Association of the inositol (1,4,5)-trisphosphate receptor ligand binding site with phosphatidylinositol (4,5)-bisphosphate and adenophostin A.
The inositol 1,4,5-trisphosphate receptor (InsP(3)R) is activated by InsP(3) binding to amino-terminal ligand binding domain (InsP(3)R-N). Recently we reported functional coupling of phosphatidylinositol (4, 5)-bisphosphate (PIP(2)) to the InsP(3)R. Specific binding of PIP(2) to InsP(3)R-N domain was postulated as a part of the InsP(3)R-PIP(2) functional coupling model. Here we utilized bacterially expressed and purified InsP(3)R-N domain to characterize its binding specificity for InsP(3), Adenophostin A (AdA) and the water-soluble PIP(2) analog dioctanoyl-(4,5)PIP(2) (ShPIP(2)). Obtained data led us to conclude that specific InsP(3), AdA, and ShPIP(2) binding sites are located within the InsP(3)R-N domain, that the extra receptor binding element responsible for enhanced binding of AdA is an integral part of the InsP(3)R-N domain, that ShPIP(2) is able to displace InsP(3) from the InsP(3)R-N, but InsP(3) or AdA is unable to completely displace ShPIP(2). These results support the InsP(3)R-PIP(2) functional coupling model and provide novel insights into InsP(3)R ligand specificity.
Glouchankova
L
L
Department of Physiology, University of Texas Southwestern Medical Center at Dallas, Dallas, Texas, 75235, USA.
Krishna
U M
UM
Potter
B V
BV
Falck
J R
JR
Bezprozvanny
I
I
D000241:Adenosine / Q000031:analogs & derivatives* / Q000378:metabolism; D000818:Animals; D001665:Binding Sites; D015220:Calcium Channels / Q000378:metabolism*; D053496:Inositol 1,4,5-Trisphosphate Receptors; D008024:Ligands; D019269:Phosphatidylinositol 4,5-Diphosphate / Q000378:metabolism*; D051381:Rats; D018160:Receptors, Cytoplasmic and Nuclear / Q000378:metabolism*; D011994:Recombinant Proteins / Q000378:metabolism
D015220:Calcium Channels; D053496:Inositol 1,4,5-Trisphosphate Receptors; D008024:Ligands; D019269:Phosphatidylinositol 4,5-Diphosphate; D018160:Receptors, Cytoplasmic and Nuclear; D011994:Recombinant Proteins; C085029:adenophostin A; D000241:Adenosine