Pharmacological and molecular characterization of the A-type muscarinic acetylcholine receptor from Anopheles gambiae.

Muscarinic acetylcholine receptors (mAChRs) which are G protein-coupled receptors play key roles in insect physiology. Whereas vertebrate mAChRs are important targets for pharmaceutical drugs, insect mAChRs are under-exploited by the agro-chemical industry. Moreover, insect mAChRs have been less well studied than their vertebrate counterparts. Their critical functions mean that a better knowledge of the insect mAChRs is crucial for the effort to develop a new molecular-level strategy for insect pest management. Almost all insects possess three mAChRs named A, B and C which differ according to their coupling effector systems and their pharmacological profile. The aim of this study was to characterize the A-type mAChR (mAChR-A) from Anopheles gambiae which is the major vector of malaria in order to develop new strategies in pest management. In this paper, we reported that mAChR-A is more expressed in adult mosquitoes than in larvae. Furthermore, using calcium imaging recordings, we found that the An. gambiae mAChR-A expressed in Sf9 cells is activated by specific muscarinic agonists acetylcholine, muscarine and oxotremorine M and blocked by several mAChR antagonists. Moreover, using inhibitors of phosphoinositide pathway such as Gα protein blocker, we have shown that an increased intracellular calcium concentration elicited by the acetylcholine application was mediated by PLC/IP3R pathway. As a rise in intracellular calcium concentration could lead to an increase in the insecticide target sensitivity, these results suggest that An. gambiae mAChR-A should not be only considered as a potential target for new molecules but also as a key element to optimize the efficacy of insecticide in vector control.