Single amino acid insertion in loop 4 confers amphotropic murine leukemia virus receptor function upon murine Pit1

Abstract

Pit1 is the human receptor for gibbon ape leukemia virus (GALV) and feline leukemia virus subgroup B (FeLV-B), while the related human protein Pit2 is a receptor for amphotropic murine leukemia virus (A-MuLV). The A-MuLV-related isolate 10A1 can utilize both Pit1 and Pit2 as receptors. A stretch of amino acids named region A was identified in Pit1 (residues 550 to 558 in loop 4) as critical for GALV and FeLV-B receptor function. We have here investigated the role of region A in A-MuLV and 10A1 entry. Insertion of a single amino acid in region A of mouse Pit1 resulted in a functional A-MuLV receptor, showing that region A plays a role in A-MuLV infection. Moreover, the downregulation of 10A1 receptor function by changes in region A of human Pit1 indicates that this region is also involved in 10A1 entry. Therefore, region A seems to play a role in infection by all viruses utilizing Pit1 and/or Pit2 as receptors.

FIG. 1

Region A sequence comparison between receptor constructs tested for A-MuLV receptor function. Pit2, the human A-MuLV receptor (26); RatPit2, the rat Pit2 homolog (15); HaPit2, the hamster Pit2 homolog (29); Pit2(K522E), Pit2 with lysine at position 522 replaced with glutamic acid (6); pOJ80, Pit2 with region A replaced by the Pit1 region A (21); MusPit1, the M. musculus musculus Pit1 homolog (; also this study); pOJ64, MusPit1 with a threonine inserted between lysine (position 553) and glutamine (position 554) (; also this study); pOJ102, Pit1 with region A replaced by the Pit2 region A (21); Pit1, the human GALV receptor (16). Positions 1 to 9 of region A correspond to positions 522 to 530 in Pit2 homologs, pOJ80, and Pit2(K522E); positions 550 to 558 in Pit1 and pOJ102; and positions 553 to 561 in pOJ64. The dash at position 1 indicates a gap, and positions 2 to 9 correspond to positions 553 to 560 in MusPit1.