Bok regulates mitochondrial fusion and morphology

Area of Science:

• Cell Biology
• Molecular Biology
• Biochemistry

Background:

• Bok (Bcl-2-related ovarian killer) is part of the Bcl-2 protein family involved in apoptosis.
• Endogenous Bok is constitutively bound to inositol 1,4,5-trisphosphate receptors (IP3Rs), a binding that stabilizes Bok.
• The precise cellular function of Bok remains controversial.

Purpose of the Study:

• To investigate the role of Bok in cellular processes, particularly its interaction with IP3Rs and its impact on calcium signaling and mitochondrial function.
• To determine if Bok influences apoptotic pathways.

Main Methods:

• CRISPR/Cas9-mediated gene editing was used to delete Bok expression.
• Calcium mobilization via IP3Rs and mitochondrial calcium influx were measured.
• Mitochondrial fusion rates, morphology, motility, spare respiratory capacity, and membrane potential were assessed.
• Responsiveness to various apoptotic stimuli was evaluated in Bok-deleted cells.

Main Results:

• Bok deletion did not alter IP3R-mediated calcium mobilization or mitochondrial calcium influx.
• Loss of Bok significantly reduced mitochondrial fusion, leading to fragmentation, which was reversed by reintroducing Bok.
• Bok deletion enhanced mitochondrial spare respiratory capacity and membrane potential.
• Bok deletion did not affect cellular responsiveness to apoptotic stimuli.

Conclusions:

• Bok's interaction with IP3Rs does not modulate IP3R-mediated calcium signaling.
• Bok is essential for maintaining mitochondrial fusion, morphology, and bioenergetic homeostasis.
• Bok does not play a significant role in the intrinsic apoptosis pathway.