Retrovirus receptor PiT-1 of the Felis catus.

We isolated a cDNA encoding a feline homolog of human PiT-1, a sodium-dependent phosphate symporter which is utilized by gibbon ape leukemia virus (GALV) as a receptor for entry into host cells. The overall homology between the human and feline receptors is 92 and 93% at the nucleotide and deduced amino acid levels, respectively. Hydropathy analyses implied ten potential membrane spanning regions and, in analogy to human and murine homologs, five extracellular and four intracellular loops. Strikingly, the amino acid sequence of the fourth extracellular loop, which is critical for GALV surface glycoprotein binding, has complete identity between the human and feline PiT-1s, while the mouse PiT-1, non-functional for GALV entry, is quite divergent. Ectopic expression of the feline PiT-1 in guinea pig cells, which are non-permissive to feline leukemia virus (FeLV), subgroup B virus, conferred susceptibility to FeLV-B infection confirming the functional ability of the cloned product to serve as a receptor for a natural retrovirus of the homologous species.