The thermodynamic properties of plasma membrane lipids play a vital role in many functions that initiate at the mammalian cell surface. Some functions are thought to occur, at least in part, because plasma membrane lipids have a tendency to separate into two distinct liquid phases. We propose that these lipid mediated functions occur because plasma membrane composition is tuned close to a miscibility critical point at physiological temperature. This hypothesis is supported by our observations of micron-sized and dynamic critical composition fluctuations in isolated plasma membranes near room temperature. In this talk, I will discuss our ongoing efforts to probe for the existence and consequences of criticality in the plasma membranes of intact cells. These recent efforts include using quantitative super-resolution fluorescence localization microscopy to monitor the organization of plasma membrane proteins in B cell lymphocytes, both in resting cells and in cells stimulated with multivalent antigen against the B cell receptor. We also have identified a range of membrane perturbations, including n-alcohols, which alter the magnitude of fluctuations in isolated vesicles. These perturbations of membrane structure are also well characterized general anesthetics, and evidence suggesting that some aspects of anesthetic function can be attributed to lipid heterogeneity will be presented.
Host: Ben Machta