The Molecular Mechanism of GRP94 Function

GRP 94是内质网Hsp 90分子伴侣，已被鉴定为有效的肿瘤排斥抗原，能够引发针对其肿瘤起源的原发性和远处转移的强烈免疫应答。 GRP 94的免疫原性活性被认为来源于尚未表征的肽结合活性。 在引发免疫应答时，GRP 94-肽复合物被抗原呈递细胞（APC）内化，并且GRP 94结合的肽重新呈递在APC I类分子上，用于激活肽特异性细胞毒性T淋巴细胞。 GRP 94的免疫原性已得到充分证实，肿瘤衍生的GRP 94目前正处于多中心III期临床试验中，作为肾细胞癌的免疫疗法。 除了其作为肿瘤抗原的活性之外，现在存在强有力的证据表明GRP 94作为蛋白质第二信使在病理性细胞死亡与免疫系统的通信中起作用。 这一结论延伸自最近的工作，表明GRP 94响应于致死性病毒感染而从细胞中释放，并且随后可以被APC加工以引发病毒特异性免疫应答。在对GRP 94功能的生物学基础的研究中，提出了两个主要的长期目标：1）定义GRP 94作为肽结合蛋白的功能的结构和调节基础; 2）定义GRP 94摄取到抗原呈递细胞中以及抗原呈递细胞内的亚细胞命运的机制。 拟议的研究将利用各种生物物理技术，用于分析蛋白质结构;生物化学技术，研究肽-GRP 94相互作用;和细胞生物学/免疫学技术，以确定GRP 94依赖性免疫反应的细胞基础。在这些研究中使用的技术的广泛范围旨在允许详细的分子描述的结构和功能的基础上的免疫原性活性的GRP 94。在实现本提案的主要目标中获得的见解预计将大大有助于分子伴侣蛋白作为用于治疗癌症和传染病的免疫剂的发展。此外，在研究中获得的定义GRP 94作为病理性细胞死亡的第二信使的作用的结果将有益于人类和动物疫苗4开发领域以及自身免疫的起源和治疗解决的研究。

GRP94, the endoplasmic reticulum Hsp90 chaperone, has been identified as a potent tumor rejection antigen, capable of eliciting vigorous immune responses against primary and distant metastases of its tumor of origin. The immunogenic activity of GRP94 is thought to derive from an as yet uncharacterized peptide binding activity. In eliciting an immune response, GRP94-peptide complexes are internalized by antigen presenting cells (APC) and the GRP94-bound peptides re-presented on the APC class I molecules for avtivation of peptide-specific cytotoxic T lymphocytes. The immunogenic properties of GRP94 are well established, and tumor-derived GRP94 is now in multi-center Phase III clinical trials as an immunotherapy for renal cell carcinoma. In addition to its activity as a tumor antigen, there now exists strong evidence that GRP94 functions as a protein second messenger in the communication of pathological cell death to the immune system. This conclusion extends from recent work demonstrating that GRP94 is released from cells in response to lethal viral infection and can subsequently be processed by APCs to elicit virus-specific immune responses. In pursuing research into the biological basis of GRP94 function, two primary long term objectives are proposed: 1) Define the structural and regulatory basis for GRP94's function as a peptide binding protein; 2) Define the mechanism of GRP94 uptake into, and subcellular fate within, antigen presenting cells. The proposed studies will draw on a variety of biophysical techniques, for the analysis of protein structure; biochemical techniques, to study peptide-GRP94 interactions; and cell biological/immunological techniques, to define the cellular basis for GRP94-dependent immune responses. The broad scope of techniques used in these studies is intended to allow a detailed molecular description of the structural and functional basis for the immunogenic activity of GRP94. Insights obtained in achieving the primary objectives of this proposal are expected to contribute significantly to the development of molecular chaperone proteins as immunotherapeutic agents for the treatment of cancer and infectious disease. In addition, results obtained in studies defining a role for GRP94 as a second messenger for pathological cell death will benefit the fields of human and animal vaccin4 development and the study of the genesis and therapeutic resolution of autoimmunity.