• P-Rex1 Controls Sphingosine 1-Phosphate Receptor Signalling, Morphology, and Cell-Cycle Progression in Neuronal Cells

      Hampson, Elizabeth; email: Elizabeth.Hampson@babraham.ac.uk; Tsonou, Elpida; email: elpida.tsonou1@astrazeneca.com; Baker, Martin J.; orcid: 0000-0002-9743-6294; email: martin.baker@manchester.ac.uk; Hornigold, David C.; orcid: 0000-0002-3354-2768; email: David.Hornigold@astrazeneca.com; Hubbard, Roderick E.; email: r.hubbard@vernalis.com; Massey, Andrew; email: a.massey@vernalis.com; Welch, Heidi C. E.; orcid: 0000-0001-7865-7000; email: heidi.welch@babraham.ac.uk (MDPI, 2021-09-18)
      P-Rex1 is a guanine-nucleotide exchange factor (GEF) that activates Rac-type small G proteins in response to the stimulation of a range of receptors, particularly G protein-coupled receptors (GPCRs), to control cytoskeletal dynamics and other Rac-dependent cell responses. P-Rex1 is mainly expressed in leukocytes and neurons. Whereas its roles in leukocytes have been studied extensively, relatively little is known about its functions in neurons. Here, we used CRISPR/Cas9-mediated P-Rex1 deficiency in neuronal PC12 cells that stably overexpress the GPCR S1PR1, a receptor for sphingosine 1-phosphate (S1P), to investigate the role of P-Rex1 in neuronal GPCR signalling and cell responses. We show that P-Rex1 is required for the S1P-stimulated activation of Rac1 and Akt, basal Rac3 activity, and constitutive cAMP production in PC12-S1PR1 cells. The constitutive cAMP production was not due to increased expression levels of major neuronal adenylyl cyclases, suggesting that P-Rex1 may regulate adenylyl cyclase activity. P-Rex1 was required for maintenance of neurite protrusions and spreading in S1P-stimulated PC12-S1PR1 cells, as well as for cell-cycle progression and proliferation. In summary, we identified novel functional roles of P-Rex1 in neuronal Rac, Akt and cAMP signalling, as well as in neuronal cell-cycle progression and proliferation.