P-Rex1 Limits the Agonist-Induced Internalisation of GPCRs Independently of its Rac-GEF Activity

Baker, M. J.; Hampson, E.; Islam, P.; Pelaez Moral, R.; Maunders, E. A.; Hornigold, K.; Tsonou, E.; Hornigold, D. C.; Hubbard, R. E.; Massey, A. J.; Welch, H. C. E.

doi:10.1101/2025.04.14.648762

bioRxiv · 10.1101/2025.04.14.648762

P-Rex1 Limits the Agonist-Induced Internalisation of GPCRs Independently of its Rac-GEF Activity

Baker, M. J.·Hampson, E.·Islam, P.·Pelaez Moral, R.·Maunders, E. A.·Hornigold, K.·Tsonou, E.·Hornigold, D. C.·Hubbard, R. E.·Massey, A. J.·Welch, H. C. E.

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Abstract

The Rac-GEF P-Rex1 mediates GPCR signalling by activating the small GTPase Rac. We show here that P-Rex1 also controls GPCR trafficking. P-Rex1 inhibits the agonist-stimulated internalisation of the GPCR S1PR1 independently of its Rac-GEF activity, through its PDZ, DEP and IP4P domains. P-Rex1 also limits the agonist-induced trafficking of CXCR4, PAR4, and GLP1R, but does not control steady-state GPCR levels, nor the agonist-induced internalisation of the RTKs PDGFR and EGFR. P-Rex1 blocks the phosphorylation required for GPCR internalisation. P-Rex1 binds Grk2, both in vitro and in cells, but does not appear to regulate Grk2 activity. We propose that P-Rex1 limits the agonist-induced internalisation of GPCRs through its interaction with Grk2 to maintain high levels of active GPCR at the plasma membrane. Therefore, P-Rex1 plays a dual role in promoting GPCR responses, by controlling GPCR trafficking through an adaptor function as well as by mediating GPCR signalling through its Rac-GEF activity. HighlightsO_LIP-Rex1 controls GPCR trafficking, independently of its Rac-GEF activity C_LIO_LIP-Rex1 limits the agonist-induced internalisation of S1PR1, CXCR4, PAR4 and GLP1R C_LIO_LIP-Rex1 does not control steady-state GPCR levels, or PDGFR and EGFR trafficking C_LIO_LIP-Rex1 binds Grk2 and inhibits the phosphorylation required for GPCR internalisation C_LI eTOC blurbP-Rex1 activates Rac downstream of GPCRs to regulate processes ranging from innate immunity to neuronal plasticity, its deregulation contributing to cancer. Here, Baker et al. show that P-Rex1 also controls GPCR trafficking, limiting agonist-induced GPCR internalisation through an adaptor function. Thus, P-Rex1 promotes GPCR responses in a dual manner. Graphical Abstract O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=200 SRC="FIGDIR/small/648762v1_ufig1.gif" ALT="Figure 1"> View larger version (54K): org.highwire.dtl.DTLVardef@20e1e2org.highwire.dtl.DTLVardef@cdd416org.highwire.dtl.DTLVardef@11f2a35org.highwire.dtl.DTLVardef@10c2b49_HPS_FORMAT_FIGEXP M_FIG C_FIG

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Baker, M. J., Hampson, E., Islam, P., Pelaez Moral, R., Maunders, E. A., Hornigold, K., Tsonou, E., Hornigold, D. C., Hubbard, R. E., Massey, A. J., Welch, H. C. E.. 2025-04-16. P-Rex1 Limits the Agonist-Induced Internalisation of GPCRs Independently of its Rac-GEF Activity. https://doi.org/10.1101/2025.04.14.648762

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