Abstract
Cell membrane roughness has been proposed as a sensitive feature to reflect cellular physiological conditions. In order to know whether membrane roughness is associated with the substrate properties, we employed the non-interferometric wide-field optical profilometry (NIWOP) technique to measure the membrane roughness of living mouse embryonic fibroblasts with different conditions of the culture substrate. By controlling the surface density of fibronectin (FN) coated on the substrate, we found that cells exhibited higher membrane roughness as the FN density increased in company with larger focal adhesion (FA) sizes. The examination of membrane roughness was also confirmed with atomic force microscopy. Using reagents altering actin or microtubule cytoskeletons, we provided evidence that the dynamics of actin filaments rather than that of microtubules plays a crucial role for the regulation of membrane roughness. By changing the substrate rigidity, we further demonstrated that the cells seeded on compliant gels exhibited significantly lower membrane roughness and smaller FAs than the cells on rigid substrate. Taken together, our data suggest that the magnitude of membrane roughness is modulated by way of actin dynamics in cells responding to substrate properties.
Highlights
The plasma membrane roughness can be defined as the deviation of the actual membrane surface topography from an ideal atomically smooth surface
Using non-interferometric wide-field optical profilometry (NIWOP), we found that the membrane roughness was enhanced with the increase of the FN concentration (Fig. 1a and b)
The correlation between the membrane roughness and the focal adhesion (FA) area implies that membrane roughness might be influenced by substrate properties through some signal transduction mechanisms related to the FAs
Summary
The plasma membrane roughness can be defined as the deviation of the actual membrane surface topography from an ideal atomically smooth surface. Yang et al reported that N-methyl-D-aspartate treatment could increase the surface roughness and stiffness of neuroblastoma cells[4] With various mechanisms, these previous studies showed that cell membrane roughness could be useful for judging the efficacy of specific stimulations presented in the microenvironment. For the membrane roughness measurements conducted on cells cultured on flat substrates, a fundamental question about the data interpretation is how the substrate properties influence the membrane roughness. We hypothesized that, when some mechanosensitive proteins in the FAs sense the differences in substrate properties and change the fine structures of cytoskeletons, the membrane roughness could reflect these responses. We coated the substrate with different concentrations of fibronectin (FN) and correlated the sizes of FAs with the membrane roughness. We used substrates of different rigidities to demonstrate the versatile sensitivities of membrane roughness to the culture environment
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