Progesterone down-regulates the open probability of the amiloride-sensitive epithelial sodium channel via a Nedd4-2-dependent mechanism

Michlig, Stéphanie; Harris, Michael; Loffing, Johannes; Rossier, Bernard C.; Firsov, Dmitri

doi:10.1074/jbc.M506308200

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Journal article

Progesterone down-regulates the open probability of the amiloride-sensitive epithelial sodium channel via a Nedd4-2-dependent mechanism

Michlig, Stéphanie Département de Pharmacologie et de Toxicologie, Université de Lausanne, Switzerland
Harris, Michael Département de Pharmacologie et de Toxicologie, Université de Lausanne, Switzerland
Loffing, Johannes Département de Médicine, Unité d'Anatomie, Université de Fribourg, Switzerland
Rossier, Bernard C. Département de Pharmacologie et de Toxicologie, Université de Lausanne, Switzerland
Firsov, Dmitri Département de Pharmacologie et de Toxicologie, Université de Lausanne, Switzerland

19.09.2005

Published in:

Journal of Biological Chemistry. - 2005, vol. 280, no. 46, p. 38264-38270

English Activation of the mitogen-activated protein (MAP) kinase cascade by progesterone in Xenopus oocytes leads to a marked down-regulation of activity of the amiloride-sensitive epithelial sodium channel (ENaC). Here we have studied the signaling pathways involved in progesterone effect on ENaC activity. We demonstrate that: (i) the truncation of the C termini of the αβγENaC subunits results in the loss of the progesterone effect on ENaC; (ii) the effect of progesterone was also suppressed by mutating conserved tyrosine residues in the Pro-X-X-Tyr (PY) motif of the C termini of the βand γ ENaC subunits (β_Y618A and γ_Y628A); (iii) the down-regulation of ENaC activity by progesterone was also suppressed by co-expression ENaC subunits with a catalytically inactive mutant of Nedd4-2, a ubiquitin ligase that has been previously demonstrated to decrease ENaC cell-surface expression via a ubiquitin-dependent internalization/degradation mechanism; (iv) the effect of progesterone was significantly reduced by suppression of consensus sites (β_T613A and γ_T623A) for ENaC phosphorylation by the extracellular-regulated kinase (ERK), a MAP kinase previously shown to facilitate the binding of Nedd4 ubiquitin ligases to ENaC; (v) the quantification of cell-surface-expressed ENaC subunits revealed that progesterone decreases ENaC open probability (whole cell P_o, wcP _o) and not its cell-surface expression. Collectively, these results demonstrate that the binding of active Nedd4-2 to ENaC is a crucial step in the mechanism of ENaC inhibition by progesterone. Upon activation of ERK, the effect of Nedd4-2 on ENaC open probability can become more important than its effect on ENaC cell-surface expression.

Faculty

Faculté des sciences et de médecine

Department

Département de Médecine

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