Forms a voltage-independent potassium channel activated by intracellular calcium (PubMed:10991935, PubMed:9287325). Activation is followed by membrane hyperpolarization. Thought to regulate neuronal excitability by contributing to the slow component of synaptic afterhyperpolarization. Inhibited by bee venom neurotoxin apamin (PubMed:10991935, PubMed:9287325). Inhibited by UCL 1684 and tetraethylammonium (TEA) (By similarity). Heterooligomer. The complex is composed of 4 channel subunits each of which binds to a calmodulin subunit which regulates the channel activity through calcium-binding (By similarity). Expressed in atrial myocytes (at protein level). Widely expressed. Belongs to the potassium channel KCNN family. KCa2.2/KCNN2 subfamily.