Caprin-1 binding to the critical stress granule protein G3BP1 is regulated by pH

Schulte, T.; Panas, M. D.; Wiliams, L.; Kedersha, N.; Fleck, J. S.; Tan, T. J. C.; Olsson, A.; Morro, A. M.; Hanke, L.; Nilvebrant, J.; Giang, K. A.; Nygren, P.-A.; Anderson, P.; Achour, A.; McInerney, G. M.

doi:10.1101/2021.02.05.429362

bioRxiv · 10.1101/2021.02.05.429362

Caprin-1 binding to the critical stress granule protein G3BP1 is regulated by pH

Schulte, T.·Panas, M. D.·Wiliams, L.·Kedersha, N.·Fleck, J. S.·Tan, T. J. C.·Olsson, A.·Morro, A. M.·Hanke, L.·Nilvebrant, J.·Giang, K. A.·Nygren, P.-A.·Anderson, P.·Achour, A.·McInerney, G. M.

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Abstract

G3BP is the central hub within the protein-RNA interaction network of stress-induced bio-molecular condensates known as stress granules (SG). The SG-associated proteins Caprin-1 and USP10 exhibit mutually exclusive binding to the structured NTF2-domain of G3BP1, thereby regulating G3BP1-mediated condensation, but with opposite effects: Caprin-1 promotes but USP10 inhibits SG formation. Herein, we present the crystal structure of G3BP1-NTF2 in complex with a Caprin-1 derived short linear motif (SLiM), which provides a molecular understanding for the mutually exclusive binding of USP10 and Caprin-1 to G3BP1. Caprin-1 but not USP10 contacts two G3BP1-NTF2 histidine residues, which was confirmed using biochemical, biophysical and cellular biological binding assays. G3BP1/Caprin-1 interactions disrupted via point mutations resulted in fewer and smaller SG condensates. In addition, biochemical binding assays demonstrated reduced binding of Caprin-1 to G3BP1 at lower pH values. Finally, ratiometric pH sensitive measurements of SGs revealed a substantial drop in pH compared to the adjacent cytosol, suggesting that reduced pH can fine-tune and regulate the G3BP1-mediated interaction network via a NTF2-mediated pH-sensitive SLiM-selection mechanism.

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Schulte, T., Panas, M. D., Wiliams, L., Kedersha, N., Fleck, J. S., Tan, T. J. C., Olsson, A., Morro, A. M., Hanke, L., Nilvebrant, J., Giang, K. A., Nygren, P.-A., Anderson, P., Achour, A., McInerney, G. M.. 2021-02-05. Caprin-1 binding to the critical stress granule protein G3BP1 is regulated by pH. https://doi.org/10.1101/2021.02.05.429362

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