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

中性粒细胞是第一个和最丰富的白细胞被运送到炎症或感染部位。中性粒细胞配备了一个抗菌武器库，可以摧毁入侵的病原体。然而，许多病原体已经想出了避免被中性粒细胞杀死的策略。化脓性链球菌（S. pyogenes）或A群链球菌（GAS）是一种革兰氏阳性细菌，就是其中之一。化脓性链球菌可引起多种人类疾病，包括咽炎（链球菌性咽喉炎）、脂肪团、脓疱疮，以及潜在致命的坏死性筋膜炎（食肉性疾病）和链球菌中毒性休克综合征。我的长期目标是了解化脓性葡萄球菌如何逃避中性粒细胞的杀伤。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。我的具体假设是，化脓性链球菌分泌的一种名为sic（链球菌补体抑制剂）的新蛋白质靶向中性粒细胞中的特定蛋白质，这些蛋白质调节其摄取微生物（吞噬）或分泌杀微生物酶的能力。我们的具体目标是：(i)识别和表征中性粒细胞中sic的特定靶点；（ii）分析sic与其蛋白靶点之间的分子相互作用，并研究sic对分泌和吞噬的分子作用。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实现我们的目标，包括质谱分析、酵母-两种杂交分析、蛋白质表达和纯化、二维凝胶电泳、免疫电子和共聚焦显微镜。这些研究将使我们能够阐明sic及其靶蛋白在中性粒细胞中的分子相互作用的功能意义。因此，我们的研究将推进我们对化脓性葡萄球菌机制的认识，这种机制是进化而来的，可以防止它被中性粒细胞破坏。

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.