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Cav1.1

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Identifiers
SymbolsCACNA1S ; CACNL1A3; CCHL1A3; Cav1.1; HOKPP; HOKPP1; MHS5; TTPP1; hypoPP
External IDsOMIM114208 MGI88294 HomoloGene37257 IUPHAR: 528 ChEMBL: 3805 GeneCards: CACNA1S Gene
RNA expression pattern
File:PBB GE CACNA1S 217515 s at tn.png
More reference expression data
Orthologs
SpeciesHumanMouse
Entrez77912292
EnsemblENSG00000081248ENSMUSG00000026407
UniProtQ13698A3KPC9
RefSeq (mRNA)NM_000069NM_001081023
RefSeq (protein)NP_000060NP_001074492
Location (UCSC)Chr 1:
201.01 – 201.08 Mb
Chr 1:
136.05 – 136.12 Mb
PubMed search[1][2]

Cav1.1 also known as the calcium channel, voltage-dependent, L type, alpha 1S subunit, (CACNA1S), is a protein which in humans is encoded by the CACNA1S gene.[1] It is also known as CACNL1A3 and the dihydropyridine receptor (DHPR, so named due to the blocking action DHP has on it).

Function

This gene encodes one of the five subunits of the slowly inactivating L-type voltage-dependent calcium channel in skeletal muscle cells. Mutations in this gene have been associated with hypokalemic periodic paralysis, thyrotoxic periodic paralysis and malignant hyperthermia susceptibility.[1]

Cav1.1 is a voltage-dependent calcium channel found in the transverse tubule of muscles. In skeletal muscle it associates with the ryanodine receptor RyR1 of the sarcoplasmic reticulum via a mechanical linkage. It senses the voltage change caused by the end-plate potential from nervous stimulation and propagated by sodium channels as action potentials to the T-tubules. It was previously thought that when the muscle depolarises, the calcium channel opens, allowing calcium in and activating RyR1, which mediates much greater calcium release from the sarcoplasmic reticulum. This is the first part of the process of excitation-contraction coupling, which ultimately causes the muscle to contract. Recent findings suggest that in skeletal muscle (but not heart muscle), calcium entry through Cav1.1 is not required; Cav1.1 undergoes a conformational change which allosterically activates RyR1.[2]

Clinical significance

In hypokalemic periodic paralysis (HOKPP), the voltage sensors in domains 2 and 4 of Cav1.1 are mutated (loss-of-function), reducing the availability of the channel to sense depolarisation, and therefore it cannot activate the ryanodine receptor as efficiently. As a result, the muscle cannot contract very well and the patient is paralysed. The condition is hypokalemic because a low extracellular potassium ion concentration will cause the muscle to repolarise to the resting potential more quickly, so any calcium conductance that does occur cannot be sustained. It becomes more difficult to reach the threshold at which the muscle can contract, and even if this is reached then the muscle is more prone to relaxing. Because of this, the severity would be reduced if potassium ion concentrations are maintained. In contrast, hyperkalemic periodic paralysis refers to gain-of-function mutations in sodium channels that maintain muscle depolarisation and therefore are aggravated by high potassium ion concentrations.[3]

The European Malignant Hyperthermia Group accepts two mutations in CACNA1S as diagnostic for malignant hyperthermia.[4]

Blockers

Cav1.1 is blocked by dihydropyridine.

See also

References

  1. ^ a b "Entrez Gene: CACNA1S calcium channel, voltage-dependent, L type, alpha 1S subunit". 
  2. ^ Proenza C, O'Brien J, Nakai J, Mukherjee S, Allen PD, Beam KG (February 2002). "Identification of a region of RyR1 that participates in allosteric coupling with the alpha(1S) (Ca(V)1.1) II-III loop". J. Biol. Chem. 277 (8): 6530–5. PMID 11726651. doi:10.1074/jbc.M106471200. 
  3. ^ Jurkat-Rott K, Lehmann-Horn F (August 2005). "Muscle channelopathies and critical points in functional and genetic studies". J. Clin. Invest. 115 (8): 2000–9. PMC 1180551. PMID 16075040. doi:10.1172/JCI25525. 
  4. ^ https://emhg.org/nc/genetics/mutations-in-ryr1/

Further reading

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External links

This article incorporates text from the United States National Library of Medicine, which is in the public domain.