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A specific combination of substrates is involved in signal transduction by the kit-encoded receptor
1Department of Chemical Immunology, Weizmann Institute of Science, Rehovot, Israel.
Abstract:
The kit protooncogene encodes a transmembrane tyrosine kinase related to the receptors for the platelet derived growth factor (PDGF-R) and the macrophage growth factor (CSF1-R), and was very recently shown to bind a stem cell factor. To compare signal transduction by the kit kinase with signaling by homologous receptors we constructed a chimeric protein composed of the extracellular domain of the epidermal growth factor receptor (EGF-R) and the transmembrane and cytoplasmic domains of kit. We have previously shown that the chimeric receptor transmits potent mitogenic and transforming signals in response to the heterologous ligand. Here we demonstrate that upon ligand binding, the ligand-receptor complex undergoes endocytosis and degradation and induces short- and long-term cellular effects. Examination of the signal transduction pathway revealed that the activated kit kinase strongly associates with phosphatidylinositol 3'-kinase activity and a phosphoprotein of 85 kd. In addition, the ligand-stimulated kit kinase is coupled to modifications of phospholipase C gamma and the Raf1 protein kinase. However, it does not lead to a significant change in the production of inositol phosphate. Comparison of our results with the known signaling pathways of PDGF-R and CSF1-R suggests that each receptor is coupled to a specific combination of signal transducers.
Insights
This study compares kit kinase signaling to homologous receptors using a chimeric protein. The activated kit kinase associates with phosphatidylinositol 3'-kinase and affects phospholipase C gamma and Raf1 protein kinase.
Area of Science:
- Molecular Biology
- Cell Signaling
- Oncogenes
Background:
- The kit protooncogene encodes a transmembrane tyrosine kinase.
- Kit kinase is related to platelet-derived growth factor receptor (PDGF-R) and colony-stimulating factor 1 receptor (CSF1-R).
- Kit kinase binds stem cell factor and transmits mitogenic signals.
Purpose of the Study:
- To compare signal transduction by the kit kinase with signaling by homologous receptors.
- To investigate the downstream signaling pathways activated by the kit kinase.
- To elucidate the cellular effects induced by ligand binding to the chimeric kit receptor.
Main Methods:
- Construction of a chimeric receptor: extracellular domain of epidermal growth factor receptor (EGF-R) fused to kit kinase domains.
- Analysis of ligand-induced endocytosis and degradation of the chimeric receptor.
- Examination of signal transduction pathways, including association with phosphatidylinositol 3 eal-kinase, phospholipase C gamma, and Raf1 protein kinase.
Main Results:
- The chimeric receptor transmits potent mitogenic and transforming signals upon heterologous ligand binding.
- Ligand-receptor complex undergoes endocytosis and degradation, inducing cellular effects.
- Activated kit kinase strongly associates with phosphatidylinositol 3 eal-kinase activity and a phosphoprotein of 85 kd.
- Ligand-stimulated kit kinase is coupled to modifications of phospholipase C gamma and Raf1 protein kinase, but not significantly to inositol phosphate production.
Conclusions:
- Kit kinase signaling involves specific associations with phosphatidylinositol 3 eal-kinase, phospholipase C gamma, and Raf1 protein kinase.
- Signal transduction pathways differ among homologous receptors like PDGF-R, CSF1-R, and kit.
- Each receptor type couples to a unique combination of signal transducers, influencing cellular responses.