Abstract
Integrin-transmitted cellular forces are crucial mechanical signals regulating a vast range of cell functions. Although various methods have been developed to visualize and quantify cellular forces at the cell–matrix interface, a method with high performance and low technical barrier is still in demand. Here we developed a force-activatable coating (FAC), which can be simply coated on regular cell culture apparatus’ surfaces by physical adsorption, and turn these surfaces to force reporting platforms that enable cellular force mapping directly by fluorescence imaging. The FAC molecule consists of an adhesive domain for surface coating and a force-reporting domain which can be activated to fluoresce by integrin molecular tension. The tension threshold required for FAC activation is tunable in 10–60 piconewton (pN), allowing the selective imaging of cellular force contributed by integrin tension at different force levels. We tested the performance of two FACs with tension thresholds of 12 and 54 pN (nominal values), respectively, on both glass and polystyrene surfaces. Cellular forces were successfully mapped by fluorescence imaging on all the surfaces. FAC-coated surfaces also enable co-imaging of cellular forces and cell structures in both live cells and immunostained cells, therefore opening a new avenue for the study of the interplay of force and structure. We demonstrated the co-imaging of integrin tension and talin clustering in live cells, and concluded that talin clustering always occurs before the generation of integrin tension above 54 pN, reinforcing the notion that talin is an important adaptor protein for integrin tension transmission. Overall, FAC provides a highly convenient approach that is accessible to general biological laboratories for the study of cellular forces with high sensitivity and resolution, thus holding the potential to greatly boost the research of cell mechanobiology.
Highlights
Cells sense and respond to the mechanical cues of the neighboring cells and surrounding extracellular matrix (ECM)
Through multiple tests of force-activatable coating (FAC) with different cell lines on different cellular culture apparatuses, we demonstrated that FAC successfully turns regular cell culture surfaces to cellular force imaging platforms which convert force signals into fluorescence signals and achieve highresolution imaging on both glass and polystyrene surfaces, the two common surfaces for cell culture
FAC can be designed with a specific molecular tension threshold that enables the selective imaging of integrin tension at different force levels (>12 pN and >54 pN in this paper)
Summary
Cells sense and respond to the mechanical cues of the neighboring cells and surrounding extracellular matrix (ECM). Cells exert forces on the ECM and transduce mechanical signals to neighboring cells. Integrin-transmitted forces play both mechanical and regulative roles in various cellular functions. In short term, these forces mechanically mediate cell adhesion, polarization and migration [3,4,5,6,7]. These forces mechanically mediate cell adhesion, polarization and migration [3,4,5,6,7] In long term, these forces are transduced to biochemical signals which are involved in cell proliferation, cancer metastasis [8, 9] and stem cell differentiation [10,11,12]. Because of the fundamental roles of these forces in cellular functions, measuring and mapping these forces have been long pursued in the study of cell mechanobiology
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