The murine homologue of the human NKp46, a triggering receptor involved in the induction of natural cytotoxicity

Abstract

The NKp46 molecule has been proposed to play the role of triggering receptor in the natural cytotoxicity mediated by human NK cells. In this study we have identified the gene encoding the murine NKp46 homologue that we termed MAR-1. The MAR-1 gene is localized on chromosome 7 that is synthenic to the human chromosome 19 where the NKp46 gene is located. MAR-1 encodes a type I transmembrane glycoprotein belonging to the immunoglobulin (Ig) superfamily that, like human NKp46, is characterized by two C2-type Ig-like domains, a transmembrane portion containing a positively charged residue and a cytoplasmic tail lacking the immunoreceptor tyrosine-based activation motif (ITAM). The MAR-1 protein is expressed on the surface of cell transfectants and displays a molecular mass of approximately 46 kDa similar to that of its human counterpart. Semiquantitative RT-PCR analysis showed that MAR-1, similar to the human NKp46, is selectively expressed by NK cells. The MAR-1 protein displays 58 % identity with the human NKp46 receptor. This high homology together with the presence of a charged amino acid (Arg) in the transmembrane portion suggest that MAR-1 may associate at the cell membrane into a multimeric complex with ITAM containing polypeptides.