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Tyrosine phosphorylation in human T lymphoma cells
Biochemical and Biophysical Research Communications
|December 28, 1983
Summary
High tyrosine protein kinase (TPK) activity was found in human T lymphoma cells, phosphorylating specific proteins. These findings suggest a conserved role for TPK substrates in lymphomas.
Area of Science:
- Biochemistry
- Cell Biology
- Oncology
Background:
- Tyrosine protein kinase (TPK) activity is elevated in murine lymphoma LSTRA.
- A 55,000 Mr protein is the primary substrate for tyrosine phosphorylation in LSTRA cells.
Purpose of the Study:
- To investigate TPK activities in human lymphoid cells.
- To identify and characterize phosphotyrosine-containing proteins in human T lymphoma cell lines.
Main Methods:
- In vitro tyrosine phosphorylation of detergent-insoluble extracts from human T lymphoma cell lines (Molt. 4, JM, Ke 37) and normal lymphocytes.
- Analysis of phosphoproteins using SDS-PAGE and partial proteolysis mapping.
Main Results:
- Two major phosphotyrosine proteins (55,000 and 35,000 Mr) were detected in all three human T lymphoma lines.
- An additional 78,000 Mr protein was found in the Ke 37 cell line.
- Similar proteins showed weak phosphorylation in normal lymphocytes.
- Partial proteolysis mapping indicated strong homology between the 55,000 Mr phosphoproteins from murine and human lymphomas.
- Tyrosine phosphorylation was active at 0°C and stimulated by Mn++ ions.
Conclusions:
- Human T lymphoma cells exhibit distinct tyrosine phosphorylation patterns compared to normal lymphocytes.
- The 55,000 Mr phosphoprotein is conserved between murine and human lymphomas, suggesting a significant functional role.
- Further investigation into the function of these phosphoproteins in transformed lymphocytes is warranted.