KCNQ potassium channels: physiology, pathophysiology, and pharmacology.

KCNQ genes encode a growing family of six transmembrane domains, single pore-loop, K(+) channel alpha-subunits that have a wide range of physiological correlates. KCNQ1 (KvLTQ1) is co-assembled with the product of the KCNE1 (minimal K(+)-channel protein) gene in the heart to form a cardiac-delayed rectifier-like K(+) current. Mutations in this channel can cause one form of inherited long QT syndrome (LQT1), as well as being associated with a form of deafness. KCNQ1 can also co-assemble with KCNE3, and may be the molecular correlate of the cyclic AMP-regulated K(+) current present in colonic crypt cells. KCNQ2 and KCNQ3 heteromultimers are thought to underlie the M-current; mutations in these genes may cause an inherited form of juvenile epilepsy. The KCNQ4 gene is thought to encode the molecular correlate of the I(K,n) in outer hair cells of the cochlea and I(K,L) in Type I hair cells of the vestibular apparatus, mutations in which lead to a form of inherited deafness. The recently identified KCNQ5 gene is expressed in brain and skeletal muscle, and can co-assemble with KCNQ3, suggesting it may also play a role in the M-current heterogeneity. This review will set this family of K(+) channels amongst the other known families. It will highlight the genes, physiology, pharmacology, and pathophysiology of this recently discovered, but important, family of K(+) channels.