The deubiquitinase OTUD7B ameliorates central nervous system autoimmunity by inhibiting degradation of glial fibrillary acidic protein and astrocyte hyperinflammation

Astrocytes are central to the pathogenesis of multiple sclerosis; however, their regulation by intrinsic post-translational ubiquitination and deubiquitination is unresolved. This study shows that the deubiquitinating enzyme OTUD7B in astrocytes confers protection against murine experimental autoimmune encephalomyelitis, a model of MS, by limiting neuroinflammation. RNA-sequencing of isolated astrocytes and spatial transcriptomics showed that in EAE OTUD7B downregulates the expression of chemokines in astrocytes of inflammatory lesions, which is associated with reduced recruitment of encephalitogenic CD4+ T cells. Furthermore, OTUD7B was essential for GFAP protein expression of astrocytes bordering inflammatory lesions. Mechanistically, OTUD7B (i) restricted TNF-induced chemokine production of astrocytes by sequential K63- and K48-deubiquitination of RIPK1 limiting NF-κB and MAPK activation and (ii) enabled GFAP protein expression by supporting GFAP mRNA expression and preventing its proteasomal degradation through K48-deubiquitination of GFAP. This dual action on TNF signaling and GFAP identifies astrocyte-intrinsic OTUD7B as a central inhibitor of astrocyte-mediated inflammation. Probe-based spatial transcriptomics from spinal cord sections of Otud7bfl/fl and GFAP-Cre Otud7bfl/fl mice at d0 and d15 post immunization with MOG peptide.

星形胶质细胞（Astrocytes）在多发性硬化（multiple sclerosis, MS）的发病机制中处于核心地位，但目前学界对其内在的翻译后泛素化与去泛素化调控机制尚未阐明。本研究证实，星形胶质细胞内的去泛素化酶OTUD7B可通过抑制神经炎症，对多发性硬化的经典动物模型——小鼠实验性自身免疫性脑脊髓炎（experimental autoimmune encephalomyelitis, EAE）起到保护作用。对分离所得星形胶质细胞的RNA测序（RNA-sequencing）与空间转录组学（spatial transcriptomics）分析显示，在EAE模型中，OTUD7B可下调炎症病灶内星形胶质细胞的趋化因子表达，这与致脑炎CD4+ T细胞的招募减少密切相关。此外，OTUD7B对于炎症病灶周边星形胶质细胞的胶质纤维酸性蛋白（Glial Fibrillary Acidic Protein, GFAP）表达至关重要。从机制层面来看，OTUD7B通过双重途径发挥调控功能：其一，对受体相互作用蛋白激酶1（Receptor-interacting serine/threonine-protein kinase 1, RIPK1）依次进行K63位与K48位去泛素化，抑制肿瘤坏死因子（Tumor Necrosis Factor, TNF）诱导的星形胶质细胞趋化因子产生，从而限制核因子κB（Nuclear Factor-κB, NF-κB）与丝裂原活化蛋白激酶（Mitogen-activated Protein Kinase, MAPK）的激活；其二，通过促进GFAP的mRNA表达，并对GFAP进行K48位去泛素化以阻止其蛋白酶体降解，从而维持GFAP的蛋白表达水平。这种同时靶向TNF信号通路与GFAP的双重作用，表明星形胶质细胞内源性的OTUD7B是星形胶质细胞介导炎症反应的核心抑制因子。本数据集包含以髓鞘少突胶质细胞糖蛋白（Myelin Oligodendrocyte Glycoprotein, MOG）肽段免疫后第0天（d0）与第15天（d15）时，Otud7b flox/flox（Otud7bfl/fl）纯合小鼠以及星形胶质细胞特异性Otud7b敲除（GFAP-Cre Otud7bfl/fl）小鼠的脊髓切片的基于探针的空间转录组学数据。