Pfizer-University of Granada-Junta de Andalucía "Centre for Genomics and Oncological Research" (GENYO), Avenida de la Ilustración 114, 18016, Granada, Spain.
Department of Physical Chemistry, Faculty of Sciences, University of Granada, 18071, Granada, Spain.
Cell Mol Immunol. 2020 Sep;17(9):954-965. doi: 10.1038/s41423-019-0254-9. Epub 2019 Jun 26.
Evidence supports a possible role of BANK1 in innate immune signaling in B cells. In the present study, we investigated the interaction of BANK1 with two key mediators in interferon and inflammatory cytokine production, TRAF6 and MyD88. We revealed by coimmunoprecipitation (CoIP) analyses the binding of BANK1 with TRAF6 and MyD88, which were mediated by the BANK1 Toll/interleukin-1 receptor (TIR) domain. In addition, the natural BANK1-40C variant showed increased binding to MyD88. Next, we demonstrated in mouse splenic B cells that BANK1 colocalized with Toll-like receptor (TLR) 7 and TLR9 and that after stimulation with TLR7 and TLR9 agonists, the number of double-positive BANK1-TLR7, -TLR9, -TRAF6, and -MyD88 cells increased. Furthermore, we identified five TRAF6-binding motifs (BMs) in BANK1 and confirmed by point mutations and decoy peptide experiments that the C-terminal domain of BANK1-full-length (-FL) and the N-terminal domain of BANK1-Delta2 (-D2) are necessary for this binding. Functionally, we determined that the absence of the TIR domain in BANK1-D2 is important for its lysine (K)63-linked polyubiquitination and its ability to produce interleukin (IL)-8. Overall, our study describes a specific function of BANK1 in MyD88-TRAF6 innate immune signaling in B cells, clarifies functional differences between the two BANK1 isoforms and explains for the first time a functional link between autoimmune phenotypes including SLE and the naturally occurring BANK1-40C variant.
有证据表明 BANK1 可能在 B 细胞的固有免疫信号转导中发挥作用。在本研究中，我们研究了 BANK1 与干扰素和炎症细胞因子产生的两个关键介质 TRAF6 和 MyD88 的相互作用。我们通过共免疫沉淀（CoIP）分析揭示了 BANK1 与 TRAF6 和 MyD88 的结合，这是由 BANK1 Toll/白介素-1 受体（TIR）结构域介导的。此外，天然的 BANK1-40C 变体与 MyD88 的结合增加。接下来，我们在小鼠脾 B 细胞中证明，BANK1 与 Toll 样受体（TLR）7 和 TLR9 共定位，并且在用 TLR7 和 TLR9 激动剂刺激后，双阳性 BANK1-TLR7、-TLR9、-TRAF6 和 -MyD88 细胞的数量增加。此外，我们在 BANK1 中鉴定了五个 TRAF6 结合基序（BMs），并通过点突变和诱饵肽实验证实，BANK1 全长（-FL）的 C 端结构域和 BANK1-Delta2（-D2）的 N 端结构域对于这种结合是必需的。功能上，我们确定 BANK1-D2 中的 TIR 结构域缺失对于其赖氨酸（K）63 连接的多泛素化及其产生白细胞介素（IL）-8 的能力很重要。总的来说，我们的研究描述了 BANK1 在 B 细胞中 MyD88-TRAF6 固有免疫信号转导中的特定功能，阐明了两种 BANK1 同工型之间的功能差异，并首次解释了包括系统性红斑狼疮在内的自身免疫表型与天然存在的 BANK1-40C 变体之间的功能联系。
