Regulation of GRP94: Targeting Novel Cancer Therapeutics

描述（由申请人提供）：GRP 94调节的机制仍然是一个开放的话题。GRP 94是含有两个相同配体结合位点的同源二聚体。这些配体结合位点是天然抗肿瘤化合物格尔德霉素（GA）和根赤霉素（RD）的靶标，并且还在ATP/ADP结合中起作用。已知腺苷及其类似物以1摩尔配体：GRP 94二聚体的化学计量结合GRP 94，并且这种结合通过负协同性调节。我们假设ATP/ADP结合功能的负协同性对引起细胞ATP/ADP水平降低的细胞应激条件提供高度敏感的响应。GA和RD竞争核苷酸结合，并且能够以2摩尔配体：GRP 94二聚体的化学计量结合GRP 94。我们假设靶向GRP 94的腺苷酸结合口袋并克服负协同性的抑制剂配体将作为一类新的癌症化疗药物发挥作用。为了检验这一假设，将研究一系列广泛的GRP 94嵌合体，以鉴定负责负协同性的分子区域。除了负协同性之外，可能还有其他对GRP 94功能至关重要的分子区域。为了定义这些额外的作用，将过表达单个GRP 94结构域并筛选显性负抑制剂活性。总之，所提出的分析将导致对GRP 94作为一种新型抗癌靶点的更好理解。

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.