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.
View: Text | PDF
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

×

Figure 9

Enzymatic activity of PDI is required for ERAD deficiency–triggered proAVP aggregation and the model.

Options: View larger image (or click on image) Download as PowerPoint
Enzymatic activity of PDI is required for ERAD deficiency–triggered proA...
(A) Sucrose fractionation followed by Western blot analyses of the proAVP protein complex (using the proAVP antibody PS41) in HRD1-deficient HEK293T cells, with or without a PDI-C56A trap mutant. Quantification of lane intensity of the proAVP Western blot is shown in Supplemental Figure 6. (B) Western blot analysis of proAVP aggregation under both nonreducing and reducing conditions in WT and PDI-deficient HEK293T cells transfected with control siRNA or siPDI, respectively. Data are representative of at least 2 independent experiments. (C) Model for the role of Sel1L-Hrd1 ERAD in proAVP conformational maturation in the ER. Physiological stress such as hyperosmolality induces the expression of proAVP and Sel1L-Hrd1 ERAD, which in turn clears misfolded proAVP — a critical process for the formation of natively folded dimers. Our data suggest that Sel1L-Hrd1 ERAD plays an important role in promoting a safe environment for nascent proteins, allowing them to reach native conformation without the distraction of aggregation, a process that may require PDI.