IDENTIFICATION AND CHARACTERIZATION OF A WIDELY EXPRESSED PHOSPHATE TRANSPORTER RETROVIRUS RECEPTOR FAMILY

The cell-surface receptors for gibbon ape leukemia virus (Glvr-1; [1]) and rat amphotropic virus (Ram-1; [2]) were recently demonstrated to serve normal cellular functions as sodium-dependent phosphate transpor ters [3, 4]. These transporters, caned PiT-1 and PiT-2, respectively, are approximately 59% identical in amino acid sequence and are members of a gene family distinct from the renal type I and type II NaPi sodi um-dependent phosphate transporters. Both PiT-1 and PiT-2 are widely d istributed in many tissues including kidney, brain, heart, liver, musc le, and bone marrow. Expression of both transporters is increased by p hosphate deprivation. The distinct structural and functional propertie s of these molecules establishes them as members of a new family of ph osphate transporters which may play a major role in phosphate uptake i n a wide variety of cell types.