Characterization of an amiloride binding region in the alpha-subunit of ENaC.

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Kelly O, Lin C, Ramkumar M, Saxena NC, Kleyman TR, Eaton DC

Characterization of an amiloride binding region in the alpha-subunit of ENaC.

Am J Physiol Renal Physiol. 2003 Dec;285(6):F1279-90. Epub 2003 Aug 19.

PubMed ID

12928313 [ View in PubMed

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Abstract

One of the defining characteristics of the epithelial sodium channel (ENaC) is its block by the diuretic amiloride. This study investigates the role of the extracellular loop of the alpha-subunit of ENaC in amiloride binding and stabilization. Mutations were generated in a region of the extracellular loop, residues 278-283. Deletion of this region, WYRFHY, resulted in a loss of amiloride binding to the channel. Channels formed from wild-type alpha-subunits or alpha-subunits containing point mutations in this region were examined and compared at the single-channel level. The open probabilities (Po) of wild-type channels were distributed into two populations: one with a high Po and one with a low Po. The mean open times of all the mutant channels were shorter than the mean open time of the wild-type (high-Po) channel. Besides mutations Y279A and H282D, which had amiloride binding affinities similar to that of wild-type alpha-ENaC, all other mutations in this region caused changes in the amiloride binding affinity of the channels compared with the wild-type channel. These data provide new insight into the relative position of the extracellular loop with respect to the pore of ENaC and its role in amiloride binding and channel gating.

DrugBank Data that Cites this Article

Drug Targets

Drug	Target	Kind	Organism	Pharmacological Action	Actions
Amiloride	Amiloride-sensitive sodium channel subunit alpha	Protein	Humans	Yes	Inhibitor	Details