(poly)Phosphoinositide phosphorylation is a marker for plasma membrane in Friend erythroleukaemic cells

Upon subcellular fractionation of (murine) Friend erythroleukaemic cells (FELCs), purified plasma membranes were identified by their high enrichment in specific marker enzymes and typical plasma membrane lipids. When FELCs were incubated for short periods with 32P i before cell fractionation, the lipid-bound radioactivity was almost exclusively present in phosphatidylinositol-4-phosphate (DPI) and phosphatidylinositol-4,5- bisphosphate (TPI), and its distribution closely matched that of the plasma membrane markers. In addition, purified plasma membranes actively incorporated 32P from [γ- 32P]ATP into polyphosphoinositides, and the specific activities of the involved kinases were again mostly enriched in the plasma membrane fraction.