Department of Pediatrics and Physiology, University of Pennsylvania School of Medicine, Philadelphia, PA 19104, USA.
Mol Biol Cell. 2010 Jul 1;21(13):2241-56. doi: 10.1091/mbc.e09-11-0930. Epub 2010 May 5.
Natural killer cells are lymphocytes specialized to participate in host defense through their innate ability to mediate cytotoxicity by secreting the contents of preformed secretory lysosomes (lytic granules) directly onto a target cell. This form of directed secretion requires the formation of an immunological synapse and occurs stepwise with actin reorganization preceding microtubule-organizing center (MTOC) polarization to the synapse. Because MTOC polarization to the synapse is required for polarization of lytic granules, we attempted to define their interrelationship. We found that compared with the time required for MTOC polarization, lytic granules converged to the MTOC rapidly. The MTOC-directed movement of lytic granules was independent of actin and microtubule reorganization, dependent on dynein motor function, occurred before MTOC polarization, and did not require a commitment to cytotoxicity. This defines a novel paradigm for rapid MTOC-directed transport as a prerequisite for directed secretion, one that may prepare, but not commit cells for precision secretory function.
自然杀伤细胞是一种淋巴细胞,通过其先天的能力,通过将预先形成的分泌溶酶体(溶酶体颗粒)的内容物直接分泌到靶细胞上来介导细胞毒性,从而专门参与宿主防御。这种定向分泌形式需要形成免疫突触,并随着肌动蛋白重组而逐步发生,微管组织中心(MTOC)向突触的极化发生在前面。因为 MTOC 向突触的极化是溶酶体颗粒极化所必需的,所以我们试图定义它们之间的关系。我们发现,与 MTOC 极化所需的时间相比,溶酶体颗粒迅速聚集到 MTOC。溶酶体颗粒向 MTOC 的定向运动独立于肌动蛋白和微管的重组,依赖于动力蛋白的功能,发生在 MTOC 极化之前,不需要对细胞毒性的承诺。这定义了一种新的快速 MTOC 定向运输的范例,作为定向分泌的前提,它可能会准备,但不会承诺细胞进行精确的分泌功能。