ULTRAVIOLET-RADIATION, THIOL REAGENTS, AND SOLUBILIZATION ENHANCE AMPA RECEPTOR-BINDING AFFINITY VIA A COMMON MECHANISM

The binding properties of membrane-bound or solubilized AMPA lpha-amin o-3-hydroxy-5-methylisoxazole-4-propionic acid)-type glutamate recepto rs from rat brain were tested following exposure to ultraviolet (UV) r adiation or incubation with the thiol reagent p-chloromercuriphenylsul fonic acid (PCMBS). Brief exposure to UV radiation (254 nm) increased [H-3]AMPA binding to brain membranes, while binding to soluble fractio ns decreased. The increase in brain membrane binding was caused by an apparent interconversion of low-affinity [H-3]AMPA binding sites into a higher-affinity state. Incubation with PCMBS caused a significant in crease in [3H]AMPA binding to brain membranes but had no significant e ffect on [H-3]AMPA binding to solubilized receptors. There was an inte raction between the PCMBS and UV effects in the brain membranes such t hat prior exposure to one of the treatments reduced the relative magni tude of the other's effects. The present results suggest that ultravio let radiation, PCMBS and solubilization all increase AMPA receptor bin ding affinity via a common mechanism.