Physics Colloquium
Friday, April 1st, 2005, 4:00 P.M.

David W. Piston

Department of Molecular Physiology and Biophysics, Department of Physics, Vanderbilt University

Sub-cellular and Multi-cellular Signaling Mechanisms Revealed by Quantitative Laser Microscopies

The convergence of newly developed instrumentation and optical probes allows us to examine quantitatively dynamic processes within ever more complicated biological systems. By using quantitative fluorescence imaging methods such as fluorescence recovery after photobleaching (FRAP) and Förster resonance energy transfer (FRET) of multi-colored GFPs fused to the glucose sensing enzyme glucokinase (GK), we have discovered that the location and activity of beta cell GK is acutely regulated by insulin. These findings provide a mechanism whereby the glucose sensing ability of the beta cell is tightly coupled to insulin signaling. We have also measured pancreatic β-cell metabolism during glucose stimulation of pancreatic islets by quantitative two-photon NAD(P)H imaging. We have developed methods to delineate quantitatively the NAD(P)H signals from the cytoplasm and mitochondria, and show that the metabolic response of these two compartments are differentially stimulated by glucose and other metabolites. Absolute levels of NAD(P)H were determined using two-photon excited fluorescence lifetime imaging (FLIM). These findings elucidate the relative contributions of glycolyticand citric acid cycle metabolism in the normal and diabetic insulin secretion pathways.

http://medschool.mc.vanderbilt.edu/facultydata/php_files/part_dept/show_part.php?id3=856