Fig. 5.

Proposed model for ECCE. (a) Resting state. (b) Activated state. α_1Sdhpr initially senses plasma membrane depolarization (ΔE_M), which triggers concurrent signals to RyR1 and possibly SOCC. The signal to RyR1 induces a conformational change (represented by changing from a trapezoid in the resting state to a pentagon in the activated state) such that RyR1 engages SOCC to activate [Ca²⁺]_o influx (gray arrow) into the cytoplasm. The Ca²⁺ is then resequestered into the SR lumen to replenish the Ca²⁺ released from the SR by means of RyR1 (black arrow) during EC coupling. (c) Depleted state showing the activation of conventional SOCE.