Regulation of mannose receptor synthesis and turnover in mouse J774 macrophages

Abstract: The mannose receptor, present on the plasma membrane of macrophages, promotes the internalization of glycoproteins and glycoconju-gates via both endocytic and phagocytic pathways. The expression of this receptor is tightly modulated during monocyte/Mf differentiation and cellular activation. We isolated clonal populations from murine J774 macrophage tumor cells, which differ in their surface expression of functional mannose receptors. To examine the potential mechanisms regulating receptor function in these cell lines, the interaction of receptor with ligand as well as recep-tor synthesis and degradation was analyzed. J774 clones with both high and low levels of mannose receptor activity were found to synthesize signifi-cant amounts of receptor protein, suggesting that the protein may be regulated at the level of synthe-sis and degradation. In J774 clones expressing very low receptor activity and protein, the half-life of mannose receptor molecules was substantially de-creased. The evolution of multiple mechanisms modulating mannose receptor function may be critical in fine-tuning the role of this receptor in antigen processing and in scavenger and host de-fense functions. J. Leukoc. Biol. 64: 85–91; 1998. Key Words: receptor regulation · glycoproteins · glycoconjugate