ALPHA-B-CRYSTALLIN IN C6 GLIOMA-CELLS SUPPORTS THEIR SURVIVAL IN ELEVATED EXTRACELLULAR K- THE IMPLICATION OF A PROTECTIVE ROLE OF ALPHA-B-CRYSTALLIN ACCUMULATION IN REACTIVE GLIA( )

It has been shown by immunohistochemical studies that alpha B-crystall in accumulates in the reactive and neoplastic glial cells in a variety of pathologic situations. However, the molecular mechanism for the in duction of alpha B-crystallin in diseased brains is still unknown. Sin ce any destructive brain lesions cause an abnormal elevation in the po tassium (K+) concentration of the extracellular space, which disturbs the regulatory mechanism of glial cell volume, we investigated the inf luence of elevated extracellular K+ on the expression of alpha B-cryst allin in glial cells. The treatment of rat C6 glioma cells with augmen ted K+ in the culture media induced an accumulation of alpha B-crystal lin mRNA in a dose-dependent manner and an accumulation of the alpha B -crystallin as well. Furthermore, an overexpression of alpha B-crystal lin in the C6 transformant transfected with a rat alpha B-crystallin c DNA conferred a resistant phenotype against the insult of elevated ext racellular K+ on the glioma cells. Thus, alpha B-crystallin may contri bute to the survival of reactive glia in the presence of a high extrac ellular Kf concentration.