Membrane IL-1: IL-1 alpha precursor binds to the plasma membrane via a lectin-like interaction

Although biologically active IL-1 associated with plasma membrane has been demonstrated in both mouse and man, a biochemical mechanism for membrane anchoring has not been described. We have analyzed the nature of membrane IL-1 in stimulated murine macrophages. We show that it consists of an IL-1 alpha precursor bound to the plasma membrane via a lectin-like interaction that is specifically dissociated with D-mannose. The dissociated IL-1 was detected as both a biological activity and, by immunoprecipitation and SDS-PAGE, as a 33 kDa IL-1 alpha precursor. Treatment of macrophages with D-mannose before fixation depleted detectable IL-1 biological activity associated with the membrane. Pro-IL-1 alpha was glycosylated in these cells, as shown by incorporation of D-14C]mannose; thus it is likely that a cell surface lectin binds pro-IL-1 via these carbohydrate residues. In addition to anchoring IL-1 precursor to the plasma membrane, this lectin-like interaction may also be important in the overall regulation of IL-1 release.