The Structural and Functional Determination of Streptococcus mutans Adherence

龋齿是一种多微生物疾病，影响全世界大部分人口， 一个合作的生态组织的和谐转向一个生态失调的框架， 病原微生物，特别是变形链球菌（SM）。对于强直性SM，粘附于牙齿 表面和/或牙齿生物膜是龋齿发病机制中的关键步骤，并且SM已经进化（i）SM- 宿主和（ii）SM-微生物相互作用，这是通过其表面蛋白（粘附素）介导的。 SM的粘附介导的相互作用包括：（A）最近发现的SM的多余的高亲和力结合。 SM粘附于唾液糖蛋白340（Gp 340）的清道夫受体富含半胱氨酸结构域（SRCR）， 其促进SM-宿主界面中的龋齿易感性;和（B）SM粘附素的暴露需要 SM-白色念珠菌（CA）生物膜形成和产酸，这增强了早期的致龋性 SM-微生物界面中的儿童龋齿。这些共同揭示了以前未知的相互作用 曾经被认为是SM上众所周知的和充分表征的粘附素。但关键的未解之谜 SM是如何介导这种冗余的，但特异性结合宿主蛋白质和其他微生物的？ 本申请的目标是确定驱动细胞凋亡的特定基序和/或分子机制。 SM的粘附性，特别是它们如何能够与多个配体结合。我们的结构和功能研究 显示SM表面粘附素主要通过两个主要结构域介导这些附着， 和C折叠。我们假设“SM表面粘附素上的V-和C-折叠介导了特异性的 通过对生物膜形成和微生物定殖至关重要的共同结合基序的相互作用”。 我们将通过三个特定目标（SA）来解决我们的假设：（a）将粘附基序映射到 口腔链球菌粘附素的V-折叠（SA 1）和（B）C-折叠（SA 2），以及（c）研究SM粘附素的作用 在SM-白色念珠菌（CA）界面（SA 3）中。 本多PD/PI研究的结果将（i）确定全球采用的结合基序/机制 通过SM粘附素之间的V-和C-折叠;（ii）确定不同和/或重叠粘附的存在 各种配体的位点;（iii）提供来自变异蛋白的各种粘附素的V-和C-折叠的比较分析 和草绿色链球菌，揭示其结合基序/机制的物种特异性差异;（iv） 表征SM粘附素在SM-CA界面的作用;和（v）阐明微生物粘附素中的变化。 生态调节SM的V-和C-折叠，特别是因为它们涉及到龋齿。 我们提出的结构分析，关键粘附基序的遗传操作和动物模型研究 将确定遵守机制，并解决SM的V-和C-折叠的知识差距，特别是 它们在促进定植和毒性方面的关键作用。这些结果将使未来的发展选择性 组合疗法以防止SM对宿主和微生物的粘附。

Dental caries is a polymicrobial disease that affects much of the human population worldwide, where the harmony of a cooperative eco-organization shifts towards a dysbiotic framework with overrepresentation of pathogenic microorganisms, particularly by Streptococcus mutans (SM). For planktonic SM, adhesion to tooth surface and/or dental biofilms is a crucial step in the pathogenesis of dental caries, and SM has evolved (i) SM- host and (ii) SM-microbial interactions, which are mediated through its surface proteins (adhesins). SM’s adhesion mediated interactions include: (A) The recent discovery of redundant high affinity binding of SM’s adhesins to the scavenger receptor cysteine rich domains (SRCR) of the salivary glycoprotein 340 (Gp340), which promotes caries susceptibility in the SM-host interface; and (B) The revelation of SM’s adhesin required for the SM-Candida albicans (CA) biofilm formation and acid production, which enhances cariogenicity in early childhood caries in the SM-microbial interface. Together these have revealed previously unknown interactions by once thought to be well-known and well-characterized adhesins on SM. Yet the key unanswered question remains, “how does SM mediate such redundant, but specific binding to host proteins and to other microbes?” The goal of this application is to determine the specific motif(s) and/or molecular mechanism(s) that drive SM’s adherence, particularly how they enable binding to multiple ligands. Our structural and functional studies show that SM’s surface adhesins mediate these attachments primarily via two major structural domains, the V- and C-fold. We hypothesize that “the V- and C-fold present on the surface adhesins of SM mediate specific interactions through common binding motif(s) that are crucial for biofilm formation and microbial colonization”. We will address our hypothesis through three specific aims (SAs) by (a) mapping the adherence motif(s) on the V-fold (SA1) and (b) C-fold (SA2) of oral streptococcal adhesins, and (c) investigating the role of SM’s adhesins in the SM-Candida albicans (CA) interface (SA3). The results from this multi-PD/PI study will (i) Determine the binding-motif(s)/mechanisms globally adopted by the V- and C-fold among SM’s adhesins; (ii) Determine the presence of distinct and/or overlapping adherence sites for various ligands; (iii) Provide a comparative analysis of the V- and C-fold of various adhesins from mutans and viridans streptococci, revealing species-specific differences in their binding-motifs/mechanisms; (iv) Characterize the role of SM adhesins at the SM-CA interface; and (v) Elucidate alternations in the microbial ecology modulated by SM’s V- and C-folds, particularly as they relate to dental caries. Our proposed structural analyses, genetic manipulation of key adhesion motif(s) and animal model studies will determine the adherence mechanisms and address the knowledge gap on SM’s V- and C-fold, particularly their crucial role in promoting colonization and virulence. The results will enable future development of selective combinatorial therapeutics to prevent SM’s adherence to host and microbes.