Heterogeneity of membrane phospholipid mobility in endothelial cells depends on cell substrate.

Cellular growth control and differentiation have been shown to be dependent on both cell-cell and cell-substrate contacts. Interactions of cells with extracellular material are critical events during embryonic development and maintenance of tissue function. Plasma membrane receptors have been described for components of the extracellular matrix such as fibronectin, laminin and various collagen types. Transmembrane signalling has been shown to be influenced by the lateral mobilities of the plasma membrane constituents. The interaction of cells with their extracellular matrix could thus have a significant effect on the mobility properties of the plasma membrane components. Here we have studied the dynamic properties of fluorescent membrane phospholipids in bovine endothelial cells using fluorescence recovery after photo-bleaching measurements. At this molecular level we find that the phospholipid lateral diffusion coefficient is dependent on the substrate upon which cells are allowed to adhere (collagen, fibronectin or a natural basement membrane) and on the topography of the cell (basal versus apical plasma membrane).