RAS-like (RAL) GTPases function in Wnt signalling-dependent intestinal stem cell proliferation and regeneration. Whether RAL proteins work as canonical RAS effectors in the intestine, and the mechanisms of how they contribute to tumourigenesis remain unclear. Here, we show that RAL GTPases are necessary and sufficient to activate EGFR/MAPK signalling in the intestine, via induction of EGFR internalisation. Knocking down Drosophila RalA from intestinal stem and progenitor cells leads to increased levels of plasma membrane-associated EGFR and decreased MAPK pathway activation. Importantly, in addition to impacting stem cell proliferation during damage-induced intestinal regeneration, this role of RAL GTPases impacts on EGFR-dependent tumorigenic growth in the intestine and in human mammary epithelium. However, the effect of oncogenic RAS in the intestine is independent from RAL function. Altogether, our results reveal previously unrecognised cellular and molecular contexts where RAL GTPases become essential mediators of adult tissue homeostasis and malignant transformation.
All data underlying the findings of this study are included in the manuscript and supporting file. Source data files have been provided for all figures containing numeric data. The entire raw data set corresponding to the work in this paper will be publicly available at the time of publication from our institutional repository http://dx.doi.org/10.5525/gla.researchdata.1142. RNA sequencing data has been deposited in GEO (accession GSE162421) and can be accessed through (https://www.ncbi.nlm.nih.gov/geo/query/acc.cgi?acc=GSE162421). Custom scripts used for quantification are available at Github: https://github.com/emltwc/TracheaProject/blob/master/Blind_scoring.ijm; https://github.com/emltwc/2018-Cell-Stem-Cell and https://github.com/emltwc/EGFRProject .
RAL GTPases mediate EGFR/MAPK signalling-driven intestinal stem cell proliferation and tumourigenesis upstream of RAS activation.NCBI Gene Expression Omnibus, GSE162421.
- Julia B Cordero
- Yachuan Yu
- Jim C Norman
- Joel Johansson
- Andrew D Campbell
- Owen J Sansom
- Alvaro Román-Fernández
- Emma Sandilands
- David M Bryant
The funders had no role in study design, data collection and interpretation, or the decision to submit the work for publication.
Animal experimentation: All animal work has been approved by a University of Glasgow internal ethics committee and performed in accordance with institutional guidelines under personal and project licenses granted by the UK Home Office (PPL PCD3046BA).
- Hugo J Bellen, Baylor College of Medicine, United States
- Received: October 7, 2020
- Accepted: June 3, 2021
- Accepted Manuscript published: June 7, 2021 (version 1)
© 2021, Nászai et al.
This article is distributed under the terms of the Creative Commons Attribution License permitting unrestricted use and redistribution provided that the original author and source are credited.