ALPHA-B-CRYSTALLIN PROTECTS GLIAL-CELLS FROM HYPERTONIC STRESS

alpha B-crystallin and the small stress protein, heat shock protein of 27 kDa (HSP27), share structural similarities and are coordinately in duced by classical stress stimuli. We have recently observed that hype rtonic stress produced by high NaCl concentrations selectively induces alpha B-crystallin in glial cells. To examine divergence of the funct ional properties of these two related proteins, we have constructed st able, alpha B-crystallin-expressing glial cell lines from the U-251 MC T glioma cells, which are normally deficient in alpha B-crystallin exp ression but constitutively express HSP27. These transfected cells line s are more resistant to acute hypertonic stress than the parental line from which they were derived. Moreover, the parental line acclimates to stepwise increases in hypertonicity and upregulates endogenous alph a B-crystallin in the process but not HSP27. The overexpression of HSP 27 and alpha B-crystallin in NIH/3T3 fibroblasts, a cell line that nor mally expresses little alpha B-crystallin and no HSP27, does not resul t in increased survival. This suggests that alpha B-crystallin interac ts with cell-type specific mechanisms to aid in protection from hypert onic stress.