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Effect of Bcl-2 overexpression on mitochondrial structure and function.
Alicia J Kowaltowski1, Ricardo G Cosso, Claudia B Campos
1Departamento de Bioquimica, Instituto de Quimica, Universidade de São Paulo, São Paulo, SP, 05508-900, Brazil. alicia@iq.usp.br
The Journal of Biological Chemistry
|September 19, 2002
Summary
The anti-apoptotic protein Bcl-2 increases fluorescent dye uptake in mitochondria, not by altering membrane potential, but by increasing mitochondrial volume and structural complexity. This structural change may explain Bcl-2's cell death prevention effects.
Area of Science:
- Cell Biology
- Mitochondrial Function
Background:
- The antiapoptotic protein Bcl-2 is known to influence mitochondrial function.
- Bcl-2 overexpression has been linked to enhanced uptake of dyes sensitive to mitochondrial membrane potential.
Purpose of the Study:
- To investigate whether Bcl-2 alters mitochondrial inner membrane ion transport.
- To determine the mechanism behind enhanced fluorescent dye uptake in Bcl-2 overexpressing cells.
Main Methods:
- Calibrated measurements of mitochondrial respiration, membrane potential, pH (deltapH), and intramitochondrial potassium ([K+]).
- Utilized digitonin-permeabilized PC12 and GT1-7 neural cells with and without Bcl-2 overexpression.
- Flow cytometry particle sizing and light scattering to assess mitochondrial structure.
Main Results:
- Bcl-2 overexpressing cells showed increased fluorescence with potential, pH, and K+-sensitive dyes.
- This increased fluorescence was due to enhanced dye accumulation, not altered membrane potential, deltapH, or [K+].
- Respiratory rates were similar between Bcl-2+ and Bcl-2- cells.
- Bcl-2 overexpressing mitochondria exhibited increased volume and structural complexity.
Conclusions:
- Bcl-2 does not alter mitochondrial membrane potential or ion transport directly.
- Enhanced dye uptake in Bcl-2+ cells is attributed to increased mitochondrial volume and structural complexity.
- These structural mitochondrial changes may underlie Bcl-2's role in preventing cell death.