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 Camk2a or Camk2b 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 Camk2a and Camk2b double knockout (Camk2af/f;Camk2bf/f;CAG-CreESR) 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.