Identification of a novel integral plasma membrane protein induced during adipocyte differentiation

Adipocyte differentiation is co-ordinately regulated by several transcripti on factors and is accompanied by changes in the expression of a variety of genes. Using mRNA differential display analysis, we have isolated a novel m RNA, DD16, specifically induced during the course of adipocyte differentiat ion. DD16 mRNAs are present in several tissues, but among the tissues teste d, a remarkably higher level of expression was found in white adipose tissu e. The DD16 cDNA encoded a polypeptide of 415 amino acids containing a sing le N-glycosylation site and an N-terminal hydrophobic stretch of 19 amino a cids forming a transmembrane segment, indicating that DD16 is a glycosylate d membrane-bound protein. Polyclonal antibodies raised against the DD16 pep tide detected immunoreactive DD16 in membrane fractions, notably the plasma membrane, Association of DD16 with the plasma membrane was further confirm ed by biotinylation studies of cell surface proteins, su suggesting that DD 16 is an integral plasma membrane protein. Therefore we propose to give DD1 6 the name APMAP (Adipocyte Plasma Membrane Associated Protein). Although t he biological function of this polypeptide is presently unknown, our data s uggest that APMAP may function as a novel protein involved in the cross-tal k of mature adipocytes with the environment.