A new twist to mechanotransduction of shear

Philippe Bergeron

(A) Illustration of shear device and subdivided squares for microscopy. (B) Time series of shear-induced shape changes in A7 and M2 cells; A7 cells undergo a mesenchymal-to-amoeboid transition (MAT) associated with a reduction in cell area whereas FLNa-null M2 cells have no significant change in morphology. (C) Using a micro fluidic device, we observe that while FLNa-null M2 cells are unresponsive to the applied shear stress, A7 cells increase mechanical work when exposed to a burst of shear flow. (D) We observe increase of Rho-FRET ratio at the cell leading edge when A7 cells that express FLNa are exposed to shear stress. Rho activity in FLNa-null M2 cells remains at original level. (E) Quantification of total FRET signal (16-bit) as a function of cell polar coordinates (see color legend).

One molecular mechanotransduction mechanism demonstrated to regulate shear-induced cell behavior is the FLNa and FilGAP interaction. When Filamin is stretched, it reduces the binding affinity for FilGAP, allowing FilGAP to interact with Rac and Cdc42. This biomechanical connection is hypothesized to enable amoeboid to mesenchymal transition (AMT) and mesenchymal-to-amoeboid transition (MAT) through spatiotemporal modulation of Rho activity and actomyosin contraction. 

We coupled a parallel-plate shear stress device with a confocal microscope to investigate the mechanical interplay between this molecular mechanism and shear stress. Confocal imaging, traction force microscopy and biomolecular experiments were performed on FLNa-expressing A7 cells that have a mesenchymal-like morphology in absence of stress and FLNa-null M2 cells that have an amoeboid morphology. 

We observed shear-stress induced mechanotransduction in cells that express FilaminA (FLNa). (Figure A-B). Using a micro-fluidic device, we confirm that FLNa is required for actuation of cell mechanical work under shear flow (Figure C). We also measured that RhoA activity increases in response to shear stress in cells that express FLNa (Figure D-E). 

Overall, we show here that dynamic FLNa and FilGAP binding is required for contractile mechanotransduction response to shear-stress.

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Dr. Allen Ehrlicher

Department of Bioengineering

McConnell Engineering Building

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Montreal, Quebec H3A 2A7

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Email: allen.ehrlicher@mcgill.ca

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