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Updated: Jul 14, 2026
Tailoring In Vivo Cytotoxicity Assays to Study Immunodominance in Tumor-specific CD8+ T Cell Responses
Published on: May 6, 2019
Protein kinase Cdelta regulates antigen receptor-induced lytic granule polarization in mouse CD8+ CTL
Jennifer S Y Ma1, Ngozi Monu, David T Shen
1Center for Cancer and Immunology, Children's National Medical Center, Children's Research Institute, 111 Michigan Avenue NW, Washington, DC 20010, USA.
Abstract:
Lytic granule exocytosis is the major pathway used by CD8+ CTL to kill virally infected and tumor cells. Despite the obvious importance of this pathway in adaptive T cell immunity, the molecular identity of enzymes involved in the regulation of this process is poorly characterized. One signal known to be critical for the regulation of granule exocytosis-mediated cytotoxicity in CD8+ T cells is Ag receptor-induced activation of protein kinase C (PKC). However, it is not known which step of the process is regulated by PKC. In addition, it has not been determined to date which of the PKC family members is required for the regulation of lytic granule exocytosis. By combination of pharmacological inhibitors and use of mice with targeted gene deletions, we show that PKCdelta is required for granule exocytosis-mediated lytic function in mouse CD8+ T cells. Our studies demonstrate that PKCdelta is required for lytic granule exocytosis, but is dispensable for activation, cytokine production, and expression of cytolytic molecules in response to TCR stimulation. Importantly, defective lytic function in PKCdelta-deficient cytotoxic lymphocytes is reversed by ectopic expression of PKCdelta. Finally, we show that PKCdelta is not involved in target cell-induced reorientation of the microtubule-organizing center, but is required for the subsequent exocytosis step, i.e., lytic granule polarization. Thus, our studies identify PKCdelta as a novel and selective regulator of Ag receptor-induced lytic granule polarization in mouse CD8+ T cells.
Insights
Protein Kinase C delta (PKCdelta) is essential for CD8+ T cell cytotoxic function. This study identifies PKCdelta as a key regulator of lytic granule polarization, crucial for adaptive T cell immunity against viral and tumor cells.
Area of Science:
- Immunology
- Cell Biology
- Molecular Biology
Background:
- Lytic granule exocytosis is vital for CD8+ cytotoxic T lymphocyte (CTL) mediated killing of infected and tumor cells.
- The molecular mechanisms regulating this essential immune pathway remain incompletely understood.
- Protein Kinase C (PKC) activation is known to regulate CTL cytotoxicity, but specific PKC family members and their roles are unclear.
Purpose of the Study:
- To identify the specific Protein Kinase C (PKC) family member regulating lytic granule exocytosis in CD8+ T cells.
- To determine the precise step in the cytotoxic pathway regulated by PKC.
- To elucidate the role of PKCdelta in adaptive T cell immunity.
Main Methods:
- Utilized pharmacological inhibitors and gene-deleted mice to investigate PKCdelta function.
- Assessed T cell activation, cytokine production, and cytolytic molecule expression.
- Examined microtubule-organizing center reorientation and lytic granule polarization.
Main Results:
- PKCdelta is indispensable for granule exocytosis-mediated lytic function in mouse CD8+ T cells.
- PKCdelta deficiency impairs lytic function but not T cell activation, cytokine production, or cytolytic molecule expression.
- PKCdelta is required for lytic granule polarization, not microtubule-organizing center reorientation.
Conclusions:
- PKCdelta is a novel and selective regulator of Ag receptor-induced lytic granule polarization.
- PKCdelta plays a critical role in the exocytosis step of CTL-mediated cytotoxicity.
- Targeting PKCdelta may offer therapeutic strategies for enhancing T cell-mediated immunity.
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