Elementary Ca 2+ Signals Through Endothelial TRPV4 Channels Regulate Vascular Function

Blood Pressure Gauge Endothelial cells line blood vessels and, by interacting with smooth muscle, can help to control blood flow. Sonkusare et al. (p. 597 ; see the Perspective by Lederer et al. ) describe how signaling in endothelial cells controls contraction of surrounding smooth muscle cells, which provides an important mechanism for control of blood pressure. A calcium-sensitive fluorescent protein was expressed in endothelial cells of mouse arteries to image small changes in calcium concentration that appear to represent opening of single TRPV4 ion channels and consequent influx of calcium into the cell. Clustering of the channels allowed cooperative activation of a handful of channels, which appeared to produce a sufficient calcium signal to open another set of calcium-sensitive potassium channels. The resulting depolarization of the endothelial cells then passes an electrical connection to smooth muscle cells through gap junctions.