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Involvement of multiple protein kinases in CD3-mediated activation of human T lymphocytes
F Chiaffarino1, M Biffi, A Luciano
1Laboratorio di Immunologia, Centro Ricerche Italfarmaco, Milano, Italy.
Abstract:
The role of different protein kinases in the process of T cell activation has been studied using several inhibitors. The model we adopted was the activation of PBMC by monoclonal antibody OKT3. The results obtained confirm that PKC and PTK are involved. Thus, the inhibitors H-7, staurosporine, and genistein exerted a dose-dependent inhibition of CD2 up-regulation, CD25 expression, IL-2 production, and cellular proliferation. On the other hand, our data indicate that PKA is not involved since the inhibitor HA1004 was ineffective. W-7, an inhibitor of Ca(2+)-CaM protein kinases, inhibited OKT3-induced modulation of cell-surface markers and PBMC proliferation, whereas a slight increase in IL-2 release was detected at the highest dose used (20 microM). Using the MLCK inhibitor ML-9, we extended our studies to the myosin light chain kinase, which influences the organization of the cytoskeleton. ML-9-inhibited PBMC activation in terms of modulation of cell-surface markers and proliferation but stimulated IL-2 production. Similar results were obtained using the cytoskeleton disruptors demecolcine and cytochalasin B. Taken together the data described herein indicate that T cell activation is a complex event in which, aside from classical signal transduction-associated kinases PKC and PTK, at least two other kinases, Ca(2+)-CaM kinases and MLCK, seem to be involved, the latter probably through correct assembly of the cytoskeleton.
Insights
Protein Kinase C (PKC) and Protein Tyrosine Kinase (PTK) are key to T cell activation. Calcium-calmodulin-dependent protein kinases and myosin light chain kinase also play roles, likely via cytoskeleton regulation.
Area of Science:
- Immunology
- Cell Biology
- Biochemistry
Background:
- T cell activation is a critical process in adaptive immunity.
- Protein kinases are crucial regulators of cellular signaling pathways.
- Understanding the specific kinases involved in T cell activation is essential for targeted immunotherapies.
Purpose of the Study:
- To investigate the roles of various protein kinases in T cell activation.
- To elucidate the signaling pathways involved in T cell activation using specific inhibitors.
- To determine the involvement of PKC, PTK, PKA, Ca(2+)-CaM kinases, and MLCK in T cell activation.
Main Methods:
- Peripheral blood mononuclear cells (PBMCs) were activated using the monoclonal antibody OKT3.
- The effects of various kinase inhibitors (H-7, staurosporine, genistein, HA1004, W-7, ML-9) and cytoskeleton disruptors (demecolcine, cytochalasin B) were assessed.
- Key indicators of T cell activation, including CD2 up-regulation, CD25 expression, IL-2 production, and cellular proliferation, were measured.
Main Results:
- PKC and PTK inhibitors (H-7, staurosporine, genistein) dose-dependently inhibited T cell activation markers, IL-2 production, and proliferation.
- PKA inhibition (HA1004) had no effect, indicating PKA is not involved.
- Ca(2+)-CaM kinase inhibition (W-7) and MLCK inhibition (ML-9) modulated cell surface markers and proliferation, with ML-9 also stimulating IL-2 production.
- Cytoskeleton disruptors mimicked some effects of ML-9, suggesting a role for the cytoskeleton.
Conclusions:
- T cell activation is a complex process involving multiple signaling pathways.
- PKC and PTK are confirmed as critical kinases in T cell activation.
- Ca(2+)-CaM kinases and MLCK are also implicated, with MLCK potentially acting through cytoskeleton organization.
- These findings highlight potential targets for modulating T cell responses.