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Partial characterization of protein tyrosine kinases in human lymphoid cells
C J Punt1, G Rijksen, B A van Oirschot
1Department of Medical Oncology, University Hospital Nijmegen, The Netherlands.
Abstract:
We have examined several aspects of protein tyrosine kinase (PTK)-activity in the cytosolic and membrane fractions of both normal and malignant lymphoid cells. The expression of the PTK-encoding oncogenes fes, abl and src, was investigated with the use of antibodies generated to their respective gene products. These antibodies recognized proteins in all cell types examined, most frequently in both the cytosolic and the membrane fraction. PTKs were partially characterized by FPLC. PTK-activities of column fractions were assayed using a non-radioactive dot blot assay. Cytosolic and membrane fractions showed FPLC patterns with a constant as well as a variable part in both normal and malignant cells, suggestive of PTKs with specialized functions in normal cell growth and transformation. Lastly, using antibodies to phosphotyrosine, we found that cytosolic fractions contained the majority of proteins phosphorylated at tyrosine in all cell types. Normal peripheral blood lymphocytes and B-lymphoma cells showed a great similarity in tyrosine phosphorylation pattern, while in tonsillar lymphocytes a clearly different pattern was found. These methods further characterize PTK-activities in lymphoid cells, and the results give evidence that PTKs in normal and malignant cells have both similar and different aspects.
Insights
Protein tyrosine kinases (PTKs) in normal and malignant lymphoid cells were studied. Similarities and differences in PTK activity and tyrosine phosphorylation were observed between cell types, suggesting specialized functions.
Area of Science:
- Biochemistry
- Molecular Biology
- Cell Biology
Background:
- Protein tyrosine kinases (PTKs) play critical roles in cellular signaling pathways.
- Dysregulation of PTKs is implicated in various cancers, including lymphomas.
- Understanding PTK activity in lymphoid cells is crucial for comprehending normal cell function and malignant transformation.
Purpose of the Study:
- To investigate and characterize protein tyrosine kinase (PTK) activity in cytosolic and membrane fractions of normal and malignant lymphoid cells.
- To examine the expression of specific PTK-encoding oncogenes (fes, abl, src) in these cells.
- To compare tyrosine phosphorylation patterns between different lymphoid cell types.
Main Methods:
- Antibodies were used to detect PTK-encoding oncogene products (fes, abl, src) and phosphotyrosine.
- Fast protein liquid chromatography (FPLC) was employed for partial characterization of PTKs.
- Non-radioactive dot blot assays were utilized to measure PTK activities in FPLC fractions.
- Tyrosine phosphorylation patterns were analyzed in cytosolic fractions.
Main Results:
- PTK-encoding oncogenes (fes, abl, src) were expressed in both normal and malignant lymphoid cells, primarily in cytosolic and membrane fractions.
- FPLC analysis revealed both constant and variable patterns of PTK activity in cytosolic and membrane fractions, suggesting specialized functions.
- The majority of tyrosine-phosphorylated proteins were found in cytosolic fractions across all cell types.
- Similar tyrosine phosphorylation patterns were observed in normal peripheral blood lymphocytes and B-lymphoma cells, but a distinct pattern was noted in tonsillar lymphocytes.
Conclusions:
- PTK activity and expression patterns exhibit both similarities and differences between normal and malignant lymphoid cells.
- The findings suggest that PTKs have specialized roles in normal lymphoid cell growth and in the process of transformation.
- The characterization of PTK activities provides further insights into the molecular mechanisms underlying lymphoid cell biology and malignancy.