Leukotoxin production by A. actinomycetemcomitans

描述：伴生放线杆菌是一种引起局限性侵袭性牙周炎的细菌。LAP是一种破坏性和侵袭性的口腔疾病，影响青少年。LAP的发病率在不同的人群中有所不同，但少数民族和弱势群体的患病频率更高。不治疗LAP会导致牙齿脱落和其他与健康相关的问题。此外，伴放线放线杆菌是引起感染性心内膜炎的Hacek细菌群的一部分，这是一种心脏瓣膜和组织的疾病。 伴生放线菌会分泌一种称为白毒素的蛋白质毒素。白斑毒素破坏人类的白细胞，并可能通过帮助放线菌逃避免疫反应而在伴生放线杆菌的发病机制中发挥重要作用。白斑毒素是一种RTX(Repeats In Toxin)毒素，包括其他重要的毒素，如螺旋杆菌α-溶血素、溶血分枝杆菌白毒素、百日咳杆菌腺苷环化酶和霍乱弧菌RTX毒素。到目前为止，关于放线菌伴生菌的白毒素是如何从细菌细胞中产生、激活和分泌的，人们知之甚少。此外，没有一种RTX毒素被结晶以解决其三维结构。 这里提出的实验将(1)确定产生活性白毒素所需的基因，(2)利用遗传学和生化方法研究基因和蛋白质，(3)生长白毒素晶体并在原子水平上解决其三维结构。我们希望这项工作能够更好地了解白毒素的产生以及这种毒素是如何导致疾病的。通过这些实验获得的结构信息将进一步阐明这类重要毒素的作用机制。这一新信息可能会导致设计出能够干扰白毒素活性并最终治疗或预防疾病的治疗剂。

DESCRIPTION: Actinobacillus actinomycetemcomitans is a bacterium that is the etiologic agent for localized aggressive periodontitis (LAP). LAP is a destructive and aggressive disease of the oral cavity that affects adolescents. The incidence of LAP varies among population groups, but afflicts minorities and the underprivileged at a higher frequency. Failure to treat LAP results in the loss of teeth and other health-related problems. In addition, A. actinomycetemcomitans is part of the HACEK group of bacteria that causes infective endocarditis, a disease of heart valves and tissue. A. actinomycetemcomitans secretes a protein toxin known as leukotoxin. Leukotoxin destroys leukocytes of humans, and likely plays a significant role in the pathogenesis of A. actinomycetemcomitans by helping the bacterium evade the immune response. Leukotoxin is an RTX (repeats in toxin) toxin that includes other important toxins such as E. coil alpha-hemolysin, M. haemolytica leukotoxin, B. pertussis adenylate cyclase, and V. cholerae RTX toxin. To date, little is known about how A. actinomycetemcomitans leukotoxin is produced, activated, and secreted from bacterial cells. In addition, none of the RTX toxins have been crystallized to have their three-dimensional structures solved. Proposed here are experiments that will (1) identify the genes that are required for production of active leukotoxin, (2) study the genes and proteins using genetic and biochemical approaches, and (3) grow crystals of leukotoxin and solve its three-dimensional structure at the atomic level. We expect this work to lead to a better understanding of leukotoxin production and how the toxin contributes to disease. The structural information gained through these experiments will shed more light on the mechanism of action of this important class of toxins. This new information may lead to the design of therapeutic agents that can disrupt leukotoxin activity and ultimately treat or prevent disease.