The munc13-4-rab27 complex is specifically required for tethering secretory lysosomes at the plasma membrane
The munc13-4-rab27 complex is specifically required for tethering secretory lysosomes at the plasma membrane
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DOI：
10.1182/blood-2011-02-339523
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发表时间：
2011-08-11
期刊：
影响因子：
20.3
通讯作者：
van der Sluijs, Peter
中科院分区：
文献类型：
--
作者：
Elstak, Edo D.;Neeft, Maaike;van der Sluijs, Peter
细胞毒性T淋巴细胞（CTL）通过分泌溶酶体的裂解分子的极化释放杀死靶细胞。 MUNC13-4功能的丧失抑制了这一过程，并导致家族性血有淋巴细胞胞毒性3型（FHL3）。 Munc13-4结合了Rab27a，但是复合物的必要性仍然神秘，因为在敲除模型中的研究表明了单独的功能。在本研究中，我们描述了Munc13-4 N末端中的非规范性RAB27A结合基序。该序列中的点突变体严重受损的RAB27A结合，允许在MUNC13-4功能中解剖Rab27a的需求。分泌溶酶体成熟不需要MUNC13-4-RAB27A复合物，如FHL3患者的CTL和肥大细胞系中的CTL互补所示，对MUNC13-4沉默。相比之下，分泌溶酶体与脱粒过程中质膜的含量释放的融合，严格要求Munc13-4-Rab27a复合物。总内反射荧光显微镜成像表明，复合物在脱粒过程中质膜下方的运动分泌溶酶体和控制对接。在表达不结合Rab27的Munc13-4点突变体的细胞中，分泌性溶酶体的失速运动倾向丢失。总而言之，这些结果发现了将分泌性溶酶体绑定到质膜的机制，这对于免疫细胞中的脱粒至关重要。 （Blood。2011; 118（6）：1570-1578）
Cytotoxic T lymphocytes (CTLs) kill target cells through the polarized release of lytic molecules from secretory lysosomes. Loss of munc13-4 function inhibits this process and causes familial hemophagocytic lymphohistiocytosis type 3 (FHL3). munc13-4 binds rab27a, but the necessity of the complex remains enigmatic, because studies in knockout models suggest separate functions. In the present study, we describe a noncanonical rab27a-binding motif in the N-terminus of munc13-4. Point mutants in this sequence have severely impaired rab27a binding, allowing dissection of rab27a requirements in munc13-4 function. The munc13-4-rab27a complex is not needed for secretory lysosome maturation, as shown by complementation in CTLs from FHL3 patients and in a mast cell line silenced for munc13-4. In contrast, fusion of secretory lysosomes with, and content release at the plasma membrane during degranulation, strictly required the munc13-4-rab27a complex. Total internal reflection fluorescence microscopy imaging revealed that the complex corrals motile secretory lysosomes beneath the plasma membrane during degranulation and controls their docking. The propensity to stall motility of secretory lysosomes is lost in cells expressing munc13-4 point mutants that do not bind rab27. In summary, these results uncovered a mechanism for tethering secretory lysosomes to the plasma membrane that is essential for degranulation in immune cells. (Blood. 2011;118(6):1570-1578)