Bax affects intracellular Ca2+ stores and induces Ca2+ wave propagation

Area of Science:

• Cell Biology
• Mitochondrial Biology
• Neuroscience

Background:

• The proapoptotic protein Bax plays a critical role in programmed cell death.
• Mitochondria are central regulators of cell death and calcium homeostasis.
• Astrocytes, crucial glial cells in the central nervous system, are involved in neuronal support and signaling.

Purpose of the Study:

• To investigate the effects of recombinant Bax (rBax) on mitochondrial function and calcium (Ca2+) homeostasis in primary cultured astrocytes.
• To elucidate the mechanisms by which Bax influences mitochondrial integrity and Ca2+ signaling.

Main Methods:

• Primary astrocyte cultures were treated with recombinant Bax (rBax).
• Mitochondrial membrane potential (Delta Psi m), respiratory rates, and cytochrome c release were assessed.
• Mitochondrial Ca2+ release was measured and modulated using inhibitors like cyclosporin A and Ruthenium Red.
• Intercellular Ca2+ signaling, including Ca2+ waves, was monitored.

Main Results:

• Recombinant Bax induced a significant loss of mitochondrial membrane potential (Delta Psi m).
• Bax treatment led to decreased respiratory rates and partial release of cytochrome c, altering mitochondrial morphology.
• Bax triggered Ca2+ release from mitochondria, which was sensitive to inhibitors of mitochondrial Ca2+ transport.
• Bax-induced mitochondrial Ca2+ release resulted in intercellular Ca2+ waves, indicating altered Ca2+ signaling.

Conclusions:

• Bax directly impacts mitochondrial integrity, leading to the loss of mitochondrial membrane potential and Ca2+ release.
• These Bax-induced mitochondrial alterations disrupt cellular Ca2+ homeostasis and promote intercellular Ca2+ signaling.
• The findings suggest a correlation between Bax-mediated mitochondrial dysfunction, Ca2+ dysregulation, and proapoptotic signaling pathways.