Welch Group

Welch Group
Welch Group

Research Summary

We study molecular mechanisms that control the Rac protein family, which regulates cell shape, cell movement, oxygen radical formation and gene expression. In particular, we study the proteins that activate Rac, so-called Rac-GEFs. A few years ago, we discovered a new type of Rac-GEF, the P-Rex family, and we have been studying the mechanisms that regulate their activity and their functional roles.

We found that P-Rex family Rac-GEFs are important for the ability of our white blood cells to defend us against bacterial and fungal infections, for the shape and electrical functions of nerve cells that control the coordination of our movements, and for the distribution of skin pigment cells during development. We also participated in studies which showed that the deregulation of the cellular amount or activity of P-Rex family Rac-GEFs contribute to cancer growth and metastasis.

Currently, our lab is investigating new functional roles of P-Rex and other Rac-GEFs, particularly in inflammatory cells, and we are inventing new ways of monitoring Rac-GEF activity.

Latest Publications

Crainiciuc G, Palomino-Segura M, Molina-Moreno M, Sicilia J, Aragones DG, Li JLY, Madurga R, Adrover JM, Aroca-Crevillén A, Martin-Salamanca S, Del Valle AS, Castillo SD, Welch HCE, Soehnlein O, Graupera M, Sánchez-Cabo F, Zarbock A, Smithgall TE, Di Pilato M, Mempel TR, Tharaux PL, González SF, Ayuso-Sacido A, Ng LG, Calvo GF, González-Díaz I, Díaz-de-María F, Hidalgo A

Transcriptional and proteomic profiling of individual cells have revolutionized interpretation of biological phenomena by providing cellular landscapes of healthy and diseased tissues. These approaches, however, do not describe dynamic scenarios in which cells continuously change their biochemical properties and downstream 'behavioural' outputs. Here we used 4D live imaging to record tens to hundreds of morpho-kinetic parameters describing the dynamics of individual leukocytes at sites of active inflammation. By analysing more than 100,000 reconstructions of cell shapes and tracks over time, we obtained behavioural descriptors of individual cells and used these high-dimensional datasets to build behavioural landscapes. These landscapes recognized leukocyte identities in the inflamed skin and trachea, and uncovered a continuum of neutrophil states inside blood vessels, including a large, sessile state that was embraced by the underlying endothelium and associated with pathogenic inflammation. Behavioural screening in 24 mouse mutants identified the kinase Fgr as a driver of this pathogenic state, and interference with Fgr protected mice from inflammatory injury. Thus, behavioural landscapes report distinct properties of dynamic environments at high cellular resolution.

+view abstract Nature, PMID: 34987220 05 Jan 2022

Hampson E, Tsonou E, Baker MJ, Hornigold DC, Hubbard RE, Massey A, Welch HCE Signalling

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.

+view abstract Cells, PMID: 34572121 18 Sep 2021

Floerchinger A, Murphy KJ, Latham SL, Warren SC, McCulloch AT, Lee YK, Stoehr J, Mélénec P, Guaman CS, Metcalf XL, Lee V, Zaratzian A, Da Silva A, Tayao M, Rolo S, Phimmachanh M, Sultani G, McDonald L, Mason SM, Ferrari N, Ooms LM, Johnsson AE, Spence HJ, Olson MF, Machesky LM, Sansom OJ, Morton JP, Mitchell CA, Samuel MS, Croucher DR, Welch HCE, Blyth K, Caldon CE, Herrmann D, Anderson KI, Timpson P, Nobis M Signalling

Assessing drug response within live native tissue provides increased fidelity with regards to optimizing efficacy while minimizing off-target effects. Here, using longitudinal intravital imaging of a Rac1-Förster resonance energy transfer (FRET) biosensor mouse coupled with in vivo photoswitching to track intratumoral movement, we help guide treatment scheduling in a live breast cancer setting to impair metastatic progression. We uncover altered Rac1 activity at the center versus invasive border of tumors and demonstrate enhanced Rac1 activity of cells in close proximity to live tumor vasculature using optical window imaging. We further reveal that Rac1 inhibition can enhance tumor cell vulnerability to fluid-flow-induced shear stress and therefore improves overall anti-metastatic response to therapy during transit to secondary sites such as the lung. Collectively, this study demonstrates the utility of single-cell intravital imaging in vivo to demonstrate that Rac1 inhibition can reduce tumor progression and metastases in an autochthonous setting to improve overall survival.

+view abstract Cell reports, PMID: 34525350 14 Sep 2021

Group Members

Heidi Welch

Group Leader

Stephen Chetwynd

PhD Student

Julia Chu

Postdoc Research Scientist

Kirsti Hornigold

Visiting Scientist

Priota Islam

PhD Student

Valdemar Johansen

Visiting Student

Polly Machin

PhD Student