Activation State-Dependent Substrate Gating in Ca(2+)/Calmodulin-Dependent Protein Kinase II

Calcium/calmodulin-dependent protein kinase II (CaMKII) is highly concentrated in the brain where its activation by the Ca(2+) sensor CaM, multivalent structure, and complex autoregulatory features make it an ideal translator of Ca(2+) signals created by different patterns of neuronal activity. We provide direct evidence that graded levels of kinase activity and extent of T(287) (T(286) α isoform) autophosphorylation drive changes in catalytic output and substrate selectivity. The catalytic domains of CaMKII phosphorylate purified PSDs much more effectively when tethered together in the holoenzyme versus individual subunits. Using multisubstrate SPOT arrays, high-affinity substrates are preferentially phosphorylated with limited subunit activity per holoenzyme, whereas multiple subunits or maximal subunit activation is required for intermediate- and low-affinity, weak substrates, respectively. Using a monomeric form of CaMKII to control T(287) autophosphorylation, we demonstrate that increased Ca(2+)/CaM-dependent activity for all substrates tested, with the extent of weak, low-affinity substrate phosphorylation governed by the extent of T(287) autophosphorylation. Our data suggest T(287) autophosphorylation regulates substrate gating, an intrinsic property of the catalytic domain, which is amplified within the multivalent architecture of the CaMKII holoenzyme.