Mapping the ruthenium red-binding site of the voltage-dependent anion channel-1

Area of Science:

• Mitochondrial biology
• Cell death pathways
• Biochemistry

Background:

• Ruthenium red (RuR) is known to interact with voltage-dependent anion channels (VDAC) in the outer mitochondrial membrane.
• This interaction has been shown to decrease channel conductance and offer protection against apoptotic cell death.

Purpose of the Study:

• To identify specific amino acid residues in murine and yeast VDAC1 that mediate the interaction with RuR.
• To elucidate the role of these residues in RuR's protective effects against cell death and inhibition of cytochrome c release.

Main Methods:

• Site-directed mutagenesis of VDAC1 in murine and yeast models.
• Reconstitution of mutated VDAC1 into lipid bilayers to assess channel conductance.
• Cell-based assays to evaluate protection against apoptosis and cytochrome c release.

Main Results:

• Mutation of specific glutamate residues in murine VDAC1 (mVDAC1) cytosolic loops inhibited RuR binding and channel closure.
• These mutations diminished RuR's protective effect against cell death induced by VDAC1 overexpression.
• RuR failed to inhibit staurosporine-induced cytochrome c release in cells expressing mutated VDAC1.
• Three glutamate residues in yeast VDAC1 were also found to be critical for RuR interaction.

Conclusions:

• Four glutamate residues in the cytosolic loops of mVDAC1 are essential for RuR binding and subsequent protection against cell death.
• RuR exerts its protective effects by directly interacting with VDAC1, inhibiting cytochrome c release, and preventing apoptosis.
• The findings highlight a direct mechanistic link between RuR, VDAC1, and the regulation of programmed cell death.