Hydrogen-deuterium exchange in vivo to measure turnover of an ALS-associated mutant SOD1 protein in spinal cord of mice.

Mutations of cytosolic Cu/Zn superoxide dismutase 1 (SOD1) in humans and overexpression of mutant human SOD1 genes in transgenic mice are associated with the motor neuron degenerative condition known as amyotrophic lateral sclerosis (ALS; Lou Gehrig's disease). Gain-of-function toxicity from the mutant protein expressed in motor neurons, associated with its misfolding and aggregation, leads to dysfunction and cell death, associated with paralyzing disease. Here, using hydrogen-deuterium exchange in intact mice in vivo, we have addressed whether an ALS-associated mutant protein, G85R SOD1-YFP, is subject to the same rate of turnover in spinal cord both early in the course of the disease and later. We find that the mutant protein turns over about 10-fold faster than a similarly expressed wild-type fusion and that there is no significant change in the rate of turnover as animals age and disease progresses.