Changing calcium: CRAC channel (STIM and Orai) expression, splicing, and posttranslational modifiers

Abstract

A wide variety of cellular function depends on the dynamics of intracellular Ca2+ signals. Especially for relatively slow and lasting processes such as gene expression, cell proliferation, and often migration, cells rely on the store-operated Ca2+ entry (SOCE) pathway, which is particularly prominent in immune cells. SOCE is initiated by the sensor proteins (STIM1, STIM2) located within the endoplasmic reticulum (ER) registering the Ca2+ concentration within the ER, and upon its depletion, cluster and trap Orai (Orai1-3) proteins located in the plasma membrane (PM) into ER-PM junctions. These regions become sites of highly selective Ca2+ entry predominantly through Orai1-assembled channels, which, among other effector functions, is necessary for triggering NFAT translocation into the nucleus. What is less clear is how the spatial and temporal spread of intracellular Ca2+ is shaped and regulated by differential expression of the individual SOCE genes and their splice variants, their heteromeric combinations and pre- and posttranslational modifications. This review focuses on principle mechanisms regulating expression, splicing, and targeting of Ca2+ release- activated Ca2+ (CRAC) channels.