Department of Parasitology, Medical College, Zhengzhou University, Zhengzhou, 450052, China.
Vet Res. 2023 Oct 2;54(1):86. doi: 10.1186/s13567-023-01217-2.
C-type lectin (CTL) is a protein that binds to saccharides and plays an important role in parasite adhesion, host cell invasion and immune evasion. Previous studies showed that recombinant T. spiralis C-type lectin (rTsCTL) promotes larval invasion of intestinal epithelium cells (IEC), whereas anti-rTsCTL antibodies inhibits larval invasion. Syndecan-1 (SDC-1) is a member of the heparan sulfate proteoglycan family which is mainly expressed on the surface of IEC and in extracellular matrices where they interact with a plethora of ligands. SDC-1 has a principal role in maintaining cell morphogenesis, establishing cell-cell adhesions, and regulating the gut mucosal barrier. The aim of this study was to investigate whether rTsCTL binds to SDC-1 on IEC, and the binding of rTsCTL with SDC-1 promotes larval invasion and its mechanism. IFA results show that rTsCTL and SDC-1 co-localized on Caco-2 cell membrane. GST pull-down and Co-IP verified the direct interaction between rTsCTL and SDC-1 on Caco-2 cells. qPCR and Western blotting revealed that rTsCTL binding to SDC-1 increased the expression of SDC-1 and claudin-2, and reduced the expression of occludin and claudin-1 in Caco-2 cells incubated with rTsCTL via the STAT3 pathway. β-Xyloside (a syndecan-1 synthesis inhibitor) and Stattic (a STAT3 inhibitor) significantly inhibited rTsCTL binding to syndecan-1 in Caco-2 cells and activation of the STAT3 pathway, abrogated the effects of rTsCTL on the expression of gut tight junctions, and impeded larval invasion. The results demonstrate that binding of rTsCTL to SDC-1 on Caco-2 cells activated the STAT3 pathway, decreased gut tight junction expression, damaged the integrity of the gut epithelial barrier, and mediated T. spiralis invasion of the gut mucosa. TsCTL might be regarded as a candidate vaccine target against T. spiralis invasion and infection.
C 型凝集素（CTL）是一种与糖结合并在寄生虫黏附、宿主细胞入侵和免疫逃避中发挥重要作用的蛋白质。先前的研究表明，重组旋毛虫 C 型凝集素（rTsCTL）促进幼虫侵袭肠上皮细胞（IEC），而抗 rTsCTL 抗体抑制幼虫侵袭。硫酸乙酰肝素蛋白聚糖-1（SDC-1）是硫酸乙酰肝素蛋白聚糖家族的成员，主要表达在 IEC 表面和细胞外基质中，与大量配体相互作用。SDC-1 在维持细胞形态发生、建立细胞间黏附以及调节肠道黏膜屏障方面起着主要作用。本研究旨在探讨 rTsCTL 是否与 IEC 上的 SDC-1 结合，以及 rTsCTL 与 SDC-1 的结合是否促进幼虫侵袭及其机制。IFA 结果显示，rTsCTL 和 SDC-1 在 Caco-2 细胞膜上共定位。GST 下拉和 Co-IP 验证了 rTsCTL 与 Caco-2 细胞上 SDC-1 的直接相互作用。qPCR 和 Western blot 显示，rTsCTL 与 SDC-1 结合增加了 SDC-1 和 Claudin-2 的表达，降低了 rTsCTL 孵育的 Caco-2 细胞中 Occludin 和 Claudin-1 的表达，通过 STAT3 途径。β-木糖苷（硫酸乙酰肝素合成抑制剂）和 Stattic（STAT3 抑制剂）显著抑制 rTsCTL 与 Caco-2 细胞中 SDC-1 的结合和 STAT3 途径的激活，阻断 rTsCTL 对肠道紧密连接表达的影响，并阻碍幼虫入侵。结果表明，rTsCTL 与 Caco-2 细胞上的 SDC-1 结合激活了 STAT3 途径，降低了肠道紧密连接的表达，破坏了肠道上皮屏障的完整性，并介导了旋毛虫对肠道黏膜的侵袭。TsCTL 可能被视为针对旋毛虫侵袭和感染的候选疫苗靶点。
