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Susana A Sánchez

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Cell Membrane heterogeneity and media stiffness

Susana A. Sánchez

Laboratorio de Interacciones Macromoleculares (LIMM). Departamento de Polímeros. Facultad de Ciencias Químicas. Universidad de Concepción. Concepción, Chile

In vivo, cells are surrounded by extracellular matrix (ECM) having different degrees of stiffness depending on their location. Adaptation of the cells to temporal and spatial changes of the ECM must involve the plasma membrane. The participation of plasma membrane in the transduction of external mechanical signals is still under study but it is postulated to be like the one involved in the translation of chemical stimulus: a mechanism where lipid domains (rafts) have the role of sequestering the required components for signaling, making them accessible by assembling and disassembling. We believe that plasma membrane fluidity is the result of areas with different order in equilibrium with each other that can be modified by external stimulus. In this report, this hypothesis was tested by studying the effect of matrix stiffness on the distribution of membrane fluidity in living cells. Our system consisted of NIH-3T3 cells immersed in matrices fabricated with different concentrations of collagen I and incubated at 37˚C. The viscoelastic properties of the collagen matrices were characterized by Rheometry, the fiber size was measured by Scanning Electron Microscopy (SEM) and the volume occupied by the fibers by reversed second harmonic generated (SHG) signal. Membrane fluidity was measured using the fluorescent dye Laurdan and spectral phasor analysis. Our results show that as the stiffness of the surrounding collagen increased, the amount of Laurdan fraction with high degree of packing also increased. Our results show that changes in the equilibrium of fluidity domains could be a very refined component of the signal transduction mechanism for cells responding to matrix structural composition.

1- Gunther G, Malacrida L, Jameson DM, Gratton E, Sánchez SA. Laurdan since Weber: the quest for visualizing membrane heterogeneity. Acc. Chem. Res. 54, 4, 976–987 (2021). 2- Gunther G, Jameson DM, Aguilar J, Sánchez SA. Scanning Fluorescence Correlation Spectroscopy comes Full Circle. Methods 140–141: 52-61 (2018). 3- Gunther G, Herlax V, Lillo MP, Sandoval-Altamirano C, Belmar L, Sánchez SA. Study of rabbit erythrocytes membrane solubilization using Laurdan and phasor analysis. Colloids and Surfaces B: Biointerfaces. 161:375–385 (2018)

Susana A Sánchez
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