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| |  Stephen D Roper, Ph.D. Professor, Physiology and Biophysics 305-243-6769 (office) 305-243-5931 (fax) Rosenstiel Medical Science Building - 4065 roper@miami.edu
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Over the years I have had the good fortune to work with the following students, postdoctoral fellows, and visiting faculty. Most of what I know comes from my collaborations with these associates:
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Dr. Patrick Avenet
Group Leader, CNS Research Department
Synthelabo Recherche
Bagneux, France.
Dr. Albertino Bigiani
Chairman, Faculty of Pharmacy
Professor of Physiology
Dipartimento di Scienze Biomediche
Università di Modena e Reggio Emilia
Modena
Italy
Dr. Eugene Delay
Professor of Biology
University of Vermont
Burlington, VT
Dr. Rona Delay
Assoc. Professor of Biology
University of Vermont
Burlington, VT
Dr. Juan Diez
Research Associate, Diabetes Research Institute
University of Miami School of Medicine
Miami, FL
Dr. Doug Ewald
Ft. Collins, Colorado
Dr. Timothy Gilbertson
Professor & Assoc Head
Department of Biology
Utah State University
Logan, UT
Dr. Kazuyoshi Kawa
Professor of Neurophysiology
Tohoku University
Sendai, Japan
Dr. Dae-Joong Kim
Professor of Anatomy
Inha University College of Medicine
Inchon, Korea
Dr. John Kinnamon
Professor of Biological Sciences
University of Denver
Denver, Colorado
Dr. Sue C. Kinnamon
Professor of Otolaryngology
University of Colorado Health Sci Center
Denver, Colorado
Dr. Chien-Ping Ko
Professor of Biological Sciences
University of Southern California
Los Angeles, California
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Dr. Kuo-Shyan Lu
Professor of Anatomy
National Taiwan University
Taipei, Taiwan
Dr. Kyung-Nyun Kim
Kim Kyung-Nyun, D.D.S., M.S.D., Ph.D.
Professor, Department of Physiology and Neuroscience, Kangnung National University,
Korea
Dr. Alan Mackay-Sim
Professor of Biomolecular & Biomedical Science
Griffith University
Queensland, Australia
Dr. Don McBride, Jr.
Associate Professor of Physiology and Biophysics
University of Texas Medical Branch
Galveston, Texas
Dr. Martha McPheeters
Program Head
Farm & Wilderness Camps
Plymouth, VT 05056
Dr. Takatoshi Nagai
Associate Professor of Physiology
Teikyo University
Tokyo, Japan
Dr. William Proctor
Research Associate in Pharmacology
University of Colorado School of Medicine
Denver, Colorado
Dr. Barbara Taylor
Associate Professor of Zoology
Oregon State University
Corvallis, Oregon
Randy Taylor
MD/PhD program
University of Colorado School of Medicine
Denver, Colorado
Dr. Mark Womble
Assistant Professor of Biological Sciences
Youngstown State University
Youngstown, Ohio
Dr. Jian Yang
Assistant Professor of Biological Sciences
Columbia University
New York, New York | |
My research focuses on the cellular and molecular biology of chemosensory transduction in taste buds. I have been interested in such questions as: What are the initial events of taste reception? Are G protein-coupled receptors involved in taste transduction? What neurotransmitters are released by taste receptor cells? What sort of signal processing occurs in taste buds? and so forth.
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An isolated rat vallate taste bud immunostained for the
taste-specific G protein, gustducin. A small group of 4-5 taste receptor cells are intensely immunopositive for gustducin. Micrograph produced by Ina Wanner. |
The sense of taste provides us with a view of our immediate chemical environment, particularly information about the safety and palatability of substances we ingest. Taste and olfaction are part of the chemical sensory systems of the body. At the most primitive level, the sense of taste guides nutrient intake. At the highest level, taste and olfaction unite to produce what we commonly term "flavor" and allow us to savor (or reject) foods. My colleagues and I are investigating the cellular and molecular mechanisms of how chemical stimuli, such as sugars, acids, salts, etc., are transduced into electrical signals by receptor cells in vertebrate taste buds. We use a combination of techniques, including patch clamp and intracellular microelectrode recordings, light and electron microscopy, immunocytochemistry, image analysis, in situ hybridization, and even animal behavioral tests to study the structure and function of receptor cells in taste buds.
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Necturus taste receptor cell filled with the fluorescent dye Lucifer yellow during a microelectrode impalement. Calibration, 20 µm (Courtesy of Jian Yang and from J Neuroscience 12:1127-1134). |
Our findings tell us that taste buds are much more complex than originally believed. There are chemical and electrical synaptic connections between taste cells. This means that there may be a certain degree of information processing in the peripheral sensory organs before signals are transmitted to higher centers in the brain. Furthermore, there are diverse mechanisms for converting taste stimuli into electrical signals. Lastly, we have identified a membrane-bound receptor that may transduce taste stimuli, particularly the taste of monosodium glutamate (MSG) ( Chaudhari, et al., 2000). This is a G-protein coupled receptor similar to a synaptic receptor found in the brain. Activation of this receptor during taste stimulation leads to an important intracellular cascade of enzymatic reactions. The net result of this cascade is the modulation of ion channels on the surface of the taste cell. Modulation of ion channels produces an electrical current in the taste cell, and this is the response that ultimately signals the presence of taste stimuli at the apical, chemosensitive tips of taste cells.
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We are using laser scanning confocal calcium imaging to view responses of taste cells in lingual slice preparations. Our data indicate that many taste receptor cells respond to multiple taste stimuli, even bitter and sweet.
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Summer, '02. This is the lab. Front row (sitting): Sukhdeep Rao, Elizabeth Pereira, Trevor Richter, Ilya Plonsky. Back row (standing): Yutaka Maruyama, Amy Hower, John Baur, Alejo Caicedo, Steve Roper
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Roper, SD (2009) Parallel processing in mammalian taste buds? Physiol & Behav 97:604-8
Roberts CD, Dvoryanchikov G, Roper SD and Chaudhari N (2009) Interaction between the second messengers cAMP and Ca2+ in mouse Presynaptic taste cells. J Physiol. 587:1657-68
Huang Y-J, Maruyama Y, Stimac R, and Roper SD (2008) Presynaptic (Type III) cells in mouse taste buds sense sour (acid) taste. J Physiol. 586:2903-12.
Kim JW, Roberts CR, Berg SA, Caicedo A, Roper SD and Chaudhari N (2008) Imaging cyclic AMP changes in pancreatic islets of transgenic reporter mice. PLoS ONE. May 7;3(5):e2127.
Anselmi F, Hernandez H, Crispino G, Seydel A, Ortolano S, Roper SD, Kessaris N, Richardson W, Rickheit G, Filippov M, Monyer H, Mammano F (2008) ATP release through connexin hemichannels and gap junction transfer of second messengers propagate Ca2+ signals across the inner ear. Proc Natl Acad Sci USA. 105:18770-5.
Huang YA, Maruyama Y, Roper SD (2008) Norepinephrine is co-released with serotonin in mouse taste buds J Neurosci 28:13088-93.
Huang YJ, Maruyama Y, Dvoryanchikov G, Pereira E, Chaudhari N, Roper SD. (2007) The role of pannexin 1 hemichannels in ATP release and cell-cell communication in mouse taste buds. Proc Natl Acad Sci USA 104: 6436-6441
Caicedo A., Pereira E., Margolskee R.F., and Roper S.D. (2003) Role of the G protein subunit alpha gustducin in taste cell responses to bitter stimuli. J. Neurosci. 23:9947-52.
Gilbertson TA, Roper SD, and Kinnamon SC. (1993) Proton currents through amiloride-sensitive Na channe ls in isolated hamster taste cells: Enhancement by vasopressin and cAMP. Neuron 10:1-20. |
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