Vasoregulation by the beta 1 subunit of the calcium-activated potassium channel

Small arteries exhibit tone, a partially contracted state that is an import ant determinant of blood pressure. In arterial smooth muscle cells, intrace llular calcium paradoxically controls both contraction and relaxation. The mechanisms by which calcium can differentially regulate diverse physiologic al responses within a single cell remain unresolved. Calcium-dependent rela xation is mediated by local calcium release from the sarcoplasmic reticulum . These 'calcium sparks' activate calcium-dependent potassium (BK) channels comprised of alpha and beta 1 subunits. Here we show that targeted deletio n of the gene for the beta 1 subunit leads to a decrease in the calcium sen sitivity of BK channels, a reduction in functional coupling of calcium spar ks to BK channel activation, and increases in arterial tone and blood press ure. The beta 1 subunit of the BK channel, by tuning the channel's calcium sensitivity, is a key molecular component in translating calcium signals to the central physiological function of vasoregulation.