Dr. Vijay Lyall
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Contact Information
Department of Physiology and Biophysics Virginia Commonwealth University P.O. Box 980551 Richmond, Virginia 23298-0551 Tel: 804-828-9759 Fax: 804-828-7382 email: vlyall@vcu.edu |
Vijay Lyall received his M.S. in Biochemistry in 1975 and Ph.D. in Biochemistry in 1981 from the Postgraduate Institute of Medical Education and Research, Chandigarh, India. He was a Postdoctoral Fellow in the Department of Physiology and Biophysics, Indiana University School of Medicine, Indianapolis, Indiana, before joining VCU in 1989.
Research
My program aims to understand the basic physiological mechanisms involved in the transduction of salty and sour taste at the receptor level in the taste receptor cells. We are interested in identifying the receptors/ion channels located in the apical membrane of taste cells that detect the presence of Na+, K+, NH4+ and H+ ions in the external environment of taste cells and the down stream intracellular signaling effectors in taste cells that lead to the activation of taste nerves. We use an integrated approach involving several independent techniques to investigate taste transduction mechanisms. We make electrophysiological recordings directly from the taste sensory nerves.At the cellular level we directly monitor ion fluxes across the apical membrane of polarized taste cells using both conventional and laser scanning confocal imaging methods to follow changes in the intracellular concentration of ions and other effectors that may change during chemosensory transduction.Using immunocytochmical methods we identify specific receptors/ion channels and transporters in taste cell membranes. Finally, using molecular biological methods we clone specific receptors/ion channels and decipher their sequence and by transfecting into a heterologous cell line, e.g. HEK 293 cell line, we study the function of the expressed receptors/ion channels using imaging and electrophysiological techniques.Using this approach we have identified TRPV1t, a variant of the pain receptor, as the amiloride-insensitive salt taste receptor in the taste cells in the anterior tongue. This has led to the discovery of several interesting compounds and drugs that modulate TRPV1t activity and thus can be used as potential salt taste enhancers or suppressers. In addition, we have identified that during acid stimulation a decrease in intracellular pH of taste cells is the proximate signal for sour taste transduction, and that the down stream activation of basolateral Na+-H+-exchanger-1 (NHE-1) in taste cells is the major adaptation mechanism for sour taste.
Teaching
I direct an advanced course in sensory transduction mechanisms and give lectures on chemosensory systems in our graduate cell physiology course and lectures on the composition of blood to students of pharmacy and dentistry. I also teach in the first-year medical student labs. My lab continues to train M.S. and Ph.D. students and postdoctoral associates.
Selected Publications
Lyall, V., Alam R.I., Phan T.H., Russell O.F., Malik S.A., Heck G.L. and DeSimone J.A. Modulation of rat chorda tympani NaCl responses and intracellular Na+ activity in polarized taste receptor cells by pH. J. General Physiology, 120: 793-815, 2002. PubMed
Lyall, V., Alam R.I., Malik S.A., Phan T.H., Vinnikova, A.K., Heck G.L. and DeSimone J.A. Basolateral Na+-H+ exchanger-1 (NHE-1) in rat taste receptor cells is involved in neural adaptation to acidic stimuli. J. Physiology (London), 556: 159-173, 2004. PubMed
Lyall, V., Heck, G.L., Vinnikova, A.K., Ghosh, S., Phan ,T.H., Alam, R.I., Russell, O.F., Malik, S.A,, Bigbee, J.W., and DeSimone, J.A. The mammalian amiloride-insensitive non-specific salt taste receptor is a vanilloid receptor-1 variant. J. Physiology (London), 558: 147-159, 2004. PubMed
Lyall, V., G.L. Heck, T-H. T. Phan, S. Mummalaneni, S.A. Malik, A.K. Vinnikova, and J.A. DeSimone. 2005. Ethanol modulates the VR-1 variant amiloride-insensitive salt taste receptor. II. Effect on chorda tympani salt responses.J. Gen. Physiol. 125: 587-600. PubMed
Lyall, V., T-H. T. Phan, S. Mummalaneni, M. Mansouri, G.L. Heck, G. Kobal, and J.A. DeSimone. Effect of nicotine on chorda tympani responses to salty and sour stimuli. J. Neurophysiol. 98: 1662-1674, 2007. DOI:10.1152/jn.00366.2007. PubMed