Loss of Pink1 modulates synaptic mitochondrial bioenergetics in the rat striatum prior to motor symptoms: concomitant complex I respiratory defects and increased complex II-mediated respiration.

Purpose: Mutations in PTEN-induced putative kinase 1 (Pink1), a mitochondrial serine/threonine kinase, cause a recessive inherited form of Parkinson's disease (PD). Pink1 deletion in rats results in a progressive PD-like phenotype, characterized by significant motor deficits starting at 4 months of age. Despite the evidence of mitochondrial dysfunction, the pathogenic mechanism underlying disease due to Pink1-deficiency remains obscure.

Experimental Design: Striatal synaptic mitochondria from 3-month-old Pink1-deficient rats were characterized using bioenergetic and mass spectroscopy (MS)-based proteomic analyses.

Results: Striatal synaptic mitochondria from Pink1-deficient rats exhibit decreased complex I-driven respiration and increased complex II-mediated respiration compared with wild-type rats. MS-based proteomics revealed 69 of the 811 quantified mitochondrial proteins were differentially expressed between Pink1-deficient rats and controls. Down-regulation of several electron carrier proteins, which shuttle electrons to reduce ubiquinone at complex III, in the Pink1-knockouts suggests disruption of the linkage between fatty acid, amino acid, and choline metabolism and the mitochondrial respiratory system.

Conclusions And Clinical Relevance: These results suggest that complex II activity is increased to compensate for loss of electron transfer mechanisms due to reduced complex I activity and loss of electron carriers within striatal nerve terminals early during disease progression. This may contribute to the pathogenesis of PD.