Signal Transduction
Characterization of a Central Ca2+/Calmodulin-dependent Protein Kinase IIα/β Binding Domain in Densin That Selectively Modulates Glutamate Receptor Subunit Phosphorylation*

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The densin C-terminal domain can target Ca2+/calmodulin-dependent protein kinase IIα (CaMKIIα) in cells. Although the C-terminal domain selectively binds CaMKIIα in vitro, full-length densin associates with CaMKIIα or CaMKIIβ in brain extracts and in transfected HEK293 cells. This interaction requires a second central CaMKII binding site, the densin-IN domain, and an “open” activated CaMKII conformation caused by Ca2+/calmodulin binding, autophosphorylation at Thr-286/287, or mutation of Thr-286/287 to Asp. Mutations in the densin-IN domain (L815E) or in the CaMKIIα/β catalytic domain (I205/206K) disrupt the interaction. The amino acid sequence of the densin-IN domain is similar to the CaMKII inhibitor protein, CaMKIIN, and a CaMKIIN peptide competitively blocks CaMKII binding to densin. CaMKII is inhibited by both CaMKIIN and the densin-IN domain, but the inhibition by densin is substrate-selective. Phosphorylation of a model peptide substrate, syntide-2, or of Ser-831 in AMPA receptor GluA1 subunits is fully inhibited by densin. However, CaMKII phosphorylation of Ser-1303 in NMDA receptor GluN2B subunits is not effectively inhibited by densin in vitro or in intact cells. Thus, densin can target multiple CaMKII isoforms to differentially modulate phosphorylation of physiologically relevant downstream targets.

Calcium Calmodulin-dependent Protein Kinase (CaMK)
Glutamate Receptors Ionotropic (AMPA, NMDA)
Protein Phosphorylation
Protein Targeting
Protein-Protein Interactions
Synapses

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*

This work was supported, in whole or in part, by National Institutes of Health Grants R01-MH063232 (to R. J. C.), F32-MH068129 (to A. J. R.), and T32-MH065215 (to A. J. B.). This work was also supported by American Heart Association Predoctoral Fellowship 0815090E (to N. J.-S.) and a UNCF-Merck postdoctoral fellowship (to A. J. B.).

The on-line version of this article (available at http://www.jbc.org) contains supplemental Fig. 1.

1

Both authors contributed equally to this work.

2

Present address: Editorial Office of Genomics, Proteomics and Bioinformatics, Beijing Institute of Genomics, Chinese Academy of Sciences, No. 7 Beitucheng West Rd., Chaoyang District, Beijing 100029, China.

3

Present address: Dept. of Neuroscience, Mount Sinai School of Medicine, Icahn Bldg., Rm. L10-26, 1425 Madison Ave., New York, NY 10029.