Cell surface expression of mouse macrosialin and human CD68 and their role as macrophage receptors for oxidized low density lipoprotein

摘要: We have previously identified a 94- to 97-kDa oxidized low density lipoprotein (LDL)-binding protein in mouse macrophages as macrosialin (MS), member of the lamp family. Earlier immunostaining studies shown that MS and its human homolog, CD68, are predominantly intracellular proteins. However, using sensitive techniques such flow cytometry (FACS) cell-surface-specific biotinylation, we now show there is significant surface expression these FACS analysis intact cells mAb FA/11 showed small but definite resident peritoneal this was greatly enhanced with thioglycollate elicitation. Biotinylation detergent-solubilized cell preparations followed by immunoprecipitation revealed 10-15% total content elicited on plasma membrane. Similar results were obtained untreated RAW 264.7 cells. THP-1 monocytic minimal CD68 unactivated (4% content). Stimulation phorbol 12-myristate 13-acetate increased both considerably. Furthermore, specific binding at 4 degrees C uptake 37 125I-labeled LDL activated inhibited 30-50% mAbs KP-1 EBM-11. Thus, although MS/CD68 steady-state represents only percentage their cellular content, proteins can play role vitro could contribute foam formation atherosclerotic lesions.