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

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.

Perilipin 5 interacts with Fatp4 at membrane contact sites to promote lipid droplet-to-mitochondria fatty acid transport

“…Protein kinase A (PKA), a crucial regulator of lipolysis, is activated through phosphorylation during fasting (Pollak et al ., 2015). Recent studies have shown that Plin5 can also be phosphorylated at Serine 155 by PKA, ablating lipolytic barrier activity and thereby allowing lipolysis (Wang, Bell, et al ., 2011; Keenan et al ., 2021). Given that lipolysis is required for LD-to-mitochondria FA trafficking, we created phosphomimetic (S155E) variants of our full length and truncated Plin5 constructs to investigate the contribution of LD-mito contacts to FA trafficking when lipolysis is active.…”

“…2 and 5). We propose that during starvation: (1) PKA phosphorylates Plin5 at serine 155 (Keenan et al ., 2021); (2) phosphorylation of Plin5 promotes lipolysis of triacylglycerol and release of FAs (Wang, Bell, et al ., 2011; MacPherson et al ., 2013; Pollak et al ., 2015); (3) released FAs are channeled from LDs to mitochondria at membrane contact sites, where Fatp4 converts FAs to fatty-acyl-CoAs, allowing; (4) transport into mitochondria for β-oxidation (Fig. 5F).…”

“…In contrast, Plin5 depletion led to reduced FA oxidation in liver (Montgomery et al ., 2019), while overexpression of Plin5 in skeletal muscle or brown adipose tissue promoted oxidative gene expression (Bosma et al ., 2013; Gallardo-Montejano et al ., 2021). Some of these cell type-specific effects may be explained by the idea that phosphorylation of Plin5 by protein kinase A can act as a switch between lipolytic barrier and pro-lipolytic functions of Plin5 (Pollak et al ., 2015; Keenan et al ., 2021). Because of these contradictory phenotypes, it has been challenging to untangle the different potential functions of Plin5.…”

Lipolysis: cellular mechanisms for lipid mobilization from fat stores

“…Perilipin-5 interaction with ATGL depends on the PKA-mediated phosphorylation of S155 in perilipin-5 (refs. 117,118 ). Interestingly, hormone-stimulated ATGL binding to perilipin-5 also promotes the translocation of FAs to the nucleus, where they act as allosteric activators of SIRT1 (ref.…”

Understanding the Role of Perilipin 5 in Non-Alcoholic Fatty Liver Disease and Its Role in Hepatocellular Carcinoma: A Review of Novel Insights

“…Nevertheless, it has been shown that phosphorylation of PLIN5 at serine 155 (S155) has important effects in hepatic lipid metabolism and glycemic control by allowing PLIN5 interaction with the lipase ATGL regulating further lipolysis [ 36 ]. Furthermore, it was recently shown that the loss of S155 phosphorylation of PLIN5 in liver impacts whole-body glucose tolerance and decreases levels of FA oxidation derived from TAGs [ 70 ].…”