title: Investigation of SUMOylation in Cellular Models of Parkinson's Disease
Creators: name: Roberts, Angus J
Publisher: name: Griffith University
Year: 2022
Subjects: subject: Parkinson’s Disease
subject: SUMOylation
subject: Age-related diseases

description: A follow-on effect of the current ageing population is the increased incidence of age-related diseases. Neurodegenerative conditions, such as, Alzheimer’s disease, Parkinson’s Disease and Huntington’s Disease, as well as cardiovascular disease and cancer have been shown to have dramatically higher risk as people age. The major neurodegenerative diseases are characterised by the progressive loss of neurons within specific brain regions, often resulting in characteristic symptomology. For many neurodegenerative conditions, there appears to be a characteristic hallmark of toxic protein aggregate deposition within the cells of the affected brain region, and even spreading of aggregates from the region of origin. Neurodegeneration drastically reduces an individuals quality of life, with the burden often handed to the people around them. With the current aetiology of many neurodegenerative conditions, such as Parkinson’s disease, not well understood, it is of vital importance to establish a greater understanding of these diseases, to progress towards disease alleviating treatments, and even cures. Parkinson’s disease (PD) is characterised by the progressive loss of the dopaminergic neurons within the substantia nigra, a brain region within the basal ganglia. This region is heavily involved with motor control. PD neurons undergo the inclusion body phenomenon, termed “Lewy” bodies. Lewy bodies are made up of aggregated, misfolded proteins, with -synuclein being shown as the primary aggregating protein. Other proteins, such as the small ubiquitin-like modifier (SUMO), have been shown co-localised to these inclusions, as well as modifying disease specific pathways. This thesis investigates the SUMOylation pathways components to further understand and establish potential biomarkers for PD. The two aims of this thesis were to investigate SUMO components in the PD-derived human olfactory neurosphere (hONs) derived cell lines, as potential biomarkers for disease (Chapter 3), and to investigate SUMO component expression in a well-established neuroblastoma PD cell assay (chapter 4). The experimental work of chapter 3 investigates the SUMO pathway components UBC-9 and SAE-2 in PD hONs derived cell lines in comparison to age-matched controls. These two proteins are the core SUMO addition enzymes. Previous studies have shown SENP-3 to be altered in PD brain tissue and PD-derived hONs cells compared to normal controls. Other SUMO enzymes UBC-9 and SAE-2 have been shown to be unchanged in PD brain tissue, but with high variability between cases and have not been investigated in the hONS model. The proteins expression levels were measured using western blotting, under two conditions: basal conditions, and under proteolytic stress via proteasome inhibitor MG132. Western blot analysis showed that both UBC-9 and SAE-2 are unchanged with the PD hONs cell lines, under basal conditions and under conditions of proteolytic stress. Findings in this chapter are consistent with post-mortem PD tissue analysis. The experimental work of chapter 4 investigates the deSUMOylase enzyme SENP-3, and the E1 enzyme SAE-2, in the SH-SY5Y potassium chloride depolarisation PD model. Previous research has shown SENP-3 to be increased in stressful conditions, and in the PD hON model and PD brain tissue. KCl depolarisation results in the formation of large inclusion bodies that are positive for -synuclein. The results show that whilst SAE-2 remains unchanged in this model, SENP-3 is significantly increased in KCl depolarised SH-SY5Y cells. Previous research has shown that SENP-3 is important in deSUMOylating targets that are involved in cellular responses to ischemia, oxygen and glucose deprivation, and oxidative stress. The results further support the hypothesis that SENP-3 is altered in disease specific settings. This body of work highlights potential roles and changes in SUMOylation pathway components in a relatively novel PD derived hONs cell line and a well-established PD SH-SY5Y cell model. Whilst UBC-9 and SAE-2 remained unchanged in the hONs cellular model of PD, SENP-3 protein expression is significantly increased in the SH-SY5Y PD model. The results collectively suggest that the SUMOylation status in these PD models’ disease settings is geared towards deSUMOylating SUMO-2/3 isoforms. The link between increased SENP-3 expression and PD pathology could provide a useful marker to improve PD diagnosis. SENP-3 enzyme inhibitors could provide a novel avenue for therapeutic intervention.