CLONING AND CHARACTERIZATION OF AN UNCOUPLING PROTEIN HOMOLOG - A POTENTIAL MOLECULAR MEDIATOR OF HUMAN THERMOGENESIS

We have identified a novel cDNA encoding a protein highly homologous t o the mammalian brown fat uncoupling protein (UCP). Unlike the known U CP, which is expressed specifically in brown adipose tissue, the UCP h omolog (UCPH) mRNA is expressed in a variety of tissues, with predomin ant expression in human white adipose tissue and skeletal muscle. In t he white adipose tissue of ob/ob and db/db mice, the UCPH transcript i s induced approximately fivefold relative to lean littermate controls. Expression of murine UCPH in yeast results in growth inhibition under conditions that require aerobic respiration, but does not affect grow th under anaerobic conditions. Furthermore, UCPH expression in yeast c auses a decrease in the mitochondrial membrane potential, as judged by staining with the potential-sensitive dye DiOC(6). These observations suggest that UCPH, like UCP, uncouples oxidative phosphorylation. The possibility that the UCPH protein is an important mediator of human t hermogenesis is discussed.