Abstract
Nicotinic acetylcholine receptors (nAChRs) are ligand-gated ion channels mediating fast cholinergic synaptic transmission in the brain and at neuromuscular junctions. We used the structure of the acetylcholine binding protein from Lymnaea stagnalis to model the chicken α7 agonist-binding domain. The initial models and a preliminary docking study suggested that position Leu118 may play an important role in determining agonist actions on α7. A prediction from these in silico studies, that L118E and L118D would retain binding to acetylcholine but L118K and L118R would not, was confirmed in electrophysiological studies on functional recombinant mutant receptors expressed in Xenopus laevis oocytes. The functional studies also demonstrated that residues at position 118 have a dramatic effect on the actions of imidacloprid (a partial agonist of wild-type α7 receptors) and its des-nitro derivative. Molecular dynamics simulations confirmed that Leu118 can strongly influence agonist binding and that the model was robust in terms of its prediction for acetylcholine binding. Together, the results indicate a role for Leu118 in influencing agonist actions on α7 nAChRs.
Footnotes
-
The support of The Medical Research Council of the UK (to A.K.J., D.B.S.) and The Wellcome Trust (to S.A., R.V., M.S.P.S., P.C.B.) is gratefully acknowledged. R.V. thanks the Overseas Research Scheme for support. P.C.B. is an RCUK Fellow. K.M. was supported by the “Academic Frontier” Project for Private Universities from the Ministry of Education, Culture, Sports, Science and Technology of Japan as well as the Integrated Research Project for Plant, Insect, and Animal using Genome Technology from the Ministry of Agriculture, Forestry and Fisheries of Japan. K.M. also acknowledges the support of the program for Basic Research Activities for Innovative Biosciences (Biooriented Technology Research Advancement Institution: BRAIN).
-
S.A. and M.S. contributed equally to this work.
-
ABBREVIATIONS: nAChR, Nicotinic acetylcholine receptor; ACh, acetylcholine; AChBP, acetylcholine binding protein; IMI, imidacloprid; DN-IMI, desnitro-imidacloprid; RMSF, root-mean-square fluctuations.
- Received September 7, 2007.
- Accepted March 13, 2008.
- The American Society for Pharmacology and Experimental Therapeutics
MolPharm articles become freely available 12 months after publication, and remain freely available for 5 years.Non-open access articles that fall outside this five year window are available only to institutional subscribers and current ASPET members, or through the article purchase feature at the bottom of the page.
|