grantor:
University of TorontoMy goal was to establish a baseline pharmacological profile for the group III mGluRs and to investigate differences in binding which may be present between the individual receptors. Of the four group III mGluRs, mGluR4 and mGluR8 displayed a high level of specific binding of [3H]-L-AP4, while no specific binding was detected for mGluR6 and mGluR7. [3H]-L-AP4 binding analyses were therefore performed for the mGluR4 and mGluR8 receptors. Results from competition experiments revealed that mGluR8 exhibited significantly higher binding affinities for group III-specific antagonists and the agonist PPG, compared to mGluR4. To investigate the basis for these binding differences, a combination of site-directed mutagenesis and molecular modeling was used to probe the ligand binding pockets of mGluR4 and mGluR8. Sequence similarity between the leucine-isoleucine-valine binding protein (LIVBP) and the mGluRs was used to model the ligand binding domain of mGluR4. Site-directed mutagenesis was used to substitute the serine 157 and glycine 158 residues of mGluR4 for their corresponding alanine residues in mGluR8. These substitutions created the mGluR4-S157A, G158A and S157A/G158A mutant receptors. (Abstract shortened by UMI.)M.Sc
