Abstract 3924: A homogenous bioluminescent system for measuring GTPase, GAP and GEF activities

Abstract

Abstract GTPases play a major role in various cellular functions such as cell signaling, cell proliferation, cell differentiation, cytoskeleton modulation and cell motility. Deregulation or mutation of these proteins has considerable consequences resulting in multiple pathological conditions. Targeting GTPases and its regulators have been challenging due to lack of convenient assays. To overcome the challenges in analyzing activities of GTPases and their regulatory proteins GTPase Activating Proteins (GAP) and Guanine Nucleotide Exchange Factors (GEF) we have developed a homogenous bioluminescent assay (GTPase/GAP/GEF-Glo) system to analyze these proteins in a simple, convenient “add-mix-read” format. Mg2+ plays a critical role in influencing affinity of GTPases with GTP/GDP and the process of nucleotide exchange. Manipulating Mg2+ concentrations in the GTPase reaction buffer allows continuous progression of the GTPase cycle and faster hydrolysis of GTP. The assay relies on enzymatic conversion of GTP remaining after the GTPase reaction to ATP and detection of the ATP using luciferin/luciferase combination. We show that the assay is sensitive, and robust when analyzing for analyzing intrinsic GTPase- activity, GAP-stimulated GTPase- activity, GAP-activity and GEF- activity. The system can also be used to analyze these proteins expressed in cells as a fusion protein performing the assay in a pulldown -format. Furthermore, there was minimal false hits when tested for compound interference using the library of pharmacologically active compounds (LOPAC) and its robustness as indicated by high Z’-factor of 0.93 and CV of 2.2%. Citation Format: Subhanjan Mondal, Kevin Hsiao, Said A. Goueli. A homogenous bioluminescent system for measuring GTPase, GAP and GEF activities. [abstract]. In: Proceedings of the 106th Annual Meeting of the American Association for Cancer Research; 2015 Apr 18-22; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Res 2015;75(15 Suppl):Abstract nr 3924. doi:10.1158/1538-7445.AM2015-3924