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Phosphorylation-mediated changes in the electrophoretic mobility of CD5 molecules
F Lozano1, J Alberola-Ila, L Places
1Servei d'Immunologia, Hospital Clinic i Provincial de Barcelona, Spain.
European Journal of Biochemistry
|October 24, 1990
Summary
Tumor promoter agents (TPA) cause post-translational modification of the CD5 antigen on human lymphocytes. This hyperphosphorylation, mediated by protein kinase C, alters CD5 molecule structure and function.
Area of Science:
- Immunology
- Cell Biology
- Biochemistry
Background:
- The CD5 antigen is a key surface protein on human lymphocytes.
- Post-translational modifications can significantly impact protein function.
- Tumor promoter agents are known to trigger cellular signaling pathways.
Purpose of the Study:
- To investigate the effect of tumor promoter agents (TPA) on the human lymphocyte surface CD5 antigen.
- To elucidate the mechanism and nature of TPA-induced CD5 modifications.
Main Methods:
- Labeling of T and B cells with [32P]orthophosphate and [35S]cysteine.
- Treatment with active tumor promoters and protein kinase C inhibitors.
- Electrophoretic analysis of CD5 protein.
- Enzymatic digestion (phosphatase and neuraminidase).
Main Results:
- TPA induced rapid, transient, and dose-dependent hyperphosphorylation of CD5 in various cell types.
- These changes were independent of RNA/protein synthesis and neuraminic acid content.
- Protein kinase C inhibitors blocked TPA-mediated CD5 alterations, confirming its involvement.
- Phosphatase digestion reversed the mobility shifts, indicating phosphorylation dependence.
- Neuraminidase digestion confirmed that surface CD5 molecules are the targets.
Conclusions:
- TPA induces post-translational modification of surface CD5 antigen via protein kinase C.
- The observed electrophoretic heterogeneity suggests structural and/or functional differences in CD5 molecules.
- This finding provides insights into CD5 regulation and potential roles in cellular responses.