Podosomes are actin-rich adhesion structures that are formed at the substrate-attached side in a variety of cell types, most prominently in cells of the monocytic lineage such as macrophages, dendritic cells and osteoclasts.

Podosomes range between 0.5 and 1 µm in size and can reach a height of up to 1 µm. They contain of more than 300 different protein components, which are arranged in an intricate architecture that consists of 3 main substructures (core, ring, cap) and 2 sets of cables.

Life cycle
Podosomes are highly dynamic, with a typical life time in the range of 2-20 min. They are initiated in zones of low contractility and their formation depends mainly on actin polymerization, while their dissociation is initated by hyperactivation of myosin IIA.

Podosomes are connected to the extracellular matrix through transmembrane proteins like integrins. They act as mechanosensors to collect information about topography and rigidity of the extracellular matrix and are able to proteolytically degrade it by localized recruitment and release of enzymes such as matrix-metalloproteinases.

During their lifespan, podosomes undergo several dynamic processes such as internal actin turnover, oscillation in size, as well as fission and fusion.

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