We report the cloning and functional characterization of myopodin, the second member of the synaptopodin gene family. Myopodin shows no significant homology to any known protein except synaptopodin. Northern blot analysis resulted in a 3.6-kb transcript for mouse skeletal and heart muscle. Western blots showed an 80-kD signal for skeletal and a 95-kD signal for heart muscle. Myopodin contains one PPXY motif and multiple PXXP motifs. Myopodin colocalizes with α-actinin and is found at the Z-disc as shown by immunogold electron microscopy. In myoblasts, myopodin shows preferential nuclear localization. During myotube differentiation, myopodin binds to stress fibers in a punctuated pattern before incorporation into the Z-disc. Myopodin can directly bind to actin and contains a novel actin binding site in the center of the protein. Myopodin has actin-bundling activity as shown by formation of latrunculin-A–sensitive cytosolic actin bundles and nuclear actin loops in transfected cells expressing green fluorescent protein–myopodin. Under stress conditions, myopodin accumulates in the nucleus and is depleted from the cytoplasm. Nuclear export of myopodin is sensitive to leptomycin B, despite the absence of a classical nuclear export sequence. We propose a dual role for myopodin as a structural protein also participating in signaling pathways between the Z-disc and the nucleus.
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29 October 2001
Article|
October 22 2001
Differentiation- and stress-dependent nuclear cytoplasmic redistribution of myopodin, a novel actin-bundling protein
Astrid Weins,
Astrid Weins
1Department of Medicine and Department of Anatomy and Cell Biology, Albert Einstein College of Medicine, Bronx, NY 10461
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Karin Schwarz,
Karin Schwarz
1Department of Medicine and Department of Anatomy and Cell Biology, Albert Einstein College of Medicine, Bronx, NY 10461
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Christian Faul,
Christian Faul
1Department of Medicine and Department of Anatomy and Cell Biology, Albert Einstein College of Medicine, Bronx, NY 10461
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Laura Barisoni,
Laura Barisoni
2Department of Pathology, Johns Hopkins University, Baltimore, MD 21287
3National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, Bethesda, MD 20892
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Wolfgang A. Linke,
Wolfgang A. Linke
4Department of Physiology, University of Heidelberg, 69120 Heidelberg, Germany
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Peter Mundel
Peter Mundel
1Department of Medicine and Department of Anatomy and Cell Biology, Albert Einstein College of Medicine, Bronx, NY 10461
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Astrid Weins
1Department of Medicine and Department of Anatomy and Cell Biology, Albert Einstein College of Medicine, Bronx, NY 10461
Karin Schwarz
1Department of Medicine and Department of Anatomy and Cell Biology, Albert Einstein College of Medicine, Bronx, NY 10461
Christian Faul
1Department of Medicine and Department of Anatomy and Cell Biology, Albert Einstein College of Medicine, Bronx, NY 10461
Laura Barisoni
2Department of Pathology, Johns Hopkins University, Baltimore, MD 21287
3National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, Bethesda, MD 20892
Wolfgang A. Linke
4Department of Physiology, University of Heidelberg, 69120 Heidelberg, Germany
Peter Mundel
1Department of Medicine and Department of Anatomy and Cell Biology, Albert Einstein College of Medicine, Bronx, NY 10461
Address correspondence to Peter Mundel, Division of Nephrology, Albert Einstein College of Medicine, 1300 Morris Park Ave., Bronx, NY 10461. Tel.: (718) 430-3219. Fax: (718) 430-8963. E-mail: [email protected]
Astrid Weins and Karin Schwarz contributed equally to this paper.
*
Abbreviations used in this paper: aa, amino acid; EST, expressed sequence tag; GFP, green fluorescent protein; lat-A, latrunculin A; LMB, leptomycin B; NES, nuclear export sequence; NLS, nuclear localization signal; NS, nuclear shuttling.
Received:
December 11 2000
Revision Received:
August 31 2001
Accepted:
September 26 2001
Online ISSN: 1540-8140
Print ISSN: 0021-9525
The Rockefeller University Press
2001
J Cell Biol (2001) 155 (3): 393–404.
Article history
Received:
December 11 2000
Revision Received:
August 31 2001
Accepted:
September 26 2001
Citation
Astrid Weins, Karin Schwarz, Christian Faul, Laura Barisoni, Wolfgang A. Linke, Peter Mundel; Differentiation- and stress-dependent nuclear cytoplasmic redistribution of myopodin, a novel actin-bundling protein . J Cell Biol 29 October 2001; 155 (3): 393–404. doi: https://doi.org/10.1083/jcb.200012039
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