Two PI 3-kinases and one PI 3-phosphatase together establish the cyclic waves of phagosomal PtdIns(3)P critical for the degradation of apoptotic cells.
Two PI 3-kinases and one PI 3-phosphatase together establish the cyclic waves of phagosomal PtdIns(3)P critical for the degradation of apoptotic cells.
复制标题
DOI：
10.1371/journal.pbio.1001245
复制
发表时间：
2012-01
期刊：
影响因子：
9.8
通讯作者：
Zhou Z
中科院分区：
文献类型：
--
作者：
Lu N;Shen Q;Mahoney TR;Neukomm LJ;Wang Y;Zhou Z
吞噬体中磷脂酰肌醇 3-磷酸水平的周期性波动由两种磷酸肌醇激酶和一种磷酸酶调节，对于吞噬体成熟和凋亡细胞的降解至关重要。磷脂酰肌醇 3-磷酸 (PtdIns(3)P) 是一种信号分子，对许多膜运输事件（包括吞噬体成熟）很重要。在吞噬体成熟过程中，吞噬体上的 PtdIns(3)P 水平以两波振荡。然而，这种振荡的生理意义仍然未知。目前，III类PI 3激酶(PI3K) Vps34被认为是唯一在吞噬体膜中产生PtdIns(3)P的激酶。我们在此报告，在线虫秀丽隐杆线虫中，II 类 PI3K PIKI-1 在产生吞噬体 PtdIns(3)P 方面发挥着新颖且至关重要的作用。在 PtdIns(3)P 出现之前，PIKI-1 以依赖于大 GTP 酶动力 (DYN-1) 的方式被募集以延伸伪足和新生吞噬体。 PIKI-1 和 VPS-34 依次作用，在吞噬体上提供重叠的 PtdIns(3)P 池。灭活 piki-1 和 vps-34 会完全消除吞噬体 PtdIns(3)P 的产生，并使吞噬体无法募集多种必需的成熟因子，从而完全阻止凋亡细胞降解。我们进一步鉴定了 MTM-1，一种 PI 3-磷酸酶，通过下调吞噬体上的 PtdIns(3)P 来拮抗 PIKI-1 和 VPS-34 的活性。值得注意的是，由于 mtm-1 失活，吞噬体 PtdIns(3)P 的持续出现会阻碍吞噬体成熟。我们的研究结果表明，由两种 PI3K 和一种 PI 3-磷酸酶的协调活动编程的 PtdIns(3)P 在吞噬体上的正确振荡模式对于吞噬体成熟至关重要。他们进一步阐明了磷酸肌醇的时间控制可逆磷酸化如何调节多步细胞事件的进展。在动物发育和成年期间，许多细胞被编程为通过称为细胞凋亡的活跃过程而死亡。这些死亡或垂死的凋亡细胞迅速被清道夫细胞吸收到膜结合的隔室（吞噬体）中，随后当其他含有消化酶的细胞内细胞器与吞噬体融合时，它们被降解，这一过程称为吞噬体成熟。凋亡细胞的吞噬作用对于发育中的组织重塑以及防止有害的炎症和自身免疫反应非常重要。在线虫（一种研究细胞凋亡的模型生物体）中，吞噬体的成熟伴随着该区室中的两波信号分子磷脂酰肌醇 3-磷酸 (PtdIns(3)P)：一波在吞噬体形成后不久形成并持续 10-15 分钟，第二波较弱，在 10 分钟后持续直至凋亡细胞被完全消化。在这项研究中，我们研究了调节这两个波的时间和长度的机制。我们发现它们是通过三种酶的顺序和组合作用建立的：两种磷酸肌醇 3-激酶，将磷酸基团添加到 PtdIns 的 3' 位点，以及一种磷酸肌醇 3-磷酸酶，将其去除。我们发现，两种激酶的失活会耗尽 PtdIns(3)P 的吞噬体，并导致吞噬体成熟和凋亡细胞降解的停滞。此外，磷酸酶催化的PtdIns(3)P的及时周转对于吞噬体成熟的逐步进展至关重要。我们的研究结果表明，由不同的激酶和磷酸酶组催化的磷酸肌醇的可逆磷酸化可能是驱动多步骤细胞内膜运输事件的一般机制。
Cyclic oscillations in the level of phosphatidylinositol 3-phosphate in phagosomes, regulated by two phosphoinositide kinases and one phosphatase, are critical for phagosome maturation and degradation of apoptotic cells. Phosphatidylinositol 3-phosphate (PtdIns(3)P) is a signaling molecule important for many membrane trafficking events, including phagosome maturation. The level of PtdIns(3)P on phagosomes oscillates in two waves during phagosome maturation. However, the physiological significance of such oscillation remains unknown. Currently, the Class III PI 3-kinase (PI3K) Vps34 is regarded as the only kinase that produces PtdIns(3)P in phagosomal membranes. We report here that, in the nematode C. elegans, the Class II PI3K PIKI-1 plays a novel and crucial role in producing phagosomal PtdIns(3)P. PIKI-1 is recruited to extending pseudopods and nascent phagosomes prior to the appearance of PtdIns(3)P in a manner dependent on the large GTPase dynamin (DYN-1). PIKI-1 and VPS-34 act in sequence to provide overlapping pools of PtdIns(3)P on phagosomes. Inactivating both piki-1 and vps-34 completely abolishes the production of phagosomal PtdIns(3)P and disables phagosomes from recruiting multiple essential maturation factors, resulting in a complete arrest of apoptotic-cell degradation. We have further identified MTM-1, a PI 3-phosphatase that antagonizes the activities of PIKI-1 and VPS-34 by down-regulating PtdIns(3)P on phagosomes. Remarkably, persistent appearance of phagosomal PtdIns(3)P, as a result of inactivating mtm-1, blocks phagosome maturation. Our findings demonstrate that the proper oscillation pattern of PtdIns(3)P on phagosomes, programmed by the coordinated activities of two PI3Ks and one PI 3-phosphatase, is critical for phagosome maturation. They further shed light on how the temporally controlled reversible phosphorylation of phosphoinositides regulates the progression of multi-step cellular events. During animal development and in adulthood many cells are programmed to die by an active process called apoptosis. These dead or dying apoptotic cells are swiftly taken up by scavenger cells into membrane-bound compartments—phagosomes—where they are subsequently degraded when other intracellular organelles containing digestive enzymes fuse with phagosomes—a process called phagosome maturation. Phagocytosis of apoptotic cells is important for tissue remodeling in development and to prevent harmful inflammatory and autoimmune responses. In nematode worms—a model organism in which to study apoptosis—phagosome maturation is accompanied by two waves of the signaling molecule phosphatidylinositol 3-phosphate (PtdIns(3)P) in this compartment: one that forms soon after the formation of the phagosome and lasts for 10–15 minutes, and a second, weaker one 10 minutes later that lasts until the apoptotic cell is fully digested. In this study, we investigated the mechanism that regulates the timing and length of these two waves. We found that they are established by the sequential and combined action of three enzymes: two phosphoinositide 3-kinases, which add a phosphate group to the 3′ site of PtdIns, and one phosphoinositide 3-phosphatase, which removes it. We showed that inactivation of both kinases depleted phagosomes of PtdIns(3)P and resulted in the arrest of phagosome maturation and degradation of apoptotic cells. In addition, the timely turnover of PtdIns(3)P catalyzed by the phosphatase was critical for the step-wise progress of phagosome maturation. Our findings suggest that reversible phosphorylation of phophoinositides, catalyzed by distinct sets of kinases and phosphatases, might be a general mechanism to drive multi-step intracellular membrane trafficking events.
登录
查看更多内容
影响因子：
3.3
作者：
He, Bin;Yu, Xiaomeng;Zhou, Zheng
通讯作者：
Zhou, Zheng
DOI：
10.1007/978-1-60761-652-8_10
发表时间：
2010-01-01
期刊：
IN VITRO MUTAGENESIS PROTOCOLS, THIRD EDITION
影响因子：
--
作者：
Lee, Jehan;Shin, Myeong-Kyun;Ryu, Wang-Shick
通讯作者：
Ryu, Wang-Shick
影响因子：
9.2
作者：
Macdougall, LK;Domin, J;Waterfield, MD
通讯作者：
Waterfield, MD
影响因子：
12.3
作者：
通讯作者：
--
影响因子：
3.3
作者：
Lu N;Shen Q;Mahoney TR;Liu X;Zhou Z
通讯作者：
Zhou Z