发热范围内的高温胁迫对淋巴细胞黏附与迁移的调控及其机制研究

Fever is a complex physiologic response to bacterial/viral infection and inflammation. Fever is critical for the maintenance of immune homeostasis and immune surveillance by promoting recruitment of lymphocytes into secondary lymphoid organs or inflammation sites in order to productively encounter foreign antigens. However, the mechanism of fever in regulating lymphocyte adhesion and transmigration is still obscure. Herein, we plan to investigate the function and mechanism of lymphocyte integrins （α4 and β2 integrins） in the regulation of lymphocyte adhesion and migration by fever. Our preliminary data have shown that although fever-range thermal stress does not affect integrin-mediated lymphocyte adhesion, it specifically promotes α4 integrin-mediated cell migration, but does not affect β2 integrin function. Further study reveals that fever-range thermal stress upregulates the expression of several heat shock proteins. Interestingly, only Hsp90 specifically interacts with integrin α4 and the interaction is upregulated by fever significantly. Overexpression of Hsp90 in lymphocytes also obviously promotes α4 integrin-mediated cell transmigration. Next, we plan to further investigate the molecular mechanism of Hsp90-α4 integrin interaction, and reveal the mechanism underlying the regulation of lymphocyte adhesion and migration by Hsp90 and α4 integrin during thermal stress. In addition, we will investigate the biological and pathological function of fever-Hsp90-α4 integrin pathway in immunity by inhibiting the Hsp90-α4 integrin interaction in mice. This study will reveal a novel mechanism of fever in promoting lymphocyte transmigration via regulating Hsp90-α4 integrin pathway.

发热是机体受到病原体感染、产生损伤或者炎症后的一种生理应激反应。发热可以促进淋巴细胞迁移到次级淋巴器官或者炎症部位而促进免疫反应，目前对发热调控淋巴细胞黏附和迁移的机制还不清楚。本项目拟从介导淋巴细胞黏附与迁移的整合素入手对该机制展开研究。目前已发现发热范围内的高温胁迫虽不影响整合素介导的淋巴细胞黏附，却特异性地促进α4整合素介导的淋巴细胞迁移。并且发热上调了淋巴细胞中多种热休克蛋白的表达，其中热休克蛋白90 （Hsp90）专一地与α4整合素结合，过表达Hsp90蛋白可显著促进α4整合素介导的细胞迁移。我们将进一步研究Hsp90与α4整合素结合的分子基础，并探究Hsp90调控α4整合素下游信号通路的分子机制，同时在动物水平抑制Hsp90与α4整合素的结合，研究发热-Hsp90-整合素通路在机体免疫中的生理功能。以上研究将揭示发热通过Hsp90调控α4整合素功能进而调节淋巴细胞迁移的新机制。

1..项目背景和主要研究内容：.免疫细胞的黏附与迁移是机体免疫与宿主防御的关键环节。免疫细胞表面的整合素与细胞所处微环境之间的交互作用对于调控免疫细胞的黏附与迁移至关重要。免疫细胞如何感应胞外微环境的变化，进而通过调控整合素与配体的黏附介导免疫细胞的组织特异性迁移，是该研究领域的重要科学问题。发热是机体受到病原体感染、产生损伤或者炎症后的一种复杂的生理应激反应，是一种重要的细胞微环境因素。发热不但可以显著地提高机体的代谢速率，而且发挥着更加主动的角色来调节机体的固有免疫和适应性免疫，从而提高机体应对感染的生存机率。发热可以促进免疫细胞迁移到次级淋巴器官或者炎症部位而促进免疫反应，对免疫稳态的维持和免疫监视非常重要，但是目前对发热调控免疫细胞黏附和迁移的机制还不清楚。.2..重要结果、关键数据和科学意义：.我们以T淋巴细胞为研究对象，探究发热通过何种机制调控T细胞的黏附和迁移。我们研究发现：发热可以通过热休克蛋白90（Hsp90）诱导α4整合素活化并传递下游信号通路，从而促进T淋巴细胞迁移。通过诱导Hsp90特异性地结合⍺4整合素，发热增强了⍺4整合素介导的淋巴细胞黏附和跨膜迁移。进一步分子机制研究发现，Hsp90结合在⍺4整合素的胞内区并通过inside-out信号通路激活⍺4整合素；一个Hsp90分子的可以同时结合两个⍺4整合素的胞内区，从而介导⍺4整合素在细胞膜表面的二聚化和聚簇现象，并激活胞内FAK-RhoA信号通路，最终促进T淋巴细胞迁移。通过构建⍺4整合素R985A突变基因敲入小鼠（Itga4R985A/R985A knock-in mice），发现在体内破坏Hsp90-⍺4整合素结合后抑制了发热诱导的T细胞迁移到引流淋巴结，并损害了T细胞对病原菌感染的清除。.总之，该研究鉴定出Hsp90-⍺4整合素信号轴作为一个灵敏的热敏感受通路，可以促进免疫细胞迁移及在病原感染时增强免疫监视、维持免疫稳态。基于本研究结果，通过改变温度或者细胞内Hsp90蛋白的表达来调控免疫细胞的定向迁移，将为病原体感染、炎症或者肿瘤的治疗提供新的解决策略。