Mitochondrial protein import stress augments alpha-synuclein aggregation and neurodegeneration independent of bioenergetics
Several genetic and environmental risk factors for Parkinson's disease have been identified that converge on mitochondria as central elements in the disease process. However, the mechanisms by which mitochondrial dysfunction contributes to neurodegeneration remain incompletely understood. Non-bioenergetic pathways of the mitochondria are increasingly appreciated, but confounding bioenergetic defects are a major barrier to experimental validation. Here, we describe a novel bioenergetics-independent mechanism by which mild mitochondrial protein import stress augments neurodegeneration. We induced this mitochondrial protein import stress in an established mouse model of Parkinson's disease expressing the A53T mutated form of human alpha-synuclein (SNCA). Mice with import stress in addition to the A53T mutation demonstrated increased size of SNCA aggregates, co-aggregation of mitochondrial preproteins with SNCA protein, worsened neurodegeneration and changes in gene expression, as determined by whole-transcriptome RNA-sequencing analysis of the forebrain (striatum), cerebellum, spinal cord, as well as heart and skeletal muscle. Overall design: Total RNA from the striatum, cerebellum, and spinal cord in wildtype and transgenic mice and analyzed using RNAseq