The role of calcium-activated potassium channels in neuronal mitochondria

• Applicant: Dr. Amalia Dolga
• Subject Area: Molecular Biology and Physiology of Neurons and Glial Cells ; Pharmacology ; Cell Biology
• Term: from 2014 to 2017
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 249667320

Several studies demonstrated that targeting small-conductance calcium-activated potassium (KCNN/SK/KCa2) channels is an emerging therapeutic strategy for several neurodegenerative conditions, including stroke, Parkinson disease or spinocerebellar ataxia type 2. The preliminary work to this proposal revealed, for the first time, that SK channels are expressed and functional in neuronal mitochondria. In the proposed project, we aim to further investigate the role of SK channels in the regulation of mitochondrial functions, using defined mitochondrial functional assays and novel mitochondria-targeted fluorescent probes to measure mitochondrial function and dysfunction, generation of ROS and mitochondria/ion channel crosstalk. Further, this project aims to decipher the molecular mechanisms mediated by mitochondrial SK channels in conditions of mitochondrial dysfunction. Using molecular genetic approaches, including SK2 channel knockout mice, dominant negative SK channels, mitochondrial localization sequence-targeted potassium SK channels, specific inhibitory peptides for each SK channel subtype, and siRNA techniques), cell biology and biochemistry (including cellular compartmentalization, protein analysis, oxidative stress analysis, mitochondrial potential assessment) and electrophysiology (patch-clamp in mitoplasts), we aim to elucidate both the physiologic and pathophysiologic function of SK channels and to predict the ability of cells to respond to stress.In this study, the following specific aims will be addressed:1. SK2 channel regulation and subcellular distribution under physiological conditions and after oxidative stress. In this project, we will address the question whether SK2 channels are involved in mitochondrial fusion and fission processes upon oxidative and cellular stress. Furthermore, we will investigate the role of SK channels on intrinsic cell death pathways.2. The functional role of SK2 channels in mitochondria. The preliminary work revealed that SK2 channels are expressed in mitochondria, however, the function of mitochondrial SK2 channels by electrophysiology and how they are involved in the regulation of mitochondrial membrane potential, mitochondrial ROS and/or mitochondrial calcium buffer capacity, and mitochondrial swelling is unknown and thus, addressed in this part of the project. In particular the project addresses the role of SK2 channels in the mitochondrial respiratory chain, in mitochondrial Ca2+ signalling and in mitochondrial ROS formation. This project investigates the function of newly identified mitochondrial SK2 channels in physiological and pathological situations. Since it is hypothesized that deregulation of cytosolic Ca2+ homeostasis contributes to mitochondrial dysfunction and, ultimately, to cell death, this project provides new approaches directed against the effects of sustained increased intracellular Ca2+ levels that play a pivotal role for progressive neurodegenerative diseases.

• DFG Programme: Research Grants
• International Connection: Italy
• Participating Persons: Professor Niels Decher, Ph.D.; Nunzianna Doti, Ph.D.; Professor Dr. Michael Müller