Adenovirus 5 E1A is responsible for increased expression of insulin receptor substrate 4 in established adenovirus 5-transformed cell lines and interacts with IRS components activating the PI3 kinase|[sol]|Akt signalling pathway

doi:doi:10.1038/onc.2008.417

Oncogene (2009) 28, 686–697; doi:10.1038/onc.2008.417; published online 24 November 2008

Adenovirus 5 E1A is responsible for increased expression of insulin receptor substrate 4 in established adenovirus 5-transformed cell lines and interacts with IRS components activating the PI3 kinase/Akt signalling pathway

N J Shimwell¹, A Martin¹, R K Bruton¹, A N Blackford¹, G G Sedgwick¹, P H Gallimore¹, A S Turnell¹ and R J A Grand¹

¹Cancer Research UK School of Cancer Sciences, University of Birmingham, Birmingham, West Midlands, UK

Correspondence: Dr RJA Grand, Cancer Research UK, School of Cancer Sciences, Institute of Cancer Studies, University of Birmingham, Edgbaston, Birmingham, West Midlands B15 2TT, UK. E-mail: R.J.A.Grand@bham.ac.uk

Received 19 June 2008; Revised 2 October 2008; Accepted 16 October 2008; Published online 24 November 2008.

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Abstract

Using mass spectrometric analysis insulin receptor substrate 4 (IRS-4) has been identified as a novel adenovirus 5 early region 1A (Ad5E1A)-binding protein. IRS-4 interacts with both the transcriptional activation domain (conserved region 3) and the N-terminal region of Ad5E1A13S. Prolonged expression of Ad5E1A13S is required for the observed dramatic increase in the levels of IRS-4 mRNA and protein in Ad5E1-transformed human cell lines. Once expressed, as well as binding to E1A and the insulin receptor, IRS-4 remains tyrosine phosphorylated and constitutively associates with the regulatory p85 subunit of phosphoinositide 3 kinase, resulting in the phosphorylation of Akt (causing activation) and GSK-3 beta (causing inhibition). Reducing IRS-4 expression using small interfering RNA (siRNA) in established Ad5E1A-expressing cell lines decreases the activation of Akt and cellular proliferation. During Ad5 infection, IRS-4 is not expressed. However, Ad5E1A associates with IRS-1, increasing Akt and GSK-3 beta phosphorylation and tyrosine phosphorylation of IRS-1 itself. We conclude that the association and altered regulation of IRS proteins by Ad5E1A contribute to the adenovirus-transformed phenotype and modulates viral infection in an Akt-dependent manner.