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Expression of the fgr protooncogene product as a function of myelomonocytic cell maturation
V Notario1, J S Gutkind, M Imaizumi
1Laboratory of Cellular Development and Oncology, National Institute of Dental Research, Bethesda, Maryland 20892.
Abstract:
The fgr protooncogene is a member of the src family of protein tyrosine kinases. Recent studies have shown that normal myelomonocytic cells and tissue macrophages are the major sites of fgr mRNA expression. In the present study, we have identified the fgr protooncogene protein product in HL60 cells and have examined its expression as a function of HL60 cell maturation. Whether induced toward monocytic or granulocytic lineages, p55c-fgr accumulated in HL60 cells during maturation. In differentiated cells, the protein was active as a protein tyrosine kinase and was localized to peripheral cell membranes. Demonstration that a myristyl group was covalently bound to the protein probably accounted for its subcellular distribution. These findings establish developmental regulation of p55c-fgr in a lineage that represents its natural site of expression.
Insights
The fgr protooncogene protein (p55c-fgr) accumulates and becomes active during HL60 cell maturation. This protein tyrosine kinase is found in cell membranes, indicating developmental regulation in its natural expression site.
Area of Science:
- Molecular Biology
- Cell Biology
- Oncogenes
Background:
- The fgr protooncogene is part of the src family of protein tyrosine kinases.
- fgr mRNA is primarily expressed in myelomonocytic cells and tissue macrophages.
Purpose of the Study:
- Identify the fgr protooncogene protein product in HL60 cells.
- Examine p55c-fgr expression during HL60 cell differentiation.
Main Methods:
- Western blotting to detect p55c-fgr.
- Cell maturation induction (monocytic and granulocytic lineages).
- Subcellular localization studies and myristylation analysis.
Main Results:
- p55c-fgr protein accumulated during HL60 cell maturation.
- Differentiated cells showed active, membrane-localized p55c-fgr.
- Myristyl group attachment was confirmed, explaining subcellular distribution.
Conclusions:
- p55c-fgr is developmentally regulated in HL60 cells during maturation.
- The protein tyrosine kinase activity and localization are linked to differentiation.
- These findings highlight the regulation of p55c-fgr in its natural cellular context.