The PLIN4 gene resides on chromosome 19 at the band 19p13.3 and contains 9 exons.[5]
Protein
This protein belongs to the perilipin family and contains 27 33-amino acid approximate tandem repeats.[11] It is also one of the perilipin members of the PATS (PLIN, ADFP, TIP47, S3-12) family, which is named after structural proteins that share high amino acid sequence similarity and associate with lipid droplets.[6] It shares a conserved C-terminal of 14 amino acid residues that folds into a hydrophobic cleft with other PATS members; however, it is missing the conserved N-terminal region of approximately 100 amino acid residues. Within the sequence of 33-amino acid repeats, PLIN4 contains a long stretch of imperfect 11-mer repeats predicted to form amphipathic helices with three helical turns per 11 amino acid residues. This 11-mer repeats tract is proposed to anchor the protein to the phospholipid monolayer of lipid droplets for its assembly, though no targeting sequence has yet been found in PLIN4.[7]
Function
PLIN4 is a member of the perilipin family, a group of proteins that coat lipid droplets in adipocytes,[8] the adipose tissue cells that are responsible for storing fat. Perilipin acts as a protective coating from the body's natural lipases, such as hormone-sensitive lipase,[9] which break triglycerides into glycerol and free fatty acids for use in metabolism, a process called lipolysis.[12] In humans, perilipin is expressed as 5 different isoforms; it is currently understood that the level of expression for each isoform is dependent on factors such as sex, body mass index, and level of endurance exercise.[13]
PLIN4 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 epinephrine) is primarily due to perilipin phosphorylation.
Clinical significance
The proteins in the Perilipin family are crucial regulators of lipid storage.[12] PLIN4 expression is elevated in obese animals and humans.
The PLIN4 gene, along with PLIN2, PLIN3, and PLIN5, have been associated with variance in body-weight regulation and may be a genetic influence on obesity risk in humans.[10]
1 2 Soenen S, Mariman EC, Vogels N, Bouwman FG, den Hoed M, Brown L, Westerterp-Plantenga MS (March 2009). "Relationship between perilipin gene polymorphisms and body weight and body composition during weight loss and weight maintenance". Physiology & Behavior. 96 (4–5): 723–8. doi:10.1016/j.physbeh.2009.01.011. PMID19385027. S2CID24747708.
↑ Universal protein resource accession number Q96Q06 for "PLIN4 - Perilipin-4 - Homo sapiens - PLIN4 gene & protein" at UniProt.
↑ Peters SJ, Samjoo IA, Devries MC, Stevic I, Robertshaw HA, Tarnopolsky MA (August 2012). "Perilipin family (PLIN) proteins in human skeletal muscle: the effect of sex, obesity, and endurance training". Applied Physiology, Nutrition, and Metabolism. 37 (4): 724–35. doi:10.1139/h2012-059. PMID22667335.
Peters SJ, Samjoo IA, Devries MC, Stevic I, Robertshaw HA, Tarnopolsky MA (August 2012). "Perilipin family (PLIN) proteins in human skeletal muscle: the effect of sex, obesity, and endurance training". Applied Physiology, Nutrition, and Metabolism. 37 (4): 724–35. doi:10.1139/h2012-059. PMID22667335.
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