New Aspects of the Contribution of ER to SOCE Regulation: The Role of the ER and ER-Plasma Membrane Junctions in the Regulation of SOCE

The junctions between the endoplasmic reticulum and the plasma membrane are essential platforms for the activation of store-operated Ca²⁺ influx. These junctions have specific dimensions and are nonuniformly distributed in polarized cells. The mechanisms involved in the formation of the junctions are currently undergoing vigorous investigation, and significant progress was attained in this research area during the last 10 years. Some cell types display stationary junctions, while in other cells, new junctions can form rapidly following cytosolic Ca²⁺ signals and/or the reduction of the Ca²⁺ concentration in the lumen of the endoplasmic reticulum; furthermore, in moving cells, junctions can undergo saltatory formation, long distance sliding, and dissolution. The proteins involved in the activation of the Ca²⁺ influx could be also involved in the formation of the junctions. The architecture, dynamics, and localization of the junctions are important for the regulation of Ca²⁺ signaling cascades and their downstream events.