title: Temperature and pharmacological rescue of a folding-defective, dominant-negative KV 7.2 mutation associated with neonatal seizures.
abstract: Benign familial neonatal seizures (BFNS) are a dominant epilepsy syndrome caused by mutations in the voltage-gated potassium channels K(V) 7.2 and K(V) 7.3. We examined the molecular pathomechanism of a BFNS-causing mutation (p.N258S) in the extracellular S5-H5 loop of K(V) 7.2. Wild type (WT) and mutant channels, expressed in both Xenopus laevis oocytes and CHO cells, were studied using electrophysiological techniques. The results revealed a pronounced loss-of-function with a dominant-negative effect of the mutant on WT K(V) 7.2 and K(V) 7.3 channels. Since single-channel recordings of K(V) 7.3-K(V) 7.2 and K(V) 7.3-N285S concatemers showed similar properties for both constructs, we hypothesized that the observed reduction in current amplitude was due to a folding and trafficking defect, which was confirmed by biochemical and immunocytochemical experiments revealing a reduced number of mutant channels in the surface membrane. Furthermore, rescuing experiments revealed that upon specific incubation of transfected CHO cells-either at lower temperatures of <30°C or in presence of the agonist retigabine (RTG)-the N258S-derived currents increased fivefold in contrast to the WT. The obtained results represent a first example of temperature and pharmacological rescue of a K(V) 7 mutation and suggest a folding and trafficking deficiency as the cause of reduced current amplitudes with a dominant-negative effect of N258S mutant proteins.
authors.affiliation: Neurological Clinic and Institute of Applied Physiology, University of Ulm, Germany.
authors.forename: Snezana
authors.initials: S
authors.lastname: Maljevic
authors.forename: Georgios
authors.initials: G
authors.lastname: Naros
authors.forename: Özlem
authors.initials: Ö
authors.lastname: Yalçin
authors.forename: Dragica
authors.initials: D
authors.lastname: Blazevic
authors.forename: Heidi
authors.initials: H
authors.lastname: Loeffler
authors.forename: Hande
authors.initials: H
authors.lastname: Cağlayan
authors.forename: Ortrud K
authors.initials: OK
authors.lastname: Steinlein
authors.forename: Holger
authors.initials: H
authors.lastname: Lerche
mesh_terms: D000818:Animals; D000873:Anthracenes / Q000494:pharmacology; D016466:CHO Cells; D006224:Cricetinae; D020936:Epilepsy, Benign Neonatal / Q000235:genetics*; D015870:Gene Expression; D006801:Humans; D051658:KCNQ2 Potassium Channel / Q000037:antagonists & inhibitors / Q000737:chemistry / Q000235:genetics*; D009154:Mutation; D009865:Oocytes; D026902:Potassium Channel Blockers / Q000494:pharmacology; D017510:Protein Folding / Q000187:drug effects; D021381:Protein Transport / Q000235:genetics; D013696:Temperature
chemical_list: C112297:10,10-bis(4-pyridinylmethyl)-9(10H)-anthracenone; D000873:Anthracenes; D051658:KCNQ2 Potassium Channel; D026902:Potassium Channel Blockers