Physiology and Biophysics Faculty

Research Interests

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.

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.

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.

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

• Google Scholar Citations
• PubMed Citations

Selected Publications

1. Tomchik SM, Berg S, Kim JW, Chaudhari N, Roper SD. (2007) Breadth of tuning and taste coding in mammalian taste buds. J Neurosci. 27:10840-8.
2. 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
3. DeFazio RA, Dvoryanchikov G, Kim J-W, Maruyama Y, Roper SD, Chaudhari N (2006) Separate populations of receptor cells and pre-synaptic cells in mouse taste buds. J. Neurosci. 26:3971-80.
4. Maruyama Y, Pereira E, Margolskee RF, Chaudhari N, Roper SD (2006) Umami responses in mouse taste cells indicate more than one receptor. J Neurosci. 26:2227-34.
5. Kim J-W, Roberts C, Maruyama Y, Berg S, Roper S, Chaudhari N (2006) Faithful expression of GFP in a functional class of taste receptor cells in a transgenic mouse. Chem Senses 31:213-9
6. Dotson CD, Roper SD, Spector AC. (2005) PLC 2-independent behavioral avoidance of prototypical bitter-tasting ligands. Chem Senses. 30:593-600.
7. Chaudhari N, Maruyama Y, Roper S, Trubey K. (2005) Multiple pathways for signaling glutamate taste in rodents. Chem Senses 30, Suppl 1:i29-i30.
8. Huang Y-J, Maruyama Y, Lu K-S, Pereira E, Plonsky I, Baur JE, Wu D, Roper SD (2005) Mouse taste buds use serotonin as a neurotransmitter. J.Neurosci. 25(4):843-7.
9. Richter TA, Dvoryanchikov GA, Chaudhari N, Roper SD. (2004) Acid-sensitive two-pore domain potassium (K2P) channels in mouse taste buds. J Neurophysiol. 92:1928-36.
10. Richter TA, Dvoryanchikov GA, Roper SD, Chaudhari N. (2004) Acid-sensing ion channel-2 is not necessary for sour taste in mice. J Neurosci. 24:4088-91.
11. 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.
12. Richter T.A., Caicedo A., Roper SD. (2003) Sour taste stimuli evoke Ca2⁺
    and pH responses in mouse taste cells. J. Physiol. (London) 547:475-83.
13. Caicedo, A., K-N Kim and S.D. Roper (2002) Detection of taste quality in taste buds. J. Physiol. (London) 544:501-509.
14. Stapleton J.R., Luellig M., Roper S.D., Delay E.R. (2002) Discrimination between the tastes of sucrose and monosodium glutamate in rats. Chem. Senses 27:375-82.
15. Caicedo, A. and S. D. Roper (2001) Taste receptor cells that discriminate between bitter stimuli. Science 291:1557-1560.
16. Caicedo, A., Jafri, M.S. and S. D. Roper (2000) Synaptic glutamate receptors in taste receptor cells revealed by in situ Ca2+ imaging. J. Neurosci. 20: 7986-8004.
17. Delay, E.R., A.J. Beaver, K.A. Wagner, J. R. Stapleton, J.O. Harbaugh, K.D. Catron and S. D. Roper (2000) Taste synergy between glutamate agonists and IMP in rats. Chem. Senses 25: 507-515
18. Caicedo, A., K. Kim and S. Roper (2000) Glutamate-induced cobalt uptake reveals non-NMDA receptors in rat taste cells. J. Comp. Neurol. 417: 315-324.
19. Chaudhari, N., A. M. Landin and S. D. Roper (2000) A metabotropic glutamate receptor variant functions as a taste receptor. Nature Neurosci. 3: 113-119.
20. Yang, H., Wanner, I. B., Roper, S. D., Chaudhari, N. (1999) An Optimized Method for In Situ Hybridization with Signal Amplification That Allows the Detection of Rare mRNAs J. Histochem. Cytochem. 47: p. 431-446.
21. 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.

Articles of Related Interest

1. Collett, C., J. Kalogeras and K. Hagland (1997) Landmarks: A Taste Sensation. J. NIH Research 9: 44-49.
2. Kreeger, K.Y. (1997) Taste researchers savor fruits of work in stimulating times. The Scientist, 11: 11-14
3. Lindemann, B. (2000) A taste for umami.Nature Neurosci. 3: 99-100
4. Brown, K. (2001) A Discriminating Taste for Bitter (in News of the Week) Science February 23; 291: 465-1466.

Curriculum Vitae

• 1967 B.S. Magna cum laude, Biology, Harvard College
• 1970 Ph.D. Physiology, University of London
• 1970-1973 Postdoctoral Fellow with Stephen Kuffler, Dept. of Neurobiology, Harvard Medical School
• 1973-1979 Assistant Professor, Dept. of Anatomy, University of Colorado Health Sciences Center
• 1979-1985 Associate Professor, Dept. of Anatomy and Dept. of Physiology, University of Colorado Health Sciences Center
• 1985 Professor, Dept. of Anatomy and Dept. of Physiology, University of Colorado Health Sciences Center
• 1985 Professor and Chairman, Dept. of Anatomy and Neurobiology, Colorado State University
• 1995-present Professor, Dept. Physiology and Biophysics, University of Miami School of Medicine