A role for the actin cytoskeleton in the initiation and maintenance of store-mediated calcium entry in human platelets.

Store-mediated Ca(2+) entry (SMCE) is a major pathway for Ca(2+) influx in many cells, yet how depletion of the intracellular Ca(2+) stores leads to the activation of Ca(2+) entry across the plasma membrane is not well understood. Recent work in platelets favors a secretion-like conformational coupling mechanism involving proteins in the plasma membrane (PM) and in the membrane of the Ca(2+) store, located in the endoplasmic reticulum (ER). The activation and maintenance of SMCE in platelets has been shown to depend on remodeling of the actin cytoskeleton, which may be required to allow trafficking of the ER toward the PM to permit coupling to occur and to stabilize this coupling once achieved. The coupling itself has been shown to involve one isoform of the inositol 1,4,5-trisphosphate receptor (IP(3)RII) and the Ca(2+)-permeable channel protein, human Trp1 (hTrp1).