HSP86 AND HSP84 EXHIBIT CELLULAR SPECIFICITY OF EXPRESSION AND CO-PRECIPITATE WITH AN HSP70 FAMILY MEMBER IN THE MURINE TESTIS

This study extends to the protein level our previous observations, whi ch had established the stage and cellular specificity of expression of hsp86 and hsp84 in the murine testis in the absence of exogenous stre ss. Immunoblot analysis was used to demonstrate that HSP86 protein was present throughout testicular development and that its levels increas ed with the appearance of differentiating germ cells. HSP86 was most a bundant in the germ cell population and was present at significantly l ower levels in the somatic cells. By contrast, the HSP84 protein was d etected in the somatic cells of the testis rather than in germ cells. The steady-state levels of HSP86 and HSP84 paralleled the pattern of t he expression of their respective mRNAs, suggesting that regulation at the level of translation was not a major mechanism controlling hsp90 gene expression in testicular cells. Immunoprecipitation analysis reve aled that a 70-kDa protein coprecipitated with the HSP86/HSP84 protein s in testicular homogenates. This protein was identified as an HSP70 f amily member by immunoblot analysis, suggesting that HSP70 and HSP90 f amily members interact in testicular cells.