Effect of erythrocyte membrane lipid dynamism on malaria invasion

本研究从红细胞膜脂质动力学的角度探讨疟原虫侵入红细胞的充要条件。为了解决这个问题，检查了以下因素对筏结构完整性和信号转导的影响：i）筏的破坏和恢复，而不影响膜脂质含量（分别将利多卡因掺入膜中和去除后），ii）胆固醇消耗（甲基- β -环糊精（MBCD）处理），iii）鞘磷脂消耗（鞘磷脂酶（SMase）处理），红细胞膜。使用这些脂质修饰的红细胞研究了筏在疟原虫入侵中的重要性。利多卡因治疗可逆地调节筏结构，而MBCD和SMase治疗不可逆地调节筏。利多卡因治疗还可逆地调节信号转导。利多卡因治疗（筏破坏）降低寄生虫的生长速度。去除利多卡因（恢复筏）后，寄生虫生长率恢复。使用同步化探针的侵袭试验表明，在2 mM或更高浓度的利多卡因存在下，寄生虫侵袭几乎完全被抑制。综上所述，疟原虫可能是通过与侧向脂质动力学有关的筏内信号转导途径侵入红细胞，并通过Gsa介导的侧向脂质动力学过程诱导红细胞膜骨架蛋白PICA磷酸化，从而促进膜内陷，这是疟原虫侵入红细胞的先决条件。利多卡因已作为局部麻醉药和全身麻醉药应用于临床。基于利多卡因可逆性中断筏依赖性信号转导的疟疾新疗法将是可能的。

In the present study, the necessary/sufficient conditions for erythrocyte invasion by malaria parasites were explored with respect to erythrocyte membrane lipid dynamism. To address this issue, effects of : i) Disruption and restoration of rafts without affecting membrane lipid content (incorporation of lidocaine into the membrane and following removal, respectively), ii) Cholesterol depletion (methyl- β -cyclodextrin (MBCD) treatment), iii) Sphingomyelin depletion (sphingomyelinase (SMase) treatment), of the erythrocyte membranes on the integrity of raft structure and signal transduction were examined. Importance of rafts in invasion by malaria parasites was studied using these lipid-modified erythrocytes.Lidocaine treatment reversibly modulated raft structure, while MBCD and SMase treatments irreversibly modulated rafts. Lidocaine treatment also modulated signal transduction reversibly. Lidocaine treatment (disruption of rafts) reduced parasite growth rate. After removal of lidocaine (restoration of rafts) parasite growth rate was recovered. Invasion assay using synchronized schizonts showed that parasite invasion was almost completely inhibited in the presence lidocaine at 2 mM or higher. Altogether, it was suggested that malaria parasites utilize signal transduction pathway accumulated in rafts, for which lateral lipid dynamism is involved, to invade erythrocytes.It is likely that malaria parasites induce PICA phosphorylation of some erythrocyte membrane skeletal proteins via Gsa-mediated process where lateral lipid dynamism is involved, facilitating membrane invagination that is the prerequisite for invasion. Lidocaine has already been applied to clinical use as local and systemic anesthetics. Novel therapy for malaria based on the reversible interruption of the raft-dependent signal transduction by lidocaine would be possible.