MACROPHAGE SURFACE GLYCOPROTEINS BINDING TO GALECTIN-3 (MAC-2-ANTIGEN)

Galectin-3 (formerly called Mac-2 antigen) is a similar to 30 kDa carb ohydrate-binding protein expressed on the surface of inflammatory macr ophages and several macrophage cell lines. We have purified from lysat es of the murine macrophage cell line WEHI-3 glycoproteins that bind t o a galectin-3 affinity column. Several of these receptors are labelle d after biotinylation of intact cells showing their location at the ce ll surface. N-terminal aminoacid sequencing of intact galectin-3-bindi ng glycoproteins isolated from preparative SDS-gels or of chemically d erived fragments showed several homologies with known proteins and ide ntification was confirmed by immunoprecipitation with specific antibod ies. The glycoproteins were shown to be: the alpha-subunit(CD11b) of t he CD11b/CD18 integrin(Mac-1 antigen); the lysosomal membrane glycopro teins LAMPs 1 and 2 which are known in part to be expressed at cell su rfaces; the Mac-3 antigen, a mouse macrophage differentiation antigen defined by the M3/84 monoclonal antibody and related immunochemically to LAMP-2; the heavy chain of CD98, a 125 kDa heterodimeric glycoprote in identified by the 4F2/RL388 monoclonal antibodies respectively on h uman and mouse monocytes/macrophages and on activated T cells. Further studies showed that CD11b/CD18, CD98 and Mac-3 are major surface rece ptors for galectin-3 on murine peritoneal macrophages elicited by thio glycollate.