Abstract

Glycosylphosphatidylinositols (GPIs) anchored proteins are commonly localized onto lipid rafts. These extracellular proteins participate in a variety of cellular functions, including as receptors for viruses and toxins. Intracellular trafficking of World Health Organization recognized mosquito-larvicidal BinAB toxin is mediated via GPI-anchored Cqm1 receptor protein in Culex mosquitoes. We confirmed conformational change in Cqm1 dimer on interaction with BinA/BinB proteins by dynamic light scattering, modelling of hydrodynamic parameters using the atomic structures, and synchrotron Small Angle solution X-ray scattering (SAXS). A reliable model of the receptor–BinB complex was also constructed from joint SAXS/SANS refinement. We confirmed electrostatic interactions of the Cqm1 ectodomain with lipid rafts reconstituted in model membranes and report receptor-dependent impairment of model liposomes by BinA/B proteins. Liposomal disruption was toxin concentration-dependent as monitored by the release of encapsulated carboxyfluorescein dye. Interestingly, BinA alone, without BinB, showed efficient efflux of the fluorescent dye in agreement with the reported high larvicidal activity of BinA variants. The study provides insight into BinA/B toxin internalization mechanism in the membrane model that is toxin internalization is mediated via receptor-dependent pore formation mechanism. It also suggests a tangible and environmentally safe strategy for control of mosquito population.

Graphic Abstract

中文翻译：

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基于脂质体的研究深入了解杀蚊幼虫 BinAB 毒素的细胞内化机制。

摘要

糖基磷脂酰肌醇 (GPI) 锚定蛋白通常位于脂筏上。这些细胞外蛋白参与多种细胞功能，包括作为病毒和毒素的受体。世界卫生组织认可的杀蚊幼虫 BinAB 毒素的细胞内运输是通过库蚊中GPI 锚定的 Cqm1 受体蛋白介导的蚊子。我们通过动态光散射、使用原子结构的流体动力学参数建模和同步加速器小角溶液 X 射线散射 (SAXS) 证实了 Cqm1 二聚体与 BinA/BinB 蛋白相互作用时的构象变化。受体-BinB 复合物的可靠模型也是通过联合 SAXS/SANS 细化构建的。我们证实了 Cqm1 胞外域与在模型膜中重建的脂筏的静电相互作用，并报告了 BinA/B 蛋白对模型脂质体的受体依赖性损伤。如通过封装的羧基荧光素染料的释放所监测的，脂质体破坏是毒素浓度依赖性的。有趣的是，在没有 BinB 的情况下，单独的 BinA 显示出荧光染料的有效流出，这与所报道的 BinA 变体的高杀幼虫活性一致。该研究深入了解了膜模型中的 BinA/B 毒素内化机制，即毒素内化是通过受体依赖性孔形成机制介导的。它还提出了控制蚊子数量的切实且环境安全的战略。

图形摘要