Sodium Channelopathies

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Voltage gated sodium channels are transmembrane polypeptides with four domains. A pore is made with all four domains through which sodium can enter the cell. There is also an ancillary beta unit for anchoring and kinetics. They are responsible for signalling the nerve fibres for generation of action potentials (See Basic Neurophysiology).

Classification

There are nine known members of sodium channels labelled Nav1.1 through Nav1.9. The associated genes are named SCN1A through SCN11A (the SCN6/7A gene is part of the Nax sub-family and has uncertain function)

Table 1. Nomenclature and some functions of voltage-gated sodium channel alpha subunits[1]
Protein name Gene Expression profile Associated channelopathies
Nav1.1 SCN1A Central neurons, [peripheral neurons] and cardiac myocytes febrile epilepsy, GEFS+, Dravet syndrome (also known as severe myclonic epilepsy of infancy or SMEI), borderline SMEI (SMEB), West syndrome (also known as infantile spasms), Doose syndrome (also known as myoclonic astatic epilepsy), intractable childhood epilepsy with generalized tonic-clonic seizures (ICEGTC), Panayiotopoulos syndrome, familial hemiplegic migraine (FHM), familial autism, Rasmussens's encephalitis and Lennox-Gastaut syndrome
Nav1.2 SCN2A Central neurons, peripheral neurons inherited febrile seizures, epilepsy, and autism spectrum disorder
Nav1.3 SCN3A Central neurons, peripheral neurons and cardiac myocytes epilepsy, pain, brain malformations
Nav1.4 SCN4A Skeletal muscle Certain non-dystrophic myotonias: Sodium channel myotonia, Paramyotonia congenita, Hyperkalaemic periodic paralysis
Nav1.5 SCN5A Cardiac myocytes, uninnervated skeletal muscle, central neurons, gastrointestinal smooth muscle cells and Interstitial cells of Cajal Cardiac: Long QT syndrome Type 3, Brugada syndrome, progressive cardiac conduction disease, familial atrial fibrillation and idiopathic ventricular fibrillation;

Gastrointestinal: Irritable bowel syndrome;

Nav1.6 SCN8A Central neurons, dorsal root ganglia, peripheral neurons, heart, glia cells Epilepsy, ataxia, dystonia, tremor
Nav1.7 SCN9A Dorsal root ganglia, sympathetic neurons, Schwann cells, and neuroendocrine cells Gain of function: SCN9A neuropathic pain syndromes: erythromelalgia,Small fibre neuropathy, paroxysmal extreme pain disorder

Loss of function: Congenital Insensitivity to Pain (CIP) a.k.a hereditary sensory and autonomic neuropathy type 2D (HSAN2D)

Nav1.8 SCN10A Dorsal root ganglia Small fibre neuropathy, autosomal recessive neuromuscular disease and epileptic encephalopathy, autosomal dominant familial episodic pain syndrome type 2 (FEPS2), Brugada syndrome , and congenital abnormalities of the kidney and urinary tract.
Nav1.9 SCN11A Dorsal root ganglia Small fibre neuropathy, autosomal dominant hereditary sensory and autonomic neuropathy type 7 (HSAN7), familial episodic pain syndrome type 3 (FEPS3)
Nax SCN7A heart, uterus, skeletal muscle, astrocytes, dorsal root ganglion cells none known

See Also

GeneReviews - SCN9A Pain Conditions

References

  1. "Sodium channel". Wikipedia (in English). 2022-12-02.

Literature Review