Michael Roe, PhD

Dr. Michael Roe and his colleagues study the genetic, structural and functional basis of intracellular calcium and cyclic nucleotide signaling in pancreatic ?-cells. The primary objectives of Dr. Roe’s research are to [1] understand the roles of endoplasmic reticulum and mitochondria in second messenger signal processing, [2] identify calcium transport proteins located on mitochondria and endoplasmic reticulum, [3] define molecular mechanisms underlying causal and temporal interplay between calcium and cyclic nucleotide signals in cells, and [4] determine whether defects in signal transduction pathways contribute to ?-cell pathophysiology.

Dr. Roe’s group is focused on understanding signal transduction in ?-cell lines, rodent and human islets of Langerhans. Multidisciplinary approaches are used including real-time confocal fluorescence imaging of single living cells and intact islets, genetically encoded biosensor technology, and ablation of specific gene expression by RNA interference. Genetically encoded biosensors are exciting new research tools that provide information about signaling dynamics within specific subcellular locations (e.g., lumen of endoplasmic reticulum, mitochondrial matrix, nucleus, Golgi apparatus, and cytoplasm) and increases our comprehension of basic signal processing essential for ?-cell insulin secretion and viability.

Dr. Roe’s research group has pioneered the application of genetically encoded calcium and cyclic nucleotide indicators targeted to subcellular compartments within ?-cells and islets by plasmid transfection, adenoviral transduction and transgenic methods. Recently, Dr. Roe and his colleagues developed novel real-time optical techniques to simultaneously measure multiple signaling pathways in ?-cells such as cytoplasmic calcium/cyclic AMP, cytoplasmic calcium/mitochondrial calcium, and cytoplasmic calcium/endoplasmic reticulum calcium. Dr. Roe’s work may have broader implications in a wide range of biological issues related to mitochondrial and endoplasmic reticulum biology, regulation of calcium signaling within and between various organelles, and generation of specific patterns of dynamic encoding and integration of cellular second messenger signaling cascades in response to cellular stimulation and stress.

Figure 1: Simultaneous imaging of cytoplasmic Ca2+ and cAMP in MIN6 ?-cells. (A) 16-bit digital images of Fura-2-loaded cells transiently expressing Epac1-camps, a genetically encoded fluorescence resonance energy transfer (FRET)-based biosensor of cAMP. The image in each panel was obtained from the same field of view using a spinning disk confocal fluorescence microscope and different excitation and emission filter sets. All cells are loaded with the Ca2+ indicator, Fura-2 (340 nm; 380 nm) and only two cells express Epac1-camps (485 nm; 535 nm). Ratio 340/380 and Ratio 485/535 pseudocolor images show the basal concentration of Ca2+ and cAMP, respectively. The color bar indicates the range of Epac1-camps FRET 485/535 ratio values in the pseudocolor display. (B) Effects of stimulating adenylyl cyclase with forskolin (FSK; 10 µM) on cAMP (red line) and Ca2+ (blue line) concentration in a single MIN6 cells. (C) Increases in cAMP and Ca2+ concentration following application of 20 mM KCl. Adapted from Landa et al. (2005) J. Biol. Chem. 280: 31294-31302 and Harbeck et al. (2006) Science STKE 2006 (353): pI6 (DOI: 10.1126/stke.3532006pI6).