title: Biochemical evidence for the differential association of metabotropic glutamate receptors within synaptic complexes.
abstract: The distribution of metabotropic glutamate (mGlu) receptors within the synapse is an important determinant of function. mGlu have been grouped together into three main sub-classes: Group I mGlu (1 and 5) are predominantly situated on the post-synaptic membrane, whereas Group III (4, 6, 7 and 8) are largely pre-synaptic. Group II mGlu (2 and 3) are distributed peripheral to the active zone, on both sides of the synaptic cleft. Methods based on a distinct pH-dependent extractability of the pre- and post-synaptic marker proteins can provide insight into the molecular organization of synaptic junctions [G.R. Phillips, J.K. Huang, Y. Wang, H. Tanaka, L. Shapiro, W. Zhang, W. Shan, K. Arndt, M. Frank, R.E. Gordon, M.A. Gawinowicz, Y. Zhao and D.R. Colman, The presynaptic particle web: ultrastructure, composition, dissolution and reconstitution, Neuron 32 (2001) 63-77]. We have applied such procedures to rat brain cortical synaptosomes to explore the biochemical evidence for the accepted localisations of metabotropic glutamate receptors. As shown previously a number of post-synaptic marker proteins remained detergent-insoluble at both pH 6 and pH 8. There was an increased extraction of a number of pre-synaptic plasma membrane and cytomatrix proteins consistent with dissolution of the pre-synaptic aspect of synaptic junctions at elevated pH. We similarly observed modest extraction of Group I mGlu at either pH consistent with their post-synaptic organization. However, we observed increased extractability of Group II mGlu at pH 8. The extractability of Group III mGlu was slightly increased at pH 8 but these receptors were largely refractory to extraction. We have also applied the approach to scaffolding proteins implicated in mGlu localisation to define the biochemical correlates of mGlu scaffolding.
authors.affiliation: School of Biological Sciences, University of Southampton, Bassett Crescent East, Southampton SO16 7PX, UK.
authors.forename: Ayodeji A
authors.initials: AA
authors.lastname: Asuni
authors.forename: Kate
authors.initials: K
authors.lastname: Lidwell
authors.forename: Vincent
authors.initials: V
authors.lastname: O'Connor
mesh_terms: D000818:Animals; D002458:Cell Fractionation / Q000379:methods; D002540:Cerebral Cortex / Q000648:ultrastructure; D005260:Female; D009419:Nerve Tissue Proteins / Q000378:metabolism; D009474:Neurons / Q000378:metabolism / Q000648:ultrastructure; D051381:Rats; D017208:Rats, Wistar; D018094:Receptors, Metabotropic Glutamate / Q000145:classification / Q000378:metabolism*; D013569:Synapses / Q000378:metabolism* / Q000648:ultrastructure*; D013574:Synaptosomes / Q000378:metabolism
chemical_list: D009419:Nerve Tissue Proteins; D018094:Receptors, Metabotropic Glutamate