Fig. 3.

Model of STIM1 function

Upon store depletion, STIM1 located in the ER unbinds Ca²⁺ and translocates to the plasma membrane to activate CRAC channel subunits that are already in the plasma membrane (left), form junctions between the Ca²⁺ store and the plasma membrane (middle) or assemble to form functional CRAC channels (right) (Zhang et al., 2005)