The von Hippel-Lindau protein sensitizes renal carcinoma cells to apoptotic stimuli through stabilization of BIMEL

von Hippel-Lindau (VHL) disease is caused by germ-line mutations in the VHL tumor suppressor gene and is the most common cause of inherited renal cell carcinoma (RCC). Mutations in the VHL gene also occur in a large majority of sporadic cases of clear-cell RCC, which have high intrinsic resistance to chemotherapy and radiotherapy. Here we show that VHL-deficient RCC cells express lower levels of the proapoptotic Bcl-2 family protein BIMEL and are more resistant to etoposide and UV radiation-induced death compared to the same cells stably expressing the wild-type VHL protein (pVHL). Reintroducing pVHL into VHL-null cells increased the half-life of BIMEL protein without affecting its mRNA expression, and overexpressing pVHL inhibited BIMEL polyubiquitination. Suppressing pVHL expression with RNA interference resulted in a decrease in BIMEL protein and a corresponding decrease in the sensitivity of RCC cells to apoptotic stimuli. Directly inhibiting BIMEL expression in pVHL-expressing RCC cells caused a similar decrease in cell death. These results demonstrate that pVHL acts to promote BIMEL protein stability in RCC cells, and that destabilization of BIMEL in the absence of pVHL contributes to the increased resistance of VHL-null RCC cells to certain apoptotic stimuli.