View the Current Issue

Article

  • The EMBO Journal (2000) 19, 4310 - 4322
  • doi:10.1093/emboj/19.16.4310

Negative regulation of cytochrome c-mediated oligomerization of Apaf-1 and activation of procaspase-9 by heat shock protein 90

Pramod Pandey1,5, Ayman Saleh2,5, Atsuko Nakazawa1, Shailendra Kumar1, Srinivasa M. Srinivasula2, Vijay Kumar1, Ralph Weichselbaum3, Carlo Nalin4, Emad S. Alnemri2,5, Donald Kufe1 and Surender Kharbanda1

  1. Dana-Farber Cancer Institute, Harvard Medical School, Boston, MA, 02115, USA.
  2. Thomas Jefferson University, Kimmel Cancer Institute, Philadelphia, PA 19107, USA
  3. Department of Radiation and Cellular Oncology, University of Chicago, Chicago, IL 60637, USA
  4. Oncology Research, Novartis Pharmaceuticals Corporation, East Hanover, NJ 07936, USA
  5. P.Pandey and A.Saleh, and E.S.Alnemri and D.Kufe contributed equally to this work

Correspondence to:

Surender Kharbanda, E-mail: surender_kharbanda@dfci.harvard.edu

Received 10 April 2000; Accepted 29 June 2000; Revised 28 June 2000

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.

  • Keywords:

    • Apaf-1,
    • apoptosis,
    • caspase-9,
    • cytochrome c,
    • Hsp90