Dual-color superresolution microscopy reveals nanoscale organization of mechanosensory podosomes

Abstract

Podosomes are multimolecular mechanosensory structures with a protrusive actin core and an adhesive ring of integrins and adaptor proteins. Dual-color direct stochastic optical reconstruction microscopy is used to reveal the nanoscale localization of the ring components αMβ2 integrin, talin, and vinculin with respect to the actin core.

Podosomes in space

“…33,34 Strikingly, the application of high-resolution imaging revealed that the podosome ring shows a discontinuous organization and in fact consists of individual clusters that surround the core. [35][36][37] Recent work also revealed the existence of a third substructure at podosomes, the so-called "cap," which localizes on top of the podosome and partially overlaps with core and ring structures. To date, only a few cap proteins have been identified, including the myosin-binding protein supervillin 32 and the formin FMNL-1.…”

“…32 Work on the function of podosomes has progressed steadily during the last decade. It is now well-accepted that they act as (1) adhesive structures, 37,46 (2) mechanosensors and-transducers, 37,47 and (3) are able to degrade extracellular matrix. 42,49 Evidence for these functions is based on (1) the presence of integrins and other ECM receptors, such as the hyaluronic acid receptor CD44 at podosomes, 47,[50][51][52] and (2) the ability of podosome components to act as mechanotransducers by converting mechanical cues into chemical signals.…”

“…These include the potential existence of substructures, which may depend on the nature or viscoelastic properties of the surrounding matrix, and the potential recruitment and release of other proteases, such as secreted MMP isoforms or the urokinase plasminogen activator system. Furthermore, it is unclear whether other functions of 2D podosomes, such as mechanosensing and transduction, 37,48 are also fulfilled by 3D podosomes. Moreover, different maturation and activation states of macrophages might affect the formation, structure, and function of 3D podosomes, as it has been shown for podosomes in 2D.…”

Surface microtopography modulates sealing zone development in osteoclasts cultured on bone

“…Podosomes, in turn, contain a central actin core, about 200 nm in diameter, oriented perpendicularly to the plasma membrane and several micrometres high [10]. The actin core of individual podosomes is surrounded by a peripheral adhesion ring, 0.5-1 mm in diameter, containing integrins and associated plaque proteins that mediate the adhesion to the bone surface [18][19][20][21][22][23]. The unique structure of podosomes, combined with their rapid turnover [18,24] and assembly into coherent SZ & 2017 The Author(s) Published by the Royal Society.…”

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

“…Podosomes are F-actinrich cone-shaped structures of B600 nm height and submicron diameter, located at the basal face of cells, perpendicular to, and in contact with the substratum via integrins at the podosome ring 8,9 . Recently, super-resolution imaging of the adhesion ring revealed that its components are organized in clusters forming a polygonal structure [10][11][12] . Podosomes are regularly spaced and interconnected through a radial F-actin network 13,14 .…”