Invadosomes at a glance.

This article is part of a Minifocus on invadopodia and podosomes. For further reading, please see related articles: ‘Matrix invasion by tumour cells: a focus on MT1-MMP trafficking to invadopodia’ by Renaud Poincloux et al. (J. Cell Sci. 122, 3015-3024), ‘Mechanisms for transcellular diapedesis: probing and pathfinding by ‘invadosome-like protrusions’’ by Christopher V. Carman (J. Cell Sci. 122, 3025-3035) and ‘Actin machinery and mechanosensitivity in invadopodia, podosomes and focal adhesions’ by Corinne Albiges-Rizo et al. (J. Cell Sci. 122, 3037-3049). Podosomes and invadopodia (which can be subsumed under the umbrella term ‘invadosomes’) are cellular structures that establish close contact with the extracellular matrix (ECM). In contrast to similar structures such as focal adhesions, they are also able to degrade components of the ECM [for a comparison between podosomes and focal adhesions, see Block et al. (Block et al., 2008)]. Invadosomes are, therefore, thought to be key structures of cell invasion. Accordingly, much effort is currently focused on their potential roles in both physiological and pathological invasive processes, such as transendothelial diapedesis and inflammation, and atherosclerosis and metastasis. This poster article provides an introduction to the field, discusses currently investigated topics in invadosome regulation and points out future challenges for invadosome-related research. Identification Podosomes and invadopodia share common features that can be used to distinguish them from other cell-matrix contacts or superficially similar structures. For example, both present as dot-like accumulations of filamentous actin (F-actin) at the substratecontacting side of the cell. Typical markers include actin-regulatory proteins such as the Arp2/3 complex, cortactin and WASP or N-WASP (Linder and Aepfelbacher, 2003; Buccione et al., 2004; Gimona and Buccione, 2006; Weaver, 2006; Linder, 2007; Buccione et al., 2009), which colocalize with the actinrich core of both structures. Moreover, many components of invadosomes are regulated by tyrosine kinase signaling, resulting in a high local enrichment of phosphotyrosine residues (Linder and Aepfelbacher, 2003; Luxenburg et al., 2006). 3009 Cell Science at a Glance