Multiple roles for Plasmodium berghei phosphoinositide-specific phospholipase C in regulating gametocyte activation and differentiation.
Multiple roles for Plasmodium berghei phosphoinositide-specific phospholipase C in regulating gametocyte activation and differentiation.
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DOI：
10.1111/j.1462-5822.2011.01591.x
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发表时间：
2011-07
影响因子：
3.4
通讯作者：
Vial HJ
中科院分区：
文献类型：
--
作者：
Raabe AC;Wengelnik K;Billker O;Vial HJ
疟原虫生命周期中的关键事件是由钙依赖性信号级联控制的，但钙释放的分子机制仍然知之甚少。伯氏疟原虫配子细胞的同步发育依赖于配子细胞暴露于蚊子来源的黄嘌呤酸 (XA) 的 10 秒内从内部储存的钙快速释放。在这里，我们探讨了磷酸肌醇特异性磷脂酶 C (PI-PLC) 调节配子体激活的功能。 XA 引发配子细胞中 PIP2 的水解和第二信使 IP3 的产生。这两个过程都被 PI-PLC 抑制剂选择性阻断，这也减少了早期 Ca2+ 信号。然而，即使在激活后 5 分钟内添加抑制剂，小配子细胞分化为小配子的过程也会受到阻碍，这表明除了钙的早期动员之外还需要 PI-PLC。相比之下，通过兰尼碱受体通道释放钙的抑制剂仅在配子体激活的第一分钟内才具有活性。使用表达荧光 PIP2/IP3 探针的转基因寄生虫证实了 PI-PLC 活性的生化测定，该探针在细胞激活时从寄生虫质膜易位至细胞质。我们的研究揭示了 Ca2+ 和 PI-PLC 活性之间复杂的相互依赖性，其中 PI-PLC 在整个配子形成过程中至关重要，这可能解释了这一过程的不可逆性。
Critical events in the life cycle of malaria parasites are controlled by calcium-dependent signalling cascades, yet the molecular mechanisms of calcium release remain poorly understood. The synchronized development of Plasmodium berghei gametocytes relies on rapid calcium release from internal stores within 10 s of gametocytes being exposed to mosquito-derived xanthurenic acid (XA). Here we addressed the function of phosphoinositide-specific phospholipase C (PI-PLC) for regulating gametocyte activation. XA triggered the hydrolysis of PIP2 and the production of the secondary messenger IP3 in gametocytes. Both processes were selectively blocked by a PI-PLC inhibitor, which also reduced the early Ca2+ signal. However, microgametocyte differentiation into microgametes was blocked even when the inhibitor was added up to 5 min after activation, suggesting a requirement for PI-PLC beyond the early mobilization of calcium. In contrast, inhibitors of calcium release through ryanodine receptor channels were active only during the first minute of gametocyte activation. Biochemical determination of PI-PLC activity was confirmed using transgenic parasites expressing a fluorescent PIP2/IP3 probe that translocates from the parasite plasmalemma to the cytosol upon cell activation. Our study revealed a complex interdependency of Ca2+ and PI-PLC activity, with PI-PLC being essential throughout gamete formation, possibly explaining the irreversibility of this process.