COBRE: DMS: CHAPERONE-MEDIATED IMMUNE REGULATION

本子项目是利用由NIH/NCRR资助的中心赠款提供的资源的众多研究子项目之一。子项目和研究者（PI）可能已经从另一个NIH来源获得了主要资金，因此可以在其他CRISP条目中表示。列出的机构是中心的，不一定是研究者的机构。钙网蛋白（CRT）和gp96 （GRP94）是内质网衍生的分子伴侣，已被确定为肿瘤排斥抗原；在小鼠模型中，它们引发预防性和治疗性抗肿瘤反应并抑制转移进展。伴侣蛋白在提高对多种小鼠肿瘤的免疫应答方面的功效已经导致了目前针对人类黑色素瘤和肾癌的iii期临床试验。抗原呈递细胞（APCs）是伴侣介导的抗肿瘤反应所必需的，其似乎源于：1)刺激抗原非依赖性先天免疫反应，包括APC的成熟、激活和细胞因子的分泌；2)通过引发针对相关抗原的肽特异性免疫反应来激活适应性免疫系统。目前，伴侣引发这些反应的机制尚不清楚。拟议研究的广泛目标是确定伴侣引起APC免疫反应的机制。我们将通过研究：1)伴侣蛋白如何进入APC MHC i类抗原呈递途径？2)清道夫受体a类在介导伴侣诱导的免疫反应中的作用是什么？这些领域的研究源于我们最近发现的清除受体，特别是SR-A和SREC-1，作为gp96和CRT在APC上的内吞受体的新作用：清除受体a类（SR-A）的表达足以赋予伴侣蛋白摄取，而SR-A-/-巨噬细胞的这一功能受损。此外，SR-A配体竞争gp96相关肽的交叉呈递。基于这些发现，我们假设清道夫受体在介导gp96和CRT刺激的免疫反应中起作用。这项拨款提案的重点是阐明清道夫受体介导伴侣的免疫作用的机制；特别是，SRs如何将伴侣蛋白及其相关肽传输到抗原递呈途径。我们将使用细胞和分子技术来确定伴侣复合物引发抗原特异性反应的机制，并使用遗传和免疫学技术来评估清除受体对伴侣介导的抗原呈递的贡献。这些研究的结果将有助于对伴侣蛋白作为免疫分子的认识。此外，通过阐明目前正在进行临床评估的治疗的潜在机制，所获得的见解将有利于免疫治疗领域，并将进一步促进抗肿瘤治疗的合理开发和应用。

This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. The subproject and investigator (PI) may have received primary funding from another NIH source, and thus could be represented in other CRISP entries. The institution listed is for the Center, which is not necessarily the institution for the investigator. Calreticulin (CRT) and gp96 (GRP94) are endoplasmic reticulum-derived molecular chaperones that have been identified as tumor rejection antigens; in murine models they elicit prophylactic and therapeutic anti-tumor responses and inhibit metastatic progression. The efficacy of chaperones in raising immune responses against a broad variety of murine tumors has led to the current phase-III clinical trials for human melanoma and renal carcinoma. Antigen-presenting cells (APCs) are required for chaperone-mediated anti-tumor responses, which appear to derive from: 1) stimulating antigen-independent innate immune responses including APC maturation, activation and cytokine secretion, and 2) activating the adaptive immune system by eliciting peptide-specific immune responses against associated antigens. At present, the mechanisms by which chaperones elicit these responses are poorly understood. The broad objective of the proposed studies is to define the mechanisms by which chaperones elicit immune responses from APC. We will do so by investigating: 1) How do chaperones access the APC MHC class-I antigen presentation pathway? 2) What is the contribution of Scavenger Receptor Class-A in mediating chaperone-elicited immune responses? These areas of investigation evoke from, and are united by, our recent identification of a novel role for scavenger receptors, SR-A and SREC-1 in particular, as endocytic receptors of both gp96 and CRT on APC: expression of Scavenger Receptor Class-A (SR-A) was sufficient to confer chaperone uptake, while SR-A-/- macrophages were impaired in this function. Additionally, SR-A ligands competed for cross-presentation of gp96-associated peptides. On the basis of these findings, we hypothesize that scavenger receptors function in mediating the immune responses stimulated by gp96 and CRT. This grant proposal focuses on elucidating the mechanisms by which scavenger receptors mediate the immunological effects of chaperones; in particular, how SRs traffic chaperones, and their associated peptides, into the antigen presentation pathway. We will test this using cellular and molecular techniques to identify the mechanisms by which chaperone complexes elicit antigen-specific responses, and genetic and immunological techniques to evaluate the contribution of scavenger receptors towards chaperone-mediated antigen presentation. Results derived from these studies will contribute to the understanding of chaperones as immunological molecules. Additionally, insights obtained will benefit the field of immunotherapy by elucidating the underlying mechanisms of a treatment that is currently undergoing clinical evaluation, and will further facilitate the rational development and application of anti-tumor therapy.