STAPHYLOCOCCAL ALPHA-TOXIN KILLS HUMAN KERATINOCYTES BY PERMEABILIZING THE PLASMA-MEMBRANE FOR MONOVALENT IONS

Incubation of human keratinocytes with nanomolar concentrations of Sta phylococcus aureus alpha-toxin leads to irreversible depletion of cell ular ATP. The toxin forms hexamers in the target cell membranes, and r apid transmembrane flux of K+, Na+, and Rb-86(+) is observed. Unexpect edly, pores formed in keratinocytes through application of low but let hal doses of alpha-toxin appeared to be considerably smaller than thos e formed in erythrocyte membranes. They permitted neither rapid influx of CA(2+) or propidium iodide, nor efflux of carboxyfluorescein. Larg er pores allowing Bur of all three markers did form when the toxin was applied at high concentrations. Flux of monovalent ions and reduction in cellular ATP levels evoked by low toxin doses correlated temporall y with a fall in oxygen consumption, which was interpreted to reflect breakdown of mitochondrial respiration. The lethal event could not be thwarted by manipulating the extracellular K+ or Ca2+ concentrations. Realization that alpha-toxin may form very small pores in nucleated ce lls is important for future research on cellular toxin effects and mem brane repair processes.