ISOLATION OF CDNAS FOR PERILIPIN-A AND PERILIPIN-B - SEQUENCE AND EXPRESSION OF LIPID DROPLET-ASSOCIATED PROTEINS OF ADIPOCYTES

The major cAMP-dependent protein kinase (A-kinase) substrate in adipoc ytes is perilipin, a protein found exclusively at the surface of the l ipid storage droplets. Using anti-perilipin serum, we have isolated tw o related classes of full-length coding cDNAs, designated perilipin A and B, from a rat adipocyte cDNA expression library. The two cDNAs der ive from two mRNA species that arise by differential splicing. The mRN As are predicted to encode perilipins A and B, proteins of 517 aa (56, 870 Da) and 422 aa (46,420 Da), respectively, which share a common 406 -aa N-terminal sequence. The predicted perilipin A contains peptides p resent in proteolytic digests of the purified 62-kDa form of perilipin from rat adipocytes, as well as the requisite consensus A-kinase phos phorylation sites. Like perilipin A, the B form is expressed in adipoc ytes and is associated with lipid storage droplets. Modeling of predic ted secondary structures fails to reveal an underlying basis for the t enacious association of perilipins with lipid droplets. These proteins exhibit a significant sequence relationship (almost-equal-to 65% simi larity through 105 aa) with only one other known protein, the adipocyt e differentiation-related protein (ADRP). Like the perilipins, ADRP ap pears to be adipocyte-specific, which suggests that they interact in a related intracellular pathway. The molecular probes for perilipins A and B described here will permit detailed analyses of their functional role(s) in lipid metabolism.