Insulin receptor substrates 1 and 2 but not Shc can activate the insulin receptor independent of insulin and induce proliferation in CHO-IR cells

Journal Article · Thu Feb 15 04:00:00 EST 2007 · Experimental Cell Research

DOI:https://doi.org/10.1016/j.yexcr.2006.11.015· OSTI ID:20972124

Niessen, Markus ^[1]; Jaschinski, Frank ^[2]; Item, Flurin ^[2]; McNamara, Morgan P ^[2]; Spinas, Giatgen A ^[2]; Trueb, Thomas ^[3]

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1. Department of Endocrinology and Diabetes, University Hospital Zurich, Ramistrasse 100, 8091 Zurich (Switzerland) and Competence Center for Systems Physiology and Metabolic Diseases, ETH Honggerberg, Schafmattstr. 18, 8093 Zurich (Switzerland)
2. Department of Endocrinology and Diabetes, University Hospital Zurich, Ramistrasse 100, 8091 Zurich (Switzerland)
3. Zentrale Dienste der Universitaet, Ausruestung und Logistik, Y10 G 22, Winterthurerstrasse 190, 8057 Zurich (Switzerland)

Ligand-activated insulin receptor (IR) attracts and phosphorylates various substrates such as insulin receptor substrates 1-4 (IRS) and Shc. To investigate how binding affinity for substrate affects signalling we generated chimeric receptors with the {beta}-chain of the insulin receptor containing NPXY motives with different affinities for receptor substrates. We found that the extent of receptor tyrosine phosphorylation positively correlates with binding affinity towards IRS1/2 but not towards Shc. Moreover, overexpression of IRS1 or IRS2 but not of Shc increased IR tyrosine phosphorylation in a dose-dependent manner, also independent of insulin. Molecular truncations of IRS1 revealed that neither the isolated PH and PTB domains nor the C-terminus with the tyrosine phosphorylation sites alone are sufficient for substrate-dependent receptor activation. Overexpression of IRS1 and IRS2 impaired insulin-induced internalization of the IR in a dose-dependent manner suggesting that IRS proteins prevent endosome-associated receptor dephosphorylation/inactivation. IRS1 and IRS2 could therefore target the activated IR to different cellular compartments. Overexpression of IRS1 and IRS2 inhibited insulin-stimulated activation of the MAP kinases Erk1/2 while it increased/induced activation of Akt/PKB. Finally, overexpression of IRS1 and IRS2 but not of Shc induced DNA synthesis in starved CHO-IR cells independent of exogenous growth factors. Our results demonstrate that variations in cellular IRS1 and IRS2 concentration affect insulin signalling both upstream and downstream and that IRS proteins could play instructive rather than just permissive roles in signal transmission.

• OSTI ID: 20972124
• Journal Information: Experimental Cell Research, Journal Name: Experimental Cell Research Journal Issue: 4 Vol. 313; ISSN 0014-4827; ISSN ECREAL
• Country of Publication: United States
• Language: English

Related Subjects

60 APPLIED LIFE SCIENCES
CELL PROLIFERATION
GROWTH FACTORS
INSULIN
PHOSPHORYLATION
PHOSPHOTRANSFERASES
RECEPTORS
SUBSTRATES
TYROSINE