Sephin1 rewires proteostasis through actin-dependent signaling

Frapporti, G.; Capuozzo, A.; Colombo, E.; Fioretti, P.; D'Amore, V. M.; Di Leva, F. S.; Lama, A.; Tripathi, V.; Medaglia, S.; Waich, S.; Montani, C.; Perez-Carrion, M. D.; Marte, A.; Onofri, F.; Gloeckner, C. J.; Marinelli, L.; Seneci, P.; Hess, M. W.; Medina, D. L.; Piccoli, G.

doi:10.64898/2026.04.20.719601

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bioRxiv · 10.64898/2026.04.20.719601

Sephin1 rewires proteostasis through actin-dependent signaling

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Abstract

The maintenance of protein homeostasis is vital for all cells. Alteration in protein handling underlies several diseases. The small molecule sephin1 is a promising clinical candidate against proteostasis disruption, but its mechanism of action is still uncertain. Our experimental evidence shows that sephin1 binds G-actin and drives actin cytoskeleton misfolding, and eventually, Golgi disintegration. At first, sephin1 impairs the autophagic flux and elicits the phosphorylation of the subunit of eIF2 and the ER-stress independent expression of CHOP via GCN2 kinase. Sephin1 also inhibits the mammalian target of rapamycin (mTORC1), activates the transcription Factor EB (TFEB), drives the expression of TFEB-direct target genes, and eventually stimulates the autophagy lysosomal pathway. Our results reveal that the actin cytoskeleton may regulate autophagy via mTORC1-TFEB complemented with the GCN2-eIF2-CHOP signaling pathway.

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Frapporti, G., Capuozzo, A., Colombo, E., Fioretti, P., D'Amore, V. M., Di Leva, F. S., Lama, A., Tripathi, V., Medaglia, S., Waich, S., Montani, C., Perez-Carrion, M. D., Marte, A., Onofri, F., Gloeckner, C. J., Marinelli, L., Seneci, P., Hess, M. W., Medina, D. L., Piccoli, G.. 2026-04-21. Sephin1 rewires proteostasis through actin-dependent signaling. https://doi.org/10.64898/2026.04.20.719601

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