Methods for studying store-operated calcium entry

Activation of surface membrane receptors coupled to phospholipase C results in the generation of cytoplasmic Ca²⁺ signals comprised of both intracellular Ca²⁺ release, and enhanced entry of Ca²⁺ across the plasma membrane. A primary mechanism for this Ca²⁺ entry process is attributed to store-operated Ca²⁺ entry, a process that is activated by depletion of Ca²⁺ ions from an intracellular store by inositol 1,4,5-trisphosphate. Our understanding of the mechanisms underlying both Ca²⁺ release and store-operated Ca²⁺ entry have evolved from experimental approaches that include the use of fluorescent Ca²⁺ indicators and electrophysiological techniques. Pharmacological manipulation of this Ca²⁺ signaling process has been somewhat limited; but recent identification of key molecular players, STIM and Orai family proteins, has provided new approaches. Here we describe practical methods involving fluorescent Ca²⁺ indicators and electrophysiological approaches for dissecting the observed intracellular Ca²⁺ signal to reveal characteristics of store-operated Ca²⁺ entry, highlighting the advantages, and limitations, of these approaches.