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Published September 19, 2006 | Published + Supplemental Material
Journal Article Open

Ca2+/calmodulin-dependent protein kinase II (CaMKII) is activated by calmodulin with two bound calciums


Changes in synaptic strength that underlie memory formation in the CNS are initiated by pulses of Ca2+ flowing through NMDA-type glutamate receptors into postsynaptic spines. Differences in the duration and size of the pulses determine whether a synapse is potentiated or depressed after repetitive synaptic activity. Calmodulin (CaM) is a major Ca2+ effector protein that binds up to four Ca2+ ions. CaM with bound Ca2+ can activate at least six signaling enzymes in the spine. In fluctuating cytosolic Ca2+, a large fraction of free CaM is bound to fewer than four Ca2+ ions. Binding to targets increases the affinity of CaM's remaining Ca2+-binding sites. Thus, initial binding of CaM to a target may depend on the target's affinity for CaM with only one or two bound Ca2+ ions. To study CaM-dependent signaling in the spine, we designed mutant CaMs that bind Ca2+ only at the two N-terminal or two C-terminal sites by using computationally designed mutations to stabilize the inactivated Ca2+-binding domains in the "closed" Ca2+-free conformation. We have measured their interactions with CaMKII, a major Ca2+/CaM target that mediates initiation of long-term potentiation. We show that CaM with two Ca2+ ions bound in its C-terminal lobe not only binds to CaMKII with low micromolar affinity but also partially activates kinase activity. Our results support the idea that competition for binding of CaM with two bound Ca2+ ions may influence significantly the outcome of local Ca2+ signaling in spines and, perhaps, in other signaling pathways.

Additional Information

Copyright © 2006 by the National Academy of Sciences. Contributed by Stephen L. Mayo, July 27, 2006. We thank K. Beckingham (Rice University, Houston, TX) for providing a plasmid encoding calmodulin, E. Winfree and laboratory for the use of their spectrofluorometer, J. Oh and E. Marcora for CaMKII, A. Ingemar for help with CaLigator, and J. Zhou for help with mass spectrometry. This work was supported by the Howard Hughes Medical Institute, the Ralph M. Parsons Foundation, and an IBM Shared University research grant (to S.L.M.), the Sloan-Schwartz Foundation (to M.H.C), and U.S. Public Health Service Grants NS047300 (to M.H.C) and NS44306 (to M.B.K.). Author contributions: J.M.S. and M.H.C. contributed equally to this work; J.M.S., M.H.C., S.M., S.L.M., and M.B.K. designed research; J.M.S., M.H.C., and S.M. performed research; J.M.S., M.H.C., S.M., S.L.M., and M.B.K. analyzed data; and J.M.S., M.H.C., and M.B.K. wrote the paper. The authors declare no conflict of interest.

Attached Files

Published - SHIpnas06b.pdf

Supplemental Material - SHIpnas06bfig6.pdf

Supplemental Material - SHIpnas06bfig7.pdf

Supplemental Material - SHIpnas06bfig8.pdf

Supplemental Material - SHIpnas06bsupp.pdf


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August 22, 2023
October 16, 2023