Abstract
Many proteins can reach the cell surface through a Golgi-independent unconventional protein secretion (UPS) pathway, particularly under cellular stress conditions. However, the molecular mechanisms that mediate UPS remain largely elusive. In this study, VPS26A-containing retromer complex, along with the sorting nexin SNX27, is identified as a regulator of UPS of transmembrane proteins, including the trafficking-deficient ∆F508 mutant CFTR, which causes cystic fibrosis, and the SARS-CoV-2 spike protein, associated with COVID-19. A targeted CRISPR knockout screen identified VPS26A as a key contributor in the UPS of ∆F508-CFTR. Subsequent molecular analyses revealed that SNX27 recruits ∆F508-CFTR to the VPS26A-VPS35-VPS29 retromer complex, facilitating its transport to the cell surface under UPS-inducing conditions. Additionally, VPS26A and SNX27 are necessary for UPS of the spike protein, enabling the formation of intact SARS-CoV-2 virions. These findings suggest that the retromer complex and SNX27, known for their roles in recycling endosomes, mediate previously unrecognized functions in the UPS of transmembrane proteins.
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All data supporting the findings of this study are available within the main text, main figures, and Supplementary Information. The original ICC image files generated in this study have been deposited in the EBI BioImage Archive under accession code S-BIAD3018. Source data are provided with this paper.
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Acknowledgements
The authors thank the Medical Illustration & Design team at Yonsei University College of Medicine for providing support with the medical illustrations, Benjamin J. Latimer for his editorial assistance, and the Yonsei-Carl Zeiss Advanced Imaging Center for their technical assistance. This research was supported by grants 2021R1I1A1A01049255 (to S.H.N.), 2022R1A2C3002917 (M.G.L.), RS-2022-NR067483 (M.G.L., J.M.L.), RS-2024-00351254 (H.-S.C.) and RS-2025-18362970 (M.G.L. and H.-S.C.) from the National Research Foundation (NRF) of Korea funded by the Ministry of Education and the Ministry of Science and ICT, and the grant RS-2024-00404555 (M.G.L.) and RS-2025-25422732 (M.G.L.) from the Korea Health Industry Development Institute (KHIDI) funded by the Ministry of Health & Welfare, Republic of Korea. M.G.L. was supported by the SBS Foundation.
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Y.J.K. and C.L. conducted the molecular experiments and analyzed the data. S.K.S. performed the CRISPR-Cas9 screening. J.W.R. and D.H.S. performed PCA analysis, MD simulations, and predicted the protein structures using AlphaFold. H.R.L. carried out the immunocytochemistry experiments. S.J.H. performed experiments with authentic virus. N.C., H.S.C., and H.-S.C. conducted the SPR assays. H.K.K. and H.S.K. designed and assisted with the CRISPR-Cas9 screening experiments. H.Y.G. designed and analyzed the experiments using AlphaFold. J.M.L. designed and analyzed experiments with authentic SARS-CoV-2. M.G.L. and S.H.N. designed and analyzed all experiments and wrote the manuscript.
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Kim, Y.J., Lee, C., Seo, S.K. et al. VPS26A retromer complex and SNX27 mediate stress-induced Golgi bypass of membrane proteins. Nat Commun (2026). https://doi.org/10.1038/s41467-026-71409-9
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DOI: https://doi.org/10.1038/s41467-026-71409-9
