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.
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-3beta (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-3beta 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.
Shimwell
N J
NJ
Cancer Research UK School of Cancer Sciences, University of Birmingham, Birmingham, West Midlands, UK.
Martin
A
A
Bruton
R K
RK
Blackford
A N
AN
Sedgwick
G G
GG
Gallimore
P H
PH
Turnell
A S
AS
Grand
R J A
RJ
D000256:Adenoviridae / Q000502:physiology; D017500:Adenovirus E1A Proteins / Q000378:metabolism* / Q000502:physiology*; D000818:Animals; D002472:Cell Transformation, Viral / Q000235:genetics; D002478:Cells, Cultured; D015972:Gene Expression Regulation, Neoplastic; D045325:HCT116 Cells; D019073:HT29 Cells; D006367:HeLa Cells; D006801:Humans; D055504:Insulin Receptor Substrate Proteins / Q000235:genetics / Q000378:metabolism*; D051058:Oncogene Protein v-akt / Q000378:metabolism / Q000502:physiology*; D019869:Phosphatidylinositol 3-Kinases / Q000378:metabolism / Q000502:physiology*; D011485:Protein Binding; D051381:Rats; D015398:Signal Transduction
D017500:Adenovirus E1A Proteins; C107686:IRS4 protein, human; D055504:Insulin Receptor Substrate Proteins; D019869:Phosphatidylinositol 3-Kinases; D051058:Oncogene Protein v-akt