CERAMIDE FORMATION DURING HEAT-SHOCK - A POTENTIAL MEDIATOR OF ALPHA-B-CRYSTALLIN TRANSCRIPTION

Ceramide has been identified as a potential second messenger that may mediate cell differentiation and apoptosis after exposure to hormonal agonists such as 1 alpha,25-dihydroxyvitamin D-3, tumor necrosis facto r alpha, or gamma-interferon. The secondary cellular events that follo w ceramide generation remain undefined, We report that in NIH WT-3T3 c ells, ceramide induces an enhancement of gene transcription of alpha B -crystallin, a small heat shock protein. The levels of alpha B-crystal lin, as measured by Northern blot and immunoblot analyses, were increa sed by the addition of an exogenous short-chain ceramide, N-acetylsphi ngosine, or by increasing endogenous intracellular ceramide by inhibit ion of glucosylceramide synthase, Similar effects were not seen in the expression of the closely related gene, Hsp25. To ascertain whether c eramide-mediated gene transcription was a feature of the heat shock re sponse, cell ceramide was measured in heat shocked cells and observed to be elevated 2-fold immediately upon the return of cells to 37 degre es C. Thus ceramide formed after heat shock treatment of 3T3 cells may mediate the transcription events associated with the cell stress resp onse.