Oral Presentation Hunter Cell Biology Meeting 2025

Loss of Akt-negative feedback rewires the insulin signalling network to potentiate the ERK pathway (119546)

Jonathan Scavuzzo 1 , Julian van Gerwen 2 , Milad Ghomlaghi 3 , Alison L Kearney 1 , Dougall M Norris 1 , Kristen C Cooke 1 , Lan K Nguyen 3 , David E James 1 , Alexis R Diaz-Vegas 1 , Sean J Humphrey 4 , James G Burchfield 1
  1. The University of Sydney, Sydney, NSW, Australia
  2. ETH, Zurich, Switzerland
  3. Monash University, Melbourne, Vic, Australia
  4. The University of Melbourne, Melbourne, Vic, Australia

Insulin orchestrates key cellular processes via the activation of numerous signalling pathways, including Akt (Protein Kinase B) and ERK (Extracellular-signal Regulated Kinase). While individual network components are well-understood, the complex interconnectivity shaped by feedback and crosstalk between distinct pathways is less established. Recently, we described novel Akt-mediated negative feedback onto IRS1/2, which limits the production of the phospholipid Phosphatidylinositol (3,4,5)-trisphosphate (PIP3) by Phosphoinositide 3-kinase (PI3K) while regulating signalling downstream of Akt (1). Given the role of PIP3 as a potent signalling molecule, we hypothesised that disrupting this feedback would cause aberrant signal transduction and the identification of novel, non-canonical regulatory mechanisms within the insulin signalling nexus. 

Here, using Mass Spectrometry-based phosphoproteomics in 3T3-L1 adipocytes, we demonstrate that acute loss of Akt-IRS negative feedback causes PI3K-dependent ERK potentiation, emphasising the importance of feedback and crosstalk in shaping the signalling landscape. Further, we utilise a mathematical modelling approach to elucidate causal mechanisms, concluding that both hyper-recruitment of GRB2-associated binding protein 2 (Gab2) and aberrant activation of p21-activated kinase 1 (PAK1) are driving pathway potentiation via upstream ERK effectors Growth factor receptor-bound protein 2 (Grb2) and RAF1, respectively.

This research highlights a novel mechanism of crosstalk between two strongly defined and highly studied signalling pathways. Due to the numerous pathologies associated with hyperactivated ERK, these data additionally suggest an aberrant signalling phenotype with diminished Akt activity, suggesting potential clinical relevance. Additionally, this study articulates the regulatory landscape sculpted by Akt feedback within insulin signalling and provides valuable insights into inhibitor directed network rewiring and a mechanistic basis for the development of targeted therapies in diabetes and cancer.

  1. A. L. Kearney, D. M. Norris, M. Ghomlaghi, M. Kin Lok Wong, S. J. Humphrey, L. Carroll, G. Yang, K. C. Cooke, P. Yang, T. A. Geddes, S. Shin, D. J. Fazakerley, L. K. Nguyen, D. E. James, J. G. Burchfield, Akt phosphorylates insulin receptor substrate to limit PI3K-mediated PIP3 synthesis. eLife 10 (2021).