Abstract

Dopamine neuron (DAn) degeneration in Parkinson’s has often been associated with altered function of the endoplasmic reticulum (ER) and the mitochondria, the main calcium (Ca²⁺) store in the cell. In this work, we sought to investigate the role of Ca²⁺ within these specific compartments in the vulnerability of DAns in Parkinson’s, using stem cell-derived DAns from patients in conjunction with Ca²⁺ imaging.

From our experiments, it appears that Parkinson’s DAns with alpha-synuclein (SNCA) and GBA mutationsdisplay decreased intracellular Ca²⁺ levels. Specific ER or mitochondria-resolved Ca²⁺ imaging confirmed that ER Ca²⁺ content is reduced in patient-derived DAns. Mitochondrial Ca²⁺ imaging highlighted an impairment in mitochondrial Ca²⁺ uptake. Intriguingly, decreased ER Ca²⁺ levels can negatively impact ER health and mitochondrial Ca²⁺ is pivotal for the maintenance of energy levels in the cell, both of which are altered in Parkinson’s.

Using novel CRISPRi technology to knockdown the expression of a set of genes involved in Ca²⁺ regulation, the mitochondrial Ca²⁺ uniporter (MCU) was identified as potentially responsible for the altered Ca²⁺ dynamics. If confirmed, this hit could be pharmacologically targeted for Parkinson’s.