PUBLICATION
The {beta}1a subunit is essential for the assembly of dihydropyridine-receptor arrays in skeletal muscle
- Authors
- Schredelseker, J., Di Biase, V., Obermair, G.J., Felder, E.T., Flucher, B.E., Franzini-Armstrong, C., and Grabner, M.
- ID
- ZDB-PUB-051116-6
- Date
- 2005
- Source
- Proceedings of the National Academy of Sciences of the United States of America 102(47): 17219-17224 (Journal)
- Registered Authors
- Grabner, Manfred, Schredelseker, Johann
- Keywords
- calcium channels, excitation-contraction coupling, tetrads, zebrafish
- MeSH Terms
-
- Animals
- Calcium Channels, L-Type/deficiency
- Calcium Channels, L-Type/genetics
- Calcium Channels, L-Type/physiology*
- Genotype
- Molecular Sequence Data
- Muscle, Skeletal/chemistry
- Muscle, Skeletal/metabolism*
- Phenotype
- Protein Processing, Post-Translational/genetics
- Protein Structure, Quaternary
- Protein Subunits/deficiency
- Protein Subunits/genetics
- Protein Subunits/physiology*
- Ryanodine Receptor Calcium Release Channel/metabolism
- Ryanodine Receptor Calcium Release Channel/physiology
- Zebrafish*
- PubMed
- 16286639 Full text @ Proc. Natl. Acad. Sci. USA
Citation
Schredelseker, J., Di Biase, V., Obermair, G.J., Felder, E.T., Flucher, B.E., Franzini-Armstrong, C., and Grabner, M. (2005) The {beta}1a subunit is essential for the assembly of dihydropyridine-receptor arrays in skeletal muscle. Proceedings of the National Academy of Sciences of the United States of America. 102(47):17219-17224.
Abstract
Homozygous zebrafish of the mutant relaxed (red(ts25)) are paralyzed and die within days after hatching. A significant reduction of intramembrane charge movements and the lack of depolarization-induced but not caffeine-induced Ca(2+) transients suggested a defect in the skeletal muscle dihydropyridine receptor (DHPR). Sequencing of DHPR cDNAs indicated that the alpha1S subunit is normal, whereas the beta1a subunit harbors a single point mutation resulting in a premature stop. Quantitative RT-PCR revealed that the mutated gene is transcribed, but Western blot analysis and immunocytochemistry demonstrated the complete loss of the beta1a protein in mutant muscle. Thus, the immotile zebrafish relaxed is a beta1a-null mutant. Interestingly, immunocytochemistry showed correct triad targeting of the alpha1S subunit in the absence of beta1a. Freeze-fracture analysis of the DHPR clusters in relaxed myotubes revealed an approximately 2-fold reduction in cluster size with a normal density of DHPR particles within the clusters. Most importantly, DHPR particles in the junctional membranes of the immotile zebrafish mutant relaxed entirely lacked the normal arrangement in arrays of tetrads. Thus, our data indicate that the lack of the beta1a subunit does not prevent triad targeting of the DHPR alpha1S subunit but precludes the skeletal muscle-specific arrangement of DHPR particles opposite the ryanodine receptor (RyR1). This defect properly explains the complete deficiency of skeletal muscle excitation-contraction coupling in beta1-null model organisms.
Genes / Markers
Expression
Phenotype
Mutations / Transgenics
Human Disease / Model
Sequence Targeting Reagents
Fish
Orthology
Engineered Foreign Genes
Mapping