaction with 14-3-3β proteins. Phosphorylated lipin tends to be localized in the cytosol, while dephosphorylated lipin is generally localized at the endoplasmic reticulum membrane, where it catalyzes the phosphatase reaction. Enhanced interaction with 14-3-3β proteins promotes cytoplasmic retention of lipin and multiple phosphorylation sites have been identified in lipin’s serine-rich domain (defined as residues 281-298) that are required for this to occur. Therefore, these residues are important for lipin’s interaction with 14-3-3β proteins and confirmation of specific phosphorylation sites is crucial in understanding the regulation of lipin. Pull down assays were performed using GST and GST-14-3-3β proteins with lipin mutants. Western Blots were used to quantify and measure lipin interaction with 14-3-3β. These experiments showed a reduction of interaction in both S285A and S287A mutated lipin compared to wild type lipin, indicating that the Ser-285 and Ser-287 residues are important regulatory phosphorylation sites on lipin. Further experimentation is necessary in order to determine how the mutation of Ser-285 and Ser-287 impacts lipin’s PAP activity in vitro and in vivo and the functional consequences of these mutations, such as in the impact on TAG synthesis.