Emily R. Liman
Department of Biological Sciences,
Sections of Neurobiology, Molecular Biology
Phone: (213) 821-1454
University of Southern California
3614 Watt Way
Los Angeles, CA 90089-2520
- B.A., Princeton University, 1985.
- Ph.D., Harvard University, 1992.
- Taste transduction
- TRP ion channels.
- Evolution of sensory systems.
Research OverviewSENSORY TRANSDUCTION AND ION CHANNEL BIOPHYSICS
Work in the Liman laboratory is focused on understanding how sensory information is detected and transduced, using a combination of electrophysiology, molecular biology, genetics and genomics. Professor Liman trained with Linda Buck, in whose lab she cloned and characterized sensory transduction components of the main olfactory and vomeronasal sysmtes (see Liman and Buck, 1992 for an example). As a research assisitant professor at Harvard she identified an ion channel essential for pheromone detection in vertebrates (TRPC2; see Liman, Corey and Dulac, 1999 for an example). Interestingly, this protein is not found in humans (it is encoded by a pseudogene), indicating that humans have lost much of their ability to respond to pheromones. Work in the Liman lab showed that the functional protein was lost in human evolution at the same time that humans developed trichromatic vision, suggesting that vision has replaced pheromone detection in human reproductive biology (Liman and Innan, 2003).
Ongoing work in the Liman lab is focused on mechanisms of taste signaling, mechanisms of pain signaling, and the identification of ion channels that contribute to these processes. In recent work, the lab showed that an ion channel responsible for the detection of spicy mustards, TRPA1, is also activated by carbon dioxide (Wang et al, 2010). This may explain some of the pungency we feel when we drink carbonated beverages. In a separate study, the lab examined the mechanism of taste transduction using genetically modified mice in which subsets of taste cells are fluorescently labeled. Using patch clamp electrophysiology and uv-uncaging of protons, the lab showed that sour taste is mediated by an apically located proton channel (Chang et al, 2010). Future experiments in the lab are aimed at identifying the molecular nature of this proton channel. The lab uses methods of molecular biology, including generation of transgenic animals, combined with patch clamp electrophysiology and calcium imaging.
See http://www.usc.edu/uscnews/story.php?id=8704 and http://www.usc.edu/uscnews/story.php?id=9616
for recent news coverage of work in the liman lab
Wang, Y. Y., Chang, R. B., and Allgood, S. D., Silver, W. L. and Liman, E. R. (2011). A TRPA1-dependent mechanism for the pungent sensation of wek acids Journal of General Physiology. 137, 493-505 (featured on the cover and in a commentary) -PubMed -Link
Chang, R. B., Waters, H., and Liman, E. R. (2010). A proton current drives action potentials in genetically identified sour taste cells. PNAS, 468, 603; 2010, Featured on the cover and in "This week in PNAS", Featured in Nature "Research Highlights" -PubMed -Link
Wang, Y. Y., Chang, R. B., and Liman, E. R. (2010). TRPA1 is a component of the nociceptive response to CO2. J Neurosci 30, 12958-12963. Featured on the cover and in "This week in the journal." Selected for a "ScienceShot" in Science -PubMed -Link
Wang, Y. Y., Chang, R. B., Waters, H. N., McKemy, D. D., and Liman, E. R. (2008). The Nociceptor Ion Channel TRPA1 Is Potentiated and Inactivated by Permeating Calcium Ions. J Biol Chem 283, 32691-32703. -PubMed -Link
Takashima Y, Daniels RL, Knowlton W, Teng J, Liman ER, McKemy DD. (2007) Diversity in the neural circuitry of cold sensing revealed by genetic axonal labeling of transient receptor potential melastatin 8 neurons. J Neurosci.27(51):14147-14157. -PubMed
Young JM, Waters H, Dong C, Fülle HJ, Liman ER. (2007) Degeneration of the olfactory guanylyl cyclase D gene during primate evolution. PLoS ONE. 2(9):e884. -PubMed
Zhang, Z., Okawa, H., Wang, Y., and Liman, E.R. (2005) Phosphatidylinositol 4,5-Bisphosphate Rescues TRPM4 Channels from Desensitization. J Biol Chem 280, 39185-39192. -PubMed
D. Liu and Liman, E.R. (2003) Intracellular Ca2+ and the phospholipid PIP2 regulate the taste transduction channel TRPM5. Proc Natl Acad Sci USA. 100(25):15160-15165. -PubMed
Liman, E.R., Corey, D.P., and Dulac, C. (1999) TRP2, a candidate transduction channel for mammalian pheromone sensory signalling. Proc. Natl. Acad. Sci. 96:5791-5796 -PubMed
Liman, E. R. and L. Buck (1994). A second subunit of the olfactory cyclic nucleotide-gated channel confers high sensitivity to cAMP. Neuron 13:611-621.
Liman, E. R., Tytgat, J. and P. Hess (1992). Subunit stoichiometry of a mammalian K+ channel determined by construction of multimeric cDNAs. Neuron 9:861-871