On the endothelial cell ISOC

Ca2+ store depletion activates both Ca2+ selective and non-selective currents in endothelial cells. Recently, considerable progress has been made in understanding the molecular make-up and regulation of an endothelial cell thapsigargin-activated Ca2+ selective current, I-SOC. Indeed, I-SOC is a relatively small inward Ca2+ current that exhibits an approximate +40 mV reversal potential and is strongly inwardly rectifying. This current is sensitive to organization of the actin-based cytoskeleton. Transient receptor potential (TRP) proteins 1 and 4 (TRPC1 and TRPC4, respectively) each contribute to the molecular basis of I-SOC, although it is TRPC4 that appears to be tethered to the cytoskeleton through a dynamic interaction with protein 4.1. Activation of I-SOC requires association between protein 4.1 and the actin-based cytoskeleton (mediated through spectrin), suggesting protein 4.1 mediates the physical communication between Ca2+ store depletion and channel activation. Thus, at present findings indicate a TRPC4-protein 4.1 physical linkage regulates I-SOC activation following Ca2+ store depletion. (C) 2003 Published by Elsevier Science Ltd.