ER-associated degradation is required for vasopressin prohormone processing and systemic water homeostasis
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
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
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 8

Enzymatic activity of PDI is required for proAVP degradation.

Options: View larger image (or click on image) Download as PowerPoint
Enzymatic activity of PDI is required for proAVP degradation. (A) Wester...
(A) Western blot analysis of immunoprecipitates of HA-agarose in proAVP- and/or PDI-transfected HEK293T cells, showing the interaction between PDI and proAVP. (B) Western blot analysis of proAVP-PDI intermediates in HEK293T cells transfected with WT proAVP plus WT or PDI-C56A trap mutant under nonreducing or reducing conditions. (C) Western blot analysis of immunoprecipitates of HA-agarose in proAVP-transfected HEK293T cells, with or without PDI knockdown (siPDI). Two panels were from the same experiment at the same exposure time, with the irrelevant lanes in the middle cut off. (D) Western blot analysis and quantification of WT proAVP protein turnover in HEK293T cells, with or without siPDI. Values represent the mean ± SEM. *P < 0.05, by Student’s t test. Data shown are representative of at least 2 independent experiments.