Cardiac type 2 inositol 1,4,5-trisphosphate receptor: interaction and modulation by calcium/calmodulin-dependent protein kinase II.
The type 2 inositol 1,4,5-trisphosphate receptor (InsP(3)R2) was identified previously as the predominant isoform in cardiac ventricular myocytes. Here we reported the subcellular localization of InsP(3)R2 to the cardiomyocyte nuclear envelope (NE). The other major known endo/sarcoplasmic reticulum calcium-release channel (ryanodine receptor) was not localized to the NE, indicating functional segregation of these channels and possibly a unique role for InsP(3)R2 in regulating nuclear calcium dynamics. Immunoprecipitation experiments revealed that the NE InsP(3)R2 associates with Ca(2+)/calmodulin-dependent protein kinase IIdelta (CaMKIIdelta), the major isoform expressed in cardiac myocytes. Recombinant InsP(3)R2 and CaMKIIdelta(B) also co-immunoprecipitated after co-expression in COS-1 cells. Additionally, the amino-terminal 1078 amino acids of the InsP(3)R2 were sufficient for interaction with CaMKIIdelta(B) and associated upon mixing following separate expression. CaMKII can also phosphorylate InsP(3)R2, as demonstrated by (32)P labeling. Incorporation of CaMKII-treated InsP(3)R2 into planar lipid bilayers revealed that InsP(3)-mediated channel open probability is significantly reduced ( approximately 11 times) by phosphorylation via CaMKII. We concluded that the InsP(3)R2 and CaMKIIdelta likely represent two central components of a multiprotein signaling complex, and this raises the possibility that calcium release via InsP(3)R2 in the myocyte NE may activate local CaMKII signaling, which may feedback on InsP(3)R2 function.
Bare
Dan J
DJ
Department of Physiology and Cardiovascular Institute, Loyola University Chicago, Maywood, Illinois 60153, USA.
Kettlun
Claudia S
CS
Liang
Mei
M
Bers
Donald M
DM
Mignery
Gregory A
GA
D000818:Animals; D019556:COS Cells; D015220:Calcium Channels / Q000378:metabolism*; D017871:Calcium-Calmodulin-Dependent Protein Kinases / Q000378:metabolism*; D002522:Chlorocebus aethiops; D005455:Fluorescent Antibody Technique; D006352:Heart Ventricles / Q000378:metabolism; D015151:Immunoblotting; D053496:Inositol 1,4,5-Trisphosphate Receptors; D009206:Myocardium / Q000378:metabolism*; D032383:Myocytes, Cardiac / Q000378:metabolism; D009685:Nuclear Envelope / Q000378:metabolism; D051381:Rats; D018160:Receptors, Cytoplasmic and Nuclear / Q000378:metabolism*
D015220:Calcium Channels; D053496:Inositol 1,4,5-Trisphosphate Receptors; D018160:Receptors, Cytoplasmic and Nuclear; D017871:Calcium-Calmodulin-Dependent Protein Kinases