ER-associated degradation is required for vasopressin prohormone processing and systemic water homeostasis
Guojun Shi, … , Martin Spiess, Ling Qi
Guojun Shi, … , Martin Spiess, Ling Qi
Published September 18, 2017
Citation Information: J Clin Invest. 2017;127(10):3897-3912. https://doi.org/10.1172/JCI94771.
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Research Article Cell biology Endocrinology

ER-associated degradation is required for vasopressin prohormone processing and systemic water homeostasis

Abstract

Peptide hormones are crucial regulators of many aspects of human physiology. Mutations that alter these signaling peptides are associated with physiological imbalances that underlie diseases. However, the conformational maturation of peptide hormone precursors (prohormones) in the ER remains largely unexplored. Here, we report that conformational maturation of proAVP, the precursor for the antidiuretic hormone arginine-vasopressin, within the ER requires the ER-associated degradation (ERAD) activity of the Sel1L-Hrd1 protein complex. Serum hyperosmolality induces expression of both ERAD components and proAVP in AVP-producing neurons. Mice with global or AVP neuron–specific ablation of Se1L-Hrd1 ERAD progressively developed polyuria and polydipsia, characteristics of diabetes insipidus. Mechanistically, we found that ERAD deficiency causes marked ER retention and aggregation of a large proportion of all proAVP protein. Further, we show that proAVP is an endogenous substrate of Sel1L-Hrd1 ERAD. The inability to clear misfolded proAVP with highly reactive cysteine thiols in the absence of Sel1L-Hrd1 ERAD causes proAVP to accumulate and participate in inappropriate intermolecular disulfide–bonded aggregates, promoted by the enzymatic activity of protein disulfide isomerase (PDI). This study highlights a pathway linking ERAD to prohormone conformational maturation in neuroendocrine cells, expanding the role of ERAD in providing a conducive ER environment for nascent proteins to reach proper conformation.

Authors

Guojun Shi, Diane R.M. Somlo, Geun Hyang Kim, Cristina Prescianotto-Baschong, Shengyi Sun, Nicole Beuret, Qiaoming Long, Jonas Rutishauser, Peter Arvan, Martin Spiess, Ling Qi

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Figure 2

HRD1 is highly enriched in AVP neurons and upregulated during water deprivation.

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HRD1 is highly enriched in AVP neurons and upregulated during water depr...
(A–C) Representative fluorescence images of Hrd1 expression in brain sections from WT mice with ad libitum access to water (A) and close-up view of the PVN (B) and SON (C). (D) Scatterplot demonstrating the relationship between Hrd1 and proAVP fluorescence mean intensity in single AVP neurons from WT mice with ad libitum access to water. (E–G) Representative fluorescence images of proAVP and Hrd1 in WT mice PVN under ad libitum access to water (E) or osmotic stress conditions. Mice were either water deprived for 72 hours (F) or given water containing 2% sodium chloride (salt-loaded) for 7 days (G). (H) Mean fluorescence intensity of proAVP and Hrd1 staining for images in E–G. (A–C) Representative images for 2 WT male mice; (D) 100 proAVP-positive neurons were quantitated. Scale bar: 10 μm. (E–G) n = 2 mice/group; (H) n = 50 AVP-positive cells from 2 mice per condition. Values represent the mean ± SEM. *P < 0.05, **P < 0.01, and ***P < 0.001, by Student’s t test. Data represent at least 2 independent experiments.