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High tyrosine kinase activity in normal nonproliferating cells
Nature
|September 5, 1983
Summary
Phosphotyrosine, a key regulator of cell proliferation, was found in low percentages in soluble fractions of most blood cells. Surprisingly, high levels were detected in particulate fractions of non-proliferating cells like platelets and red blood cells.
Area of Science:
- Biochemistry
- Cell Biology
- Hematology
Background:
- Protein phosphorylation, particularly at serine and threonine residues, regulates cellular processes.
- Tyrosine phosphorylation is increasingly linked to cell proliferation, viral transformation, and growth factor signaling (e.g., EGF, PDGF, insulin).
Purpose of the Study:
- To compare protein kinases and phosphoproteins in normal versus leukaemic human hematopoietic cells.
- To investigate the distribution of phosphoserine, phosphothreonine, and phosphotyrosine in different blood cell fractions.
Main Methods:
- In vitro phosphorylation of proteins from various human blood cell fractions.
- Hydrolysis of phosphorylated proteins.
- Quantification of phosphoserine, phosphothreonine, and phosphotyrosine percentages.
Main Results:
- Phosphotyrosine constituted less than 1% of soluble fractions in polymorphonuclear cells, mononuclear cells, platelets, and red blood cells.
- Unexpectedly high percentages of phosphotyrosine were found in the particulate fractions of non-proliferating cells, including platelets and red blood cells.
Conclusions:
- The distribution of phosphotyrosine differs significantly between soluble and particulate cellular fractions.
- Non-proliferating cells, such as platelets and red blood cells, exhibit unique phosphotyrosine profiles in their particulate components.
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