Belon Claudine, Gannoun-Zaki Laïla, Lutfalla Georges, Kremer Laurent, Blanc-Potard Anne-Béatrice
Laboratoire de Dynamique des Interactions Membranaires Normales et Pathologiques, Universités Montpellier 2 et 1, Place Eugène Bataillon, 34095, Montpellier, Cedex 05, France; Centre National de la Recherche Scientifique, UMR5235, Montpellier, France.
Laboratoire de Dynamique des Interactions Membranaires Normales et Pathologiques, Universités Montpellier 2 et 1, Place Eugène Bataillon, 34095, Montpellier, Cedex 05, France; Centre National de la Recherche Scientifique, UMR5235, Montpellier, France; Institut national de la santé et de la recherche médicale, Montpellier, France.
PLoS One. 2014 Dec 29;9(12):e116052. doi: 10.1371/journal.pone.0116052. eCollection 2014.
MgtC is a virulence factor involved in intramacrophage growth that has been reported in several intracellular pathogens, including Mycobacterium tuberculosis and Salmonella enterica serovar Typhimurium. MgtC participates also in adaptation to Mg2+ deprivation. Herein, we have constructed a mgtC mutant in Mycobacterium marinum to further investigate the role of MgtC in mycobacteria. We show that the M. marinum mgtC gene (Mma mgtC) is strongly induced upon Mg2+ deprivation and is required for optimal growth in Mg2+-deprived medium. The behaviour of the Mma mgtC mutant has been investigated in the Danio rerio infection model using a transgenic reporter zebrafish line that specifically labels neutrophils. Although the mgtC mutant is not attenuated in the zebrafish embryo model based on survival curves, our results indicate that phagocytosis by neutrophils is enhanced with the mgtC mutant compared to the wild-type strain following subcutaneous injection. Increased phagocytosis of the mutant strain is also observed ex vivo with the murine J774 macrophage cell line. On the other hand, no difference was found between the mgtC mutant and the wild-type strain in bacterial adhesion to macrophages and in the internalization into epithelial cells. Unlike the role reported for MgtC in other intracellular pathogens, Mma MgtC does not contribute significantly to intramacrophage replication. Taken together, these results indicate an unanticipated function of Mma MgtC at early step of infection within phagocytic cells. Hence, our results indicate that although the MgtC function is conserved among pathogens regarding adaptation to Mg2+ deprivation, its role towards phagocytic cells can differ, possibly in relation with the specific pathogen's lifestyles.
MgtC是一种参与巨噬细胞内生长的毒力因子，已在包括结核分枝杆菌和鼠伤寒沙门氏菌血清型鼠伤寒杆菌在内的几种细胞内病原体中被报道。MgtC也参与对镁离子缺乏的适应。在此，我们构建了一株海分枝杆菌的mgtC突变体，以进一步研究MgtC在分枝杆菌中的作用。我们发现，海分枝杆菌mgtC基因（Mma mgtC）在镁离子缺乏时被强烈诱导，并且是在缺镁培养基中最佳生长所必需的。使用特异性标记中性粒细胞的转基因报告斑马鱼品系，在斑马鱼感染模型中研究了Mma mgtC突变体的行为。尽管基于生存曲线，mgtC突变体在斑马鱼胚胎模型中没有减毒，但我们的结果表明，皮下注射后，与野生型菌株相比，mgtC突变体的中性粒细胞吞噬作用增强。在体外，用小鼠J774巨噬细胞系也观察到突变菌株的吞噬作用增加。另一方面，在细菌对巨噬细胞的粘附和内化到上皮细胞方面，mgtC突变体与野生型菌株之间没有发现差异。与MgtC在其他细胞内病原体中所报道的作用不同，Mma MgtC对巨噬细胞内复制没有显著贡献。综上所述，这些结果表明Mma MgtC在吞噬细胞感染的早期阶段具有意想不到的功能。因此，我们的结果表明，尽管MgtC在病原体适应镁离子缺乏方面的功能是保守的，但其对吞噬细胞的作用可能不同，这可能与特定病原体的生活方式有关。
