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IP3 receptors – lessons from analyses ex cellula

Accepted version
Peer-reviewed

Type

Article

Change log

Authors

Taylor, CW 
Rossi, Ana 

Abstract

Inositol 1,4,5-trisphosphate receptors (IP3Rs) are widely expressed intracellular channels that release Ca2+ from the endoplasmic reticulum (ER). We review how studies of IP3Rs removed from their intracellular environment (‘ex cellula’), alongside similar analyses of ryanodine receptors, have contributed to understanding IP3R behaviour. Analyses of permeabilized cells demonstrated that the ER is the major intracellular Ca2+ store, and that IP3 stimulates Ca2+ release from it. Radioligand binding confirmed that the 4,5-phosphates of IP3 are essential for activating IP3Rs, and facilitated IP3R purification and cloning, which paved the way to structural analyses. Reconstitution of IP3Rs into lipid bilayers and patch-clamp recording from the nuclear envelope established that IP3Rs have a large conductance and select weakly between Ca2+ and other cations. Structural analyses are now revealing how IP3 binding to the N-terminus of the tetrameric IP3R opens the pore 7nm away from the IP3-binding core (IBC). Communication between the IBC and pore passes through a nexus of interleaved domains contributed by structures associated with the pore and cytosolic domains, which together contribute to a Ca2+-binding site. These structural analyses provide a plausible explanation for the suggestion that IP3 gates IP3Rs by first stimulating Ca2+ binding, which leads to pore opening and Ca2+ release.

Description

Keywords

Bilayer recording, Ca2+ channel, Endoplasmic reticulum, IP3 receptor, Ion channel structure, Nuclear patch-clamp, Permeabilized cell, Radioligand binding, Ryanodine receptor, Animals, Calcium, Calcium Signaling, Endoplasmic Reticulum, Humans, Inositol 1,4,5-Trisphosphate, Inositol 1,4,5-Trisphosphate Receptors, Ryanodine Receptor Calcium Release Channel

Journal Title

Journal of Cell Science

Conference Name

Journal ISSN

1477-9137
1477-9137

Volume Title

132

Publisher

The Company of Biologists Ltd.
Sponsorship
Wellcome Trust (101844/Z/13/Z)
Biotechnology and Biological Sciences Research Council (BB/P005330/1)