Moriwaki Kenta, Bertin John, Gough Peter J, Chan Francis Ka-Ming
Department of Pathology, Program in Immunology & Microbiology, University of Massachusetts Medical School, Worcester, MA 01655; and.
Pattern Recognition Receptor Discovery Performance Unit, Immuno-Inflammation Therapeutic Area, GlaxoSmithKline, Collegeville, PA 19422.
J Immunol. 2015 Feb 15;194(4):1938-44. doi: 10.4049/jimmunol.1402167. Epub 2015 Jan 7.
Caspase 8, the initiator caspase for death receptor-induced apoptosis, functions as a negative regulator of receptor interacting protein kinase 3 (RIPK3), an essential factor for TNF-, TLR3-, and TLR4-induced necroptosis. In certain situations, caspase 8 can also participate in pro-IL-1β processing. However, the biochemical complex that mediates caspase 8-mediated processing is not defined. In this study, we show that RIPK3 is crucial for caspase 1- and caspase 8-mediated pro-IL-1β and pro-IL-18 processing in bone marrow-derived dendritic cells (BMDCs) in response to LPS stimulation. Caspase 8-mediated pro-IL-1β processing requires intact RIPK1, RIPK3, TRIF, and FADD. In response to LPS, a complex that contains RIPK1, RIPK3, FADD, and caspase 8 is formed. Surprisingly, RIPK3-specific kinase inhibitors strongly enhanced caspase 8 activation and pro-IL-1β processing in LPS-stimulated BMDCs. However, studies in BMDCs expressing the kinase-inactive RIPK3-K51A mutant or RIPK1-K45A mutant showed that the kinase activity of neither RIPK1 nor RIPK3 is required for LPS-induced caspase 8 activation and IL-1β secretion. Hence, RIPK3 is an unexpected positive regulator of caspase 8 activity that promotes IL-1β maturation in BMDCs.
半胱天冬酶8是死亡受体诱导的细胞凋亡的起始半胱天冬酶，作为受体相互作用蛋白激酶3（RIPK3）的负调节因子发挥作用，RIPK3是肿瘤坏死因子、Toll样受体3和Toll样受体4诱导的坏死性凋亡的关键因子。在某些情况下，半胱天冬酶8也可参与白细胞介素-1β前体的加工。然而，介导半胱天冬酶8介导的加工的生化复合物尚未明确。在本研究中，我们发现RIPK3对于骨髓来源的树突状细胞（BMDCs）中半胱天冬酶1和半胱天冬酶8介导的白细胞介素-1β前体和白细胞介素-18前体的加工至关重要，这一过程是对脂多糖（LPS）刺激的反应。半胱天冬酶8介导的白细胞介素-1β前体加工需要完整的RIPK1、RIPK3、TRIF和FADD。在对LPS的反应中，形成了一个包含RIPK1、RIPK3、FADD和半胱天冬酶8的复合物。令人惊讶的是，RIPK3特异性激酶抑制剂在LPS刺激的BMDCs中强烈增强了半胱天冬酶8的激活和白细胞介素-1β前体的加工。然而，对表达激酶失活的RIPK3-K51A突变体或RIPK1-K45A突变体的BMDCs的研究表明，LPS诱导的半胱天冬酶8激活和白细胞介素-1β分泌既不需要RIPK1也不需要RIPK3的激酶活性。因此，RIPK3是半胱天冬酶8活性的一个意外的正调节因子，它促进BMDCs中白细胞介素-1β的成熟。
