KCNH1

Potassium voltage-gated channel subfamily H member 1 (K_V10.1, EAG1) is a protein that in humans is encoded by the ''KCNH1'' gene. Mutations in ''KCNH1'' cause genetic epilepsy and developmental encephalopathies, and aberant expression is associated with tumor progression.

Function

Expression of KCNH1 is predominantly restricted to the adult central nervous system. The ''KCNH1'' gene encodes a homotetrameric highly-conserved voltage-gated potassium channel (K_V10.1) thought to be responsible for reestablishing the membrane potential of excitatory neurons in response to high frequency firing.

K_V10.1 is a non-inactivating delayed rectifier potassium channel. Like other voltage-gated potassium ion channels, opening of the K_V10.1 channel pore is triggered by membrane depolarisation, which results in an outward flow of potassium ions to rectify the baseline membrane potential. K_V10.1 is slow to open when triggered and does not undergo an inactivation state after closing.

Structurally, K_V10.1 is composed of four identical subunits that are each 989 residues long (111.4 kDa). Each subunit is composed of a PAS domain, transmembrane voltage-sensing and pore domains, a C-linker, and an intracellular cyclic nucleotide-binding homology domain. Alternative splicing of this gene results in two transcript variants encoding distinct isoforms that differ by the inclusion or exclusion of 27 amino acids between the S3 and S4 helices of the voltage-sensing domain.

KCNH1 expression is activated at the onset of myoblast differentiation and known to play roles in the cell cycle and cell proliferation.

Pathologies

Gabbett and colleagues described Temple–Baraitser syndrome (TBS) in 2008, naming the condition after English clinical geneticists Profs Karen Temple and Michael Baraitser. TBS is categorized by intellectual disabilities, epilepsy, atypical facial features, and aplasia of the nails.

It was later demonstrated that '' de novo'' missense mutations in the ''KCNH1'' gene cause deleterious gain of function in the voltage-gated potassium channel, resulting in TBS. Patients with '' de novo'' mutations in KCNH1 were found to be affected by epilepsy, while children born with germline mutations from mosaic probands were affected by TBS. This provides further evidence of the role that genetic mosaicism plays in the etiology of neurological disorders. Type 1 Zimmermann–Laband syndrome was later found to be caused by similar missense mutations in ''KCNH1''. This has led some researchers to believe that type 1 Zimmermann-Laband and Temple-Baraitser syndromes are different manifestations of the same disorder.

Overexpression of KCNH1 may confer a growth advantage to cancer cells and favor tumor cell proliferation, as KCNH1 overexpression has been observed in 70% of solid tumors.

Interactions

KCNH1 has been shown to interact with KCNB1 and is inhibited by the highly-conserved secondary messenger calmodulin in the presence of calcium.

See also

* Voltage-gated potassium channel
* Voltage-gated ion channel
* Channelopathy
* HERG

References

Further reading

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External links

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Human Disease Genes - ''KCNH1''

{{Ion channels, g3

PAS-domain-containing proteins