Functional and morphological features of skeletal muscle from mutant mice lacking both type 1 and type 3 ryanodine receptors.
1. We generated mice with targeted disruptions in the genes for both ryanodine receptor type 1 (RyR-1) and type 3 (RyR-3) to study the functional roles of RyR subtypes in skeletal muscle. 2. In permeabilized myocytes lacking both the RyRs, the Ca(2+)-induced Ca2+ release (CICR) mechanism was completely lost, and caffeine failed to induce Ca2+ release. 3. Replacement of potassium methanesulphonate in an experimental intracellular solution with choline chloride resulted in Ca2+ release in the wild-type muscle but not in the mutant muscle lacking RyR-1. 4. The double-mutant mice exhibited more severe muscular degeneration than RyR-1-deficient mice with formation of large vacuoles and swollen mitochondria while structural coupling between T-tubules and the sarcoplasmic reticulum was retained. 5. These results demonstrate that CICR is mediated solely by RyR-1 and RyR-3 in skeletal muscle cells, and suggest that RyR-1 is involved in Cl(-)-induced Ca2+ release. The results also suggest the presence of molecular components other than RyRs responsible for the triad formation. RyR-3 may have a role in the normal morphogenesis of skeletal muscle cells, although functionally it can be replaced by RyR-1.
Ikemoto
T
T
Department of Pharmacology, Saitama Medical School, Japan.
Komazaki
S
S
Takeshima
H
H
Nishi
M
M
Noda
T
T
Iino
M
M
Endo
M
M
D000818:Animals; D002118:Calcium / Q000378:metabolism; D015220:Calcium Channels / Q000172:deficiency* / Q000235:genetics*; D002148:Calmodulin-Binding Proteins / Q000172:deficiency* / Q000235:genetics*; D002712:Chlorides / Q000378:metabolism; D066298:In Vitro Techniques; D051379:Mice; D008818:Mice, Neurologic Mutants; D008854:Microscopy, Electron; D008870:Microtubules / Q000378:metabolism / Q000648:ultrastructure; D018485:Muscle Fibers, Skeletal / Q000378:metabolism / Q000648:ultrastructure; D009124:Muscle Proteins / Q000172:deficiency* / Q000235:genetics*; D018482:Muscle, Skeletal / Q000033:anatomy & histology / Q000502:physiology* / Q000648:ultrastructure; D009154:Mutation / Q000502:physiology*; D019837:Ryanodine Receptor Calcium Release Channel
D015220:Calcium Channels; D002148:Calmodulin-Binding Proteins; D002712:Chlorides; D009124:Muscle Proteins; D019837:Ryanodine Receptor Calcium Release Channel; D002118:Calcium