Holmes, Sophie and Parkin, Edward (2018) The effect of glucagon-like peptide-1 (GLP-1) receptor agonists on cell viability, ADAM10 maturation and the proteolysis of ADAM10 substrates in SH-SY5Y cells. PhD thesis, Lancaster University.
2018HolmesMSc.pdf - Published Version
Available under License Creative Commons Attribution-NoDerivs.
Download (1MB)
Abstract
Arguably the causative agent of Alzheimer's disease (AD), amyloid beta (Aβ)- peptides, are generated by sequential proteolysis of the amyloid precursor protein (APP) by β- and γ-secretase activities. Alternatively, APP can be processed nonamyloidogenically by an α-secretase activity that cleaves within the Aβ-domain, precluding the formation of intact Aβ-peptides and liberating a neuroprotective fragment, sAPPα. This latter proteolytic event is catalysed by a disintegrin and metalloproteinase (ADAM) 10. Recent research has suggested that glucagon-like peptide-1 (GLP-1) analogues; Lixisenatide, Dulaglutide, Liraglutide, and Exenatide (Exendin-4), currently used to treat diabetes, may also be beneficial in the treatment of neurodegenerative conditions such as AD, as they have been shown to exert neuroprotective properties. Research has also suggested that one of these compounds, exendin-4, can enhance the amount of membrane-associated ADAM10. The current study, therefore, aims to determine firstly; whether GLP-1 analogues can protect neuroblastoma, SH-SY5Y cells, against chemical stressors of relevance to AD and, secondly, whether these compounds alter ADAM10 maturation/activity and the proteolysis of the enzyme's substrates, APP, prion protein (PrP) and neuroligin1 (NLGN-1). Cells treated with hydrogen peroxide (as an oxidative stressor), cobalt chloride (as a hypoxic mimic), methylglyoxal (MG) or thapsigargin (TG) (as Endoplasmic Reticulum stressors) were co-treated with or without GLP-1 analogues and cell viability was subsequently monitored along with the expression and proteolysis of ADAM10 and its substrates. The results of the study showed that the GLP-1 analogue, liraglutide, had no major effect in terms of protecting SH-SY5Y cells against any of the afore-mentioned chemical stressors. However, a second compound, exendin-4, was protective against TG-induced cytotoxicity. Thapsigargin impaired the proteolytic maturation of ADAM10 suggesting a decrease in the activity of the enzyme but exendin-4 was unable to reverse this effect. Nonetheless, exendin-4 was able to partly reverse the inhibitory effect of TG on the expression of endogenous APP, and shedding of over-expressed NLGN1, and sAPPα in cells over-expressing APP695. Interestingly, TG caused an increase in expression of APP695, and an intracellular accumulation of PrP and, subsequently, did not alter the cell surface ADAM-mediated shedding of this protein. Collectively, these data indicate that liraglutide was ineffective in the protection of SH-SY5Y cells against the chemical stressors employed. However, exendin-4, is mildly protective against thapsigargin-mediated oxidative stress and is able to partly restore the TG-induced decrease in expression of endogenous APP, and shedding of APP695 and NLGN1. Unusually though, this latter effect was not associated with restored proteolytic maturation of ADAM10.