Phosphoproteomic Analysis of Cortical Tissue from Mice Lacking Both CaMKIIα and CaMKIIβ Identifies Novel In Vivo Substrates

Ca²⁺/calmodulin-dependent protein kinase II (CaMKII) plays a critical role in calcium signaling. Several studies have shown that mice with single <i>Camk2a</i> or <i>Camk2b</i> gene knockouts are viable, yet exhibit distinct phenotypes, whereas the double knockout of both genes is lethal. These findings indicate that each gene can have distinct roles and that they also partially compensate for each other in yet unknown essential brain functions. In order to provide insight into potential novel CaMKII functions, we performed parallel phosphoproteomic analyses on nonstimulated cortex tissues from inducible <i>Camk2a</i> and <i>Camk2b</i> double knockout (<i>Camk2a</i>^<i>f/f</i><i>;Camk2b</i>^<i>f/f</i><i>;CAG-Cre</i>^<i>ESR</i>) mice and from wild type mice. A total of 5622 phosphorylated peptides derived from 2080 proteins were identified. Phosphorylation at serine/threonine residues in 130 proteins was downregulated in the double knockout mice, including residues in 113 proteins that have not previously been identified as potential CaMKII substrates. Comparison of amino acid sequences surrounding the downregulated phosphorylation residues provided new insights into the CaMKII-substrate consensus sequences in vivo. This data set provides an important resource for future studies examining novel roles for CaMKII in the brain.