Regulation of GRP94: Targeting Novel Cancer Therapeutics

描述(申请人提供)：GRP94的调控机制仍然是一个开放的话题。GRP94是一个含有两个相同配体结合位点的同源二聚体。这些配体结合部位是天然抗肿瘤化合物格尔达那霉素(GA)和自由基(RD)的靶点，也在ATP/ADP结合中发挥作用。已知腺苷及其类似物以1摩尔配体：GRP94二聚体的化学计量比与GRP94结合，这种结合是通过负协同作用来调节的。我们假设，ATP/ADP结合的负协同作用对引起细胞ATP/ADP水平下降的细胞应激条件提供高度敏感的反应。GA和RD竞争核苷酸结合，并能够以2-摩尔配体：GRP94二聚体的化学计量比与GRP94结合。我们假设，靶向GRP94的腺苷核苷酸结合口袋并覆盖负协同作用的抑制配体将作为一类新的癌症化疗药物发挥作用。为了验证这一假设，我们将研究一系列广泛的GRP94嵌合体，以确定负责负协同作用的分子的区域(S)。除了负的协作性，分子中可能还有其他区域对GRP94的功能至关重要。为了定义这种额外的作用，将过度表达单个GRP94结构域，并筛选出显性负抑制活性。总之，拟议的分析将使人们更好地理解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.