TY - JOUR
T1 - Mutations at the same residue (R50) of Kir6.2 (KCNJ11) that cause neonatal diabetes produce different functional effects
AU - Shimomura, Kenju
AU - Girard, Christophe A J
AU - Proks, Peter
AU - Nazim, Joanna
AU - Lippiat, Jonathan D.
AU - Cerutti, Franco
AU - Lorini, Renata
AU - Ellard, Sian
AU - Hattersely, Andrew T.
AU - Barbetti, Fabrizio
AU - Ashcroft, Frances M.
PY - 2006
Y1 - 2006
N2 - Heterozygous mutations in the human Kir6.2 gene (KCNJ11), the pore-forming subunit of the ATP-sensitive K+ channel (KATP channel), are a common cause of neonatal diabetes. We identified a novel KCNJ11 mutation, R50Q, that causes permanent neonatal diabetes (PNDM) without neurological problems. We investigated the functional effects this mutation and another at the same residue (R50P) that led to PNDM in association with developmental delay. Wild-type or mutant Kir6.2/SUR1 channels were examined by heterologous expression in Xenopus oocytes. Both mutations increased resting whole-cell currents through homomeric and heterozygous KATP channels by reducing channel inhibition by ATP, an effect that was larger in the presence of Mg 2+. However the magnitude of the reduction in ATP sensitivity (and the increase in the whole-cell current) was substantially larger for the R50P mutation. This is consistent with the more severe phenotype. Single-R50P channel kinetics (in the absence of ATP) did not differ from wild type, indicating that the mutation primarily affects ATP binding and/or transduction. This supports the idea that R50 lies in the ATP-binding site of Kir6.2. The sulfonylurea tolbutamide blocked heterozygous R50Q (89%) and R50P (84%) channels only slightly less than wild-type channels (98%), suggesting that sulfonylurea therapy may be of benefit for patients with either mutation.
AB - Heterozygous mutations in the human Kir6.2 gene (KCNJ11), the pore-forming subunit of the ATP-sensitive K+ channel (KATP channel), are a common cause of neonatal diabetes. We identified a novel KCNJ11 mutation, R50Q, that causes permanent neonatal diabetes (PNDM) without neurological problems. We investigated the functional effects this mutation and another at the same residue (R50P) that led to PNDM in association with developmental delay. Wild-type or mutant Kir6.2/SUR1 channels were examined by heterologous expression in Xenopus oocytes. Both mutations increased resting whole-cell currents through homomeric and heterozygous KATP channels by reducing channel inhibition by ATP, an effect that was larger in the presence of Mg 2+. However the magnitude of the reduction in ATP sensitivity (and the increase in the whole-cell current) was substantially larger for the R50P mutation. This is consistent with the more severe phenotype. Single-R50P channel kinetics (in the absence of ATP) did not differ from wild type, indicating that the mutation primarily affects ATP binding and/or transduction. This supports the idea that R50 lies in the ATP-binding site of Kir6.2. The sulfonylurea tolbutamide blocked heterozygous R50Q (89%) and R50P (84%) channels only slightly less than wild-type channels (98%), suggesting that sulfonylurea therapy may be of benefit for patients with either mutation.
KW - [ATP], intracellular ATP concentration
KW - hetR50P, heterozygous R50P
KW - hetR50Q, heterozygous R50Q
KW - homR50P, homomeric R50P
KW - homR50Q, homomeric R50Q
KW - IC, half-maximal inhibitory concentration
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U2 - 10.2337/db05-1640
DO - 10.2337/db05-1640
M3 - Article
C2 - 16731833
AN - SCOPUS:33748288147
VL - 55
SP - 1705
EP - 1712
JO - Diabetes
JF - Diabetes
SN - 0012-1797
IS - 6
ER -