MOLECULAR-SPECIES OF SPHINGOMYELIN IN SPHINGOMYELINASE-SENSITIVE AND SPHINGOMYELINASE-RESISTANT POOLS OF HL-60 CELLS

This study of sphingomyelin molecular species in undifferentiated and differentiated (granulocytic form) HL-60 cells demonstrated only minor differences in the distribution of species between the sphingomyelina se-sensitive and sphingomyelinase-resistant pools of sphingomyelin in these cells. The two most prominent species of sphingosine present in both the undifferentiated and differentiated cells were those containi ng 16:0 (slightly higher in the sphingomyelinase-resistant membranes) and 24:1 N-acyl moieties. Cell differentiation exerted little effect o n the distribution of molecular species of sphingomyelin between the s phingomyelinase-sensitive and sphingomyelinase-resistant pools in HL-6 0 cells, although the levels of N-palmitoyl sphinganine were significa ntly lower and the N-nervonoyl sphingosine higher in both pools from t he differentiated cells. Our results indicate the same species of sphi ngomyelin, available at both the outer layer of the plasma membrane an d inner layer of the plasma membrane (plus intracellular membranes) of HL-60 cells, serve as-precursors for generation of the ceramides that participate in signal transduction processes initiated by cell activa tion.