Structural highlights
Disease
[CAC1S_MOUSE] Defects in Cacna1s are the cause of muscular dysgenesis (MDG), a lethal autosomal recessive disorder in which there is total lack of excitation-contraction coupling in homozygotes, and which results in complete skeletal muscle paralysis. A single nucleotide deletion yields a protein with an altered and truncated C-terminus.[1]
Function
[CACB1_MOUSE] The beta subunit of voltage-dependent calcium channels contributes to the function of the calcium channel by increasing peak calcium current, shifting the voltage dependencies of activation and inactivation, modulating G protein inhibition and controlling the alpha-1 subunit membrane targeting. [CAC1S_MOUSE] Voltage-sensitive calcium channels (VSCC) mediate the entry of calcium ions into excitable cells and are also involved in a variety of calcium-dependent processes, including muscle contraction, hormone or neurotransmitter release, gene expression, cell motility, cell division and cell death. The isoform alpha-1S gives rise to L-type calcium currents. Long-lasting (L-type) calcium channels belong to the 'high-voltage activated' (HVA) group. They are blocked by dihydropyridines (DHP), phenylalkylamines, benzothiazepines, and by omega-agatoxin-IIIA (omega-Aga-IIIA). They are however insensitive to omega-conotoxin-GVIA (omega-CTx-GVIA) and omega-agatoxin-IVA (omega-Aga-IVA). Calcium channels containing the alpha-1S subunit play an important role in excitation-contraction coupling in skeletal muscle.
Publication Abstract from PubMed
Excitation-contraction (EC) coupling in skeletal muscle requires a physical interaction between the voltage-gated calcium channel dihydropyridine receptor (DHPR) and the ryanodine receptor Ca2+ release channel. Although the exact molecular mechanism that initiates skeletal EC coupling is unresolved, it is clear that both the alpha1 and beta subunits of DHPR are essential for this process. Here, we employed a series of techniques, including size-exclusion chromatography-multi-angle light scattering, differential scanning fluorimetry, and isothermal calorimetry, to characterize various biophysical properties of the skeletal DHPR beta subunit beta1a Removal of the intrinsically disordered N and C termini and the hook region of beta1a prevented oligomerization, allowing for its structural determination by X-ray crystallography. The structure had a topology similar to that of previously determined beta isoforms, which consist of SH3 and guanylate kinase domains. However, transition melting temperatures derived from the differential scanning fluorimetry experiments indicated a significant difference in stability of approximately 2-3 degrees C between the beta1a and beta2a constructs, and the addition of the DHPR alpha1s I-II loop (alpha-interaction domain) peptide stabilized both beta isoforms by approximately 6-8 degrees C. Similar to other beta isoforms, beta1a bound with nanomolar affinity to the alpha-interaction domain, but binding affinities were influenced by amino acid substitutions in the adjacent SH3 domain. These results suggest that intramolecular interactions between the SH3 and guanylate kinase domains play a role in the stability of beta1a while also providing a conduit for allosteric signaling events.
Structural and biophysical analyses of the skeletal dihydropyridine receptor beta subunit beta1a reveal critical roles of domain interactions for stability.,Norris NC, Joseph S, Aditya S, Karunasekara Y, Board PG, Dulhunty AF, Oakley AJ, Casarotto MG J Biol Chem. 2017 May 19;292(20):8401-8411. doi: 10.1074/jbc.M116.763896. Epub, 2017 Mar 28. PMID:28351836[2]
From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine.
See Also
References
- ↑ Chaudhari N. A single nucleotide deletion in the skeletal muscle-specific calcium channel transcript of muscular dysgenesis (mdg) mice. J Biol Chem. 1992 Dec 25;267(36):25636-9. PMID:1281468
- ↑ Norris NC, Joseph S, Aditya S, Karunasekara Y, Board PG, Dulhunty AF, Oakley AJ, Casarotto MG. Structural and biophysical analyses of the skeletal dihydropyridine receptor beta subunit beta1a reveal critical roles of domain interactions for stability. J Biol Chem. 2017 May 19;292(20):8401-8411. doi: 10.1074/jbc.M116.763896. Epub, 2017 Mar 28. PMID:28351836 doi:http://dx.doi.org/10.1074/jbc.M116.763896
