KCNQ channels belong to a family of potassium ion channels with crucial roles in physiology and disease. Heteromers of KCNQ2/3 subunits constitute the neuronal M channels. Inhibition of M currents, by pathways that stimulate phospholipase C activity, controls excitability throughout the nervous system. Here we show that a common feature of all KCNQ channels is their activation by the signaling membrane phospholipid phosphatidylinositol-bis-phosphate (PIP(2)). We show that wortmannin, at concentrations that prevent recovery from receptor-mediated inhibition of M currents, blocks PIP(2) replenishment to the cell surface. Moreover, we identify a C-terminal histidine residue, immediately proximal to the plasma membrane, mutation of which renders M channels less sensitive to PIP(2) and more sensitive to receptor-mediated inhibition. Finally, native or recombinant channels inhibited by muscarinic agonists can be activated by PIP(2). Our data strongly suggest that PIP(2) acts as a membrane-diffusible second messenger to regulate directly the activity of KCNQ currents.

Inwardly rectifying K(+) (Kir) channels are important regulators of resting membrane potential and cell excitability. The activity of Kir channels is critically dependent on the integrity of channel interactions with phosphatidylinositol 4,5-bisphosphate (PIP(2)). Here we identify and characterize channel-PIP(2) interactions that are conserved among Kir family members. We find basic residues that interact with PIP(2), two of which have been associated with Andersen's and Bartter's syndromes. We show that several naturally occurring mutants decrease channel-PIP(2) interactions, leading to disease.

We report that ANO1 (also known as TMEM16A) Ca 2+ -activated Cl − channels in small neurons from dorsal root ganglia are preferentially activated by particular pools of intracellular Ca 2+ . These ANO1 channels can be selectively activated by the G protein-coupled receptor (GPCR)-induced release of Ca 2+ from intracellular stores, but not by Ca 2+ influx through voltage-gated Ca 2+ channels. This ability to discriminate between Ca 2+ pools was achieved by the tethering of ANO1-containing plasma membrane domains, which also contained GPCRs such as bradykinin receptor-2 and protease-activated receptor-2, to juxtamembrane regions of the endoplasmic reticulum. Interaction of the C-terminus and the first intracellular loop of ANO1 with IP 3 R1 (inositol 1,4,5-trisphosphate receptor 1) contributed to the tethering. Disruption of membrane microdomains blocked the ANO1 and IP 3 R1 interaction and resulted in the loss of coupling between GPCR signaling and ANO1. The junctional signaling complex enabled ANO1-mediated excitation in response to specific Ca 2+ signals rather than to global changes in intracellular Ca 2+ .

The activity of specific inwardly rectifying potassium (Kir) channels is regulated by any of a number of different modulators, such as protein kinase C, G q -coupled receptor stimulation, pH, intracellular Mg 2؉ or the ␤␥-subunits of G proteins. Phosphatidylinositol 4,5-bisphosphate (PIP 2 ) is an essential factor for maintenance of the activity of all Kir channels. Here, we demonstrate that the strength of channel-PIP 2 interactions determines the sensitivity of Kir channels to regulation by the various modulators. Furthermore, our results suggest that differences among Kir channels in their specific regulation by a given modulator may reflect differences in their apparent affinity of interactions with PIP 2 .