Negative regulation of cytochrome c-mediated oligomerization of Apaf-1 and activation of procaspase-9 by heat shock protein 90 |
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| Authors: | Pandey P Saleh A Nakazawa A Kumar S Srinivasula S M Kumar V Weichselbaum R Nalin C Alnemri E S Kufe D Kharbanda S |
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| Affiliation: | Dana-Farber Cancer Institute, Harvard Medical School, Boston, MA 02115, USA. |
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| Abstract: | The release of cytochrome c from mitochondria results in the formation of an Apaf-1-caspase-9 apoptosome and induces the apoptotic protease cascade by activation of procaspase-3. The present studies demonstrate that heat shock protein 90 (Hsp90) forms a cytosolic complex with Apaf-1 and thereby inhibits the formation of the active complex. Immunodepletion of Hsp90 depletes Apaf-1 and thereby inhibits cytochrome c-mediated activation of caspase-9. Addition of purified Apaf-1 to Hsp90-depleted cytosolic extracts restores cytochrome c-mediated activation of procaspase-9. We also show that Hsp90 inhibits cytochrome c-mediated oligomerization of Apaf-1 and thereby activation of procaspase-9. Furthermore, treatment of cells with diverse DNA-damaging agents dissociates the Hsp90-Apaf-1 complex and relieves the inhibition of procaspase-9 activation. These findings provide the first evidence for a negative cytosolic regulator of cytochrome c-dependent apoptosis and for involvement of a chaperone in the caspase cascade. |
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