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Anti-apoptotic signaling by a colony-stimulating factor-1 receptor/insulin receptor chimera with a juxtamembrane
J E Boehm1, O V Chaika, R E Lewis
1Eppley Institute for Research in Cancer and Allied Diseases, University of Nebraska Medical Center, Omaha, Nebraska 68198-6805, USA.
Abstract:
The intracellular mechanisms used by insulin and insulin-like growth factors to block programmed cell death are unknown. To identify receptor structures and signaling pathways essential for anti-apoptotic effects on cells, we have created a chimeric receptor (colony-stimulating factor-1 receptor/insulin receptor chimera (CSF1R/IR)) connecting the extracellular, ligand-binding domain of the colony-stimulating factor-1 (CSF-1) receptor to the transmembrane and cytoplasmic domains of the insulin receptor. Upon activation with CSF-1, the CSF1R/IR phosphorylates itself and intracellular substrates in a manner characteristic of normal insulin receptors. CSF-1 treatment protected cells expressing the CSF1R/IR from staurosporine-induced apoptosis. A chimeric receptor (CSF1R/IRDelta960) with a deletion of 12 amino acids from its juxtamembrane domain was constructed and expressed. CSF-1-treated cells expressing the CSF1R/IRDelta960 are unable to phosphorylate IRS-1 and Shc (Chaika, O. V., Chaika, N., Volle, D. J., Wilden, P. A. , Pirrucello, S. J., and Lewis, R. E. (1997) J. Biol. Chem. 272, 11968-11974). CSF-1 stimulated glucose uptake, mitogen-activated protein kinases, and IRS-1-associated phosphatidylinositol 3' kinase in cells expressing the CSF1R/IR but not in cells expressing the CSF1R/IRDelta960. Surprisingly, the CSF1R/IRDelta960 was as effective as the CSF1R/IR in mediating CSF-1 protection of cells from staurosporine-induced apoptosis. These observations indicate that the anti-apoptotic effects of the insulin receptor cytoplasmic domain can be mediated by signaling pathways distinct from those requiring IRS-1 and Shc.
Insights
Insulin receptor signaling pathways distinct from IRS-1 and Shc mediate anti-apoptotic effects. A chimeric receptor demonstrated that CSF-1 protection from cell death occurs independently of these specific pathways.
Area of Science:
- Cell biology
- Molecular signaling
- Apoptosis research
Background:
- The mechanisms by which insulin and insulin-like growth factors prevent programmed cell death (apoptosis) are not fully understood.
- Identifying the specific receptor structures and intracellular signaling pathways involved is crucial for understanding these anti-apoptotic effects.
Purpose of the Study:
- To investigate the role of specific intracellular signaling pathways in mediating the anti-apoptotic effects of the insulin receptor.
- To determine if insulin receptor-mediated protection from apoptosis can occur independently of IRS-1 and Shc signaling.
Main Methods:
- Construction and expression of a chimeric receptor (CSF1R/IR) combining the CSF-1 receptor's extracellular domain with the insulin receptor's intracellular domains.
- Creation of a modified chimeric receptor (CSF1R/IRDelta960) with a deletion in the juxtamembrane domain.
- Activation of chimeric receptors with CSF-1 and assessment of downstream signaling (phosphorylation of substrates, glucose uptake, MAPK, PI3K) and apoptosis resistance.
Main Results:
- The CSF1R/IR chimera, when activated by CSF-1, mimicked insulin receptor signaling and protected cells from staurosporine-induced apoptosis.
- The CSF1R/IRDelta960 chimera failed to phosphorylate IRS-1 and Shc and did not stimulate key downstream pathways like PI3K.
- Despite the signaling defects, CSF1R/IRDelta960 mediated protection from apoptosis as effectively as the intact CSF1R/IR.
Conclusions:
- The anti-apoptotic function of the insulin receptor's cytoplasmic domain can be dissociated from IRS-1 and Shc signaling.
- Distinct signaling pathways, independent of IRS-1 and Shc, are capable of mediating the anti-apoptotic effects of the insulin receptor.