Ma Jennifer S Y, Monu Ngozi, Shen David T, Mecklenbräuker Ingrid, Radoja Nadezda, Haydar Tarik F, Leitges Michael, Frey Alan B, Vukmanovic Stanislav, Radoja Sasa
Center for Cancer and Immunology, Children's National Medical Center, Children's Research Institute, 111 Michigan Avenue NW, Washington, DC 20010, USA.
J Immunol. 2007 Jun 15;178(12):7814-21. doi: 10.4049/jimmunol.178.12.7814.
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.
溶细胞颗粒胞吐作用是CD8⁺细胞毒性T淋巴细胞（CTL）用于杀伤病毒感染细胞和肿瘤细胞的主要途径。尽管该途径在适应性T细胞免疫中具有明显的重要性，但参与这一过程调控的酶的分子特性却鲜为人知。已知对CD8⁺T细胞中颗粒胞吐介导的细胞毒性调控至关重要的一个信号是抗原受体诱导的蛋白激酶C（PKC）激活。然而，尚不清楚该过程的哪一步受PKC调控。此外，迄今为止尚未确定PKC家族成员中哪一个是溶细胞颗粒胞吐作用调控所必需的。通过联合使用药理学抑制剂和基因敲除小鼠，我们发现PKCδ是小鼠CD8⁺T细胞中颗粒胞吐介导的溶细胞功能所必需的。我们的研究表明，PKCδ是溶细胞颗粒胞吐作用所必需的，但对于TCR刺激后的激活、细胞因子产生和溶细胞分子的表达并非必需。重要的是，PKCδ缺陷的细胞毒性淋巴细胞中缺陷的溶细胞功能可通过PKCδ的异位表达得以逆转。最后，我们表明PKCδ不参与靶细胞诱导的微管组织中心的重新定向，但对于随后的胞吐步骤，即溶细胞颗粒极化是必需的。因此，我们的研究确定PKCδ是小鼠CD8⁺T细胞中抗原受体诱导的溶细胞颗粒极化的一种新型选择性调节因子。
