Perilipin 5 S155 phosphorylation by PKA is required for the control of hepatic lipid metabolism and glycemic control

Stacey N Keenan,William De Nardo,Jieqiong Lou,Ralf B Schittenhelm,Magdalene K Montgomery,James G Granneman,Elizabeth Hinde,Matthew J Watt

doi:10.1194/jlr.ra120001126

Stacey N Keenan, William De Nardo + Show 6 more

Open Access

https://doi.org/10.1194/jlr.ra120001126

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Abstract

Perilipin 5 (PLIN5) is a lipid-droplet-associated protein that coordinates intracellular lipolysis in highly oxidative tissues and is thought to regulate lipid metabolism in response to phosphorylation by protein kinase A (PKA). We sought to identify PKA phosphorylation sites in PLIN5 and assess their functional relevance in cultured cells and the livers of mice. We detected phosphorylation on S155 and identified S155 as a functionally important site for lipid metabolism. Expression of phosphorylation-defective PLIN5 S155A in Plin5 null cells resulted in decreased rates of lipolysis and triglyceride-derived fatty acid oxidation. FLIM-FRET analysis of protein-protein interactions showed that PLIN5 S155 phosphorylation regulates PLIN5 interaction with adipose triglyceride lipase at the lipid droplet, but not with α-β hydrolase domain-containing 5. Re-expression of PLIN5 S155A in the liver of Plin5 liver-specific null mice reduced lipolysis compared with wild-type PLIN5 re-expression, but was not associated with other changes in hepatic lipid metabolism. Furthermore, glycemic control was impaired in mice with expression of PLIN5 S155A compared with mice expressing PLIN5. Together, these studies demonstrate that PLIN5 S155 is required for PKA-mediated lipolysis and builds on the body of evidence demonstrating a critical role for PLIN5 in coordinating lipid and glucose metabolism.

Highlights

Lipid droplets are intracellular organelles that provide a depot for triglyceride storage in almost all cells and are a central point for the control of cellular energy homeostasis
These results suggest that Perilipin 5 (PLIN5) couples catecholamine activation of protein kinase A (PKA) and lipid droplet lipolysis with transcriptional regulation of mitochondrial proteins to enhance the capacity for mitochondrial fatty acid oxidation
Analysis of the predicted amino acid sequence of murine PLIN5 identified putative PKA phosphorylation sites (NetPhos 3.1) at S155, S161, and S163, which were highly conserved in other vertebrates (Fig. 1A)

Summary

Introduction

Lipid droplets are intracellular organelles that provide a depot for triglyceride storage in almost all cells and are a central point for the control of cellular energy homeostasis. A new role for PLIN5 was recently identified showing that catecholamine stimulation induces PLIN5 serine 155 phosphorylation, resulting in PLIN5 nuclear translocation, where it forms transcriptional complexes with peroxisome proliferatoractivated receptor-gamma coactivator-1-α (PGC-1α) and sirtuin 1 (SIRT1) to induce expression of PGC-1α target genes, increasing mitochondrial capacity [28, 29] These results suggest that PLIN5 couples catecholamine activation of PKA and lipid droplet lipolysis with transcriptional regulation of mitochondrial proteins to enhance the capacity for mitochondrial fatty acid oxidation

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