Functional polymorphisms in the α-subunit of the human epithelial Na+ channel increase activity

Qiusheng Tong, Anil G. Menon, James D Stockand

Research output: Contribution to journalArticle

26 Citations (Scopus)

Abstract

Activity of the epithelial Na+ channel (ENaC) is limiting for Na+ reabsorption at the distal nephron. Gain-of-function mutations in ENaC cause Liddle's syndrome: a severe form of inheritable hypertension. Several polymorphisms in α-hENaC possibly associated with abnormal Na + handling by the kidney and the salt-sensitive hypertension prevalent in black populations have been reported. The functional effects of α-hENaC polymorphisms on channel activity, however, remain controversial and have not been directly tested in a mammalian background. We ask here whether polymorphisms at positions 334, 618, and 663 in α-hENaC influence channel activity. Activity of wild-type (A334, C618, A663) and polymorphic ENaC expressed in Chinese hamster ovary cells was assessed with patch-clamp electrophysiology. While the A334T polymorphism had little effect on macroscopic ENaC currents, the C618F and A663T polymorphisms significantly increased ENaC activity >3.3- and 1.6-fold, respectively. Similarly, polymorphic ENaC had greater activity compared with wild-type channels in excised patches with activity of C618F and A663T channels increased 3.8- and 2.6-fold, respectively. Unitary channel conductances and reversal potentials were not different for polymorphic and wild-type ENaC. Increases in activity resulted primarily from increases in the apparent number of active (polymorphic) channels in the plasma membrane. Moreover, addition of a reducing agent to the cytosol significantly increased activity of wild-type ENaC equal to that of C618F polymorphic channels but had no effect on these latter channels. These results are consistent with the C618F and A663T polymorphisms leading to elevated ENaC activity with the possibility that they facilitate altered Na+ handling by the kidney.

Original languageEnglish (US)
JournalAmerican Journal of Physiology - Renal Physiology
Volume290
Issue number4
DOIs
StatePublished - Apr 2006

Fingerprint

Epithelial Sodium Channels
Liddle Syndrome
Hypertension
Kidney
Electrophysiology
Reducing Agents
Nephrons
Cricetulus
Cytosol
Ovary
Salts
Cell Membrane
Mutation

Keywords

  • Hypertension
  • Liddle's syndrome
  • Sequence variations

ASJC Scopus subject areas

  • Physiology

Cite this

Functional polymorphisms in the α-subunit of the human epithelial Na+ channel increase activity. / Tong, Qiusheng; Menon, Anil G.; Stockand, James D.

In: American Journal of Physiology - Renal Physiology, Vol. 290, No. 4, 04.2006.

Research output: Contribution to journalArticle

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AB - Activity of the epithelial Na+ channel (ENaC) is limiting for Na+ reabsorption at the distal nephron. Gain-of-function mutations in ENaC cause Liddle's syndrome: a severe form of inheritable hypertension. Several polymorphisms in α-hENaC possibly associated with abnormal Na + handling by the kidney and the salt-sensitive hypertension prevalent in black populations have been reported. The functional effects of α-hENaC polymorphisms on channel activity, however, remain controversial and have not been directly tested in a mammalian background. We ask here whether polymorphisms at positions 334, 618, and 663 in α-hENaC influence channel activity. Activity of wild-type (A334, C618, A663) and polymorphic ENaC expressed in Chinese hamster ovary cells was assessed with patch-clamp electrophysiology. While the A334T polymorphism had little effect on macroscopic ENaC currents, the C618F and A663T polymorphisms significantly increased ENaC activity >3.3- and 1.6-fold, respectively. Similarly, polymorphic ENaC had greater activity compared with wild-type channels in excised patches with activity of C618F and A663T channels increased 3.8- and 2.6-fold, respectively. Unitary channel conductances and reversal potentials were not different for polymorphic and wild-type ENaC. Increases in activity resulted primarily from increases in the apparent number of active (polymorphic) channels in the plasma membrane. Moreover, addition of a reducing agent to the cytosol significantly increased activity of wild-type ENaC equal to that of C618F polymorphic channels but had no effect on these latter channels. These results are consistent with the C618F and A663T polymorphisms leading to elevated ENaC activity with the possibility that they facilitate altered Na+ handling by the kidney.

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