Feel the force: Podosomes in mechanosensing

Cells interact with their environment through highly localized contact structures. Podosomes represent a subgroup of cell-matrix contacts, which is especially prominent in cells of the monocytic lineage such as monocytes, macrophages and dendritic cells, but also in a variety of other cell types. Comparable to other adhesion structures, podosomes feature a complex architecture, which forms the basis for their extensive repertoire of sensory and effector functions. These functions are mainly linked to interactions with the extracellular matrix and comprise well known properties such as cell-matrix adhesion and extracellular matrix degradation. A more recent discovery is the ability of podosomes to act as mechanosensory devices, by detecting rigidity and topography of the substratum. In this review, we focus especially on the molecular events involved in mechanosensing by podosomes, the structural elements of podosomes that enable this function, as well as the intra- and extracellular signals generated downstream of podosome mechanosensing.