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_q/11 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.