Proteomic profiling of cranial (superior) cervical ganglia reveals Beta-amyloid and ubiquitin proteasome system perturbations in an equine multiple system neuropathy.

Equine grass sickness (EGS) is an acute, predominantly fatal, multiple system neuropathy of grazing horses with reported incidence rates of approximately 2%. An apparently identical disease occurs in multiple species including but not limited to cats, dogs, and rabbits. Although the precise aetiology remains unclear, ultrastructural findings have suggested that the primary lesion lies in the glycoprotein biosynthetic pathway of specific neuronal populations. The goal of this study was therefore to identify the molecular processes underpinning neurodegeneration in EGS. Here we use a bottom up approach beginning with the application of modern proteomic tools to the analysis of cranial (superior) cervical ganglion (CCG – a consistently affected tissue) from EGS affected patients and appropriate control cases postmortem. In what appears to be the first proteomic application of modern proteomic tools to equine neuronal tissues and/or to an inherent neurodegenerative disease oflarge animals (not a model of human disease), we identified 2311 proteins in CCG extracts, with 320 proteins increased and 186 decreased by greater than 20% relative to controls.Further examination of selected proteomic candidates by quantitative fluorescent western blotting (QFWB) and sub-cellular expression profiling by immunohistochemistry, highlighted a previously unreported dysregulation in proteins commonly associated with protein misfolding/aggregation responses seen in a myriad of human neurodegenerative conditions, including but not limited to amyloid precursor protein (APP), microtubule associated protein(Tau) and multiple components of the ubiquitin proteasome system (UPS). Differentially expressed proteins eligible for in silico pathway analysis clustered predominantly into the following biofunctions: 1. Diseases & disorders including; neurological disease, skeletal & muscular disorders; 2. Molecular and cellular functions: including cellular assembly & organisation, cell-to-cell signalling and interaction (including epinephrine, dopamine & adrenergic signalling and receptor function) and small molecule biochemistry. Interestingly,whilst the biofunctions identified in this study may represent pathways underpinning EGS induced neurodegeneration, this is also the first demonstration of potential molecular conservation (including previously unreported dysregulation of the UPS and APP) spanning the degenerative cascades from an apparently unrelated condition of large animals, to smallanimal models with altered neuronal vulnerability, and human neurological conditions.Importantly, this study highlights the feasibility and benefits of applying modern proteomic techniques to veterinary investigations of neurodegenerative processes in diseases of large animals.