Staphylococcus aureus alpha-toxin. 1. Effect on protein phosphorylation in myelin

It has previously been demonstrated that staphylococcal alpha-toxin can selectively induce disruption of myelin sheaths in the central nervous system, albeit the exact mechanism is not known. In this report we show for the first time that the staphylococcal alpha-toxin could stimulate the endogenous phosphorylation of several proteins, including myelin basic protein (Mr = 18,500) in purified guinea pig brain myelin. This stimulatory effect does not require the presence of calcium and is distinct from those modulated by calcium and phospholipids. In vitro phosphorylation of isolated myelin basic protein by the purified catalytic subunit of cAMP-dependent protein kinase was enhanced in the presence of alpha-toxin, whereas the reaction catalyzed by protein kinase C, a Ca2+-activated and phospholipid-dependent protein kinase, was not affected. These results suggest that some of the toxic effects of staphylococcal alpha-toxin on myelin may be mediated through post-translation covalent modification, such as phosphorylation of specific proteins.