CONSTITUTIVE EXPRESSION OF HEAT-SHOCK PROTEIN-70 AND PROTEIN-90 IN RAT CEREBELLUM

Exposure to heat shock and other stressful conditions activates in cel ls of all organisms a specific genetic program. This enhances the synt hesis of proteins with a protective role against cellular damage, call ed heat shock proteins (hsps). Furthermore, in the mammalian nervous s ystem, a considerable amount of hsps is also synthesized under normal conditions suggesting that they play an important role in the metaboli sm of unstressed cells. In this study we analysed the constitutive exp ression of proteins belonging to the hsp70 and hsp90 family in the rat cerebellum using immunocytochemistry with specific monoclonal antibod ies. Our results showed that an intense immunostaining was evident,but was restricted in certain distinct cerebellar areas only, while no di fferences in the distribution of the two hsps were found. The stronges t response was detected in the Purkinje neurons but deep cerebellar nu clei were also positive. In no case glial cells were found to be react ive for hsps despite their strong response for specific markers like g lial fibrillary acid protein (astrocytes) and cyclic nucleotide phosph odiesterase (oligodendrocytes). These data indicate that both the hsp7 0 and hsp90 family have fundamental physiological functions in cerebel lar neurons while they seem to play only a minor role in the metabolis m of glial cells.