CALCIUM-ACTIVATED K+ CHANNELS - METABOLIC-REGULATION

Calcium-activated potassium (K(Ca)) channels are highly modulated by a large spectrum of metabolites. Neurotransmitters, hormones, lipids, and nucleotides are capable of activating and/or inhibiting K(Ca) channels. Studies from the last few years have shown that metabolites modulate the activity of K(Ca) channels via: (1) a change in the affinity of the channel for Ca2+ (K1/2 is modified), (2) a parallel shift in the voltage axis of the activation curves, or (3) a change in the slope (effective valence) of the voltage dependence curve. The shift of the voltage dependence curve can be a direct consequence of the change in the affinity for Ca2+. Recently, the mechanistic steps involved in the modulation of K(Ca) channels are being uncovered. Some interactions may be direct on K(Ca) channels and others may be mediated via G-proteins, second messengers, or phosphorylation. The information given in this review highlights the possibility that K(Ca) channels can be activated or inhibited by metabolites without a change in the intracellular Ca2+ concentration.