Jiangsu Key Laboratory for Biodiversity and Biotechnology, College of Life Sciences, Nanjing Normal University, Nanjing 210023, China.
Jiangsu Key Laboratory for Biodiversity and Biotechnology, College of Life Sciences, Nanjing Normal University, Nanjing 210023, China; Laboratory of Quality and Safety Risk Assessment for Agro-Products of the Ministry of Agriculture (Jinan), Institute of Quality Standard and Testing Technology for Agro-Products, Shandong Academy of Agricultural Sciences, Jinan, Shandong, China.
Int J Biol Macromol. 2023 Dec 31;253(Pt 2):126707. doi: 10.1016/j.ijbiomac.2023.126707. Epub 2023 Sep 7.
Latrophilin is a member of adhesion GPCRs involved in various physiological pro1cesses. The extracellular fragment of Tribolium castaneum Latrophilin (TcLph) contains a galactose-binding lectin (GBL) domain. However, the biological function of GBL domain remains mysterious. Here, we initially studied the role of TcLph in recognizing pathogens through its GBL domain and then triggering immune defense in invertebrates. Results showed that GBL domain was highly conserved, and its predicted 3D structure was similar to rhamnose-binding lectin domain of mouse Latrophilin-1 with a unique α/β fold and two long loops. Molecular docking and ELISA results revealed the GBL domain can bind to D-galactose, L-rhamnose, lipopolysaccharide and peptidoglycan. The recombinant extracellular segment of TcLph and the recombinant GBL exhibited strong agglutinating and binding activities to all tested bacteria in a Ca-dependent manner. Moreover, TcLph was markedly induced after infection by Escherichia coli or Staphylococcus aureus, while its silencing exacerbated bacterial loads and larvae mortality. TcLph-deficient larvae significantly decreased the transcription levels of antimicrobial peptides and prophenoloxidase activating system-related genes, leading to a significant reduction in phenoloxidase activity. It indicated that TcLph functioned as a pattern recognition receptor in pathogen recognition and activated immune responses to eliminate invasive microbes, suggesting a potential target for insecticides.
拉托蛋白是参与多种生理过程的粘附 GPCR 家族的一员。赤拟谷盗拉托蛋白（TcLph）的细胞外片段含有半乳糖结合凝集素（GBL）结构域。然而，GBL 结构域的生物学功能仍然神秘。在这里，我们初步研究了 TcLph 通过其 GBL 结构域识别病原体并在无脊椎动物中触发免疫防御的作用。结果表明，GBL 结构域高度保守，其预测的 3D 结构与小鼠拉托蛋白-1的鼠李糖结合凝集素结构域相似，具有独特的 α/β 折叠和两个长环。分子对接和 ELISA 结果表明，GBL 结构域可以与 D-半乳糖、L-鼠李糖、脂多糖和肽聚糖结合。TcLph 的重组细胞外片段和重组 GBL 以 Ca 依赖性方式强烈凝集和结合所有测试的细菌。此外，感染大肠杆菌或金黄色葡萄球菌后 TcLph 明显诱导，而其沉默加剧了细菌负荷和幼虫死亡率。TcLph 缺陷型幼虫显著降低抗菌肽和酚氧化酶激活系统相关基因的转录水平，导致酚氧化酶活性显著降低。这表明 TcLph 在病原体识别中作为模式识别受体发挥作用，并激活免疫反应以消除入侵的微生物，这表明它可能是杀虫剂的潜在靶标。
