WNK1 promotes water homeostasis by acting as a central osmolality sensor for arginine vasopressin release
Xin Jin, Jian Xie, Chia-Wei Yeh, Jen-Chi Chen, Chih-Jen Cheng, Cheng-Chang Lien, Chou-Long Huang
Xin Jin, Jian Xie, Chia-Wei Yeh, Jen-Chi Chen, Chih-Jen Cheng, Cheng-Chang Lien, Chou-Long Huang
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Research Article Endocrinology Nephrology

WNK1 promotes water homeostasis by acting as a central osmolality sensor for arginine vasopressin release

Abstract

Maintaining internal osmolality constancy is essential for life. Release of arginine vasopressin (AVP) in response to hyperosmolality is critical. Current hypotheses for osmolality sensors in circumventricular organs (CVOs) of the brain focus on mechanosensitive membrane proteins. The present study demonstrated that intracellular protein kinase WNK1 was involved. Focusing on vascular-organ-of-lamina-terminalis (OVLT) nuclei, we showed that WNK1 kinase was activated by water restriction. Neuron-specific conditional KO (cKO) of Wnk1 caused polyuria with decreased urine osmolality that persisted in water restriction and blunted water restriction–induced AVP release. Wnk1 cKO also blunted mannitol-induced AVP release but had no effect on osmotic thirst response. The role of WNK1 in the osmosensory neurons in CVOs was supported by neuronal pathway tracing. Hyperosmolality-induced increases in action potential firing in OVLT neurons was blunted by Wnk1 deletion or pharmacological WNK inhibitors. Knockdown of Kv3.1 channel in OVLT by shRNA reproduced the phenotypes. Thus, WNK1 in osmosensory neurons in CVOs detects extracellular hypertonicity and mediates the increase in AVP release by activating Kv3.1 and increasing action potential firing from osmosensory neurons.

Authors

Xin Jin, Jian Xie, Chia-Wei Yeh, Jen-Chi Chen, Chih-Jen Cheng, Cheng-Chang Lien, Chou-Long Huang

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Figure 11

Wnk1 deletion reduces hypertonicity-induced spike generation in PVN-projecting OVLT neurons.

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Wnk1 deletion reduces hypertonicity-induced spike generation in PVN-pro...
(A) Schematic of the virus-mediated KO of Wnk1 in PVN-projecting OVLT neurons via injection of Cre-expressing retrograde virus at the PVN region. (B) Representative coronal section of the mouse brain injected with Cre-expressing virus at the PVN region. Scale bar: 1 mm. (C) Overlay of epifluorescence and IR-DIC images showing Cre-expressing neurons in the OVLT region. Scale bar: 10 μm. A recording pipette attached to a Cre-expressing cell was illustrated. (D) Top: Representative traces of spontaneous firing recorded from a NaCl-R neuron (R; cyan trace) and a NaCl-NR neuron (NR; red trace) in the WT mice. Bottom: Histogram of z score from the representative NaCl-R and NaCl-NR cells. (E) Distribution of the Δz score in response to 5 mM NaCl stimulation of all recorded neurons in WT mice. The dashed line indicates 0.5. (F) Pie chart showing distribution of NaCl-R and NaCl-NR PVN-projecting OVLT neurons in WT mice. (G) Top: Representative traces of spontaneous firing recorded from a NaCl-R neuron and a NaCl-NR neuron in the Wnk1–conditional KO (cKO) mice. Bottom: Histogram of z score from the representative NaCl-R and NaCl-NR cells. (H) Distribution of the Δz score in response to 5 mM NaCl stimulation of all recorded neurons in Wnk1-cKO mice. The dashed line indicates 0.5. (I) Pie chart showing distribution of NaCl-R and NaCl-NR PVN-projecting OVLT neurons in Wnk1-cKO mice. *P = 0.032, between F and I, 2-tailed Fisher’s exact test. The WT group consists of recordings of 22 cells from 13 mice; the cKO group consists of 24 cells from 11 mice.