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J Mol Cell Cardiol. 2012 Feb;52(2):312-6. doi: 10.1016/j.yjmcc.2011.06.005. Epub 2011 Jun 12.

Calmodulin binding proteins provide domains of local Ca2+ signaling in cardiac myocytes.

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Department of Biomedical Engineering, Robert M. Berne Cardiovascular Research Center, University of Virginia, Charlottesville, VA 22908, USA.


Calmodulin (CaM) acts as a common Ca(2+) sensor for many signaling pathways, transducing local Ca(2+) signals into specific cellular outcomes. Many of CaM's signaling functions can be explained by its unique biochemical properties, including high and low affinity Ca(2+)-binding sites with slow and fast kinetics, respectively. CaM is expected to have a limited spatial range of action, emphasizing its role in local Ca(2+) signaling. Interactions with target proteins further fine-tune CaM signal transduction. Here, we focus on only three specific cellular targets for CaM signaling in cardiac myocytes: the L-type Ca(2+) channel, the ryanodine receptor, and the IP(3) receptor. We elaborate a working hypothesis that each channel is regulated by two distinct functional populations of CaM: dedicated CaM and promiscuous CaM. Dedicated CaM is typically tethered to each channel and directly regulates channel activity. In addition, a local pool of promiscuous CaM appears poised to sense local Ca(2+) signals and trigger downstream pathways such as Ca(2+)/CaM dependent-protein kinase II and calcineurin. Understanding how promiscuous CaM coordinates multiple distinct signaling pathways remains a challenge, but is aided by the use of mathematical modeling and a new generation of fluorescent biosensors. This article is part of a special issue entitled "Local Signaling in Myocytes."

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