Fig. 1.

Simplified model. A. Biochemical reactions of CaMKII. The kinase activity is turned on by Ca²⁺/calmodulin stimulation or autocatalytic phosphorylation. B. Biochemical reaction for phosphatase. The phosphatase activity is turned on by dephosphorylation, which is produced either by Ca²⁺ stimulation or autocatalytic dephosphorylation. K and P indicate kinase and phosphatase respectively; pK and pP are the phosphorylated forms of enzymes; * indicates active enzyme. C. Simplified reaction scheme. Gray shading represents spine structure. Pointed and circled arrows indicate the activation and the inhibition pathways, respectively. Ca²⁺ influx through NMDAR can activate CaMKII (K) and protein phosphatase (P) in a manner that depends on the concentration of Ca²⁺. CaMKII and phosphatase can self-activate themselves and inhibit each other. Active kinase and phosphatase control AMPAR insertion and removal, respectively.