TRIM45 Causes Neuronal Damage by Aggravating Microglia-Mediated Neuroinflammation Upon Cerebral Ischemia and Reperfusion Injury

Background: Excessive and unresolved neuroinflammation is a key component of the pathological cascade in brain injuries such as ischemic stroke. Tripartite motif-containing 45 (TRIM45) is a ubiquitin E3 ligase involved in various critical biological processes. However, the role of TRIM45 in cerebral ischemia remains unknown. Methods: Expression of TRIM45 was measured using qRT-PCR and western blotting in primary cultured microglia. The microglia-specific TRIM45-knockdown mice subjected to cerebral ischemia-reperfusion injury were applied to investigated the impact of TRIM45 knockdown in microglia on neuroinflammation, using a combination of immunofluorescence staining, percent brain infarct area and a serious of neurobehavioral tests. Findings: TRIM45 protein was highly expressed in the peri-infarct areas of mice subjected to cerebral ischemia-reperfusion injury. TRIM45 knockdown significantly decreased proinflammatory cytokine and chemokine production. Mechanistically, TRIM45 constitutively interacted with TAB2, and consequently facilitated the Lys-63-linked polyubiquitination of TAB2, leading to the formation of TAB1-TAK1-TAB2 complex and activation of TAK1, which was ultimately followed by activation of the NF-kB signaling pathway. More importantly, microglia-specific knockdown of TRIM45 in mice significantly reduced the infarct size, mitigated neurological deficit scores, and improved cognitive function after ischemic stroke. Interpretation:  Our study reveals that the TRIM45-TAB2 axis is a crucial checkpoint that controls NF-kB signaling in microglia during cerebral ischemia-reperfusion injury. Therefore, targeting TRIM45 may represent an attractive therapeutic target. Funding: This study was supported by funding from the National Natural Science Foundation of China (No.31800896), China Postdoctoral Science Foundation (No.2018T110752 and No.2017M620310), and Tongji Hospital (HUST) Foundation for Excellent Young Scientist (No.2020YQ17). Declaration of Interest: None to declare. Ethical Approval: All animal experiments were performed in accordance with the Guide for the Care and Use of Laboratory Animals (National Academies Press, 2011) and were approved by the IACUC of Tongji Medical College, Huazhong University of Science and Technology.