Encapsulated Streptococcus suis inhibits activation of signaling pathways involved in phagocytosis
Encapsulated Streptococcus suis inhibits activation of signaling pathways involved in phagocytosis
复制标题
DOI：
10.1128/iai.72.9.5322-5330.2004
复制
发表时间：
2004-09-01
影响因子：
3.1
通讯作者：
Olivier, M
中科院分区：
文献类型：
--
作者：
Segura, M;Gottschalk, M;Olivier, M
猪链球菌2型是一种重要的人畜共患脑膜炎病原体。以往的研究报道，与非包囊突变体相比，包囊S。suis能够抵抗吞噬作用。然而，S. suis避免吞噬作用是未知的。阐明S.猪的抗吞噬作用，我们比较了包囊菌株及其未包囊突变体诱导Akt和蛋白激酶C（PKC）激活的能力，Akt和PKC是磷脂酰肌醇3-激酶（PI-3 K）途径的下游激酶，已知参与吞噬过程。结果表明，在用未包封的突变体感染J774巨噬细胞后，Akt和PKCalpha磷酸化水平高，而包封的菌株显示PI-3 K/Akt/PKCalpha信号通路的活化减少，以及几种蛋白酪氨酸事件。这些结果与细胞内细菌的数量相关。用特异性PI-3 K或PKC抑制剂预处理的巨噬细胞显示Akt和PKCalpha磷酸化水平降低，导致吞噬作用降低50%。通过使用磷酸酶抑制剂以及SHP-1缺陷型巨噬细胞来评价磷酸酶在抗吞噬机制中的作用。只有在不存在SHP-1的情况下，被包裹的S. suis显著增加，导致Akt磷酸化水平与未包囊化菌株相似，表明包囊化的S.猪。最后，当纯化S.将猪荚膜多糖（CPS）加入到巨噬细胞中，未观察到磷酸化事件。此外，CPS和包囊S. SUI能够抑制未包封的突变体的摄取。这些结果提示CPS在S.猪下调吞噬作用。
Streptococcus suis capsular type 2 is an important zoonotic agent of meningitis. Previous studies reported that, in contrast to nonencapsulated mutants, encapsulated S. suis is able to resist phagocytosis. However, the mechanisms by which S. suis avoids phagocytosis are unknown. To elucidate the signaling pathway(s) involved in S. suis antiphagocytosis, we compared the ability of an encapsulated strain and its nonencapsulated mutant to induce the activation of Akt and protein kinase C (PKC), which are downstream kinases of the phosphatidylinositol 3-kinase (PI-3K) pathway, known to be involved in the phagocytosis processes. The results demonstrated high levels of Akt and PKCalpha phosphorylation after infection of J774 macrophages with the nonencapsulated mutant, whereas the encapsulated strain showed reduced activation of PI-3K/Akt/PKCalpha signaling pathway, as well as several protein tyrosine events. These results correlated with the number of intracellular bacteria. Macrophages pretreated with specific PI-3K or PKC inhibitors showed reduced levels of Akt and PKCalpha phosphorylation, resulting in 50% reduction of phagocytosis. The role of phosphatases in the antiphagocytic mechanisms was evaluated by using phosphatase inhibitors, as well as SHP-1-deficient macrophages. Only in the absence of SHP-1 did the phagocytosis of encapsulated S. suis significantly increase, leading to Akt phosphorylation levels similar to those observed with the nonencapsulated strain, indicating activation of this important SH2 domain-containing tyrosine phosphatase by encapsulated S. suis. Finally, when purified S. suis capsular polysaccharide (CPS) was added to macrophages, no phosphorylation events were observed. In addition, CPS and encapsulated S. suis were able to inhibit the uptake of the nonencapsulated mutant. These results suggest the importance of CPS in the mechanisms, whereby S. suis downmodulates phagocytosis.