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Published on: November 22, 2024
Loss-of-function phenotype of a PKCθT219A knockin mouse strain
Nikolaus Thuille1, Kerstin Siegmund2, Victoria Klepsch2
1Department for Pharmacology and Genetics, Medical University Innsbruck, Innsbruck, Austria. Nikolaus.Thuille@i-med.ac.at.
Background:
Protein kinase C θ has been established as an important signaling intermediate in T-effector-cell activation and survival pathways by controlling activity of the key transcription factors NF-κB and NFAT. Previous studies identified an activation-induced auto-phosphorylation site at Thr-219, located between the tandem C1 domains of the regulatory fragment in PKCθ, as a structural requirement for its correct membrane translocation and the subsequent transactivation of downstream signals leading to IL-2 production in a human T cell line.
Methods:
The present work aimed to define the role of this phosphorylation switch on PKCθ in a physiological context through a homozygous T219A knockin mouse strain. T cell activation was analyzed by H3-thymidine uptake (proliferative response), qRT-PCR and luminex measurements (cytokine production). NFAT and NF-κB transactivation responses were estimated by Gel mobility shift and Alpha Screen assays. Frequencies of T cell subsets were analyzed by flow cytometry.
Results:
Despite a normal T cell development, in vitro activated effector T cells clearly revealed a requirement of Thr-219 phosphorylation site on PKCθ for a transactivation of NF-κB and NFAT transcription factors and, subsequently, robust IL-2 and IFN-γ expression.
Conclusion:
This phenotype is reminiscent of the PKCθ knockout T cells, physiologically validating that this (p) Thr-219 auto-phosphorylation site indeed critically regulates PKCθ function in primary mouse T cells.
Insights
The Thr-219 phosphorylation site on Protein Kinase C theta (PKCθ) is crucial for T-cell activation. This site regulates key transcription factors NF-κB and NFAT, impacting cytokine production like IL-2 and IFN-γ.
Area of Science:
- Immunology
- Cell Biology
- Molecular Signaling
Background:
- Protein Kinase C theta (PKCθ) is a key signaling molecule in T-effector cell activation and survival.
- An activation-induced auto-phosphorylation site at Thr-219 in PKCθ is essential for membrane translocation and downstream signaling, including IL-2 production.
Purpose of the Study:
- To investigate the physiological role of the Thr-219 phosphorylation site on PKCθ function.
- To define the impact of this phosphorylation switch in a relevant biological context using a T219A knockin mouse model.
Main Methods:
- Generation of a homozygous T219A knockin mouse strain.
- Analysis of T cell activation, including proliferation (H3-thymidine uptake) and cytokine production (qRT-PCR, Luminex).
- Assessment of transcription factor activity (NFAT, NF-κB) using Gel mobility shift and Alpha Screen assays; T cell subset analysis via flow cytometry.
Main Results:
- T cells from T219A knockin mice showed impaired transactivation of NF-κB and NFAT transcription factors upon in vitro activation.
- A significant reduction in IL-2 and IFN-γ expression was observed in activated T cells lacking the Thr-219 phosphorylation site.
- T cell development was unaffected, indicating a specific role in T cell activation pathways.
Conclusions:
- The Thr-219 auto-phosphorylation site on PKCθ is critically required for regulating its function in primary mouse T cells.
- This finding physiologically validates the importance of the Thr-219 phosphorylation site as a regulatory switch for PKCθ activity in T cell immune responses.
- The observed phenotype closely mimics that of PKCθ knockout T cells, underscoring the functional significance of Thr-219 phosphorylation.
