IMMUNODOMINANT STRESS PROTEINS OF P. GINGIVALIS

在我们实验室进行的研究表明，牙龈卟啉单胞菌HtpG应激蛋白（Hsp90的原核同源物）与牙周病的病因有关。我们已经报道了抗hsp90抗体水平升高，伴随牙龈假单胞菌定植，与牙周健康有关。HtpG信息的转录也被发现在患病的龈下菌斑中上调7-10倍。Hsp90同源物具有促进其他微生物致病性的优先性。对白色念珠菌单一Hsp90表位的免疫已被证明可对全身念珠菌病提供保护。我们实验室的研究表明，牙龈卟啉菌HtpG与人类Hsp90具有显著的同源性，但由于其独特的c端区域，与其他HtpG蛋白明显不同。我们发现HtpG定位于牙龈假单胞菌膜和细胞外囊泡，并与其他原核和真核Hsp90同源物发生交叉反应。我们的研究结果表明，当牙龈假单胞菌进入宿主细胞质室时，HtpG很容易参与宿主细胞的侵袭过程，并干扰正常的宿主细胞功能。用牙龈假单胞菌htpG基因转染KB细胞可刺激这些细胞产生IL-8。这一应用为进一步研究HtpG分子模拟在牙龈卟啉卟啉致病性中的作用提供了新的思路。以前对其他病原微生物的研究似乎使用Hsp90同源物作为毒力因子，这纯粹是描述性的。我们的应用是独特的，虽然我们将提出评估HtpG在粘附和侵袭机制中的作用，我们也提出阐明新的致病机制，微生物如牙龈假单胞菌利用分子模拟来破坏正常的真核细胞功能。由于最明确定义的真核hsp90介导的机制涉及信号转导途径，这些将是我们研究的主要焦点。本研究拟验证的假设是：1)HtpG在粘附和侵袭宿主细胞中发挥作用；2)一旦内化，真核细胞内Hsp90/TRAP1介导的信号转导机制就会被牙龈假单胞菌的HtpG通过分子模拟破坏。这导致正常炎症细胞因子对牙龈假单胞菌和其他口腔微生物入侵的反应被破坏。

Studies performed in our laboratory implicate the Porphyromonas gingivalis HtpG stress protein, the prokaryotic homologue of Hsp90, in the etiology of periodontal disease. We have reported that elevated levels of anti-Hsp90 antibodies, concomitant with P. gingivalis colonization, are associated with periodontal health. Transcription of HtpG message was also found to be upregulated 7-10-fold in P. gingivalis obtained from diseased subgingival plaque. There is a precedence for Hsp90 homologues contributing to pathogenicity of other microorganisms. Immunity to a single Hsp90 epitope of Candida albicans has been demonstrated to confer protection against systemic candidiasis. Studies performed by our laboratory have revealed that P. gingivalis HtpG has a significant degree of homology with human Hsp90, but remains clearly distinct from other HtpG proteins due to its unique C-terminal region. We have found that HtpG is localized to P. gingivalis membranes and extracellular vesicles, and that it cross-reacts with other prokaryotic and eukaryotic Hsp90 homologues. Our findings suggest that HtpG is readily accessible to participate in host cellular invasion processes, as well as to interfere with normal host cell functions one P. gingivalis enters the host cytoplasmic compartment. Transfection of KB cells with the P. gingivalis htpG gene stimulates IL-8 production by these cells. This application proposes to extend our investigations into the role that molecular mimicry by HtpG plays in the pathogenicity of P. gingivalis. Previous studies of other pathogenic microorganisms which appear to use the Hsp90 homologue as a virulence factor have been purely descriptive. Our application is unique in that while will propose to evaluate the role of HtpG in adherence and invasion mechanisms, we also propose to elucidate novel pathogenic mechanism(s) by which microorganisms such as P. gingivalis utilize molecular mimicry to disrupt normal eukaryotic cell function(s). Since the most clearly defined eukaryotic Hsp90-mediated mechanisms involved signal transduction pathways, these will be the primary foci of our investigations. The hypothesis to be tested in this study is: 1) HtpG plays a role in adherence and invasion of host cells; and 2) once internalized, signal transduction mechanisms mediated by Hsp90/TRAP1 within eukaryotic cells are disrupted by the HtpG of P. gingivalis through molecular mimicry. This leads to disruption of normal inflammatory cytokine responses to microbial invasion by P. gingivalis and other oral microorganisms.