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Receptor functions and ligand-dependent transforming potential of a chimeric kit proto-oncogene
1Department of Chemical Immunology, Weizmann Institute of Science, Rehovot, Israel.
Abstract:
The c-kit proto-oncogene, the cellular homolog of the transforming gene of a feline retrovirus, encodes a transmembrane tyrosine kinase homologous to receptors for growth factors. To study the cellular function of c-kit, we constructed a chimeric molecule composed of the extracellular portion of the receptor for epidermal growth factor (EGF) and the transmembrane and cytoplasmic domains of p145kit. The hybrid molecule was properly expressed in murine fibroblasts and displayed specific binding of EGF (Kd, 3 x 10(-8) M). Activation of the chimeric receptor by EGF stimulated the tyrosine kinase activity of kit and led to the generation of a potent mitogenic signal. Moreover, cells expressing the chimeric receptor acquired a transformed phenotype once they were stimulated with the heterologous ligand.
Insights
The c-kit proto-oncogene encodes a tyrosine kinase. A chimeric receptor study revealed that epidermal growth factor (EGF) binding to a hybrid molecule stimulated c-kit kinase activity, inducing cell proliferation and transformation.
Area of Science:
- Molecular biology
- Cell signaling
- Oncogenesis
Background:
- The c-kit proto-oncogene encodes a transmembrane tyrosine kinase.
- c-kit is homologous to growth factor receptors, suggesting a role in cellular signaling.
- Understanding c-kit's function is crucial for cancer research.
Purpose of the Study:
- To investigate the cellular function of the c-kit proto-oncogene.
- To determine if a chimeric receptor could activate c-kit signaling.
- To explore the effects of heterologous ligand stimulation on c-kit activity.
Main Methods:
- Constructed a chimeric receptor combining the extracellular domain of the epidermal growth factor (EGF) receptor with p145kit domains.
- Expressed the chimeric receptor in murine fibroblasts.
- Assessed EGF binding, tyrosine kinase activity, and mitogenic signaling upon EGF stimulation.
Main Results:
- The chimeric receptor was successfully expressed and specifically bound EGF.
- EGF activation of the chimeric receptor stimulated p145kit tyrosine kinase activity.
- Cells expressing the chimeric receptor exhibited a transformed phenotype upon EGF stimulation, indicating a potent mitogenic signal.
Conclusions:
- The c-kit tyrosine kinase can be activated by a heterologous ligand through a chimeric receptor.
- EGF-mediated activation of the chimeric receptor leads to cellular transformation.
- This study provides insights into the signaling mechanisms and oncogenic potential of c-kit.