Attenuation of the Phosphatidylinositol 3-Kinase/Akt Signaling Pathway by Porphyromonas gingivalis Gingipains RgpA, RgpB, and Kgp
Attenuation of the Phosphatidylinositol 3-Kinase/Akt Signaling Pathway by Porphyromonas gingivalis Gingipains RgpA, RgpB, and Kgp
复制标题
DOI：
10.1074/jbc.m114.591610
复制
发表时间：
2015-02-20
影响因子：
4.8
通讯作者：
Ohara, Naoya
中科院分区：
文献类型：
--
作者：
Nakayama, Masaaki;Inoue, Tetsuyoshi;Ohara, Naoya
牙龈卟啉单胞菌是引起牙周炎等牙周疾病的主要病原菌。我们研究了牙龈卟啉单胞菌感染对牙龈上皮细胞中PI 3 K/Akt（蛋白激酶B）信号通路的影响。在这里，我们发现活的牙龈卟啉单胞菌，而不是热灭活的牙龈卟啉单胞菌，减少了Akt在Thr-308和Ser-473的磷酸化，这意味着Akt活性的降低。实际上，Akt上游的PI 3 K也被牙龈卟啉单胞菌灭活。此外，糖原合成酶激酶3 α/β、雷帕霉素的哺乳动物靶标和Bad（它们是PI 3 K/Akt级联中的下游蛋白）也被去磷酸化，这是与牙龈卟啉单胞菌导致的Akt失活一致的现象。然而，这些事件不需要细菌和宿主细胞之间的直接相互作用，并且不依赖于牙龈卟啉单胞菌侵入细胞。牙龈卟啉菌蛋白酶特异性抑制剂和牙龈卟啉菌蛋白酶缺陷型牙龈卟啉单胞菌突变体KDP 136的使用揭示了牙龈卟啉菌蛋白酶及其蛋白酶活性对于PI 3 K和Akt的失活是必不可少的。PI 3 K调节亚基p85 α和膜蛋白之间的关联被野生型牙龈卟啉单胞菌破坏。此外，野生型牙龈卟啉单胞菌减少了PDK 1向质膜的转运，但KDP 136没有减少，表明PI 3 K几乎不产生磷脂酰肌醇3，4，5-三磷酸。因此，很可能PI 3 K不能通过牙龈卟啉菌蛋白酶将稳态的细胞外刺激传递到细胞内信号通路。综上所述，我们的研究结果表明，牙龈卟啉单胞菌通过牙龈卟啉单胞菌蛋白酶的蛋白水解作用减弱PI 3 K/Akt信号通路，导致PI 3 K/Akt依赖性细胞功能失调和上皮屏障破坏。
Porphyromonas gingivalis is a major pathogen of periodontal diseases, including periodontitis. We have investigated the effect of P. gingivalis infection on the PI3K/Akt (protein kinase B) signaling pathway in gingival epithelial cells. Here, we found that live P. gingivalis, but not heat-killed P. gingivalis, reduced Akt phosphorylation at both Thr-308 and Ser-473, which implies a decrease in Akt activity. Actually, PI3K, which is upstream of Akt, was also inactivated by P. gingivalis. Furthermore, glycogen synthase kinase 3 alpha/beta, mammalian target of rapamycin, and Bad, which are downstream proteins in the PI3K/Akt cascade, were also dephosphorylated, a phenomenon consistent with Akt inactivation by P. gingivalis. However, these events did not require direct interaction between bacteria and host cells and were independent of P. gingivalis invasion into the cells. The use of gingipain-specific inhibitors and a gingipain-deficient P. gingivalis mutant KDP136 revealed that the gingipains and their protease activities were essential for the inactivation of PI3K and Akt. The associations between the PI3K regulatory subunit p85 alpha and membrane proteins were disrupted by wild-type P. gingivalis. Moreover, PDK1 translocation to the plasma membrane was reduced by wild-type P. gingivalis, but not KDP136, indicating little production of phosphatidylinositol 3,4,5-triphosphate by PI3K. Therefore, it is likely that PI3K failed to transmit homeostatic extracellular stimuli to intracellular signaling pathways by gingipains. Taken together, our findings indicate that P. gingivalis attenuates the PI3K/Akt signaling pathway via the proteolytic effects of gingipains, resulting in the dysregulation of PI3K/Akt-dependent cellular functions and the destruction of epithelial barriers.