Functional analysis of G-protein coupled receptors using a new fluorescein lactone-based intracellularcalciumindicator

Abstract

Calcium flux assays are preferred methods in drug discovery for characterizing G-protein coupled receptors (GPCRs) and screening GPCR agonists and antagonists. A new fluorescent Ca²⁺ indicator has been developed to provide improved fluorescence-based assays for detecting intracellular Ca²⁺ mobilization of GPCR targets. This first fluorescein lactone-based Ca²⁺ indicator has >100 times fluorescence enhancement upon calcium binding. It has an intracellular Ca²⁺-induced fluorescence signal more than ∼2 fold brighter than Fluo-4 AM, and ∼4 times brighter than Fluo-3 AM, the two most popular fluorescent Ca²⁺ indicators.