The Grb2 splice variant, Grb3-3, is a negative regulator of RAS activation

  • Commun Biol. 2022 Sep 28;5(1):1029. doi: 10.1038/s42003-022-03985-7.
Caroline Seiler  #  1 ,  Amy K Stainthorp  #  1 ,  Sophie Ketchen  #  1 ,  Christopher M Jones  1  2  3 ,  Kate Marks  4 ,  Philip Quirke  4 ,  John E Ladbury  5
Affiliations
  • 1. School of Molecular and Cellular Biology, University of Leeds, Leeds, UK.
  • 2. Radiotherapy Research Group, Faculty of Medicine & Health, University of Leeds, Leeds, UK.
  • 3. Leeds Cancer Centre, The Leeds Teaching Hospitals NHS Trust, Leeds, UK.
  • 4. University of Leeds School of Medicine, Leeds Institute of Medical Research, Pathology and Data Analytics, University of Leeds, Leeds, UK.
  • 5. School of Molecular and Cellular Biology, University of Leeds, Leeds, UK. [email protected].
  • # Contributed equally.
PMID: 36171279 DOI: 10.1038/s42003-022-03985-7
Abstract

Activation of Ras is crucial in driving cellular outcomes including proliferation, differentiation, migration and Apoptosis via the MAPK pathway. This is initiated on recruitment of Grb2, as part of a Grb2-Sos complex, to an up-regulated receptor tyrosine kinase (RTK), enabling subsequent interaction of Sos with the plasma membrane-localised Ras. Aberrant regulation at this convergence point for RTKs in MAPK signalling is a key driver of multiple cancers. Splicing of the GRB2 gene produces a deletion variant, Grb3-3, that is incapable of binding to RTKs. We show that, despite maintaining the ability to bind to Sos, the Grb3-3-Sos complex remains in the cytoplasm, unable to engage with Ras. Competition between Grb2 and Grb3-3 for binding to C-terminal proline-rich sequences on Sos modulates MAPK signalling. Additionally, we demonstrate that splicing is regulated by heterogenous nuclear riboproteins C1/C2, and that normal and malignant colon tissue show differential Grb3-3 expression.