Plectin deposition at podosome rings requires myosin contractility

Authors

  • Annica Gad,

    1. Department of Cell Biology and Oncology, Consorzio Mario Negri Sud, Via Nazionale 8a, I-66030 Santa Maria Imbaro, Italy
    Current affiliation:
    1. Ludwig Institute for Cancer Research, P.O. Box 595, 751 24 Uppsala, Sweden.
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  • Sibylle Lach,

    1. Department of Cell Biology and Oncology, Consorzio Mario Negri Sud, Via Nazionale 8a, I-66030 Santa Maria Imbaro, Italy
    Current affiliation:
    1. SALK Labor GmbH, Müllner Hauptstr. 48, 5020 Salzburg, Austria.
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  • Luca Crimaldi,

    1. Department of Cell Biology and Oncology, Consorzio Mario Negri Sud, Via Nazionale 8a, I-66030 Santa Maria Imbaro, Italy
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  • Mario Gimona

    Corresponding author
    1. Department of Cell Biology and Oncology, Consorzio Mario Negri Sud, Via Nazionale 8a, I-66030 Santa Maria Imbaro, Italy
    • Department of Cell Biology and Oncology, Consorzio Mario Negri Sud, Unit of Actin Cytoskeleton Regulation, Via Nazionale 8a, I-66030 Santa Maria Imbaro, Italy
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Abstract

Metalloproteinase-dependent tissue invasion requires the formation of podosomes and invadopodia for localized matrix degradation. Actin cytoskeleton remodeling via Arp2/3-mediated actin polymerization is essential for podosome formation, and dynamic microtubules have an important role in maintaining podosome turnover in macrophages and osteoclasts. Little is known, however, about the involvement of the intermediate filament cytoskeleton in formation, stabilization, and turnover of podosomes. Here we show that vimentin intermediate filaments colocalize with the early sites of podosome formation at the stress fiber - focal adhesion interface in cultured vascular smooth muscle cells, but do not directly contribute to podosome formation, or stabilization. In unstimulated A7r5 cells the cytolinker protein plectin poorly colocalized with vimentin and the microdomains, but following induction by phorbol ester accumulated in the rings that surround the podosomes. In plectin-deficient A7r5 cells actin stress fiber remodelling is reduced in response to PDBu, and small podosomes remain localized at stable actin stress fibres. Pharmacological inhibition of actomyosin contractility by blebbistatin leads to an aberrant localization of podosomes away from the cell periphery and induces failure of plectin to surround the outer perimeter of these invasive adhesions. Taken together, we conclude that plectin is involved in growth and maturation of podosomes by reducing focal adhesion and stress fiber turnover, and that actomyosin-dependent contractility is required for the peripheral localization and specific deposition of plectin at the podosome rings. Cell Motil. Cytoskeleton 2008. © 2008 Wiley-Liss, Inc.

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