雷帕霉素通过Ca2+-CaMKII介导的PTEN/Akt-Erk1/2信号调控hsBAFF刺激的B细胞外泌体分泌机制研究

Malignant proliferation of B cells caused by excessive BAFF is an important cause of autoimmune diseases. In recent years, the role of exosomes in autoimmune diseases has been emphasized. However, it remains unclear whether BAFF-induced autoimmune diseases are associated with exosomes.We have found that BAFF can promote the secretion of B cell exosomes, which may be related to Ca2 + -CaMKII-mediated pathway.Our recent researches show that rapamycin regulates BAFF-activated B cells via Ca2+-CaMKII mediated PTEN/Akt-Erk1/2 pathway,and rapamycin can inhibit BAFF-promoted exosomes release,however the relationship between rapamycin and BAFF-increased exosomes release is not clear.To confirm this hypothesis, we investigated the effect of rapamycin on secretion of BAFF-stimulated B cell exosomes by up-regulating PTEN or down-regulating CaMKII, Akt, and finally validating our hypothesis at the mouse model level.The findings will increase our understanding of the pathogenic mechanisms of BAFF-induced autoimmune diseases and broaden the medicinal value of rapamycin.

过量BAFF导致的B细胞恶性增殖是自身免疫疾病的重要病因。近年来外泌体在自身免疫疾病中所起的作用受到重视，然而是否BAFF诱发自身免疫疾病与外泌体有关还不得而知。我们已经发现BAFF能够促进B细胞外泌体的分泌，可能与Ca2+-CaMKII介导的信号有关。我们最新实验表明，雷帕霉素可以从Ca2+-CaMKII介导的PTEN/Akt-Erk1/2信号调控BAFF刺激的B细胞，而且雷帕霉素能够抑制BAFF促进的外泌体分泌，然而其中是否与上述信号有关还需要进一步验证。为证实该假设，我们通过上调PTEN或下调CaMKII，Akt，在体外层面研究雷帕霉素对BAFF刺激B细胞外泌体分泌的影响，最后在小鼠模型层面验证我们的假设。研究结果将增加我们对BAFF引发的自身免疫疾病发病机制的了解，并且拓宽雷帕霉素的药用价值。

B细胞刺激因子（BAFF）对于B细胞的存活十分重要，但过量BAFF会导致的B细胞恶性增殖从而发生自身免疫疾病。雷帕霉素能够有效抑制BAFF诱导的B细胞增殖存活，但是机制还不明确。本项目中我们发现雷帕霉素能够引起B细胞周期G1期阻滞从而抑制BAFF激活的细胞增殖，并且雷帕霉素通过调控抗凋亡蛋白家族/凋亡蛋白家族表达控制BAFF激活的细胞存活。进一步发现雷帕霉素对BAFF的抑制作用可能与胞内Ca2+的变化有关，雷帕霉素通过抑制BAFF调控的Ca2+-CaMKII-PTEN/Akt-Erk1/2信号轴影响B细胞增殖存活。并且雷帕霉素通过该信号轴影响了BAFF刺激的外泌体分泌。过表达PTEN或钝化Akt活性都能够增强雷帕霉素的抑制作用，而使用mTOR抑制剂，Akt抑制剂都能产生与雷帕霉素类似的对BAFF上调的Ca2+的抑制效果。BAPTA/AM，EGTA，2-APB，verapamil等不同细胞器的Ca2+螯合剂，KN93抑制CaMKII或者下调CaMKII活性都能够强化雷帕霉素的作用。我们的结果说明雷帕霉素通过阻碍mTORC1/2介导的Ca2+上调和Ca2+-CaMKII-PTEN/Akt-Erk1/2-外泌体信号轴抑制BAFF促进的B细胞增殖和存活。该研究结果将增加我们对BAFF引发的自身免疫疾病发病机制的了解，并且拓宽雷帕霉素的药用价值。