Proteomics profiling of Neuronal Mitochondria

Mitochondria are the ‘power-houses’ of all cells, generating ATP to fuel numerous pathways which are vital for cellular form and function (1). Neuronal processes and synapses present a constant demand for ATP to maintain ionic gradients and neurotransmission events (2), promoting sub-populations of mitochondria to be enriched pre- and post-synaptically (3, 4). These mitochondria display unique enzymatic (5), calcium buffering (6, 7) and antioxidant properties (8) and have thus been associated in the pathogenesis of a variety of neurodegenerative diseases where the synapse is the primary target. In this study, we employed label-free proteomics to characterize the proteomes of synaptic and non-synaptic mitochondria following biochemical isolation (5). Discrete proteomic profiles exist between the two subpopulations of mitochondria and a molecular fingerprint of these differences is seemingly conserved between mammalian species. The majority of the constituents of this grouping have been previously associated with diseases of the nervous system. In addition, bioinformatic analysis of this conserved expression pattern indicated that differences in the properties of protein complex I may represent an important specialisation of synaptic mitochondria. Following this, in vivo assays of mitochondrial candidates using Drosophila larval fillet preparations were performed. Our data demonstrates that selective knock-down of intrinsic mitochondrial proteins alter synaptic morphology which may contribute to pathological processes during ageing and disease.