Essential control of an endothelial cell I (SOC) by the spectrin membrane skeleton

Mechanism(s) underlying activation of store-operated Ca(2+) entry currents, I (SOC), remain incompletely understood. F-actin configuration is an important determinant of channel function, although the nature of interaction between the cytoskeleton and I (SOC) channels is unknown. We examined whether the spectrin membrane skeleton couples Ca(2+) store depletion to Ca(2+) entry. Thapsigargin activated an endothelial cell I (SOC) (−45 pA at −80 mV) that reversed at +40 mV, was inwardly rectifying when Ca(2+) was the charge carrier, and was inhibited by La(3+) (50 μM). Disruption of the spectrin–protein 4.1 interaction at residues A207-V445 of βSpIIΣ1 decreased the thapsigargin-induced global cytosolic Ca(2+) response by 50% and selectively abolished the endothelial cell I (SOC), without altering activation of a nonselective current through cyclic nucleotide–gated channels. In contrast, disruption of the spectrin–actin interaction at residues A47-K186 of βSpIIΣ1 did not decrease the thapsigargin-induced global cytosolic Ca(2+) response or inhibit I (SOC). Results indicate that the spectrin–protein 4.1 interaction selectively controls I (SOC), indicating that physical coupling between calcium release and calcium entry is reliant upon the spectrin membrane skeleton.