sphingosine-kinase and 1-10-phenanthroline

Cleavage of membrane-associated L-selectin regulates leukocyte rolling on vascular endothelium at sites of inflammation. We report that rapid and massive shedding of L-selectin occurs from granulocytes attacked by the pore-forming bacterial toxin streptolysin O (SLO). Shedding was not induced by an SLO mutant that retained binding capacity but lacked pore-forming activity. Cells permeabilized with SLO exhibited a 1.5-fold increase in the activity of neutral sphingomyelinase, which was accompanied by increased ceramide formation. L-selectin cleavage was inducible by treatment of cells with bacterial sphingomyelinase, and also through exogenous application of a cell-permeable ceramide analog. Our data identify a novel path to the shedding process and show that activation of neutral sphingomyelinase with the generation of ceramide is an important event underlying enhanced sheddase function in cells permeabilized by a pore-forming toxin.

Topics: Bacterial Proteins; Cell Membrane Permeability; Ceramides; Dipeptides; Enzyme Activation; Enzyme Inhibitors; Granulocytes; Humans; Hydroxamic Acids; Isoenzymes; L-Selectin; N-Formylmethionine Leucyl-Phenylalanine; Phenanthrolines; Phosphotransferases (Alcohol Group Acceptor); Second Messenger Systems; Sphingomyelin Phosphodiesterase; Sphingosine; Staurosporine; Streptolysins