MOLECULAR-CLONING OF CDNA-ENCODING A NOVEL PLATELET-ENDOTHELIAL CELL TETRA-SPAN ANTIGEN, PETA-3

Platelet-endothelial cell tetra-span antigen (PETA-3) was originally i dentified as a novel human platelet surface glycoprotein, gp27, which was detected by a monoclonal antibody (MoAb), 14A2.H1. Although this g lycoprotein is present in low abundance on the platelet surface, MoAb 14A2.H1 stimulates platelet aggregation and mediator release. We now r eport isolation of a cDNA clone encoding PETA-3 from a library derived from the megakaryoblastic leukemia cell line MO7e. The clone encodes an open reading frame of 253 amino acids that displays 25% to 30% amin o acid sequence identity with several members of the newly defined Tet raspan, or Transmembrane 4 superfamily. These proteins consist of four conserved putative transmembrane domains with a large divergent extra cellular loop between the third and fourth membrane-spanning regions, PETA-3 has a single consensus sequence for N-linked glycosylation loca ted in this extracellular loop. A single PETA-3 RNA transcript (1.6 kb ) was detected in RNA isolated from MO7e cells, bane marrow stromal ce lls, the C11 endothelial cell line, and several myeloid leukemia cell lines. No transcript was detected in the lymphoblastoid cell lines MOL T-4 and BALM-1. This pattern correlates well with previous protein exp ression data. Northern blot analysis of RNA from a range of human tiss ues indicated that the transcript was present in most tissues, the not able exception being brain. (C) 1995 by The American Society of Hemato logy.