SK2 channels regulate mitochondrial respiration and mitochondrial Ca²⁺ uptake

Area of Science:

• Neuroscience
• Mitochondrial Biology
• Ion Channel Function

Background:

• Mitochondrial calcium overload and altered metabolism contribute to neuronal death.
• Small conductance calcium-activated potassium (SK) channels are known neuroprotective agents.
• The precise role of inner mitochondrial membrane-localized SK channels in neuroprotection is not fully understood.

Purpose of the Study:

• To elucidate the neuroprotective mechanism of mitochondrial SK channels.
• To investigate the impact of SK channel activation on mitochondrial calcium ([Ca2+]m) uptake and respiration.
• To determine the role of mitochondrial SK2 channels in neuronal resilience against cell death.

Main Methods:

• Mitochondrial calcium levels were measured using time-lapse aequorin and FRET-based probes.
• High-resolution respirometry assessed mitochondrial respiration and complex I activity.
• Pharmacological activation and genetic manipulation (overexpression) of mitochondrial SK2 channels were employed.

Main Results:

• SK channel activation attenuated mitochondrial calcium ([Ca2+]m) uptake.
• Pharmacological activation and overexpression of mitochondrial SK2 channels reduced mitochondrial respiration and complex I activity.
• Reduced mitochondrial reactive oxygen species (ROS) formation was observed.
• Overexpression of mitochondria-targeted SK2 channels conferred enhanced mitochondrial resilience against neuronal death, an effect blocked by a dominant-negative SK2 channel.

Conclusions:

• Mitochondrial SK channels, particularly SK2, offer neuroprotection by decreasing mitochondrial calcium ([Ca2+]m) uptake.
• SK channel activation reduces mitochondrial respiration and complex I activity, leading to decreased ROS production.
• This pathway is crucial for enhancing mitochondrial resilience and preventing neuronal death in conditions of sustained mitochondrial damage.