Localised PtdIns(3,4,5)P3 or PtdIns(3,4)P2 at the phagocytic cup is required for both phagosome closure and Ca2+ signalling in HL60 neutrophils
Localised PtdIns(3,4,5)P3 or PtdIns(3,4)P2 at the phagocytic cup is required for both phagosome closure and Ca2+ signalling in HL60 neutrophils
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DOI：
10.1242/jcs.02756
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发表时间：
2006-02-01
影响因子：
4
通讯作者：
Hallett, MB
中科院分区：
文献类型：
--
作者：
Dewitt, S;Tian, W;Hallett, MB
几个事件伴随着整合素介导的骨髓细胞吞噬作用。这些包括局部伪足和吞噬杯的形成，随后是Ca 2+信号传导。然而，局部磷脂酰肌醇（3，4，5）三磷酸[PtdIns（3，4，5）P-3]的产生也有作用。在这里，我们报告说，在表达PH-Akt-GFP的嗜酸性HL-60细胞中，iC 3b包被的酵母聚糖颗粒（直径2 μ m）通过β 2整联蛋白的结合诱导不完全的吞噬杯形成之前，PtdIns（3，4，5）P-3或磷脂酰肌醇（3，4）二磷酸[PtdIns（3，4）P-2]生产或Ca 2+信号。然后这些磷酸肌醇在吞噬杯和Ca 2+信号传导和吞噬体关闭的位点局部积累。虽然光漂白显示PH-Akt-GFP在胞质溶胶中可自由扩散并且能够从吞噬杯解离，但其被限制于形成的但开放的吞噬体的质膜，并且即使连接也未能扩散到周围的质膜或邻近的吞噬杯中。磷酸肌醇（PI）3-激酶的抑制或膜胆固醇的消耗抑制Ca 2+信号转导和吞噬体关闭，但对颗粒结合或吞噬杯的形成没有影响。因此，我们得出结论，PtdIns（3，4，5）P-3或PtdIns（3，4）P-2的产生不是启动吞噬杯形成的事件所必需的，但PtdIns（3，4，5）P-3锚定在吞噬杯是吞噬体关闭和Ca 2+信号传导的必要步骤。
Several events accompany integrin-mediated phagocytosis by myeloid cells. These include local pseudopod and phagocytic cup formation followed by Ca2+ signalling. However, there is also a role for localised phosphatidylinositol (3,4,5) trisphosphate [PtdIns(3,4,5)P-3] production. Here we report that in neutrophilic HL-60 cells expressing PH-Akt-GFP, binding of iC3b-coated zymosan particles (2 mu m in diameter) via beta 2 integrin induces an incomplete phagocytic cup to form before either PtdIns(3,4,5)P-3 or phosphatidylinositol (3,4) bisphosphate [PtdIns(3,4)P-2] production or Ca2+ signalling. These phosphoinositides then accumulated locally at the site of the phagocytic cup and Ca2+ signalling and phagosome closure follows immediately. Although photobleaching showed that PH-Akt-GFP was freely diffusible in the cytosol and able to dissociate from the phagocytic cup, it was restricted to the plasma membrane of the formed but open phagosome and failed to diffuse into the surrounding plasma membrane or neighbouring phagocytic cups even if connected. Inhibition of phosphoinositide (PI) 3-kinase or depletion of membrane cholesterol inhibited both Ca2+ signalling and phagosome closure, but had no effect on particle binding or phagocytic cup formation. We therefore conclude that PtdIns(3,4,5)P-3 or PtdIns(3,4)P-2 generation was not required for the events that initiate the formation of the phagocytic cup, but that anchoring of PtdIns(3,4,5)P-3 at the phagocytic cup is an essential step for phagosome closure and Ca2+ signalling.