The genus Echinococcus of cestode parasites includes important pathogens of humans and livestock animals. Transcriptomic and genomic studies on E. granulosus and E. multilocularis uncovered striking expansion of monodomain Kunitz proteins. This expansion is accompanied by the specialization of some family members away from the ancestral protease inhibition function to fulfill cation channel blockade functions. Since cation channels are involved in immune processes, we tested the effects on macrophage physiology of two E. granulosus Kunitz-type inhibitors of voltage-activated cation channels (K_v) that are close paralogs. Both inhibitors, EgKU-1 and EgKU-4, inhibited production of the Th1/Th17 cytokine subunit IL-12/23p40 by macrophages stimulated with the TLR4 agonist LPS. In addition, EgKU-4 but not EgKU-1 inhibited production of the inflammatory cytokine IL-6. These activities were not displayed by EgKU-3, a family member that is a protease inhibitor without known activity on cation channels. EgKU-4 potently inhibited macrophage proliferation in response to M-CSF, whereas EgKU-1 displayed similar activity but with much lower potency, similar to EgKU-3. We discuss structural differences, including a heavily cationic C-terminal extension present in EgKU-4 but not in EgKU-1, that may explain the differential activities of the two close paralogs.

绦虫的棘球绦虫属包括人和牲畜的重要病原体。E. granulosus和E. multilocularis 的转录组学和基因组研究揭示了单域 Kunitz 蛋白的惊人扩展。这种扩张伴随着一些家庭成员的专业化，远离祖先的蛋白酶抑制功能，以实现阳离子通道阻断功能。由于阳离子通道参与免疫过程，我们测试了两种E. granulosus Kunitz 型电压激活阳离子通道 (K _v )抑制剂对巨噬细胞生理的影响，它们是密切的旁系同源物。两种抑制剂，例如KU-1 和EgKU-4 通过 TLR4 激动剂 LPS 刺激巨噬细胞抑制 Th1/Th17 细胞因子亚基 IL-12/23p40 的产生。此外，Eg KU-4 而非Eg KU-1 抑制炎性细胞因子IL-6 的产生。Eg KU-3没有表现出这些活性，该家族成员是一种蛋白酶抑制剂，对阳离子通道没有已知的活性。例如， KU-4 响应 M-CSF 有效抑制巨噬细胞增殖，而Eg KU-1 表现出类似的活性，但效力低得多，类似于Eg KU-3。我们将讨论的结构差异，包括重阳离子C-末端存在于扩展例如KU-4而不是在例如KU-1，这可以解释两个接近的旁系同源物的不同活动。