QUICK SEARCH:   [advanced] Author: Keyword(s): Year:  Vol:  Page:

Vol. 18, Issue 12, 5024-5033, December 2007

This Article Full Text Full Text (PDF) Supplemental Materials All Versions of this Article: E07-02-0185v1 E07-02-0185v2 18/12/5024    most recent Alert me when this article is cited Alert me if a correction is posted Services Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via Google Scholar Google Scholar Articles by Vest, R. S. Articles by Bayer, K. U. Search for Related Content PubMed PubMed Citation Articles by Vest, R. S. Articles by Bayer, K. U.

Dual Mechanism of a Natural CaMKII Inhibitor

Department of Pharmacology, University of Colorado Denver-School of Medicine, Aurora, CO 80045

Submitted February 28, 2007; Revised September 19, 2007; Accepted October 5, 2007
Monitoring Editor: Tom U. Martin

Ca²⁺/calmodulin (CaM)-dependent protein kinase II (CaMKII) is a major mediator of cellular Ca²⁺ signaling. Several inhibitors are commonly used to study CaMKII function, but these inhibitors all lack specificity. CaM-KIIN is a natural, specific CaMKII inhibitor protein. CN21 (derived from CaM-KIIN amino acids 43–63) showed full specificity and potency of CaMKII inhibition. CNs completely blocked Ca²⁺-stimulated and autonomous substrate phosphorylation by CaMKII and autophosphorylation at T305. However, T286 autophosphorylation (the autophosphorylation generating autonomous activity) was only mildly affected. Two mechanisms can explain this unusual differential inhibitor effect. First, CNs inhibited activity by interacting with the CaMKII T-site (and thereby also interfered with NMDA-type glutamate receptor binding to the T-site). Because of this, the CaMKII region surrounding T286 competed with CNs for T-site interaction, whereas other substrates did not. Second, the intersubunit T286 autophosphorylation requires CaM binding both to the "kinase" and the "substrate" subunit. CNs dramatically decreased CaM dissociation, thus facilitating the ability of CaM to make T286 accessible for phosphorylation. Tat-fusion made CN21 cell penetrating, as demonstrated by a strong inhibition of filopodia motility in neurons and insulin secrection from isolated Langerhans' islets. These results reveal the inhibitory mechanism of CaM-KIIN and establish a powerful new tool for dissecting CaMKII function.

The online version of this article contains supplemental material at MBC Online (http://www.molbiolcell.org).

* These authors contributed equally to this work.

Address correspondence to: K. Ulrich Bayer (ulli.bayer{at}uchsc.edu).