Cell volume changes regulate slick (Slo2.1), but not slack (Slo2.2) K+ channels

Area of Science:

• Neuroscience
• Cell Biology
• Ion Channel Physiology

Background:

• Slick (Slo2.1) and Slack (Slo2.2) are widely distributed high-conductance K+ channels in the CNS.
• Both channels are activated by Na+ and Cl-, with Slick channels also regulated by ATP.
• Their roles in cell excitability and ion transport, including cell volume regulation, are hypothesized.

Purpose of the Study:

• To investigate the sensitivity of Slick and Slack channels to small, rapid changes in cell volume.
• To explore the underlying mechanisms responsible for this volume sensitivity.

Main Methods:

• Co-expression of Slick and Slack channels with aquaporin 1 in Xenopus laevis oocytes.
• Induction of ~5% cell volume changes using hypotonic or hypertonic media.
• Measurement of whole-cell currents using two-electrode voltage clamp.

Main Results:

• Slick channels showed significant stimulation (196%) with cell swelling and inhibition (57%) with cell shrinkage.
• Slack channels exhibited complete insensitivity to similar cell volume fluctuations.
• The volume sensitivity of Slick channels was independent of the actin cytoskeleton, ATP release, or vesicle fusion.

Conclusions:

• Slick channels are strongly sensitive to small cell volume changes, unlike Slack channels.
• Slick channels are identified as the sole high-conductance K+ channels significantly responsive to cell volume fluctuations.
• Further research is needed to fully elucidate the mechanisms behind Slick channel volume sensitivity.