Inositol 1,4,5-trisphosphate receptor in skeletal muscle: differential expression in myofibres.
The role of inositol 1,4,5-trisphosphate as a second messenger in signal transduction has been well established in many cell types. However, conflicting reports have led to a controversy regarding the role, if any, of inositol 1,4,5-trisphosphate signalling in skeletal muscle. Indeed, expression of the inositol 1,4,5-trisphosphate receptor has not previously been demonstrated in skeletal muscle. In the present study we used in situ hybridization, immunohistochemistry, and [3H]-inositol 1,4,5-trisphosphate binding to demonstrate that rat skeletal muscle fibres contain inositol 1,4,5-trisphosphate receptors. RNAse protection and partial sequencing suggested that the inositol 1,4,5-trisphosphate receptors expressed in skeletal muscle was most similar to the non-neuronal form of the type 1 inositol 1,4,5-trisphosphate receptor. While in situ hybridization showed inositol 1,4,5-trisphosphate receptor mRNA in all types of skeletal myofibres, immunodetectable inositol 1,4,5-trisphosphate receptor protein and specific [3H]-inositol 1,4,5-trisphosphate binding sites were preferentially expressed in slow oxidative (type I) and fast oxidative-glycolytic (type IIA) fibres, but not in fast glycolytic (type IIB) fibres. These findings indicate that an inositol 1,4,5-trisphosphate receptor is preferentially expressed in oxidative fibres of skeletal muscle.
D000818:Animals; D001665:Binding Sites; D015220:Calcium Channels / Q000235:genetics*; D017403:In Situ Hybridization; D015544:Inositol 1,4,5-Trisphosphate / Q000378:metabolism; D053496:Inositol 1,4,5-Trisphosphate Receptors; D018656:Muscle Fibers, Fast-Twitch / Q000502:physiology; D018657:Muscle Fibers, Slow-Twitch / Q000502:physiology*; D018482:Muscle, Skeletal / Q000166:cytology / Q000502:physiology* / Q000648:ultrastructure; D012333:RNA, Messenger / Q000032:analysis; D051381:Rats; D017207:Rats, Sprague-Dawley; D018160:Receptors, Cytoplasmic and Nuclear / Q000235:genetics*; D015398:Signal Transduction / Q000502:physiology; D014316:Tritium
D015220:Calcium Channels; D053496:Inositol 1,4,5-Trisphosphate Receptors; D012333:RNA, Messenger; D018160:Receptors, Cytoplasmic and Nuclear; D014316:Tritium; D015544:Inositol 1,4,5-Trisphosphate