ER-liquid condensate contacts sequester FAM134B/C and RhoA to govern cell morphology

Jimenez-Moreno, N.; Karageorgiou, A.; Winnington-Ingram, K.; Wills, J.; Pednekar, C.; Pearson, M.; Gerasimavicius, L.; Wheeler, A.; Marsh, J. A.; Verkade, P.; von Kriegsheim, A.; Lane, J. D.; Wilkinson, S.

doi:10.1101/2025.11.01.685922

bioRxiv · 10.1101/2025.11.01.685922

ER-liquid condensate contacts sequester FAM134B/C and RhoA to govern cell morphology

Jimenez-Moreno, N.·Karageorgiou, A.·Winnington-Ingram, K.·Wills, J.·Pednekar, C.·Pearson, M.·Gerasimavicius, L.·Wheeler, A.·Marsh, J. A.·Verkade, P.·von Kriegsheim, A.·Lane, J. D.·Wilkinson, S.

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Abstract

ER-phagy receptors have elusive physiological functions beyond ER remodelling. Here, we use proximity biotinylation to identify their cytoplasmic interactomes. Secondary CRISPR/Cas9 screening reveals regulators of the prototypical FAM134B/C receptors, which include PRKAR1A, canonically known as a subunit of PKA. PRKAR1A directly binds an amphipathic helix in the otherwise disordered cytoplasmic domain of FAM134B. Super-resolution, FRAP and CLEM imaging reveal novel interorganellar contacts between liquid-like condensates of cAMP-bound PRKAR1A and the ER. Condensates promote clustering of ER-embedded FAM134B/C with LC3B, independently of regulation of PKA by PRKAR1A. Proteomics reveal that cytoplasmic RhoA interacts with FAM134B/C clusters and that sequestration of both these molecules occurs within lysosomes embedded within the proximal condensates. This results in reduced actomyosin contractility and ER-condensate interactions thusly determine cell morphology and cancer cell invasion modality. In summary, ER-condensate contacts mediated by FAM134B/C are novel cellular degradation hubs that coordinate ER and cellular remodelling.

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Jimenez-Moreno, N., Karageorgiou, A., Winnington-Ingram, K., Wills, J., Pednekar, C., Pearson, M., Gerasimavicius, L., Wheeler, A., Marsh, J. A., Verkade, P., von Kriegsheim, A., Lane, J. D., Wilkinson, S.. 2025-11-03. ER-liquid condensate contacts sequester FAM134B/C and RhoA to govern cell morphology. https://doi.org/10.1101/2025.11.01.685922

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