Chemokines are a superfamily of structurally related chemotactic cytokines exerting significant roles in acting as a bridge between the innate and adaptive immune responses. In this study, we identified three CXC motif chemokine 10 (CXCL10) homologues (QsCXCL10-1, QsCXCL10-2 and QsCXCL10-3) from giant spiny frog Quasipaa spinosa. All three deduced QsCXCL10 proteins contained four conserved cysteine residues as found in other known CXC chemokines. Phylogenetic analysis showed that QsCXCL10-1, 2, 3 and other CXCL10s in amphibian were grouped together to form a separate clade. These three QsCXCL10s were highly expressed in spleen and blood. Upon infection with Staphylococcus aureus or Aeromonas hydrophila, the expressions of QsCXCL10s were markedly increased in spleen and blood during biotic stresses. Meanwhile, the QsCXCL10s transcription in liver could also be up-regulated under abiotic stresses such as cold and heat stresses. The recombinant proteins of frog CXCL10 homologues were produced and purified in E. coli and possessed similar but differential bioactivities. Both rCXCL10-1 and rCXCL10-2 had strong effects on the up-regulation of pro-inflammatory cytokines (TNF-α, IL-1β and IL-8) in vivo, whereas rCXCL10-3 induced a weak expression of these cytokines. Moreover, the rCXCL10-1 and rCXCL10-2 could strongly promote splenocyte proliferation and induce lymphocytes migration, while rCXCL10-3 had limited effects on these biological processes. All three frog chemokines triggered their functional activities by engaging CXC motif chemokine receptor 3 (CXCR3). Taken together, these results revealed that the three QsCXCL10s had similar but differential functional activities in mediating immune responses and host defenses, which might contribute to a better understanding of the functional evolution of CXCL10 in vertebrates.

中文翻译：

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巨型刺蛙 Quasipaa spinosa 中三个 CXCL10 同源物的功能差异。

趋化因子是结构相关的趋化细胞因子的超家族，在作为先天免疫反应和适应性免疫反应之间的桥梁方面发挥着重要作用。在这项研究中，我们从巨型刺蛙 Quasipaa spinosa 中鉴定了三个 CXC 基序趋化因子 10 (CXCL10) 同源物（QsCXCL10-1、QsCXCL10-2 和 QsCXCL10-3）。所有三种推导的 QsCXCL10 蛋白都含有四个保守的半胱氨酸残基，如在其他已知 CXC 趋化因子中发现的那样。系统发育分析表明，两栖动物中的 QsCXCL10-1、2、3 和其他 CXCL10s 组合在一起形成一个单独的进化枝。这三个 QsCXCL10s 在脾脏和血液中高度表达。感染金黄色葡萄球菌或嗜水气单胞菌后，在生物胁迫期间，脾脏和血液中 QsCXCL10s 的表达显着增加。同时，肝脏中的 QsCXCL10s 转录也可以在非生物胁迫（如冷热胁迫）下上调。青蛙 CXCL10 同源物的重组蛋白在大肠杆菌中生产和纯化，具有相似但不同的生物活性。rCXCL10-1 和 rCXCL10-2 都对体内促炎细胞因子（TNF-α、IL-1β 和 IL-8）的上调有强烈影响，而 rCXCL10-3 则诱导这些细胞因子的弱表达。此外，rCXCL10-1 和 rCXCL10-2 可以强烈促进脾细胞增殖并诱导淋巴细胞迁移，而 rCXCL10-3 对这些生物过程的影响有限。所有三种青蛙趋化因子都通过与 CXC 基序趋化因子受体 3 (CXCR3) 结合来触发它们的功能活动。综合起来，