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 sphingomyelinase-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 containing 16:0 (slightly higher in the sphingomyelinase-resistant membranes) and 24:1 N-acyl moieties. Cell differentiation exerted little effect on the distribution of molecular species of sphingomyelin between the sphingomyelinase-sensitive and sphingomyelinase-resistant pools in HL-60 cells, although the levels of N-palmitoyl sphinganine were significantly lower and the N-nervonoyl sphingosine higher in both pools from the differentiated cells. Our results indicate the same species of sphingomyelin, available at both the outer layer of the plasma membrane and 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 activation.