The role of calmodulin for inositol 1,4,5-trisphosphate receptor function.
Intracellular calcium release is a fundamental signaling mechanism in all eukaryotic cells. The ryanodine receptor (RyR) and inositol 1,4,5-trisphosphate receptor (IP(3)R) are intracellular calcium release channels. Both channels can be regulated by calcium and calmodulin (CaM). In this review we will first discuss the role of calcium as an activator and inactivator of the IP(3)R, concluding that calcium is the most important regulator of the IP(3)R. In the second part we will further focus on the role of CaM as modulator of the IP(3)R, using results of the voltage-dependent Ca(2+) channels and the RyR as reference material. Here we conclude that despite the fact that different CaM-binding sites have been characterized, their function for the IP(3)R remains elusive. In the third part we will discuss the possible functional role of CaM in IP(3)-induced Ca(2+) release (IICR) by direct and indirect mechanisms. Special attention will be given to the Ca(2+)-binding proteins (CaBPs) that were shown to activate the IP(3)R in the absence of IP(3).
Nadif Kasri
Nael
N
Laboratorium voor Fysiologie, K.U.Leuven Campus Gasthuisberg O/N, Herestraat 49, B-3000, Leuven, Belgium.
Bultynck
Geert
G
Sienaert
Ilse
I
Callewaert
Geert
G
Erneux
Christophe
C
Missiaen
Ludwig
L
Parys
Jan B
JB
De Smedt
Humbert
H
D000818:Animals; D001665:Binding Sites; D019703:Calcineurin / Q000502:physiology; D002118:Calcium / Q000378:metabolism*; D015220:Calcium Channels / Q000378:metabolism; D020013:Calcium Signaling; D002135:Calcium-Binding Proteins / Q000502:physiology; D054732:Calcium-Calmodulin-Dependent Protein Kinase Type 2; D017871:Calcium-Calmodulin-Dependent Protein Kinases / Q000502:physiology; D002147:Calmodulin / Q000502:physiology*; D015544:Inositol 1,4,5-Trisphosphate / Q000737:chemistry / Q000502:physiology*; D000072181:Inositol Polyphosphate 5-Phosphatases; D010744:Phosphoric Monoester Hydrolases / Q000378:metabolism; D017853:Phosphotransferases (Alcohol Group Acceptor) / Q000378:metabolism; D017434:Protein Structure, Tertiary; D019837:Ryanodine Receptor Calcium Release Channel / Q000737:chemistry / Q000378:metabolism
D015220:Calcium Channels; D002135:Calcium-Binding Proteins; D002147:Calmodulin; D019837:Ryanodine Receptor Calcium Release Channel; D015544:Inositol 1,4,5-Trisphosphate; D017853:Phosphotransferases (Alcohol Group Acceptor); C051038:Inositol 1,4,5-trisphosphate 3-kinase; D054732:Calcium-Calmodulin-Dependent Protein Kinase Type 2; D017871:Calcium-Calmodulin-Dependent Protein Kinases; D019703:Calcineurin; D010744:Phosphoric Monoester Hydrolases; D000072181:Inositol Polyphosphate 5-Phosphatases; D002118:Calcium