Small-conductance calcium-activated potassium channel family (KCa2)

The KCa2 family, also known as small-conductance calcium-activated potassium (SK) channels, comprises three subtypes: KCa2.1, KCa2.2, and KCa2.3 [1, 6]. These channels are voltage-independent and are activated by increases in intracellular calcium, mediated through their constitutive association with calmodulin [1, 3]. In the central nervous system, they are critical for regulating neuronal excitability and synaptic plasticity by contributing to the medium afterhyperpolarization that follows action potentials [1, 9]. Beyond neurons, KCa2 channels are expressed in the heart, where they play a role in atrial repolarization, and in the vascular endothelium, where they contribute to vasodilation [6, 10]. Dysregulation of KCa2 channels is linked to several pathologies, including atrial fibrillation, ataxia, and neurodegenerative disorders like Alzheimer's and Parkinson's disease [2, 8, 9]. Pharmacological strategies involve the use of activators to reduce hyperexcitability in conditions like ataxia or inhibitors to treat cardiac arrhythmias [2, 8]. Current drug development efforts are focused on identifying subtype-selective modulators to minimize off-target effects in the heart or brain [1, 8]. Notable compounds include the activator chlorzoxazone and the clinical-stage inhibitor AP30663 [5, 8].

Other names

SK channelsSmall-conductance calcium-activated potassium channelsKCNN familySK1-3KCa2.x

Positive or negative allosteric modulation of calcium sensitivity via the calmodulin-binding domain, or direct blockade of the ion-conducting pore [1, 8, 12].