FIGURE 10.

HSP86 stabilizes HTT. A, 293T cells were cotransfected with HTT fragment cDNA and either empty vector or HSP86 cDNA. After 72 h, cells cotransfected with HSP86 expressed higher levels of the fragments as assessed by Western blot. Intriguingly, N586-transfected cells displayed a 2.6× increase in fragment levels, and N552 transfected cells displayed a 1.4-fold increase. B, this increase in fragment levels did not occur with endogenous HTT in the same cells. C, inhibition of HSP90 by 17-DMAG leads to a significant decrease in HTT fragment levels. Cells were transfected and cultured for 48 h and then treated with pan-HSP90 inhibitor 17-DMAG (500 nm) or DMSO vehicle control for 24 h. The N552-transfected cells displayed a 2× reduction in fragment levels upon HSP90 inhibition, and the N586 cells displayed a 2.4× reduction upon HSP90 inhibition. D, inhibition of HSP90 by 17-DMAG leads to significant reduction of endogenous HTT in transfected 293T cells. Quantitation of endogenous HTT levels from cells treated in C is shown. In contrast with overexpression, transient inhibition of HSP90 is sufficient to reduce endogenous HTT by 2-fold.