A junctophilin-caveolin interaction enables efficient coupling between ryanodine receptors and BK channels in the Ca microdomain of vascular smooth muscle.

Functional coupling between large-conductance Ca-activated K (BK) channels in the plasma membrane (PM) and ryanodine receptors (RyRs) in the sarcoplasmic reticulum (SR) is an essential mechanism for regulating mechanical force in most smooth muscle (SM) tissues. Spontaneous Ca release through RyRs (Ca sparks) and subsequent BK channel activation occur within the PM-SR junctional sites. We report here that a molecular interaction of caveolin-1 (Cav1), a caveola-forming protein, with junctophilin-2 (JP2), a bridging protein between PM and SR, positions BK channels near RyRs in SM cells (SMCs) and thereby contributes to the formation of a molecular complex essential for Ca microdomain function.

Conversion of Ca oscillation into propagative electrical signals by Ca-activated ion channels and connexin as a reconstituted Ca clock model for the pacemaker activity.

Conversion of intracellular Ca signals to electrical activity results in multiple and differing physiological impacts depending on cell types. In some organs such as gastrointestinal and urinary systems, spontaneous Ca oscillation in pacermaker cells can function essentially as a Ca clock mechanism, which has been originally found in pacemaking in sinoatrial node cell of the heart. The conversion of discrete Ca clock events to spontaneous electrical activity is an essential step for the initiation and propagation of pacemaker activity through the multicellular organs resulting in synchronized physiological functions.

The multiple expression of Ca²⁺-activated Cl⁻ channels via homo- and hetero-dimer formation of TMEM16A splicing variants in murine portal vein.

Ca(2+)-activated Cl(-) channel (CaCC) often plays substantial roles in the regulation of membrane excitability in smooth muscle cells (SMCs). TMEM16A, a member of the TMEM16 family, has been suggested as the molecular entity responsible for CaCC in several types of SMCs. In this study, the expression of TMEM16A splicing variants and their contribution to CaCC activity were examined in murine portal vein SMCs (mPVSMCs).