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了疟原虫侵袭红细胞的充分必要条件。为了解决这个问题，我们研究了：1)在不影响膜脂含量的情况下破坏和恢复筏（分别将利多卡因掺入膜中和随后去除），2)胆固醇消耗（甲基β -环糊精（MBCD）处理），3)鞘磷脂消耗（鞘磷脂酶（SMase）处理），红细胞膜对筏结构完整性和信号转导的影响。利用脂质修饰红细胞研究了筏在疟疾寄生虫入侵中的重要性。利多卡因治疗可可逆调节木筏结构，而MBCD和SMase治疗可不可逆调节木筏结构。利多卡因治疗也可逆地调节信号转导。利多卡因治疗（破坏木筏）降低了寄生虫的生长速度。去除利多卡因（恢复筏）后，寄生虫生长速度恢复。同步分裂体侵袭试验表明，在利多卡因作用下，2 mM或更高的浓度下，寄生虫的侵袭几乎完全被抑制。综上所述，疟原虫利用筏中积累的信号转导途径侵入红细胞，并参与了侧脂质动力学。疟疾寄生虫很可能通过gsa介导的过程诱导某些红细胞膜骨架蛋白的异食虫磷酸化，其中涉及侧脂质动力，促进膜内陷，这是入侵的先决条件。利多卡因已作为局部和全身麻醉剂应用于临床。基于利多卡因可逆阻断筏依赖性信号转导的疟疾新疗法将成为可能。

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.