Mutations in the extracellular loop of alpha-rENaC alter sensitivity to amiloride and reactive species.

Academic Article

Abstract

  • We studied the effects of two mutations of the extracellular loop of the alpha-subunit of the (ENaC) on amiloride-sensitive current in Xenopus laevis oocytes and the inhibition of this current by 3-morpholinosydnonimine (SIN-1). Injection of oocytes with wild-type (wt) alpha-,beta-,gamma-rENaC cRNA (8.3 ng/subunit) resulted 48-72 h later in inward Na(+) currents (-5.5 +/- 0.8 microA; means +/- SE at -100 mV; n = 21), which were completely inhibited by amiloride. Oocytes injected with either alpha(Y279A)- or alpha(Y283A)- and beta-,gamma-rENaC cRNAs had significantly lower Na(+) currents. Furthermore, alpha(Y279A)-,beta-,gamma-rENaC-injected oocytes had a higher K(i) for amiloride (0.54 +/- 0.97 vs. 0.10 +/- 0.04 microM; P < 0.01). Exposure of oocytes to SIN-1 (1 mM) for 5 min decreased both total Na(+) and amiloride-sensitive currents across wt and alpha(Y279A)- but not alpha(Y283A)-,beta-,gamma-rENaC. Furthermore, exposure to SIN-1 increased the K(i) for amiloride across wt but not alpha(Y279A)-,beta-,gamma-rENaC-injected oocytes. These data indicate that both tyrosines are important for proper ENaC function and their oxidative modifications contribute to altered ENaC function.
  • Published In

    Keywords

  • Amiloride, Animals, Diuretics, Epithelial Sodium Channels, Molsidomine, Mutation, Oocytes, Patch-Clamp Techniques, Peroxynitrous Acid, RNA, Messenger, Reactive Oxygen Species, Sodium Channels, Xenopus laevis
  • Digital Object Identifier (doi)

    Author List

  • Chen L; Fuller CM; Kleyman TR; Matalon S
  • Start Page

  • F1202
  • End Page

  • F1208
  • Volume

  • 286
  • Issue

  • 6