CD63, a member of tetraspan transmembrane protein family, induces cellular spreading by reaction with monoclonal antibody on substrata

In our previous paper, we reported that a monoclonal antibody (MAb) 710F, which recognizes a cell surface glycoprotein, induces morphological change in monocytic cells, promoting cellular adhesion and extensive spreading on tissue culture dishes [Koyama ef al,, Biochem. Biophys, Res. Commun., 168 (1990) 898-904], We report here that the antigen was identified to be CD63, a member of tetraspan transmembrane protein family, by purification of the antigen molecule and subsequent cDNA cloning, The identity was further evidenced by sequential immunoprecipitation experiments using MAb 710F and anti-CD63, MAb2.28, and by their reactions with insect cells infected with baculovirus carrying CD63 expression cassette. Furthermore, the MAb2.28 exhibited cell-spreading activity, although to a lesser extent than MAb710F, suggesting the participation of CD63 in adhesion and spreading of monocytic cells. (C) 1998 Academic Press.