Effects of Deceased Mitochondrial Ca2+ Uptake in an in vitro Model of Parkinson's Disease

Abstract

Parkinson's disease is characterized by a progressive and selective loss of dopaminergic neurons in the substantia nigra pars compacta (SNc) of the midbrain. All cells use Ca2+ among other ions to produce signals that regulate cell function. Ca2+ signals in neurons alter electrical activity and stimulate release of neurotransmitters. One of the roles of mitochondria is to help maintain appropriate concentrations of Ca2+ within the cell. The mitochondrial calcium uniporter (MCU) allows Ca2+ into the mitochondria matrix. Under stress conditions, more cytosolic Ca2+ is present in the cell, which can cause excessive Ca2+ uptake by the MCU. It is thought that this excess mitochondrial Ca2+ uptake causes mitochondrial dysfunction which may promote Parkinson's disease. A mechanism that regulates excess mitochondrial Ca2+ uptake in dopaminergic cells might reveal a new target for therapeutic strategies to halt the progressive degeneration of SNc neurons in Parkinson's disease. One such mechanism would be to inhibit MCU, then test if this inhibition protects the cell from high levels of cytosolic Ca2+. For this experiment, we inhibited the activity of the MCU by expressing a dominant‐negative (DN) MCU variant, restricting Ca2+ uptake into the mitochondria matrix of SH‐SY5Y cells, a dopaminergic cell line, that are treated with the dopaminergic neurotoxin, 6‐hydroxydopamine (6‐OHDA). Resulst showed that the expression of DN‐MCU does not reduce cell death, and in this case, is promoting cell death. The expression of DN‐MCU may generate persistent excessive levels of cytosolic Ca2+, generating stress conditions that ultimately lead to cell death and the promotion of Parkinson's disease.Support or Funding InformationThanks to Amy Lee's lab for the intensive training during the summer of 2016. Funding for this project was provided by the Summer Research Opportunities Program, a Carver Trust Collaborative Pilot Grant and, the Ponce Research Initiative for Scientific Enhancement (RISE) under the grant # 2R25GM096955.