The complex regulatory function of the ligand-binding domain of the inositol 1,4,5-trisphosphate receptor.
The inositol 1,4,5-trisphosphate (IP(3)) receptor (IP(3)R) can be divided in three functionally distinct regions: a ligand-binding domain, a modulatory domain and a channel domain. Numerous regulatory mechanisms including inter- and intra-molecular protein-protein interactions and phosphorylation events act via these domains to regulate the function of the IP(3)R. Regulation at the level of the ligand-binding domain primarily affects the affinity for IP(3). The extent of IP(3)-induced Ca(2+) release (IICR) is, however, not only determined by the affinity for IP(3) but also by the effectiveness of the coupling between ligand binding and channel opening. As a result, regulation as well as malfunction of IICR may be affected by both steps in the activation mechanism. The 3D structures of the two subdomains of the ligand-binding domain have recently been determined by X-ray diffraction analysis. This allows a more detailed molecular explanation of the regulatory events situated at the ligand-binding domain of the IP(3)R. In this review, we will focus on recent structural and functional data on the ligand-binding domain that have extended and clarified the view on the molecular mechanisms of IP(3)R regulation.
Devogelaere
Benoit
B
Laboratory of Molecular and Cellular Signalling, Division of Physiology, Department of Molecular Cell Biology, Katholieke Universiteit Leuven, Leuven, Belgium.
Verbert
Leen
L
Parys
Jan B
JB
Missiaen
Ludwig
L
De Smedt
Humbert
H
D001665:Binding Sites; D002118:Calcium / Q000378:metabolism; D002135:Calcium-Binding Proteins / Q000378:metabolism; D053496:Inositol 1,4,5-Trisphosphate Receptors / Q000737:chemistry* / Q000378:metabolism; D008024:Ligands; D017434:Protein Structure, Tertiary
D002135:Calcium-Binding Proteins; D053496:Inositol 1,4,5-Trisphosphate Receptors; D008024:Ligands; D002118:Calcium