DNA-Based Optical Sensors for Forces in Cytoskeletal Networks

Mechanicalforces are relevant for many biological processes, fromwound healing and tumor formation to cell migration and differentiation.Cytoskeletal actin is largely responsible for responding to forcesand transmitting them in cells, while also maintaining cell shapeand integrity. Here, we describe a FRET-based hybrid DNA-protein tensionsensor that is designed to sample transient forces in actin networksby employing two actin-binding motifs with a fast off-rate attachedto a central DNA hairpin loop. Such a sensor will be useful to monitorrapidly changing stresses in the cell cytoskeleton. We use fluorescencelifetime imaging to determine the FRET efficiency and thereby theconformational state of the sensor, which makes the measurement robustagainst intensity variations. We demonstrate the applicability ofthe sensor by confocal microscopy and by monitoring crosslinking activityin in vitro actin networks by bulk rheology.