SpyA, a novel S. pyogenes ADP-ribosyltransferase

描述(申请人提供)：化脓性链球菌是一种普遍存在且用途广泛的人类病原体。由这种微生物引起的感染范围从相对轻微和常见的咽炎和脓疱病到急性和危及生命的坏死性筋膜炎和中毒性休克。链球菌疾病的广泛范围部分是由于产生了许多和不同的细胞外毒素和酶。这笔赠款的重点是最近描述的一种链球菌毒素，我们称之为Spy A，即化脓性链球菌ADP核糖化毒素。SPYA将NAD的ADP核糖部分转移到细胞骨架蛋白波形蛋白、肌动蛋白和原肌球蛋白上。虽然肌动蛋白被其他ADP-核糖转移酶修饰，但波形蛋白和原肌球蛋白不是常见的靶标。肌动蛋白和波形蛋白细丝是需要运动的细胞功能所必需的，例如伤口愈合过程中的细胞迁移和吞噬作用。Spya是外毒素C3家族的成员之一，与该家族的每个成员相似，没有明显的受体结合结构域，或与二元毒素相关联的结合结构域。我们认为，Spya通过胆固醇依赖的细胞溶血素SLO产生的毛孔进入真核细胞。这笔赠款的目标是(1)确定SpA在链球菌感染中的作用，(2)表征其新的进入机制，(3)表征这种毒素的结构和生化活性。

DESCRIPTION (provided by applicant): Streptococcus pyogenes is a ubiquitous and versatile human pathogen. Infections due to this organism range from the relatively mild and common pharyngitis and impetigo to the acute and life-threatening necrotizing fasciitis and toxic shock. The wide spectrum of streptococcal disease results in part from the production of the many and varied extracellular toxins and enzymes. The focus of this grant is a recently described streptococcal toxin we term Spy A, for S. pyogenes ADP-ribosylating toxin. SpyA transfers the ADP-ribose portion of NAD onto the cytoskeletal proteins vimentin, actin, and tropomyosin. While actin is modified by other ADP-ribosyltransferases, vimentin and tropomyosin are not common targets. Actin and vimentin filaments are needed for cellular functions requiring motility, such as cell migration during wound healing and phagocytosis. SpyA is a member of the C3 family of exotoxins, and similar to each member of this family, does not have an obvious receptor-binding domain, or associated binding domain as found with binary toxins. We proposed that SpyA gains entrance into the eukaryotic cell using a pore produced by the cholesterol dependent cytolysin SLO. The goals of this grant are (1) to determine the role of SpyA in streptococcal infections, (2) to characterize its novel entry mechanism and (3) to characterize the structure and biochemical activity of this toxin.