Abstract
The PAT proteins, named after the three PLIN/ADRP/TIP47 (PAT) proteins, PLIN for perilipin, ADRP for adipose differentiation-related protein and TIP47 for tail-interacting protein of 47 kDa, now officially named M6PRBP1 for mannose-6-phosphate receptor binding protein 1, is a set of intracellular lipid droplet binding proteins. They are localized in the outer membrane monolayer enveloping lipid droplets and are involved in the metabolism of intracellular lipid. This work describes the cloning and sequencing of porcine PLIN and M6PRBP1 cDNAs, the chromosome mapping of these two genes, as well as the expression pattern of porcine PAT genes. Sequence analysis shows that the porcine PLIN cDNA contains an open reading frame of 1551 bp encoding 516 amino acids and that the porcine M6PRBP1 cDNA contains a coding region of 1320 bp encoding 439 amino acids. Comparison of PLIN and M6PRBP1 amino-acid sequences among various species reveals that porcine and bovine proteins are the most conserved. Porcine PLIN and M6PRBP1 genes have been mapped to pig chromosomes 7 and 2, respectively, by radiation hybrid analysis using the IMpRH panel. Expression analyses in pig showed a high expression of PLIN mRNA in adipose tissue, M6PRBP1 mRNA in small intestine, kidney and spleen and ADRP mRNA in adipose tissue, lung and spleen.
Highlights
Intracellular neutral lipid storage droplets, essential organelles of eukaryotic cells, are required for energy balance, membrane biosynthesis, cholesterol metabolism and lipid trafficking
Perilipin is a phosphoprotein involved in the hormone-stimulated lipolysis and its expression is highly restricted to adipocytes and steroidogenic cells [5, 20]
Perilipin is phosphorylated by cAMP-dependent protein kinase A (PKA) and recruits hormone-sensitive lipase (HSL) to the lipid droplets, thereby promoting lipolysis [19, 21]
Summary
Intracellular neutral lipid storage droplets, essential organelles of eukaryotic cells, are required for energy balance, membrane biosynthesis, cholesterol metabolism and lipid trafficking. Animal lipid storage droplets contain a set of proteins called the PAT domain family proteins that include perilipin (PLIN), adipose differentiation-related protein (ADRP), and mannose6-phosphate receptor binding protein 1 (M6PRBP1) previously named tailinteracting protein of 47 kDa (TIP47). The PAT family proteins share extensive amino acid sequence similarity, especially at their N-termini. They are associated with lipid droplets, and involved in the lipid droplets formation and degradation [9,18]. It has been shown that in human adipose tissue, perilipin expression increases with obesity [11], that perilipin promotes triacylglycerol (TAG) storage in adipocytes by regulating the rate of basal lipolysis and that it is required to maximize hormonally stimulated lipolysis [13, 25]. The functions of M6PRBP1 in lipid metabolism are not as well known as those of PLIN
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