Veugelers Kirstin, Motyka Bruce, Frantz Christine, Shostak Irene, Sawchuk Tracy, Bleackley R Chris
Department of Biochemistry, University of Alberta, Edmonton, AB, Canada.
Blood. 2004 May 15;103(10):3845-53. doi: 10.1182/blood-2003-06-2156. Epub 2004 Jan 22.
Cytotoxic T lymphocytes and natural killer cells destroy target cells via the directed exocytosis of lytic effector molecules such as perforin and granzymes. The mechanism by which these proteins enter targets is uncertain. There is ongoing debate over whether the most important endocytic mechanism is nonspecific or is dependent on the cation-independent mannose 6-phosphate receptor. This study tested whether granzyme B endocytosis is facilitated by dynamin, a key factor in many endocytic pathways. Uptake of and killing by the purified granzyme B molecule occurred by both dynamin-dependent and -independent mechanisms. However most importantly, serglycin-bound granzyme B in high-molecular-weight degranulate material from cytotoxic T lymphocytes predominantly followed a dynamin-dependent pathway to kill target cells. Similarly, killing by live cytotoxic T lymphocytes was attenuated by a defect in the dynamin endocytic pathway, and in particular, the pathways characteristically activated by granzyme B were affected. We therefore propose a model where degranulated serglycin-bound granzymes require dynamin for uptake.
细胞毒性T淋巴细胞和自然杀伤细胞通过定向胞吐溶细胞效应分子（如穿孔素和颗粒酶）来破坏靶细胞。这些蛋白质进入靶细胞的机制尚不清楚。关于最重要的内吞机制是非特异性的还是依赖于不依赖阳离子的甘露糖6-磷酸受体，目前仍在争论。本研究测试了发动蛋白（许多内吞途径中的关键因子）是否促进颗粒酶B的内吞作用。纯化的颗粒酶B分子的摄取和杀伤通过依赖发动蛋白和不依赖发动蛋白的机制发生。然而，最重要的是，来自细胞毒性T淋巴细胞的高分子量脱颗粒物质中与丝甘蛋白结合的颗粒酶B主要遵循依赖发动蛋白的途径来杀伤靶细胞。同样，发动蛋白内吞途径缺陷会减弱活细胞毒性T淋巴细胞的杀伤作用，特别是颗粒酶B特征性激活的途径受到影响。因此，我们提出一个模型，即脱颗粒的与丝甘蛋白结合的颗粒酶需要发动蛋白来摄取。
