REGULATION OF MANNOSE RECEPTOR SYNTHESIS AND TURNOVER IN MOUSE J774 MACROPHAGES

The mannose receptor, present on the plasma membrane of macrophages, p romotes the internalization of glycoproteins and glycoconjugates via b oth endocytic and phagocytic pathways. The expression of this receptor is tightly modulated during monocyte/M phi differentiation and cellul ar activation. We isolated clonal populations from murine J774 macroph age tumor cells, which differ in their surface expression of functiona l mannose receptors, To examine the potential mechanisms regulating re ceptor function in these cell Lines, the interaction of receptor with ligand as well as receptor synthesis and degradation was analyzed. J77 4 clones with both high and low levels of mannose receptor activity we re found to synthesize significant amounts of receptor protein, sugges ting that the protein may be regulated at the level of synthesis and d egradation. In J774 clones expressing very low receptor activity and p rotein, the half-life of mannose receptor molecules was substantially decreased. The evolution of multiple mechanisms modulating mannose rec eptor function may be critical in fine-tuning the role of this recepto r in antigen processing and in scavenger and host defense functions.