Identification of the nuclear receptor CAR:HSP90 complex in mouse liver and recruitment of protein phosphatase 2A in response to phenobarbital.

The nuclear receptor CAR, a phenobarbital (PB)-responsive transcription factor, translocates into the nucleus of hepatocytes after PB induction. In non-induced mice, CAR forms a physical complex with heat shock protein 90 (HSP90) in the cytoplasm. In response to PB induction, protein phosphatase 2A is recruited to the CAR:HSP90 complex. This recruitment may lead CAR to translocate into the nucleus, consistent with the inhibitions of nuclear CAR accumulation in PB-induced mouse primary hepatocytes by okadaic acid as well as by geldanamycin.