School of Public Health, Dalian Medical University, No. 9W. Lvshun South Road, Dalian 116044, China.
State Key Laboratory of Natural Products and Functions, Institute of Materia Medica, Chinese Academy of Medical Sciences ＆ Peking Union Medical College, Beijing 100050, China.
Redox Biol. 2018 Apr;14:600-608. doi: 10.1016/j.redox.2017.11.010. Epub 2017 Nov 9.
The activation of microglial NADPH oxidase (NOX2) induced by α-synuclein has been implicated in Parkinson's disease (PD) and other synucleinopathies. However, how α-synuclein activates NOX2 remains unclear. Previous study revealed that both toll-like receptor 2 (TLR2) and integrin play important roles in α-synuclein-induced microglial activation. In this study, we found that blocking CD11b, the α chain of integrin αβ, but not TLR2 attenuated α-synuclein-induced NOX2 activation in microglia. The involvement of CD11b in α-synuclein-induced activation of NOX2 was further confirmed in CD11b microglia by showing reduced membrane translocation of NOX2 cytosolic subunit p47 and superoxide production. Mechanistically, α-synuclein bound to CD11b and subsequently activated Rho signaling pathway. α-Synuclein induced activation of RhoA and downstream ROCK but not Rac1 in a CD11b-dependent manner. Moreover, siRNA-mediated knockdown of RhoA impeded NOX2 activation in response to α-synuclein. Furthermore, we found that inhibition of NOX2 failed to interfere with the activation of RhoA signaling and interactions between α-synuclein and CD11b, further confirming that NOX2 was the downstream target of CD11b. Finally, we found that genetic deletion of CD11b abrogated α-synuclein-induced NOX2 activatoin in vivo. Taken together, our results indicated that integrin CD11b mediates α-synuclein-induced NOX2 activation through a RhoA-dependent pathway, providing not only a novel mechanistic insight but also a new potential therapeutic target for synucleinopathies.
α-突触核蛋白诱导的小胶质细胞 NADPH 氧化酶（NOX2）的激活与帕金森病（PD）和其他突触核蛋白病有关。然而，α-突触核蛋白如何激活 NOX2 仍不清楚。先前的研究表明，Toll 样受体 2（TLR2）和整合素在α-突触核蛋白诱导的小胶质细胞激活中都发挥着重要作用。在这项研究中，我们发现，阻断整合素 αβ 的 α 链 CD11b，但不是 TLR2，可减轻α-突触核蛋白诱导的小胶质细胞中 NOX2 的激活。通过显示 NOX2 胞质亚基 p47 的膜易位和超氧化物产生减少，在 CD11b 小胶质细胞中进一步证实了 CD11b 参与α-突触核蛋白诱导的 NOX2 激活。在机制上，α-突触核蛋白与 CD11b 结合，随后激活 Rho 信号通路。α-突触核蛋白以 CD11b 依赖的方式诱导 RhoA 和下游 ROCK 的激活，但不诱导 Rac1 的激活。此外，siRNA 介导的 RhoA 敲低可阻止α-突触核蛋白诱导的 NOX2 激活。此外，我们发现抑制 NOX2 并不能干扰 RhoA 信号的激活和α-突触核蛋白与 CD11b 之间的相互作用，这进一步证实了 NOX2 是 CD11b 的下游靶点。最后，我们发现 CD11b 的基因缺失消除了体内α-突触核蛋白诱导的 NOX2 激活。总之，我们的结果表明，整合素 CD11b 通过 RhoA 依赖性途径介导α-突触核蛋白诱导的 NOX2 激活，不仅提供了新的机制见解，而且为突触核蛋白病提供了新的潜在治疗靶点。
