title: In vitro recovery of ATP-sensitive potassium channels in β-cells from patients with congenital hyperinsulinism of infancy.
abstract: OBJECTIVE
  Congenital hyperinsulinism in infancy (CHI) is characterized by unregulated insulin secretion from pancreatic β-cells; severe forms are associated with defects in ABCC8 and KCNJ11 genes encoding sulfonylurea receptor 1 (SUR1) and Kir6.2 subunits, which form ATP-sensitive K(+) (K(ATP)) channels in β-cells. Diazoxide therapy often fails in the treatment of CHI and may be a result of reduced cell surface expression of K(ATP) channels. We hypothesized that conditions known to facilitate trafficking of cystic fibrosis transmembrane regulator (CFTR) and other proteins in recombinant expression systems might increase surface expression of K(ATP) channels in native CHI β-cells.
  
  
  METHODS
  Tissue was isolated during pancreatectomy from eight patients with CHI and from adult cadaver organ donors. Patients were screened for mutations in ABCC8 and KCNJ11. Isolated β-cells were maintained at 37°C or 25°C and in the presence of 1) phorbol myristic acid, forskolin and 3-isobutyl-1-methylxanthine, 2) BPDZ 154, or 3) 4-phenylbutyrate. Surface expression of functional channels was assessed by patch-clamp electrophysiology.
  
  
  RESULTS
  Mutations in ABCC8 were detected for all patients tested (n = 7/8) and included three novel mutations. In five of eight patients, no changes in K(ATP) channel activity were observed under different cell culture conditions. However, in three patients, in vitro recovery of functional K(ATP) channels occurred. Here, we report the first cases of recovery of defective K(ATP) channels in human β-cells using modified cell culture conditions.
  
  
  CONCLUSIONS
  Our study establishes the principle that chemical modification of K(ATP) channel subunit trafficking could be of benefit for the future treatment of CHI.
authors.affiliation: Faculty of Life Sciences, University of Manchester, Manchester, UK.
authors.forename: Philippa D
authors.initials: PD
authors.lastname: Powell
authors.forename: Christine
authors.initials: C
authors.lastname: Bellanné-Chantelot
authors.forename: Sarah E
authors.initials: SE
authors.lastname: Flanagan
authors.forename: Sian
authors.initials: S
authors.lastname: Ellard
authors.forename: Raoul
authors.initials: R
authors.lastname: Rooman
authors.forename: Khalid
authors.initials: K
authors.lastname: Hussain
authors.forename: Mars
authors.initials: M
authors.lastname: Skae
authors.forename: Peter
authors.initials: P
authors.lastname: Clayton
authors.forename: Pascale
authors.initials: P
authors.lastname: de Lonlay
authors.forename: Mark J
authors.initials: MJ
authors.lastname: Dunne
authors.forename: Karen E
authors.initials: KE
authors.lastname: Cosgrove
mesh_terms: D018528:ATP-Binding Cassette Transporters / Q000235:genetics / Q000378:metabolism; D001581:Benzothiadiazines / Q000494:pharmacology; D002478:Cells, Cultured; D002675:Child, Preschool; D044903:Congenital Hyperinsulinism / Q000378:metabolism*; D003499:Cyclic S-Oxides / Q000494:pharmacology; D006801:Humans; D007223:Infant; D007231:Infant, Newborn; D050417:Insulin-Secreting Cells / Q000187:drug effects / Q000378:metabolism*; D054086:KATP Channels / Q000235:genetics / Q000378:metabolism*; D008954:Models, Biological; D009154:Mutation; D010180:Pancreatectomy; D018408:Patch-Clamp Techniques; D010654:Phenylbutyrates / Q000494:pharmacology; D010703:Phorbol Esters / Q000494:pharmacology; D024661:Potassium Channels, Inwardly Rectifying / Q000235:genetics / Q000378:metabolism; D011955:Receptors, Drug / Q000235:genetics / Q000378:metabolism; D064233:Sulfonylurea Receptors; D000099161:Kcnj11 Channel
chemical_list: D018528:ATP-Binding Cassette Transporters; D001581:Benzothiadiazines; D003499:Cyclic S-Oxides; D054086:KATP Channels; D010654:Phenylbutyrates; D010703:Phorbol Esters; D024661:Potassium Channels, Inwardly Rectifying; D011955:Receptors, Drug; D064233:Sulfonylurea Receptors; D000099161:Kcnj11 Channel; C577507:ABCC8 protein, human; C468751:BPDZ 154; C119222:phorbol-12-myristate; C075773:4-phenylbutyric acid