Malik Z A, Iyer S S, Kusner D J
Inflammation Program, Graduate Program in Immunology, University of Iowa and Veterans Administration Medical Center, Iowa City, IA 52242, USA.
J Immunol. 2001 Mar 1;166(5):3392-401. doi: 10.4049/jimmunol.166.5.3392.
Mycobacterium tuberculosis successfully parasitizes macrophages by disrupting the maturation of its phagosome, creating an intracellular compartment with endosomal rather than lysosomal characteristics. We have recently demonstrated that live M. tuberculosis infect human macrophages in the absence of an increase in cytosolic Ca(2+) (Ca(2+)), which correlates with inhibition of phagosome-lysosome fusion and intracellular viability. In contrast, killed M. tuberculosis induces an elevation in Ca(2+) that is coupled to phagosome-lysosome fusion. We tested the hypothesis that defective activation of the Ca(2+)-dependent effector proteins calmodulin (CaM) and CaM-dependent protein kinase II (CaMKII) contributes to the intracellular pathogenesis of tuberculosis. Phagosomes containing live M. tuberculosis exhibited decreased levels of CaM and the activated form of CaMKII compared with phagosomes encompassing killed tubercle bacilli. Furthermore, ionophore-induced elevations in Ca(2+) resulted in recruitment of CaM and activation of CaMKII on phagosomes containing live M. tuberculosis. Specific inhibitors of CaM or CaMKII blocked Ca(2+) ionophore-induced phagosomal maturation and enhanced the bacilli's intracellular viability. These results demonstrate a novel role for CaM and CaMKII in the regulation of phagosome-lysosome fusion and suggest that defective activation of these Ca(2+)-activated signaling components contributes to the successful parasitism of human macrophages by M. tuberculosis.
结核分枝杆菌通过破坏吞噬体的成熟来成功寄生巨噬细胞，从而形成一个具有内体而非溶酶体特征的细胞内区室。我们最近证明，活的结核分枝杆菌在不增加胞质Ca(2+)（Ca(2+)）的情况下感染人类巨噬细胞，这与吞噬体-溶酶体融合的抑制及细胞内存活能力相关。相反，经杀死的结核分枝杆菌会诱导Ca(2+)升高，这与吞噬体-溶酶体融合相关。我们检验了这样一种假说，即Ca(2+)依赖性效应蛋白钙调蛋白（CaM）和CaM依赖性蛋白激酶II（CaMKII）的激活缺陷促成了结核病的细胞内发病机制。与包含经杀死的结核杆菌的吞噬体相比，含有活的结核分枝杆菌的吞噬体显示出CaM和CaMKII激活形式的水平降低。此外，离子载体诱导的Ca(2+)升高导致CaM募集并激活包含活的结核分枝杆菌的吞噬体上的CaMKII。CaM或CaMKII的特异性抑制剂阻断了Ca(2+)离子载体诱导的吞噬体成熟，并增强了杆菌的细胞内存活能力。这些结果证明了CaM和CaMKII在吞噬体-溶酶体融合调节中的新作用，并表明这些Ca(2+)激活的信号成分的激活缺陷促成了结核分枝杆菌对人类巨噬细胞的成功寄生。
