Differentiation- and stress-dependent nuclear cytoplasmic redistribution of myopodin, a novel actin-bundling protein

Astrid Weins, Karin Schwarz, Christian Faul, Laura Barisoni, Wolfgang A. Linke, Peter Mundel

Research output: Contribution to journalArticle

88 Scopus citations

Abstract

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 alpha-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.

Original languageEnglish (US)
Pages (from-to)393-403
Number of pages11
JournalJournal of Cell Biology
Volume155
Issue number3
DOIs
StatePublished - Oct 29 2001

Keywords

  • Actin-binding protein
  • Muscle differentiation
  • Nuclear-cytoplasmic translocation
  • Synaptopodin gene family
  • Z-disc

ASJC Scopus subject areas

  • Cell Biology

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