Perilipin

Perilipin, also known as lipid droplet-associated protein or PLIN, is a is_associated_with::protein that, in humans, is encoded by the PLIN is_associated_with::gene. The perilipins are a family of proteins that associates with the surface of lipid droplets. Phosphorylation of perilipin is essential for the mobilization of fats in adipose tissue.

Function
Perilipin is a protein that coats is_associated_with::lipid droplets in is_associated_with::adipocytes, the is_associated_with::fat-storing cells in is_associated_with::adipose tissue. Perilipin acts as a protective coating from the body’s natural is_associated_with::lipases, such as is_associated_with::hormone-sensitive lipase, which break is_associated_with::triglycerides into is_associated_with::glycerol and free is_associated_with::fatty acids for use in is_associated_with::metabolism, a process called lipolysis. In humans, perilipin is expressed in three different isoforms, A, B, and C, and perilipin A is the most abundant protein associated with the adipocyte lipid droplets.

Perilipin is hyperphosphorylated by PKA following β-adrenergic receptor activation. Phosphorylated perilipin changes conformation, exposing the stored lipids to hormone-sensitive lipase-mediated lipolysis. Although PKA also phosphorylates hormone-sensitive lipase, which can increase its activity, the more than 50-fold increase in fat mobilization (triggered by is_associated_with::epinephrine) is primarily due to perilipin phosphorylation.

Clinical significance
Perilipin is an important regulator of lipid storage. Perilipin expression is elevated in is_associated_with::obese animals and humans. Perilipin-null mice eat more food than is_associated_with::wild-type mice, but gain 1/3 less fat than wild-type mice on the same diet; perilipin-null mice are thinner, with more lean muscle mass. Perilipin-null mice also exhibit enhanced is_associated_with::leptin production and a greater tendency to develop is_associated_with::insulin resistance than wild-type mice.

Polymorphisms in the human perilipin (PLIN) gene have been associated with variance in body-weight regulation and may be a genetic influence on obesity risk in humans. In particular, variants 13041A>G and 14995A>T have been associated with increased risk of obesity in women and 11482G>A has been associated with decreased perilipin expression and increased lipolysis in women.

Perilipin family of proteins
Perilipin is part of a gene family with five currently-known members. In is_associated_with::vertebrates, closely related genes include adipophilin (also known as adipose differentiation-related protein), TIP47, and is_associated_with::LSDP5 (also called MLDP and OXPAT). Insects express related proteins, is_associated_with::LSD1 and is_associated_with::LSD2, in fat bodies.