cAMP synthesis and degradation by phagosomes regulate actin assembly and fusion events: consequences for mycobacteria
cAMP synthesis and degradation by phagosomes regulate actin assembly and fusion events: consequences for mycobacteria
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DOI：
10.1242/jcs.03091
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发表时间：
2006-09-01
影响因子：
4
通讯作者：
Griffiths, Gareth
中科院分区：
文献类型：
--
作者：
Kalamidas, Stefanos A.;Kuehnel, Mark P.;Griffiths, Gareth
我们最近发现，肌动蛋白的组装吞噬体膜促进融合与晚期内吞细胞器在巨噬细胞。此外，脂质诱导吞噬体肌动蛋白也刺激了这一融合过程。在感染病原性分枝杆菌的巨噬细胞中，肌动蛋白刺激脂质导致病原体破坏增加，而抑制剂促进其生长。提出了一个模型，其中吞噬体膜肌动蛋白组装提供的轨道，溶酶体向吞噬体移动，从而促进融合。在这里，我们研究了cAMP如何影响吞噬体肌动蛋白组装在体外，吞噬体肌动蛋白，酸化和晚期融合事件在J774巨噬细胞。乳胶珠吞噬体显示具有腺苷酸环化酶活性，其合成cAMP，和磷酸二酯酶活性，其降解cAMP。该系统由蛋白激酶A（PKA）调节。增加cAMP水平抑制，而降低cAMP水平刺激，肌动蛋白组装在体外和细胞内。增加cAMP水平也抑制吞噬体-溶酶体融合和酸化的细胞，而减少cAMP有相反的效果。高cAMP水平诱导的非致病性耻垢分枝杆菌和致病性结核分枝杆菌的巨噬细胞的吞噬体内生长的增加，而低cAMP水平或PKA的抑制与增加的细菌破坏。我们认为，吞噬体cAMP-PKA系统的行为作为一个分子开关，调节吞噬体肌动蛋白和成熟的巨噬细胞。
We showed recently that actin assembly by phagosomal membranes facilitates fusion with late endocytic organelles in macrophages. Moreover, lipids that induced phagosomal actin also stimulated this fusion process. In macrophages infected with pathogenic mycobacteria actin-stimulatory lipids led to an increase in pathogen destruction, whereas inhibitors facilitated their growth. A model was proposed whereby phagosomal membrane actin assembly provides tracks for lysosomes to move towards phagosomes, thereby facilitating fusion. Here, we investigated how cAMP affected phagosomal actin assembly in vitro, and phagosomal actin, acidification and late fusion events in J774 macrophages. Latex bead phagosomes are shown to possess adenylyl cyclase activity, which synthesizes cAMP, and phosphodiesterase activity, which degrades cAMP. The system is regulated by protein kinase A (PKA). Increasing cAMP levels inhibited, whereas decreasing cAMP levels stimulated, actin assembly in vitro and within cells. Increasing cAMP levels also inhibited phagosome-lysosome fusion and acidification in cells, whereas reducing cAMP had the opposite effect. High cAMP levels induced an increase in intraphagosomal growth in macrophages of both the non-pathogenic Mycobacterium smegmatis and the pathogenic Mycobacterium tuberculosis, whereas low cAMP levels or inhibition of PKA correlated with increased bacterial destruction. We argue that the phagosome cAMP-PKA system behaves as a molecular switch that regulates phagosome actin and maturation in macrophages.