Mitochondrial Dysfunction and BCL2 Interactions in SOD1-Mediated Motor Neuron Death

• Headline: Mitochondrial Impairment and BCL2 Sequestration in Mutant SOD1-Induced Motor Neuron Apoptosis

• Introduction: Subcellular pathology in familial ALS heavily implicates mitochondrial failure as a primary driver of motor neuron demise. Misfolded, demetallated, and reduced SOD1 monomers translocate into mitochondria, where they disrupt energy homeostasis and activate intrinsic apoptotic cascades.

• Mitochondrial Pathogenic Cascade:

  • Protein Import Inhibition: Mutant aggregates block the translocase of the outer membrane (TOM) complex, halting vital matrix protein import.

  • BCL2 Interaction: Mutant SOD1 forms toxic aggregates specifically with BCL2 proteins in spinal cord mitochondria (sparing non-vulnerable tissues like the liver), altering mitochondrial outer membrane permeability and opening the permeability transition pore (PTP).

  • Cytochrome c Release: PTP opening triggers cytochrome c release into the cytoplasm, caspase activation, ATP depletion, and calcium dysregulation resulting in cellular apoptosis.