Ultraviolet radiation,thiol reagents,and solubilization enhance AMPA receptor binding affinity via a common mechanism

The binding properties of membrane-bound or solubilized AMPA (alpha-amino-3-hydroxy-5-methylisoxazole-4-propionic acid)-type glutamate receptors from rat brain were tested following exposure to ultraviolet (UV)_radiation or incubation with the thiol reagent p-chloromercuriphenyl-sulfonic acid (PCMBS). Brief exposure to UV radiation (254 nm) increased ³H]AMPA binding to brain membranes, while binding to soluble fractions decreased. The increase in brain membrane binding was caused by an apparent interconversion of low-affinity ³H]AMPA binding sites into a higher-affinity state. Incubation with PCMBS caused a significant increase in ³H]AMPA binding to brain membranes but had no significant effect on ³HAMPA binding to solubilized receptors. There was an interaction between the PCMBS and UV effects in the brain membranes such that prior exposure to one of the treatments reduced the relative magnitude of the other's effects. The present results suggest that ultraviolet radiation, PCMBS and solubilization all increase AMPA receptor binding affinity via a common mechanism.