Our goals are to understand the molecular interactions controlling protein and lipid mobility and distribution in cell membranes, the roles of these mechanisms in interactions between cells, and the relationships between derangements in these mechanisms and the pathophysiology of disease. We have designed and constructed a time-resolved scanning fluorescence microscope photometer for interactive study at the single-cell and subcellular levels on the microsecond-millisecond time scale. A second microscope has complementary capabilities: sub-micron spatial resolution in x, y, and z axes and the ability to monitor fluorescence emission in two wavelength regions simultaneously. A third microscope is interfaced with an intensified CCD camera for image processing and analysis at sub-second time resolution. We are now designing and constructing an apparatus for tracking and manipulating individual cell surface receptor molecules using computer-enhanced digital imaging and laser optical tweezers technologies.
Using these instruments, we are investigating: 1) Membrane dynamics in normal and abnormal erythroid cells, including the identification and measurement of molecular interactions that control the lateral mobility, rotational mobility, and surface distribution of individual band 3, glycophorin A, aquaporin-1, transferrin receptor, and fibronectin receptor molecules in mature erythrocytes and developing erythroid cells. 2) Mobility and adhesion of sickle blood cell membrane components, including molecular mechanisms that mediate hemolysis of sickle erythrocytes and novel adhesive interactions among sickle erythrocytes, leukocytes, and vascular endothelial cells. 3) Lateral mobility, cell surface distribution, and two-dimensional adhesive interactions of T lymphocyte adhesion molecules. We are studying the functional role of receptor lateral mobility and its regulation by intracellular signal transduction pathways. A glass-supported planar lipid bilayer system and a novel analysis to quantify the two-dimensional dissociation constant are used to study adhesion of lymphoid cells to bilayers reconstituted with purified adhesion molecules having defined physical properties. 4) Induced redistribution of cell surface receptors and cytoskeletal structures by alternating current electric fields. Of interest are the kinetics, extent, and molecular mechanisms of redistribution. Graduate student rotation projects are available in each of these areas.
Selected Publications:
Cho MR, Eber SW, Liu SC, Lux SE, Golan DE. 1998. Regulation
of band 3 rotational mobility by ankyrin in intact human red cells.
Biochemistry 37:17828-17835.
Cho MR, Knowles DW, Smith BL, Moulds JJ, Agre P, Mohandas N, Golan DE. 1999. Membrane dynamics of the water transport protein aquaporin-1 in intact human red cells. Biophysical Journal 76:1136-1144.
Liu SJ, Golan DE. 1999. T cell stimulation through the T
cell receptor/CD3 complex regulates CD2 lateral mobility by a calcium/calmodulin
dependent mechanism. Biophysical Journal 76:1679-1692.