Regulation of GRP94: Targeting Novel Cancer Therapeutics

描述（由申请人提供）：GRP94的监管机制仍然是一个开放的话题。GRP94是一种同源二聚体，含有两个相同的配体结合位点。这些配体结合位点是天然抗肿瘤化合物格尔达霉素（GA）和根尖醇（RD）的靶点，也参与ATP/ADP的结合。已知腺苷及其类似物以1mol配体GRP94二聚体的化学计量与GRP94结合，这种结合是通过负协同性调节的。我们假设ATP/ADP结合功能的负协同性对细胞应激条件提供了高度敏感的反应，从而导致细胞ATP/ADP水平降低。GA和RD竞争核苷酸结合，能够以2摩尔配体：GRP94二聚体的化学计量与GRP94结合。我们假设，靶向GRP94的腺苷核苷酸结合袋并克服负协同作用的抑制剂配体将作为一类新的癌症化疗药物。为了验证这一假设，研究人员将对大量GRP94嵌合体进行研究，以确定分子中负责负协同性的区域。除了负协同性外，分子中可能还有其他区域对GRP94的功能至关重要。为了确定这些额外的作用，将过度表达单个GRP94结构域并筛选显性阴性抑制剂活性。总之，所提出的分析将使我们更好地了解GRP94作为一种新的抗癌靶点。

DESCRIPTION (provided by applicant): The mechanism of GRP94 regulation remains an open topic. GRP94 is a homodimer containing two identical ligand-binding sites. These ligand-binding sites are targets for the natural anti-tumor compounds geldanamycin (GA) and radicicol (RD) and also function in ATP/ADP binding. Adenosine and its analogues are known to bind GRP94 at a stoichiometry of 1 mol ligand: GRP94 dimer and such binding is regulated through negative cooperativity. We hypothesize that the negative cooperativity of ATP/ADP binding functions to provide a highly sensitive response to cell stress conditions that elicit a decrease in cellular ATP/ADP levels. GA and RD compete nucleotide binding and are able to bind GRP94 at a stoichiometry of 2-mol ligand: GRP94 dimer. We hypothesize that inhibitor ligands that target the adenosine nucleotide binding pocket of GRP94 and override negative cooperativity will function as a novel class of cancer chemotherapeutics. To examine this hypothesis, a broad array of GRP94 chimera will be studied to identify the region(s) of the molecule responsible for the negative cooperativity. In addition to negative cooperativity, there are likely to be other regions of the molecule critical to GRP94 function. To define such additional roles, individual GRP94 domains will be over-expressed and screened for dominant negative inhibitor activity. Together, the proposed analysis will lead to a greater understanding of GRP94 as a novel anti-cancer target.