A novel inositol glycophospholipid (IGPL) and the serum dependence of its metabolism in bovine adrenocortical cells

Abstract

Adrenocortical cells in primary culture actively incorporated [ 3H]-inositol into phosphatidylinositol (PI) and its mono (PIP) and bisphosphate (PIP 2) derivatives. In addition to these well known phosphoinositides, a novel inositol-containing component was detected in the cell lipid extract when analyzed by proper chromatographic systems. This component was also labeled when the cells were provided with 32P or radioactive fatty acids and a distinctive character was its ability to incorporate [ 3H]-glucosamine. This novel phospholipid was thus characterized as an inositol glycophospholipid (IGPL). Study of IGPL metabolism in adrenocortical cells disclosed that the presence of serum in the culture medium strikingly increased glucosamine as well as inositol incorporation by a factor of about 10 and 5, respectively, within 36 hours. These observations suggest that IGPL turnover rate, especially at the level of its inositol-glycan moiety may be regulated by extracellular signals. A possible role of IGPL in membrane signalling systems and cell regulation remains to be clarified.