Wan, QiaoqiaoKim, Seung JoonYokota, HirokiNa, Sungsoo2025-05-232025-05-232013Wan Q, Kim SJ, Yokota H, Na S. Differential activation and inhibition of RhoA by fluid flow induced shear stress in chondrocytes. Cell Biol Int. 2013;37(6):568-576. doi:10.1002/cbin.10072https://hdl.handle.net/1805/48331Physical force environment is a major factor that influences cellular homeostasis and remodelling. It is not well understood, however, as a potential role of force intensities in the induction of cellular mechanotransduction. Using a fluorescence resonance energy transfer-based approach, we asked whether activities of GTPase RhoA in chondrocytes are dependent on intensities of flow-induced shear stress. We hypothesized that RhoA activities can be either elevated or reduced by selecting different levels of shear-stress intensities. The result indicates that C28/I2 chondrocytes have increased RhoA activities in response to high shear stress (10 or 20 dyn/cm(2) ), whereas a decrease in activity was seen with an intermediate shear stress of 5 dyn/cm(2) . No changes were seen under low shear stress (2 dyn/cm(2) ). The observed two-level switch of RhoA activities is closely linked to the shear-stress-induced alterations in actin cytoskeleton and traction forces. In the presence of constitutively active RhoA (RhoA-V14), intermediate shear stress suppressed RhoA activities, while high shear stress failed to activate them. In chondrocytes, expression of various metalloproteinases is, in part, regulated by shear and normal stresses through a network of GTPases. Collectively, the data suggest that intensities of shear stress are critical in differential activation and inhibition of RhoA activities in chondrocytes.en-USPublisher PolicyFluorescence resonance energy transfer (FRET)Mechanical loadingCartilageRho GTPaseActin cytoskeletonTraction forceArticle