(17) THE ROLE OF MITOCHONDRIA IN APOPTOSIS

R. Eliseev, T. Gunter, L. Buntinas, K. Gunter
Department of Biochemistry and Biophysics, University of Rochester, Rochester, NY

Mitochondria have been shown to play a role in the regulation of apoptosis. Mitochondrial intermembrane protein cytochrome c can participate in the activation of certain caspases - enzymes that execute apoptosis. The possible mechanism of such release is the rupture of the outer mitochondrial membrane caused by the swelling of organelles after the activation of the mitochondrial permeability transition (MPT) pore.

We measured the release of cytochrome c from isolated mitochondria undergoing the MPT using the western blotting assay and found that cytochrome c release started right after the activation of the MPT.

In another set of experiments we induced apoptosis in HL-60 cells with etoposide. At different times after the induction of apoptosis we measured TPP+ uptake by mitochondria in digitonin - permeabilized cells with TPP+-sensitive electrode. It gave us the relative measure of mitochondrial membrane potential. We detected a substantial decrease in this value at 2 hours after the induction of apoptosis which might indicate the activation of the MPT. Cytochrome c release from mitochondria in these cells also started at that time.

Our data provide another evidence that cytochrome c release from mitochondria during apoptosis is mediated by the MPT.

Supported by AHA NY State Affiliate grant 960166.