Protrusion force microscopy reveals oscillatory force generation and mechanosensing activity of human macrophage podosomes.

Anna Labernadie, Anaïs Bouissou, Patrick Delobelle, Stéphanie Balor, Raphael Voituriez, Amsha Proag, Isabelle Fourquaux, Christophe Thibault, Christophe Vieu, Renaud Poincloux, Guillaume M Charrière, Isabelle Maridonneau-Parini

Index: Nat. Commun. 5 , 5343, (2014)

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Abstract

Podosomes are adhesion structures formed in monocyte-derived cells. They are F-actin-rich columns perpendicular to the substrate surrounded by a ring of integrins. Here, to measure podosome protrusive forces, we designed an innovative experimental setup named protrusion force microscopy (PFM), which consists in measuring by atomic force microscopy the deformation induced by living cells onto a compliant Formvar sheet. By quantifying the heights of protrusions made by podosomes onto Formvar sheets, we estimate that a single podosome generates a protrusion force that increases with the stiffness of the substratum, which is a hallmark of mechanosensing activity. We show that the protrusive force generated at podosomes oscillates with a constant period and requires combined actomyosin contraction and actin polymerization. Finally, we elaborate a model to explain the mechanical and oscillatory activities of podosomes. Thus, PFM shows that podosomes are mechanosensing cell structures exerting a protrusive force.