TI - Identification of the Ca2+/calmodulin -dependent protein kinase II regulatory phosphorylation site in the alpha-amino-3-hydroxyl-5-methyl-4-isoxazole-propionate-type glutamate receptor . AB - Ca2+/CaM-dependent protein kinase II ( CaM-KII ) can phosphorylate and potentiate responses of alpha-amino3-hydroxyl-5-methyl-4-isoxazole-propionate-type glutamate receptors in a number of systems , and recent studies implicate this mechanism in long term potentiation , a cellular model of learning and memory . In this study we have identified this CaM-KII regulatory site using deletion and site -specific mutants of glutamate receptor 1 ( GluR1 ) . Only mutations affecting Ser831 altered the 32P peptide maps of GluR1 from HEK-293 cells co-expressing an activated CaM-KII . Likewise , when CaM-KII was infused into cells expressing GluR1 , the Ser831 to Ala mutant failed to show potentiation of the GluR1 current . The Ser831 site is specific to GluR1 , and CaM-KII did not phosphorylate or potentiate current in cells expressing GluR2 , emphasizing the importance of the GluR1 subunit in this regulatory mechanism . Because Ser831 has previously been identified as a protein kinase C phosphorylation site , this raises the possibility of synergistic interactions between CaM-KII and protein kinase C in regulating synaptic plasticity .