title: Confined lateral diffusion of membrane receptors as studied by single particle tracking (nanovid microscopy). Effects of calcium-induced differentiation in cultured epithelial cells.
abstract: The movements of E-cadherin, epidermal growth factor receptor, and transferrin receptor in the plasma membrane of a cultured mouse keratinocyte cell line were studied using both single particle tracking (SPT; nanovid microscopy) and fluorescence photobleaching recovery (FPR). In the SPT technique, the receptor molecules are labeled with 40 nm-phi colloidal gold particles, and their movements are followed by video-enhanced differential interference contrast microscopy at a temporal resolution of 33 ms and at a nanometer-level spatial precision. The trajectories of the receptor molecules obtained by SPT were analyzed by developing a method that is based on the plot of the mean-square displacement against time. Four characteristic types of motion were observed: (a) stationary mode, in which the microscopic diffusion coefficient is less than 4.6 x 10(-12) cm2/s; (b) simple Brownian diffusion mode; (c) directed diffusion mode, in which unidirectional movements are superimposed on random motion; and (d) confined diffusion mode, in which particles undergoing Brownian diffusion (microscopic diffusion coefficient between 4.6 x 10(-12) and 1 x 10(-9) cm2/s) are confined within a limited area, probably by the membrane-associated cytoskeleton network. Comparison of these data obtained by SPT with those obtained by FPR suggests that the plasma membrane is compartmentalized into many small domains 300-600 nm in diameter (0.04-0.24 microns2 in area), in which receptor molecules are confined in the time scale of 3-30 s, and that the long-range diffusion observed by FPR can occur by successive movements of the receptors to adjacent compartments. Calcium-induced differentiation decreases the sum of the percentages of molecules in the directed diffusion and the stationary modes outside of the cell-cell contact regions on the cell surface (which is proposed to be the percentage of E-cadherin bound to the cytoskeleton/membrane-skeleton), from approximately 60% to 8% (low- and high-calcium mediums, respectively).
authors.affiliation: Department of Pure and Applied Sciences, University of Tokyo, Japan.
authors.forename: A
authors.initials: A
authors.lastname: Kusumi
authors.forename: Y
authors.initials: Y
authors.lastname: Sako
authors.forename: M
authors.initials: M
authors.lastname: Yamamoto
mesh_terms: D000818:Animals; D055592:Biophysical Phenomena; D001703:Biophysics; D015820:Cadherins / Q000378:metabolism; D002118:Calcium / Q000494:pharmacology; D002454:Cell Differentiation / Q000187:drug effects; D002460:Cell Line; D002462:Cell Membrane / Q000187:drug effects / Q000378:metabolism; D004058:Diffusion; D066246:ErbB Receptors / Q000378:metabolism; D005453:Fluorescence; D017979:Gold Colloid; D015603:Keratinocytes / Q000166:cytology / Q000187:drug effects / Q000378:metabolism*; D008565:Membrane Proteins / Q000378:metabolism; D051379:Mice; D008857:Microscopy, Interference; D008954:Models, Biological; D010777:Photochemistry; D011956:Receptors, Cell Surface / Q000378:metabolism*; D011990:Receptors, Transferrin / Q000378:metabolism
chemical_list: D015820:Cadherins; D017979:Gold Colloid; D008565:Membrane Proteins; D011956:Receptors, Cell Surface; D011990:Receptors, Transferrin; D066246:ErbB Receptors; D002118:Calcium