Probing the Archazolid Pharmacophore Using Plant-Based V-ATPase Assays

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DESCRIPTION (provided by applicant): The archazolids are a family of recently isolated natural products that display powerful growth inhibitory activity against a number of human cancer cell lines based on selective vacuolar-type ATPase (V-ATPase) inhibition, however the mechanism by which these compound achieve their activity is not completely understood. A long-term goal of the proposed research is to create a new class of small-molecule V-ATPase inhibitor therapeutics based on a thorough understanding of archazolid inhibitory activity. The objective of this application is to develop a synthesis of simplified archazolid-derived V-ATPase inhibitors and assay using convenient plant-based V-ATPase assays. This is driven by a central hypothesis that the comparison of the V-ATPase inhibitory activity of systematically modified archazolid-derivatives will provide crucial insights into the archazolid pharmacophore. The rationale for the proposed research is that once it is known how the archazolids inhibit V-ATPase function, it will become possible to rationally design small molecule V-ATPase inhibitors with enhanced pharmacological properties resulting in new approaches for the treatment of various diseases. Guided by strong preliminary data, this hypothesis will be tested by pursuing two specific aims: 1) Develop a synthesis of simplified archazolid analogues; and 2) Develop two plant-based V-ATPase assays. Under the first aim, a synthetic strategy featuring a TMS-allylation/Peterson elimination sequence for stereoselective substituted triene synthesis that has already produced the entirety of the archazolid carbon framework will be used to prepare a series of modified archazolid B derivatives. The V-ATPase inhibitory activity of advanced synthetic intermediates and completed compounds will then be tested using the techniques developed under the second aim. Specifically, GFP-Arabidopsis will be used to identify active compounds that can then be evaluated in a dose-dependent manner using an Arabidopsis root-growth assay. The proposed research is innovative because it represents a departure from the traditional plecomacrolide approach to V-ATPase research by providing research tools to better elucidate archazolid activity. This contribution is significant because it aims to elucidate a nove mode of V-ATPase binding and inhibition. In addition to providing further insights into V-ATPase structure and function, the results have the potential to lead to new approaches for the development of V-ATPase inhibitor drugs to treat various severe diseases including osteoporosis and cancer.