Phosphorylation of the membrane-bound acetylcholine receptor: inhibition by diphenylhydantoin.

Purified postsynaptic membranes can be used as a model system to study the regulation of synaptic membrane proteins. These membranes contain protein kinase activity that phosphorylates the acetylcholine receptor (AChR). We find that diphenylhydantoin (DPH) interacts with these membranes to inhibit phosphorylation of the membrane-bound AChR. DPH appears to alter the availability of postsynaptic membrane proteins for phosphorylation by a synaptic membrane protein kinase. The concentration of DPH that produces half-maximal inhibition of AChR phosphorylation is about 5 x 10(-5) M. This suggests that one of the specific effects of DPH in the nervous system may be related to inhibition of phosphorylation of postsynaptic membrane proteins.