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Peer-reviewedCC BY-NC-SA 4.0Molecular Biology of the Cell

Adenovirus early proteins E1A and E3-19K reveal separable regulatory states of the ER stress sensor IRE1a

  • Debkanya Sengupta1
  • Shikha Srivastava2
  • Fedor Bezrukov1
  • Silvio Hemmi3
  • Urs F. Greber3
  • Vibhu Prasad1
  1. 1Department of Microbiology and Molecular Medicine, Faculty of Medicine, University of Geneva, Rue Michel-Servet 1, CH-1211 Geneva 4, Switzerland
  2. 2Heidelberg University, Medical Faculty Heidelberg, Department of Infectious Diseases, Molecular Virology, Center for Integrative Infectious Disease Research (CIID), Im Neuenheimer Feld 344, 69120 Heidelberg, Germany
  3. 3Department of Molecular Life Sciences, University of Zurich, Winterthurerstrasse 190, CH-8057 Zurich, Switzerland
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Abstract

The unfolded protein response (UPR) controls cellular homeostasis and viral infections. It is canonically initiated by dissociation of ER chaperone BiP/GRP78 from lumenal domains of transmembrane sensor proteins, including the central UPR sensor inositol-requiring enzyme 1 alpha (IRE1a). This results in IRE1a activation and splicing of X-box binding protein 1 (XBP1) mRNA, leading to transcriptional activation of XBP1 for cellular adaptation and sustained infection. Human adenovirus (AdV) preferentially activates the IRE1a-XBP1 pathway through the viral membrane protein E3-19K, yet the mechanisms underlying this selective activation remain unclear. Here, we show that AdV uses two distinct early proteins to dissociate BiP from IRE1a and activate IRE1a-mediated XBP1 splicing. The immediate early protein E1A forms a complex with the cytoplasmic domain of IRE1a, sufficient to dissociate BiP from IRE1a without inducing XBP1 splicing or UPR activation. In contrast, E3-19K is expressed downstream of E1A, associates with the lumenal domain of IRE1a, and induces XBP1 splicing without promoting BiP dissociation from IRE1a. Both proteins were detected in IRE1a-containing complexes, consistent with stepwise viral regulation. Together, our findings show that canonical IRE1a activation hallmarks can be mechanistically separated during viral infection, revealing distinct AdV-regulated IRE1a activation states with discrete upstream and downstream signaling outputs.

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Cite

BibTeXRIS
BibTeX
@article{sengupta2026adenovirus,
  title = {{Adenovirus early proteins E1A and E3-19K reveal separable regulatory states of the ER stress sensor IRE1a}},
  author = {Debkanya Sengupta and Shikha Srivastava and Fedor Bezrukov and Silvio Hemmi and Urs F. Greber and Vibhu Prasad},
  journal = {Molecular Biology of the Cell},
  year = {2026},
  month = oct,
  doi = {10.1091/mbc.e26-06-0273},
  url = {https://doi.org/10.1091/mbc.e26-06-0273},
  note = {CC BY-NC-SA 4.0},
}
RIS
TY  - JOUR
TI  - Adenovirus early proteins E1A and E3-19K reveal separable regulatory states of the ER stress sensor IRE1a
AU  - Debkanya Sengupta
AU  - Shikha Srivastava
AU  - Fedor Bezrukov
AU  - Silvio Hemmi
AU  - Urs F. Greber
AU  - Vibhu Prasad
PY  - 2026
DA  - 2026/10/26
JO  - Molecular Biology of the Cell
DO  - 10.1091/mbc.e26-06-0273
UR  - https://doi.org/10.1091/mbc.e26-06-0273
AB  - The unfolded protein response (UPR) controls cellular homeostasis and viral infections. It is canonically initiated by dissociation of ER chaperone BiP/GRP78 from lumenal domains of transmembrane sensor proteins, including the central UPR sensor inositol-requiring enzyme 1 alpha (IRE1a). This results in IRE1a activation and splicing of X-box binding protein 1 (XBP1) mRNA, leading to transcriptional activation of XBP1 for cellular adaptation and sustained infection. Human adenovirus (AdV) preferentially activates the IRE1a-XBP1 pathway through the viral membrane protein E3-19K, yet the mechanisms underlying this selective activation remain unclear. Here, we show that AdV uses two distinct early proteins to dissociate BiP from IRE1a and activate IRE1a-mediated XBP1 splicing. The immediate early protein E1A forms a complex with the cytoplasmic domain of IRE1a, sufficient to dissociate BiP from IRE1a without inducing XBP1 splicing or UPR activation. In contrast, E3-19K is expressed downstream of E1A, associates with the lumenal domain of IRE1a, and induces XBP1 splicing without promoting BiP dissociation from IRE1a. Both proteins were detected in IRE1a-containing complexes, consistent with stepwise viral regulation. Together, our findings show that canonical IRE1a activation hallmarks can be mechanistically separated during viral infection, revealing distinct AdV-regulated IRE1a activation states with discrete upstream and downstream signaling outputs.
SN  - 1059-1524
SN  - 1939-4586
ER  -