NLRP3 regulates a non-canonical platform for caspase-8 activation during epithelial cell apoptosis
NLRP3 regulates a non-canonical platform for caspase-8 activation during epithelial cell apoptosis
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DOI：
10.1038/cdd.2016.14
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发表时间：
2016-08-01
影响因子：
12.4
通讯作者：
Muruve, D. A.
中科院分区：
文献类型：
--
作者：
Chung, H.;Vilaysane, A.;Muruve, D. A.
Nod-like receptor，pyrin containing 3（NLRP 3）是一种典型的激活巨噬细胞炎性小体的半胱天冬酶-1。NLRP 3也在肾脏和肠道的上皮中表达;然而，其功能在很大程度上仍不确定。缺乏Nlrp 3的原代小鼠肾小管上皮细胞（TEC）显示肿瘤坏死因子（TNF）受体和CD 95下游的凋亡减少。TEC被鉴定为II型凋亡细胞，其通过caspase-9激活caspase-8、tBid和线粒体凋亡，这些反应在Nlrp 3-/-细胞中减少。在TNF α/放线菌酮（TNF α/CHX）诱导的外源性细胞凋亡过程中，caspase-8的激活依赖于衔接蛋白（adaptor protein），即含有CARD的细胞凋亡相关斑点样蛋白（ASC），而完全不依赖于caspase-1或caspase-11。TEC和原代人近端肾小管上皮细胞（HPTC）没有激活典型的炎性小体，半胱天冬酶-1，IL-1 β分泌响应TNF α/CHX或NLRP 3依赖性触发剂，如ATP或尼日利亚菌素。在细胞分级分离研究和共聚焦显微镜，NLRP 3共定位与ASC和caspase-8在斑点状复合物在线粒体凋亡过程中。响应于TNF α/CHX的NLRP 3/ASC/半胱天冬酶-8斑点的形成是TNFR信号传导的下游并且依赖于钾流出。上皮ASC斑点存在于经历细胞凋亡的肠样组织中和野生型但非Nlrp 3-/-或ASC-/-小鼠在体内输尿管单侧梗阻后的受损小管中。这些数据表明，NLRP 3和ASC形成了一个保守的非经典平台的半胱天冬酶-8激活，独立的炎症体，调节上皮细胞内的凋亡。
Nod-like receptor, pyrin containing 3 (NLRP3) is characterized primarily as a canonical caspase-1 activating inflammasome in macrophages. NLRP3 is also expressed in the epithelium of the kidney and gut; however, its function remains largely undefined. Primary mouse tubular epithelial cells (TEC) lacking Nlrp3 displayed reduced apoptosis downstream of the tumor necrosis factor (TNF) receptor and CD95. TECs were identified as type II apoptotic cells that activated caspase-8, tBid and mitochondrial apoptosis via caspase-9, responses that were reduced in Nlrp3-/- cells. The activation of caspase-8 during extrinsic apoptosis induced by TNF alpha/cycloheximide (TNF alpha/CHX) was dependent on adaptor protein apoptosis-associated speck-like protein containing a CARD (ASC) and completely independent of caspase-1 or caspase-11. TECs and primary human proximal tubular epithelial cells (HPTC) did not activate a canonical inflammasome, caspase-1, or IL-1 beta secretion in response to TNF alpha/CHX or NLRP3-dependent triggers, such as ATP or nigericin. In cell fractionation studies and by confocal microscopy, NLRP3 colocalized with ASC and caspase-8 in speck-like complexes at the mitochondria during apoptosis. The formation of NLRP3/ASC/caspase-8 specks in response to TNF alpha/CHX was downstream of TNFR signaling and dependent on potassium efflux. Epithelial ASC specks were present in enteroids undergoing apoptosis and in the injured tubules of wild-type but not Nlrp3-/- or ASC-/- mice following ureteric unilateral obstruction in vivo. These data show that NLRP3 and ASC form a conserved non-canonical platform for caspase-8 activation, independent of the inflammasome that regulates apoptosis within epithelial cells.