Article abstract
Nature Cell Biology 2, 318 - 325 (2000)
Published online: 28 April 2000 | doi:10.1038/35014006
Changes in intramitochondrial and cytosolic pH: early events that modulate caspase activation during apoptosis
Shigemi Matsuyama1, Juan Llopis2,4, Quinn L. Deveraux1, Roger Y. Tsien2,3 & John C. Reed1
Abstract
Mitochondria trigger apoptosis by releasing caspase activators, including cytochrome c (cytC). Here we show, using a pH-sensitive green fluorescent protein (GFP), that mitochondria-dependent apoptotic stimuli (such as Bax, staurosporine and ultraviolet irradiation) induce rapid, Bcl-2-inhibitable mitochondrial alkalinization and cytosol acidification, followed by cytC release, caspase activation and mitochondrial swelling and depolarization. These events are not induced by mitochondria-independent apoptotic stimuli, such as Fas. Activation of cytosolic caspases by cytC in vitro is minimal at neutral pH, but maximal at acidic pH, indicating that mitochondria-induced acidification of the cytosol may be important for caspase activation; this finding is supported by results obtained from cells using protonophores. Cytosol acidification and cytC release are suppressed by oligomycin, a FoF1-ATPase/H +-pump inhibitor, but not by caspase inhibitors. Ectopic expression of Bax in wild-type, but not FoF1/H+-pump-deficient, yeast cells similarly results in mitochondrial matrix alkalinization, cytosol acidification and cell death. These findings indicate that mitochondria-mediated alteration of intracellular pH may be an early event that regulates caspase activation in the mitochondrial pathway for apoptosis.
- Programme on Apoptosis and Cell Death Regulation, The Burnham Institute, 10901 North Torrey Pines Road, La Jolla, California 92037, USA
- Department of Pharmacology, University of California at San Diego, San Diego, California 92093, USA
- Division of Cellular and Molecular Medicine, Howard Hughes Medical Institute, San Diego, California 92093 , USA
- Present address: Facultad de Medicina, Universidad de Castilla – La Mancha, Campus Universitario s/n, 02071 Albacete, Spain
Correspondence to: John C. Reed1 e-mail: jreed@burnham-institute.org
