The Minimal Domain of Adipose Triglyceride Lipase (ATGL) Ranges until Leucine 254 and Can Be Activated and Inhibited by CGI-58 and G0S2, Respectively

Adipose triglyceride lipase (ATGL) is the rate-limiting enzyme of lipolysis. ATGL specifically hydrolyzes triacylglycerols (TGs), thereby generating diacylglycerols and free fatty acids. ATGL's enzymatic activity is co-activated by the protein comparative gene identification-58 (CGI-58) and inhibited by the protein G0/G1 switch gene 2 (G0S2). The enzyme is predicted to act through a catalytic dyad (Ser47, Asp166) located within the conserved patatin domain (Ile10-Leu178). Yet, neither an experimentally determined 3D structure nor a model of ATGL is currently available, which would help to understand how CGI-58 and G0S2 modulate ATGL's activity. In this study we determined the minimal active domain of ATGL. This minimal fragment of ATGL could still be activated and inhibited by CGI-58 and G0S2, respectively. Furthermore, we show that this minimal domain is sufficient for protein-protein interaction of ATGL with its regulatory proteins. Based on these data, we generated a 3D homology model for the minimal domain. It strengthens our experimental finding that amino acids between Leu178 and Leu254 are essential for the formation of a stable protein domain related to the patatin fold. Our data provide insights into the structure-function relationship of ATGL and indicate higher structural similarities in the N-terminal halves of mammalian patatin-like phospholipase domain containing proteins, (PNPLA1, -2,- 3 and -5) than originally anticipated

Symptomatic lipid storage in carriers for the PNPLA2 gene

Item does not contain fulltextNeutral lipid storage disease comprises a heterogeneous group of inherited disorders characterized by severe accumulation of cytoplasmic triglyceride droplets in several tissues and neutrophils. A novel type of autosomal recessive lipid myopathy due to PNPLA2 mutations was recently described with associated cardiac disease, myopathy and frequent infections, but without ichthyosis. Here we describe the clinical and biochemical characteristics of a long surviving patient and report on four carrier family members with diverse clinical involvement. Interestingly, heterozygous patients show neutral lipid storage in muscle and in the keratocytes of the skin, Jordans' bodies, mild myopathy and frequent infections. Biochemical analysis of fibroblasts obtained from patients revealed increased triglyceride storage and reduced lipid droplet-associated triglyceride hydrolase activity. Together, our data implicate that the wild-type allele cannot fully compensate for the mutated dysfunctional allele of PNPLA2 leading to triglyceride accumulation in muscle and mild myopathy in PNPLA2 mutation carriers. The presence of neutral lipid droplets in the skin in PNPLA2 mutation carriers strengthens the link between NLSD and other neutral lipid storage diseases with ichthyosis

Adipocyte lipases and lipid droplet-associated proteins: insight from transgenic mouse models.

International audienceAdipose tissue lipolysis is the catabolic process whereby stored triacylglycerol (TAG) is broken down by lipases into fatty acids and glycerol. Here, we review recent insights from transgenic mouse models. Genetic manipulations affecting lipases are considered first, followed by transgenic models of lipase co-factors and lastly non-lipase lipid droplet (LD)-associated proteins. The central role of hormone-sensitive lipase (HSL), long considered to be the sole rate-limiting enzyme of TAG hydrolysis, has been revised since the discovery of adipose triglyceride lipase (ATGL). It is now accepted that ATGL initiates TAG breakdown producing diacylglycerol, which is subsequently hydrolyzed by HSL. Furthermore, lipase activities are modulated by co-factors whose deletion causes severe metabolic disturbances. Another major advance has come from the description of the involvement of non-lipase proteins in the regulation of lipolysis. The role of perilipins has been extensively investigated. Other newly discovered LD-associated proteins have also been shown to regulate lipolysis

Lipid droplet dynamics and insulin sensitivity upon a 5-day high-fat diet in Caucasians and South Asians

A 5-day High-Fat High-Calorie diet (HFHC-diet) reduces insulin-stimulated glucose disposal (Rd) in South Asian, but not Caucasian healthy lean males. We aimed to investigate if differences in myocellular lipid handling are underlying this differential response. A two-step hyperinsulinemic-euglycemic clamp and muscle biopsies were performed in 12 healthy lean Caucasian and South Asian males (BMI <25 kg/m(2), 19-25 years) before and after a 5-day HFHC-diet (regular diet + 375 mL cream/day; 1275 kcal/day; 94% fat). Triglyceride extractions and Western Blots for lipid droplet and mitochondrial proteins were performed. Intramyocellular lipid content and HFHC-diet response were similar between ethnicities (group effect: P = 0.094; diet effect: +similar to 30%, P = 0.044). PLIN5 protein content increased upon the HFHC-diet (P = 0.031) and tended to be higher in South Asians (0.87 +/- 0.42 AU vs. 1.35 +/- 0.58 AU, P = 0.07). 4-HNE tended to increase in South Asians upon the HFHC-diet (interaction effect: P = 0.057). In Caucasians Delta PLIN5 content correlated with Delta R-d (Caucasians: r = 0.756, P = 0.011; South Asians: r = -0.085, P = 0.816), while in South Asians Delta 4-HNE associated with Delta PLIN5 content (Caucasians: r = 0.312, P = 0.380; South Asians: r = 0.771, P = 0.003). These data indicate that in Caucasians, PLIN5 may be protective against HFHC-diet induced insulin resistance, which for reasons not yet understood is not observed in South Asians, who possess increased lipid peroxidation levels