Interactions between the streptococcal inhibitor of complement (sic) protein and its targets in neutrophils

中性粒细胞是第一个也是最丰富的白细胞，被输送到炎症或感染的部位。中性粒细胞配备了抗菌剂武器库，可以摧毁入侵的病原体。然而，许多病原体已经想出了避免中性粒细胞致死的策略。化脓性链球菌或A组链球菌(GAS)是革兰氏阳性菌之一。化脓性葡萄球菌可引起多种人类疾病，包括咽炎(链球菌咽喉炎)、脂肪团、脓疱病，以及可能致命的坏死性筋膜炎(食肉疾病)和链球菌中毒性休克综合征。我的长期目标是了解化脓性链球菌是如何逃避中性粒细胞的杀戮的。我的一般假设是，化脓性链球菌分泌的外毒素与中性粒细胞防御机制的蛋白质成分相互作用，以防止微生物被杀死。我的特定假设是，化脓性链球菌分泌的一种名为SIC(补体链球菌抑制物)的新蛋白质，针对中性粒细胞中的特定蛋白质，这些蛋白质调节其吞噬微生物(吞噬)或分泌杀微生物酶的能力。我们的具体目标是(I)确定和表征中性粒细胞中SIC的特定靶点，以及(Ii)分析SIC与其蛋白靶点之间的分子相互作用，并检测SIC对分泌和吞噬功能的分子作用。我们将结合细胞和分子生物学、免疫学和生物化学的现代方法来追求我们的目标，包括质谱学、酵母双杂交分析、蛋白质表达和纯化、二维凝胶电泳以及免疫电子和共聚焦显微镜。这些研究将使我们能够阐明中性粒细胞中SIC与其蛋白质靶标之间的分子相互作用的功能意义。因此，我们的研究将促进我们对化脓性链球菌机制的了解，这些机制的进化是为了防止中性粒细胞破坏它。

The neutrophil is the first and most abundant leukocyte to be delivered to a site of inflammation or infection. Neutrophils are equipped with an antimicrobial arsenal that destroys invading pathogens. However, many pathogens have devised strategies to avoid killing by neutrophils. Streptococcus pyogenes (S. pyogenes) or group A Streptococcus (GAS), a gram-positive bacterium, is one of them. S. pyogenes can cause a variety of human diseases, including pharyngitis (strep throat), cellulites, impetigo, and the potentially fatal necrotizing fascitis (flesh eating disease) and streptococcal toxic shock syndrome. My long-term objective is to understand how S. pyogenes evades killing by neutrophils. My general hypothesis is that exotoxins secreted by S. pyogenes interact with protein components of the neutrophil defense machineries to prevent killing of the microorganism. My specific hypothesis is that a novel protein named sic (streptococcal inhibitor of complement), which is secreted by S. pyogenes, targets specific proteins in neutrophils which regulate its ability to ingest microorganisms (phagocytosis) or secrete microbicidal enzymes. Our specific objectives are to (i) identify and characterize the specific targets of sic in neutrophils and (ii) to analyze the molecular interactions between sic and its protein targets, and examine the molecular effect of sic on secretion and phagocytosis. We will use a combination of modern methodologies in cellular and molecular biology, immunology and biochemistry to pursue our goals, including mass spectrometry, yeast-two hybrid analysis, protein expression and purification, two-dimensional gel electrophoresis, and immunoelectron and confocal microscopy. These investigations will allow us to elucidate the functional significance of the molecular interactions between sic and its protein targets in neutrophils. Thus, our studies will advance our knowledge of S. pyogenes mechanisms that evolved to prevent its destruction by neutrophils.