Fig. 7.
Podosome ring modeling estimates nN tensile forces. a Schematic and equation for modeled podosome tensile forces on an SLB. Modeled podosome consist of a 1 μm outer radius and a 0.3 μm inner radius. The actin core exerts protrusion forces on the SLB, and the integrin receptors in the adhesion ring apply tensile forces. Modeled podosomes were parameterized using data from Fig. 2 and Supplementary Fig. 18. Scale bar, 2.5 μm. b Plot of ring tensile forces as a function of the per receptor force, FInt. The dashed line indicates total tensile forces assuming 1 probe per biotinylated lipid, and the black data point represents the minimum force predicted by MT-FLIM. Confidence intervals and error bars correspond to 0.5 to 2 probes per biotinylated lipid. c Model of podosome forces on an SLB. Individual podosomes exert protrusion forces on the SLB with the actin core, while integrin receptors tug on RGD ligands in the ring domain. Podosomes experience strong mechanical coupling between protrusive and tensile forces. This coupling is focused within a single podosome and is weak in-between podosomes. This equilibrium can be shifted through myosin or actin inhibition. Podosomes with more actin content have smaller depletion areas and exert less tension. Receptor clusters that are not associated with podosomes do not experience detectable forces. Source data are provided as a Source Data file