title: TRPC3-interacting triadic proteins in skeletal muscle.
abstract: The expression of TRPC3 (canonical-type transient receptor potential cation channel type 3) is tightly regulated during skeletal muscle cell differentiation, and a functional interaction between TRPC3 and RyR1 [(ryanodine receptor type 1), an SR (sarcoplasmic reticulum) Ca2+-release channel] regulates the gain of SR Ca2+ release during EC (excitation-contraction) coupling. However, it has not been possible to demonstrate direct protein-protein interactions between TRPC3 and RyR1. To identify possible candidate(s) for a linker protein(s) between TRPC3 and RyR1 in skeletal muscle, in the present study we performed MALDI-TOF (matrix-assisted laser-desorption ionization-time-of-flight) MS analysis of a cross-linked triadic protein complex from rabbit skeletal triad vesicles and co-immunoprecipitation assays using primary mouse skeletal myotubes. From these studies, we found that six triadic proteins, that are known to regulate RyR1 function and/or EC coupling [TRPC1, JP2 (junctophilin 2), homer, mitsugumin 29, calreticulin and calmodulin], interacted directly with TRPC3 in a Ca2+-independent manner. However we again found no direct interaction between TRPC3 and RyR1. TRPC1 was identified as a potential physical link between TRPC3 and RyR1, as it interacted with both TRPC3 and RyR1, and JPs showed subtype-specific interactions with both RyR1 and TRPC3 (JP1-RyR1 and JP2-TRPC3). These results support the hypothesis that TRPC3 and RyR1 are functionally engaged via linker proteins in skeletal muscle.
authors.affiliation: Department of Physiology, College of Medicine, The Catholic University of Korea, Seoul 137-701, Korea.
authors.forename: Jin Seok
authors.initials: JS
authors.lastname: Woo
authors.forename: Do Han
authors.initials: DH
authors.lastname: Kim
authors.forename: Paul D
authors.initials: PD
authors.lastname: Allen
authors.forename: Eun Hui
authors.initials: EH
authors.lastname: Lee
mesh_terms: D000818:Animals; D002454:Cell Differentiation; D002478:Cells, Cultured; D003432:Cross-Linking Reagents / Q000737:chemistry; D051379:Mice; D018345:Mice, Knockout; D015394:Molecular Structure; D018482:Muscle, Skeletal / Q000166:cytology / Q000378:metabolism*; D032446:Myoblasts / Q000166:cytology / Q000378:metabolism; D011485:Protein Binding; D019837:Ryanodine Receptor Calcium Release Channel / Q000172:deficiency / Q000235:genetics / Q000378:metabolism*; D050052:TRPC Cation Channels / Q000235:genetics / Q000378:metabolism*
chemical_list: D003432:Cross-Linking Reagents; D019837:Ryanodine Receptor Calcium Release Channel; D050052:TRPC Cation Channels; C104603:TRPC3 cation channel; C096351:transient receptor potential cation channel, subfamily C, member 1