The influence of cellular
lipid composition on the specific binding of [20-3H]
phorbol-12,13-dibutyrate to intact human promyelocytic
leukemia cells was investigated. Cellular
phospholipid composition could be manipulated by culturing cells in serum-free, chemically defined media containing base analogues of
phospholipid polar head groups. Human promyelocytic
leukemia cells grown in the presence of
dimethylethanolamine, monomethylethanolamine, 3-aminopropanol, or isopropylethanolamine assimilated these natural and unnatural base moieties into endogenous
phospholipids to the extent that 22 to 52% of the cell
glycerophospholipids contained the base analogue. The formation of the
phospholipid analogues was accompanied by a pronounced reduction in the levels of intracellular
choline and
ethanolamine glycerophospholipids. Analogue-supplemented cultures exhibited a reduced growth rate compared to control cells maintained in
choline-containing medium. Specific [20-3H ]
phorbol-12,13-dibutyrate binding was examined in
lipid-altered cells and shown to be markedly higher (approximately 200% of control) in cells grown with dimethyl- or monomethylethanolamine. In contrast, exposure of cells to 3-aminopropanol or isopropylethanolamine resulted in a major reduction in [20-3H]
phorbol-12,13-dibutyrate binding. Only minimal changes in nonspecific binding occurred between control and experimental cells. Because
phorbol esters are highly membrane targeted, it is possible that
phospholipid modification or the resulting changes in membrane organization influence receptor dynamics.