Interactions of the oral pathogen, A. actinomycetemcomitans, with collagen

描述（由申请人提供）：牙周病是一组炎症性疾病，导致牙龈和牙齿支撑结构的破坏。组织的丧失是由于特定龈下细菌的定殖引起的宿主免疫应答的不平衡。这种微生物区系也被认为是口腔外疾病的来源。伴放线菌聚集杆菌是一种革兰氏阴性牙周病病原体，与慢性和局部侵袭性牙周病有关。该病原体可引起多种播散性口腔外疾病，包括感染性心内膜炎和心血管疾病的加重。然而，A.放线菌共生菌在口腔中定殖或渗透和扩散到远处组织的能力仍然难以捉摸。这些组织共享共同的细胞外基质（ECM）蛋白，包括胶原蛋白。我们的小组已经确定了一种新的蛋白质，细胞外基质蛋白粘附素A（EmaA），这是至关重要的细菌与胶原蛋白的相互作用，是一个被证明的毒力决定因素的感染性心内膜炎的启动。综上所述，A.伴放线菌表达细胞表面粘附素，其结合胶原蛋白，最丰富的ECM蛋白，用于建立感染灶。因此，我们认为，ECM定植作为一个水库的再感染的龈沟和传播到外 口腔部位。 EmaA粘附素由A.放线菌共生体，插入外膜以组装独特的触角状表面附属物，这些附属物对于胶原蛋白结合至关重要。然而，单体的蛋白质大小和序列是血清型特异性的。此外，EmaA被O-多糖（O-PS）糖后修饰，这对与胶原蛋白结合至关重要。有趣的是，这种EmaA修饰共享O-PS生物合成所需的相同酶。聚糖部分在与胶原相互作用中的具体作用仍不明确。这个应用程序的目标是 阐明该病原体在口腔定植并传播至其他组织的机制。为了实现这一目标，我们提出了以下具体目标：1）确定来自血清型B细菌的EmaA的聚糖部分的定位和组成; 2）确定EmaA基因型和细菌血清型在胶原结合中的作用;和3）EmaA/胶原相互作用的生物化学和生物物理学确定。确定EmaA活性结合部分的性质将有助于理解该蛋白在A.伴放线菌从这项研究中获得的这种粘附素的分子机制的新见解将导致分子的发展，破坏和/或减少这种病原体的组织定植。

DESCRIPTION (provided by applicant): Periodontal disease represents a group of inflammatory diseases, which lead to the destruction of the gingiva and the supporting structures of the teeth. The loss of tissue results from an imbalance of the host immune response induced by the colonization of specific sub-gingival bacteria. This microflora is also considered the source for extra-oral diseases. Aggregatibacter actinomycetemcomitans is a Gram-negative periodontal pathogen associated with both the chronic and localized aggressive forms of the disease. Multiple disseminated extra-oral diseases are attributed to this pathogen including infective endocarditis and the potentiation of cardiovascular disease. However, the tropism used by A. actinomycetemcomitans to colonize the oral cavity or infiltrate and disseminate to distant tissues has remained elusive. These tissues share common extracellular matrix (ECM) proteins including collagen. Our group has identified a novel protein, extracellular matrix protein adhesin A (EmaA), which is critical for the interaction of the bacterium with collagens and is a proven virulence determinant for the initiation of infective endocarditis. In summary, A. actinomycetemcomitans expresses a cell surface adhesin that binds collagen, the most abundant ECM protein, for establishing infectious foci. Therefore, we posit that ECM colonization acts as a reservoir for re-infection of the gingival sulcus and dissemination to extra oral sites. The EmaA adhesin is composed of three identical monomers unique to A. actinomycetemcomitans that intercalate in the outer membrane to assemble unique antenna-like surface appendages essential for collagen binding. However, the protein size and sequence of the monomers is serotype specific. Furthermore, EmaA is posttranslationally modified with O-polysaccharide (O-PS) sugars that are crucial for binding to collagen. Interestingly, this EmaA modification shares the same enzymes required for O-PS biosynthesis. The specific role of the glycan moieties in the interaction with collagen remains undefined. The goal of this application is to elucidate the mechanism(s) utilized by this pathogen for colonizing the oral cavity and disseminating to other tissues. To achieve this goal we propose the following specific aims: 1) determine the localization and composition of the glycan moiety of EmaA from serotype b bacteria; 2) determine the role of EmaA genotype and bacterial serotype in collagen binding; and 3) biochemical and biophysical determination of the EmaA/collagen interaction. Defining the nature of the active binding moiety of EmaA will aid in understanding the role of this protein in the pathogenesis of A. actinomycetemcomitans. The new insights gained from this study into the molecular mechanism of this adhesin will lead to the development of molecules to disrupt and/or diminish tissue colonization by this pathogen.