Altered ER Homeostasis and Mitochondria ER Network in PINK1 Deficient Parkinson's Disease Models

Abstract

Parkinson's disease (PD) is one of the most common neurodegenerative diseases, affecting 1% of the population over 60 years old. The pathological hallmarks of PD include loss of dopaminergic neruons in the substantia nigra pars compacta and formation of alpha-synuclein positive intracellular inclusions named Lewy bodies. Although majority of PD cases are sporadic, mutations in numerous genes (e.g. alpha-synuclein, LRRK2, PINK1, Parkin) have been linked to the development of familial PD. Growing evidence from genetic and toxicological models as well as human PD brain studies suggests that endoplasmic reticulum (ER) stress is one of the features which contributes to neurodegeneration in PD. Increased ER stress has been descried in post-mortem brain tissues from PD patients as well as cellular models of PD with overexpression of mutant alpha-synuclein. However, it is still unclear whether altered ER homeostasis play a role in receive forms of PD. Here we investigated ER function and mitochondria-ER network in PINK1-deficient cellular models for Parkinson's disease. We observed and increased ER calcium release upon stimulation with SERCA inhibitor thapsigargin which is accompanied by increase mitochondria calcium uptake in PINK1 deficient SH-SY5Y neuroblastoma cells, as measured by genetically encode ER calcium probe (ERD1) and X-Rhod 1 respectively. These results indicated an increased contact between mitochondria and ER. We further confirmed this using both immunohistochemistry staining with GRP75 as mitochondria maker and calnexin as ER marker and live cell imaging using TMRM as mitochondria marker and ER-GFP as maker for ER. Furthermore, altered ER stress markers were also detected in PINK1 deficient cells. Further examination of the impact of altered ER-mitochondria contact on neuronal survival will be presented at the conference. Altogether, our results suggests an altered ER homeostasis in PINK1-deficient cellular models of PD.