Microdomain organization and the role of second messengers microdomain organization of SOCE signaling

Abstract

Store-operated calcium entry (SOCE) occurs at specialized regions where the endoplasmic reticulum and plasma membranes are closely apposed. Several molecules converge in these junctions to form a complex that spatiotemporally circumscribes SOCE signaling. We have named recently this complex as SOCIC (Store Operated Calcium Influx Complex). There is a growing list of SOCIC members, including the Ca 2+ sensor and channel activator STIM1, the Orai and TRPC1 channels, SOCE regulators as CaM and CRACR2A, and SOCE-regulated proteins as SERCA and adenylyl cyclases. Considering that under physiological conditions Ca 2+ entry is transient, SOCIC should be a dynamic structure that goes through assembly and disassembly cycles depending on cell requirements, and on the depleted state of intracellular Ca 2+ stores. Moreover SOCIC seems to assembly at specialized regions of plasma membrane known as lipid rafts. In this chapter we discuss the evidence supporting the idea that SOCE occurs at microdomains and introduce the SOCIC components known so far. Then we illustrate some ideas on how this complex is assembled and disassembled. Finally we address the evidence of physiological and pathological implications of the microdomain organization of SOCE.