CHOLESTEROL REGULATES THE CELL-SURFACE EXPRESSION OF GLYCOPHOSPHOLIPID-ANCHORED CD14 ANTIGEN ON HUMAN MONOCYTES

The CD14 antigen which is expressed on human monocytes and macrophages is a phosphatidylinositol-linked surface protein. We investigated the effects of cellular cholesterol depletion and repletion on cell surface expression of this glycoprotein. Adherent normal human monocytes were cultured for four days in media containing delipidated fetal calf serum which depleted cellular cholesterol. Immunofluorescence analysis demonstrated a markedly diminished surface expression of CD14 on cells cultured in delipidated serum compared to normal serum. Expression of CD64 (high-affinity Fc receptors, FcgammaRI) also was reduced under these conditions. This inhibition of CD14 expression was overcome by addition to the culture medium of cholesterol, low density lipoprotein, or very low density lipoprotein. All of these supplements replenished cellular cholesterol. Expression of CD64(FcgammaRI) was not restored by addition of cholesterol. These observations indicate that cholesterol can regulate the surface expression of some phosphatidylinositol-anchored glycoproteins.