Perilipin Promotes Hormone-sensitive Lipase-mediated Adipocyte Lipolysis via Phosphorylation-dependent and -independent Mechanisms

Harvard University, Cambridge, Massachusetts, United States
Journal of Biological Chemistry (Impact Factor: 4.57). 07/2006; 281(23):15837-44. DOI: 10.1074/jbc.M601097200
Source: PubMed


Hormone-sensitive lipase (HSL) is the predominant lipase effector of catecholamine-stimulated lipolysis in adipocytes. HSL-dependent lipolysis in response to catecholamines is mediated by protein kinase A (PKA)-dependent phosphorylation of perilipin A (Peri A), an essential lipid droplet (LD)-associated protein. It is believed that perilipin phosphorylation is essential for the translocation of HSL from the cytosol to the LD, a key event in stimulated lipolysis. Using adipocytes retrovirally engineered from murine embryonic fibroblasts of perilipin null mice (Peri-/- MEF), we demonstrate by cell fractionation and confocal microscopy that up to 50% of cellular HSL is LD-associated in the basal state and that PKA-stimulated HSL translocation is fully supported by adenoviral expression of a mutant perilipin lacking all six PKA sites (Peri Adelta1-6). PKA-stimulated HSL translocation was confirmed in differentiated brown adipocytes from perilipin null mice expressing an adipose-specific Peri Adelta1-6 transgene. Thus, PKA-induced HSL translocation was independent of perilipin phosphorylation. However, Peri Adelta1-6 failed to enhance PKA-stimulated lipolysis in either MEF adipocytes or differentiated brown adipocytes. Thus, the lipolytic action(s) of HSL at the LD surface requires PKA-dependent perilipin phosphorylation. In Peri-/- MEF adipocytes, PKA activation significantly enhanced the amount of HSL that could be cross-linked to and co-immunoprecipitated with ectopic Peri A. Notably, this enhanced cross-linking was blunted in Peri-/- MEF adipocytes expressing Peri Adelta1-6. This suggests that PKA-dependent perilipin phosphorylation facilitates (either direct or indirect) perilipin interaction with LD-associated HSL. These results redefine and expand our understanding of how perilipin regulates HSL-mediated lipolysis in adipocytes.

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Available from: Andrew S Greenberg, Dec 20, 2013
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    • "lipolysis in fasted mice, explaining the lack of preferential depletion of any particular class or individual species of fatty acid within adipose TAG. Thus, although results from our work differ from prior reports, they do not disagree with the notion of a predominant role for HSL in mediating the selective hydrolysis of PUFA in adipose tissue when lipolysis is maximally stimulated and HSL is fully activated (Miyoshi et al. 2006), such as during a prolonged fast. Our results, however, extend this work by characterizing effects occurring during a short-term fast. "
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    ABSTRACT: We investigated the effect of short-term fasting on coordinate changes in the fatty acid composition of adipose triacylglycerol (TAG), serum non-esterified fatty acids (NEFA), liver TAG, and serum TAG and phospholipids in mice fed ad libitum or fasted for 16 h overnight. In contrast to previous reports under conditions of maximal lipolysis, adipose tissue TAG was not preferentially depleted of n-3 PUFA or any specific fatty acids, nor were there any striking changes in the serum NEFA composition. Short-term fasting did, however, increase the hepatic proportion of n-3 PUFA, and almost all individual species of n-3 PUFA showed relative and absolute increases. The relative proportion of n-6 PUFA in liver TAG also increased but to a lesser extent, resulting in a significant decrease in the n-6:n-3 PUFA ratio (from 14.3 ± 2.54 to 9.6 ± 1.20), while the proportion of MUFA decreased significantly and SFA proportion did not change. Examination of genes involved in PUFA synthesis suggested that hepatic changes in the elongation and desaturation of precursor lipids could not explain this effect. Rather, an increase in the expression of fatty acid transporters specific for 22:6n-3 and other long-chain n-3 and n-6 PUFA likely mediated the observed hepatic enrichment. Analysis of serum phospholipids indicated a specific increase in the concentration of 22:6n-3 and 16:0, suggesting increased specific synthesis of DHA-enriched phospholipid by the liver for recirculation. Given the importance of blood phospholipid in distributing DHA to neural tissue, these findings have implications for understanding the adipose-liver-brain axis in n-3 PUFA metabolism.
    Genes & Nutrition 11/2015; 10(6). DOI:10.1007/s12263-015-0490-2 · 2.79 Impact Factor
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    • "The majority of HSL is located in the cytoplasm. With PKA activation HSL is phosphorylated , translocates to the LD and binds to phosphorylated plin1 where it hydrolyzes primarily diacylglycerol (DAG) produced by ATGL's actions (Miyoshi et al, 2006). MGL is thought to be constitutively active and completes the lipolytic reaction. "
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    • "The outcome of these reactions is a shift from storage to mobilization of fatty acids from triacylglycerol [4], [5]. PKA also promotes the rapid translocation of hormone sensitive lipase (HSL) from the cytosol to the lipid droplet, which interacts with PLIN1 and contributes to maximal lipolysis [6]. However, PLIN1 expression is restricted to adipocytes and steroidogenic tissues [7], raising the possibility that other proteins perform similar functions to PLIN1. "
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    ABSTRACT: Lipolysis involves the sequential breakdown of fatty acids from triacylglycerol and is increased during energy stress such as exercise. Adipose triglyceride lipase (ATGL) is a key regulator of skeletal muscle lipolysis and perilipin (PLIN) 5 is postulated to be an important regulator of ATGL action of muscle lipolysis. Hence, we hypothesized that non-genomic regulation such as cellular localization and the interaction of these key proteins modulate muscle lipolysis during exercise. PLIN5, ATGL and CGI-58 were highly (>60%) colocated with Oil Red O (ORO) stained lipid droplets. PLIN5 was significantly colocated with ATGL, mitochondria and CGI-58, indicating a close association between the key lipolytic effectors in resting skeletal muscle. The colocation of the lipolytic proteins, their independent association with ORO and the PLIN5/ORO colocation were not altered after 60 min of moderate intensity exercise. Further experiments in cultured human myocytes showed that PLIN5 colocation with ORO or mitochondria is unaffected by pharmacological activation of lipolytic pathways. Together, these data suggest that the major lipolytic proteins are highly expressed at the lipid droplet and colocate in resting skeletal muscle, that their localization and interactions appear to remain unchanged during prolonged exercise, and, accordingly, that other post-translational mechanisms are likely regulators of skeletal muscle lipolysis.
    PLoS ONE 07/2014; 9(7):e103062. DOI:10.1371/journal.pone.0103062 · 3.23 Impact Factor
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