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Molecular and Cellular Biology, December 2007, p. 8215-8227, Vol. 27, No. 23
0270-7306/07/$08.00+0 doi:10.1128/MCB.00950-07
Copyright © 2007, American Society for Microbiology. All Rights Reserved.

Department of Medicine,1 Zena and Michael A. Wiener Cardiovascular Institute, Mount Sinai School of Medicine, New York, New York 100292
Received 29 May 2007/ Returned for modification 6 July 2007/ Accepted 22 September 2007
Spatial and temporal resolution of intracellular signaling can be achieved by compartmentalizing transduction units. Myopodin is a dual-compartment, actin-bundling protein that shuttles between the nucleus and the Z-disc of myocytes in a differentiation- and stress-dependent fashion. Importin
binding and nuclear import of myopodin are regulated by serine/threonine phosphorylation-dependent binding of myopodin to 14-3-3. Here we show that in the heart myopodin forms a Z-disc signaling complex with
-actinin, calcineurin, Ca2+/calmodulin-dependent kinase II (CaMKII), muscle-specific A-kinase anchoring protein, and myomegalin. Phosphorylation of myopodin by protein kinase A (PKA) or CaMKII mediates 14-3-3 binding and nuclear import in myoblasts. Dephosphorylation of myopodin by calcineurin abrogates 14-3-3ß binding. Activation of PKA or inhibition of calcineurin in adult cardiac myocytes releases myopodin from the Z-disc and induces its nuclear import. The identification of myopodin as a direct target of PKA, CaMKII, and calcineurin defines a novel intracellular signaling pathway whereby changes in Z-disc dynamics may translate into compartmentalized signal transduction in the heart.
Published ahead of print on 8 October 2007.
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