The mitochondrial permeability transition pore: A molecular target for amyotrophic lateral sclerosis therapy

Effective therapies are needed for the treatment of amyotrophic lateral sclerosis (ALS), a fatal type of motor neuron disease. Morphological, biochemical, molecular genetic, and cell/animal model studies suggest that mitochondria have potentially diverse roles in neurodegenerative disease mechanisms and neuronal cell death. In human ALS, abnormalities have been found in mitochondrial structure, mitochondrial respiratory chain enzymes, and mitochondrial cell death proteins indicative of some non-classical form of programmed cell death. Mouse models of ALS are beginning to reveal possible principles governing the biology of selective neuronal vulnerability that implicate mitochondria. This minireview summarizes work on the how malfunctioning mitochondria might contribute to neuronal death in ALS through the biophysical entity called the mitochondrial permeability pore (mPTP). The major protein components of the mPTP are enriched in mouse motor neurons. Early in the course of disease in ALS mice expressing human mutant superoxide dismutase-1, mitochondria in motor neurons undergo trafficking abnormalities and dramatic remodeling resulting in the formation of mega-mitochondria and coinciding with increased protein carbonyl formation and nitration of mPTP components. The genetic deletion of a major mPTP component, cyclophilin D, has robust effects in ALS mice by delaying disease onset and extending survival. Thus, attention should be directed to the mPTP as a rational target for the development of drugs designed to treat ALS.