Cloning of a navel scavenger receptor cysteine-rich type I transmembrane molecule (M160) expressed by human macrophages

We report the cloning of a novel human type I cell surface Ag mainly expres sed by macrophages. The primary structure was established by molecular clon ing, which yielded a 4579-bp cDNA sequence encoding a polypeptide chain of 1453 amino acid residues with 16 potential N-glycosylation sites. We design ated this molecule M160, The domain organization features 12 scavenger rece ptor cysteine-rich domains followed by a, transmembrane region and a cytopl asmic domain that occurs in two forms, a predominant form (M160-alpha) of 7 1 residues and an alternatively spliced form (M160-beta) of 39 residues. M1 60-alpha contains three possible phosphorylation sites, which are lost in t he alternatively spliced form, RT-PCR analyses showed M160 to be expressed by alveolar macrophages and by the monocyte cell lines HL60, U937, and THP1 , but not by Jurkat or Raji cells. Stimulation of U937 cells with phorbol e ster resulted in an increased expression of M160 from day 5 onward. RT-PCR analysis of 19 different human tissues showed signals for M160-alpha of var ying intensity in all tissues, whereas M160-beta was confined to the spleen . We conclude that M160 is a new member of the scavenger receptor cysteine- rich superfamily expressed by the monocyte/macrophage cell lineage.