Control of Mac-2 surface expression on murine macrophage cell lines.
Mac-2 antigen, a 32-kDa murine macrophage cell-surface protein expressed on thioglycollate-elicited peritoneal exudate cells at higher levels than other macrophages, is a member of the S-(soluble) galactoside-binding lectin family with homologies to carbohydrate-binding proteins of other cell types. Murine macrophage cell lines can be ordered in a linear differentiation sequence according to their expression of Mac-2 and other surface markers (Leenen et al., Differentiation 1986. 32: 157.) We show here that antigen expression in macrophage cell lines can be regulated at the level of protein secretion. WEHI-3 cells, classified as immature macrophages by virtue of their low level of surface Mac-2 expression synthesize similar amounts of the antigen as more mature J774.2 and P388.D1 cells that express high amounts of surface Mac-2, but unlike these latter cell lines WEHI-3 cells fail to secrete the protein. Exogenously added Mac-2 binds efficiently to WEHI-3 cells and putative Mac-2-binding carbohydrates are expressed equally on WEHI-3, J774.2 and P388.D1 cells as judged by binding of plant lectins of known carbohydrate-binding specificities. Mac-2 secretion and surface expression in WEHI-3 cells is not significantly enhanced by calcium ionophore A23187, a powerful stimulator of Mac-2 secretion in other cells and a moderate stimulator in J774.2 and P388.D1 cells. WEHI-3 cells provide a valuable system for studying the mechanism of intracellular transport and secretion of Mac-2, a protein that lacks a signal sequence and does not enter the classical secretory pathway.
National Institute for Medical Research, London, UK.
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Hughes
D000818:Animals; D000911:Antibodies, Monoclonal; D000943:Antigens, Differentiation / Q000096:biosynthesis* / Q000302:isolation & purification; D015153:Blotting, Western; D002460:Cell Line; D004591:Electrophoresis, Polyacrylamide Gel; D005434:Flow Cytometry; D037502:Galectin 3; D037102:Lectins; D008264:Macrophages / Q000166:cytology* / Q000276:immunology*; D051379:Mice; D011233:Precipitin Tests
D000911:Antibodies, Monoclonal; D000943:Antigens, Differentiation; D037502:Galectin 3; D037102:Lectins