Hepatocyte UBE4A protects against MASLD/MASH by maintaining ER homeostasis via UBXN4 interaction
- 1Department of Cellular and Systems Pharmacology, University of Florida College of Pharmacy
Abstract
Molecular understanding of the regulation of endoplasmic reticulum (ER) functions in healthy and MASLD livers is limited. Here, we elucidate that Ube4A, a cytosolic E3 ubiquitin ligase, protects against MASLD development by maintaining ER homeostasis during nutritional stress. Hepatocyte-Ube4A deletion (HUKO) augments Gubra-Amylin-diet (GAN-D)-induced steatosis, inflammation, insulin resistance, ER stress and markers of steatohepatitis of the liver in both sexes of mice. Proteomic studies reveal that in addition to altered metabolic and fibrogenic pathways, levels of many ER proteins are also changed in HUKO livers. Impaired ER functions sensitize HUKO livers to nutrition- or chemical (tunicamycin)-induced ER stress. Moreover, HUKO primary hepatocytes exhibit increased ER stress. Furthermore, Ube4A maintains ER homeostasis by facilitating ER-associated protein degradation (ERAD). The lipogenic protein SCD1 is identified as one of the ERAD targets of Ube4A. SCD1 stability and triglyceride accumulation are amplified in HUKO primary hepatocytes. The liver Ube4A-interactome studies identified the ERAD mediator UBXN4 as a major Ube4A interacting protein. Alphafold3-based molecular modelling and interaction site mapping analyses pinpointed the Ube4A binding residues for UBXN4. ER-localized Ube4A-UBXN4 complex facilitates ERAD (e.g., SCD1) and UBXN4-binding deficient Ube4A mutants fail to enhance this process. Finally, Ube4A and UBXN4 are downregulated in the livers of human MASLD and MASH patients and this complex is diminished in GAN-D-fed mouse livers. In conclusion, Ube4A preserves ER homeostasis by maintaining ERAD via its interaction with UBXN4, which maintains liver health. Enhancing levels and/or preserving interaction of these proteins may offer new therapeutic strategies for MASLD treatment.
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BibTeX
@misc{challa2026hepatocyte,
title = {{Hepatocyte UBE4A protects against MASLD/MASH by maintaining ER homeostasis via UBXN4 interaction}},
author = {N. L. Challa and V. Babu and M. Chakraborty and M. Hayes and G. Kumar and K. S. McCommis and C. W. Vander Kooi and D. Carpenter and I. Ramos and S. Kattekola and A. Padakanti and S. Patel and K. Mills and S. Gupta and L. Lantier and B. A. Neuschwander-Tetri and A. Chakraborty},
howpublished = {bioRxiv},
year = {2026},
month = oct,
doi = {10.64898/2026.10.07.757434},
url = {https://www.biorxiv.org/content/10.64898/2026.10.07.757434v1},
note = {CC BY},
}
RIS
TY - UNPB
TI - Hepatocyte UBE4A protects against MASLD/MASH by maintaining ER homeostasis via UBXN4 interaction
AU - N. L. Challa
AU - V. Babu
AU - M. Chakraborty
AU - M. Hayes
AU - G. Kumar
AU - K. S. McCommis
AU - C. W. Vander Kooi
AU - D. Carpenter
AU - I. Ramos
AU - S. Kattekola
AU - A. Padakanti
AU - S. Patel
AU - K. Mills
AU - S. Gupta
AU - L. Lantier
AU - B. A. Neuschwander-Tetri
AU - A. Chakraborty
PY - 2026
DA - 2026/10/07
PB - bioRxiv
DO - 10.64898/2026.10.07.757434
UR - https://www.biorxiv.org/content/10.64898/2026.10.07.757434v1
AB - Molecular understanding of the regulation of endoplasmic reticulum (ER) functions in healthy and MASLD livers is limited. Here, we elucidate that Ube4A, a cytosolic E3 ubiquitin ligase, protects against MASLD development by maintaining ER homeostasis during nutritional stress. Hepatocyte-Ube4A deletion (HUKO) augments Gubra-Amylin-diet (GAN-D)-induced steatosis, inflammation, insulin resistance, ER stress and markers of steatohepatitis of the liver in both sexes of mice. Proteomic studies reveal that in addition to altered metabolic and fibrogenic pathways, levels of many ER proteins are also changed in HUKO livers. Impaired ER functions sensitize HUKO livers to nutrition- or chemical (tunicamycin)-induced ER stress. Moreover, HUKO primary hepatocytes exhibit increased ER stress. Furthermore, Ube4A maintains ER homeostasis by facilitating ER-associated protein degradation (ERAD). The lipogenic protein SCD1 is identified as one of the ERAD targets of Ube4A. SCD1 stability and triglyceride accumulation are amplified in HUKO primary hepatocytes. The liver Ube4A-interactome studies identified the ERAD mediator UBXN4 as a major Ube4A interacting protein. Alphafold3-based molecular modelling and interaction site mapping analyses pinpointed the Ube4A binding residues for UBXN4. ER-localized Ube4A-UBXN4 complex facilitates ERAD (e.g., SCD1) and UBXN4-binding deficient Ube4A mutants fail to enhance this process. Finally, Ube4A and UBXN4 are downregulated in the livers of human MASLD and MASH patients and this complex is diminished in GAN-D-fed mouse livers. In conclusion, Ube4A preserves ER homeostasis by maintaining ERAD via its interaction with UBXN4, which maintains liver health. Enhancing levels and/or preserving interaction of these proteins may offer new therapeutic strategies for MASLD treatment.
ER -