Research article

Luciferase activity under direct ligand-dependent control of a muscarinic acetylcholine receptor

Doreen Thor , Diana Le Duc , Rainer Strotmann and Torsten Schöneberg

Department of Molecular Biochemistry, Institute of Biochemistry, Medical Faculty, University of Leipzig, Johannisallee 30, 04103 Leipzig, Germany

author email corresponding author email

BMC Biotechnology 2009, 9:46doi:10.1186/1472-6750-9-46

Published:	18 May 2009

Abstract

Background

Controlling enzyme activity by ligand binding to a regulatory domain of choice may have many applications e.g. as biosensors and as tools in regulating cellular functions. However, until now only a small number of ligand-binding domains have been successfully linked to enzyme activity. G protein-coupled receptors (GPCR) are capable of recognizing an extraordinary structural variety of extracellular signals including inorganic and organic molecules. Ligand binding to GPCR results in conformational changes involving the transmembrane helices. Here, we assessed whether ligand-induced conformational changes within the GPCR helix bundle can be utilized to control the activity of an integrated enzyme.

Results

As a proof of principle, we inserted the luciferase amino acid sequence into the third intracellular loop of the M₃ muscarinic acetylcholine receptor. This fusion protein retained both receptor and enzyme function. Receptor blockers slightly but significantly reduced enzyme activity. By successive deletion mutagenesis the enzyme activity was optimally coupled to ligand-induced conformational helix movements.

Conclusion

Our results demonstrate that in engineered GPCR-enzyme chimeras, intracellular enzyme activity can be directly controlled by a GPCR serving as the extracellular ligand-binding domain.