Defining the role of mSMGP/mPIP as an immunoregulatory molecule in host defense

假设：小鼠颌下腺蛋白（mSMGP）是一种重要的免疫调节分子，在先天和适应性免疫宿主防御中均发挥作用。建议：研究mSMGP对适应性免疫系统的影响，并描述其先天抗菌活性的机制。我的实验室对颌下腺的生物学和生理学很感兴趣。与大多数其他哺乳动物一样，小鼠的下颌下腺具有内分泌和外分泌功能，是合成多种生物活性多肽的场所，包括激素、生长因子和消化酶。这些蛋白质中的许多都被很好地研究和表征，然而，其他一些蛋白质的功能仍然难以捉摸。我已经确定了一个在这个腺体中高度表达的基因，我们将其蛋白质命名为小鼠颌下腺蛋白（mSMGP）。mSMGP的功能尚未明确。根据这一初步发现，我们随后发现，mSMGP不仅在唾液腺中表达，而且在病原体的重要免疫入口（如皮肤、眼睛和耳朵）以及由这些组织（如唾液、眼泪和汗水）产生的体液中发现的分泌蛋白中也表达。我们进一步证明，mSMGP结合并聚集细菌，包括几种人类和小鼠口腔菌株，阻止它们的增殖和传播。这些观察结果使我们假设mSMGP在先天宿主防御中起作用。然而，关于mSMGP可能在免疫中发挥更广泛作用的线索来自于对人类同源物进行的其他研究，这些研究显示，与mSMGP一样，不仅具有与细菌菌株结合的能力，而且能够与CD4分子结合并抑制T淋巴细胞凋亡。此外，我们使用mSMGP敲除模型作为解决蛋白质功能的工具，我们证明敲除小鼠具有异常淋巴细胞，表现出异常增殖率，Th1和可能的Th2免疫反应受损，并且对利什曼原虫感染的易感性增加。我们首次证明了mSMGP参与细胞介导的免疫。我们还发现，KO小鼠唾液聚集口腔细菌的效果较差，口腔菌群的组成与野生型小鼠不同，主要来自链球菌属。此外，我们发现mSMGP功能的丧失导致一类唾液蛋白的上调，这些蛋白最近被认为是疾病的标记。我们目前的目标是研究mSMGP在细胞介导免疫中的作用，并描述mSMGP抗菌活性的机制。迄今为止，人们对防止入侵生物或感染，特别是通过口腔污染的保护知之甚少。提出的研究是极少数从口腔角度研究感染现象的研究之一。我预计这项研究将对mSMGP的功能和生物学产生重要的见解，并将进一步有助于增加我们对颌下腺生物学和免疫的理解。

Defining a role for mSMGP as an immunoregulatory molecule in host defense HYPOTHESIS: The mouse submaxillary (submandibular) gland protein, mSMGP, is an important immunoregulatory molecule that plays a role in both innate and adaptive immune host defense. PROPOSAL: To examine mSMGP’s influence on the adaptive immune system and to delineate the mechanisms of its innate antimicrobial activities. My laboratory is interested in the biology and physiology of the submandibular gland. The submandibular gland in the mouse, as in most other mammals, exhibits both endocrine and exocrine functions, and is the site of synthesis of several biologically active polypeptides, including hormones, growth factors, and digestive enzymes. Many of these proteins are well studied and characterized, however, the function of several others remain elusive. I have identified a gene that is highly expressed in this gland and whose protein we termed the mouse submaxillary gland protein (mSMGP). The function of mSMGP has not been delineated. Following this initial discovery, we subsequently found that not only was mSMGP expressed in salivary glands, but was also expressed at immunologically important ports of entry for pathogens, such as skin, eyes and ears and the secreted protein found in the bodily fluids produced by these tissues such as saliva, tears and sweat. We further demonstrated that mSMGP binds to and aggregates bacteria including several human and mouse oral strains, prohibiting their multiplication and spread. These observations led us to hypothesize that mSMGP plays a role in innate host defense. However, clues that mSMGP may have a broader role in immunity have come from other studies carried out on a human homologue which was shown, like mSMGP, not only to possess the ability to bind to bacterial strains but was capable of binding to the CD4 molecule and inhibit T lymphocyte apoptosis. Furthermore, using a mSMGP knockout model which we generated as a tool to address protein function, we demonstrated that knockout mice had abnormal lymphocytes that exhibited abnormal proliferation rates, had impaired Th1 and possibly, Th2 immune responses and had increased susceptibility to Leishmania major infection. We demonstrated for the first time that mSMGP was involved in cell mediated immunity. We also showed that KO mice saliva was less effective in aggregating oral bacteria and that the composition of the oral flora was different from its wild type counterpart, with a preponderance of representation from the genus Streptococcus. Additionally we showed that loss of mSMGP function resulted in the up regulation of a class of salivary proteins recently identified as putative markers of disease. Our current objectives are to investigate the role of the mSMGP in cell mediated immunity and to delineate the mechanism of mSMGP antimicrobial activities. Protection against invading organisms or infection, particularly via oral contamination is to date, poorly understood. The proposed studies are among the very few that approach the infection phenomenon from an oral perspective. I anticipate this study will yield critical insights into the function and biology of the mSMGP, and will further contribute to increasing our understanding of submandibular gland biology and immunity.