Faculty

Curriculum Vitae

• B.S., California State University at Long Beach, 1982
• Ph.D. Pharmacology (with Neil Nathanson), University of Washington, 1987
• Postdoc, Molecular Neurobiology (with Jim Patrick), Salk Institute for Biological Studies, 1987-1988
• Postdoc, Neuroscience (with Jim Patrick), Baylor College of Medicine
  1989-1991
• Assistant Professor, Department of Molecular and Cellular Pharmacology, University of Miami School of Medicine, 1991 -1997
• Associate Professor, Department of Molecular and Cellular Pharmacology, University of Miami School of Medicine, 1997 - 2003
• Professor, Department of Molecular and Cellular Pharmacology, University of Miami School of Medicine, 2003 ­ present
• Vice-Chairman, Department of Molecular and Cellular Pharmacology, University of Miami School of Medicine, 2004 - 2008
• Interim Chairman, Department of Molecular and Cellular Pharmacology, University of Miami School of Medicine, 2008 – present

Research Interests

The research interests of my laboratory lie within the general area of receptor structure and function, with a particular emphasis on ligand recognition.  The central focus of our research program has, for many years, been the nicotinic acetylcholine receptors of the mammalian nervous system.  More recently, we have shifted much of our research effort into the area of mammalian and insect olfactory receptors.

Mammalian Olfactory Receptors
            Several years ago, we became interested in mammalian olfactory receptors (ORs).  The process of olfaction is an immense ligand recognition task and mammalian olfaction is particularly impressive.  Humans, who are thought to have relatively poor olfactory abilities when compared to other mammals, can detect hundreds of thousands (perhaps millions) of compounds and when trained, can reliably identify several thousand compounds.  To accomplish this remarkable feat of ligand recognition, the olfactory system employs a vast family of odorant receptors (~350 ORs in humans, ~1000 ORs in mouse).  ORs are thought to be employed in a combinatorial fashion, with each odorant recognized by a group of ORs and each OR recognizing a variety of odorant molecules.  Thus, understanding the odorant specificities of individual ORs is critical to understanding odorant coding.  In addition, the study of ORs may provide benefits beyond the chemosensory field.  Mammalian ORs are G-protein coupled receptors and the study of the structural basis for ligand specificity among ORs offers the opportunity to examine the strategies employed by GPCRs to recognize a wide variety of ligand structural features.  This could provide insight into the fundamental principles of ligand recognition by this therapeutically important receptor class and these insights could be of value in future rational drug design efforts.
            While there are many benefits to be derived from the study of OR ligand specificity, progress in this area has been slow.  This is because ORs have been difficult to functionally characterize in exogenous expression systems.  We have used Xenopus oocytes, an expression system useful in the expression and characterization “difficult” receptors, in combination with robotic electrophysiology to develop a robust assay for the functional analysis of mammalian ORs.  This assay involves co-expression in the oocyte of an OR, an olfactory specific G-protein (Gaolf) and the cystic fibrosis transmembrane regulator.  This has allowed us to begin to examine the molecular basis for ligand specificity among a variety of mammalian ORs.  In our initial OR publication (Abaffy et al., 2006), we completed the first analysis of all members of a mouse OR subfamily.  We found that while the individual receptive range for each member of this family is distinct, these receptive ranges overlap to form one contiguous subfamily receptor range.  In our next OR publication (Abaffy et al., 2007), we explored the structural basis for the differences in ligand preference between two members of this subfamily.  We combined mutagenesis and functional analysis with protein homology modeling and computational ligand docking to provide insight into the ability of these ORs to distinguish odorant ligands on the basis of small differences in ligand structure (a single carbon, in this case).  Currently, we are expanding our analysis of mammalian ORs by conducting detailed ligand screens of mouse ORs with known ligands (a small group), as well as by conducting large-scale screens of mouse, human and canine ORs with no known ligands (the vast majority).  In our structural work, we are using the Substituted Cysteine Accessibility Method (SCAM) to determine the orientation of transmembrane helices with respect to the ligand-binding pocket.  This is important because the transmembrane domains of many ORs are too divergent from rhodopsin and b-adrenergic receptors (the homology modeling templates) to be easily aligned on the basis of sequence comparison.  We are also currently collaborating with Doron Lancet’s group (Weizmann Institute of Science, Rehovot, Israel) to examine the contribution of ORs to variation in human olfactory sensitivities (Menashe et al., 2007), and with King Wai Yau’s group (Johns Hopkins University) to examine odorant selectivity among mouse ORs.

Support:
NIH, RO1 DC008119, “Ligand Recognition Among Mammalian Odorant Receptors”, P.I.: Charles W. Luetje
DARPA, 07-21-Add-8-FP-013, “Synthetic Olfaction for Real-World Applications”, L.S.I.: Paul Rhodes.

Insect Olfactory Receptors
            Recently, we have also become interested in insect olfactory receptors.  These receptors had long been assumed to be GPCRs, much like mammalian ORs.  However, recent work has challenged this assumption by demonstrating that insect ORs have a membrane topology that is divergent from that of GPCRs (Benton et al., 2006, PLoS Biology 4: e20) and that these receptors are ligand-gated ion channels (Sato et al., 2008, Nature 452: 1002-1006; Wicher et al., 2008, Nature 452: 1007-1011).  We are collaborating with Hugh Robertson’s group (University of Illinois at Urbana-Champaign) and Kevin Wanner’s group (Montana State University) to investigate the functional and structural properties of insect ORs.  We adapted our Xenopus oocyte assay for the characterization of insect ORs and have succeeded in making the first identification of a ligand-receptor pair in the honeybee (Wanner et al., 2007).  Our identification of the receptor for a honeybee sex pheromone represents the first identification of a pheromone-receptor pair in a social insect. We are currently exploring structural features of insect ORs using Drosophila ORs, using both conventional and SCAM mutagenesis approaches.  We are also pursuing projects to study the chemosensory receptors of several other insect species. 

Support:
USDA 2008-35302-18815, “Functional genomics of host seeking, host selection, and mating behavior in Nasonia vitripennis and the parasitic Hymenoptera”, P.D.: Hugh Robertson

Neuronal Nicotinic Receptors
            Neuronal nAChRs are of interest for several reasons.  Nicotinic ligands are potentially useful as anxiolytics and analgesics, and in the treatment of neurological disorders such as schizophrenia, Parkinson's disease, and Alzheimer's disease.  Neuronal nAChRs are also the sites at which nicotine exerts its psychoactive and addictive effects.  Thus, pharmacological intervention at neuronal nAChRs holds promise for treating the effects of diseases of the central nervous system and for understanding and treating addictive processes.  Critical to the realization of this potential is the development of selective nAChR ligands.  I first began working in this field as a postdoctoral fellow in Jim Patrick’s laboratory and I continued to pursue this interest when I started my own laboratory.  The early work in my laboratory focused on the agonist binding sites of these receptors, with a particular interest in identifying the determinants of receptor subtype selectivity.  With the availability of the atomic structure of the ACh Binding Protein in 2001, we began to incorporate protein homology modeling into our research efforts.
            More recently, we shifted our focus to the subunit-subunit interfaces, within heteromeric neuronal nAChRs, that do not bind agonist.  We found that some neuronal nAChRs are strongly potentiated by ionic zinc (Hsiao et al., 2001), which has recently emerged as an endogenous modulator of nervous system function.  We have localized the sites at which zinc potentiates neuronal nAChRs to subunit-subunit interfaces that alternate with those that bind ACh (Hsiao et al., 2006).  We have recently shown that zinc potentiates the whole cell current response by increasing the single channel burst duration (Hsiao et al., 2008).  Zinc potentiation sites of neuronal nAChRs are of considerable interest as they are analogous, both structurally and functionally, to the benzodiazepine binding sites of GABAA receptors.  As might be expected, we are keenly interested in identifying therapeutically useful compounds that act at the zinc binding sites of neuronal nAChRs. 
            We are currently exploring the structure and function of the zinc potentiation site with conventional mutagenesis, as well as the Substituted Cysteine Accessibility Method (SCAM).  We are also currently collaborating with Ivy Carroll’s group (Research Triangle Institute) to examine the functional effects of modifications to the structure of epibatidine (an exceptionally potent nicotinic agonist).

Support:
NIH, RO1 MH066038, “Potentiation of Neuronal Nicotinic Receptors by Zinc”, P.I.: Charles W. Luetje.

Recent Publications

Repicky, S.E., Luetje, C.W. (2008) Molecular receptive range variation among mouse odorant receptors for aliphatic carboxylic acids.  Manuscript in revision.

Hsiao, B., Mihalak, K.B., Magleby, K.L., Luetje, C.W. (2008) Zinc potentiates neuronal nicotinic receptors by increasing burst duration. Journal of Neurophysiology 99: 999-1007.

Menashe, I., Abaffy, T., Hasin, Y., Goshen, S., Yahalom, V., Luetje, C.W., Lancet, D. (2007) Genetic Elucidation of Human Hyperosmia to Isovaleric Acid. PLoS Biology 5: e284.

Wanner*, K.W., Nichols*, A.S., Walden, K.K.O., Brockmann, A., Luetje, C.W., Robertson, H.M. (2007) A honeybee odorant receptor for the queen substance 9-oxo-2-decenoic acid.  Proceedings of the National Academy of Sciences 104: 14383-14388. *equal contributions.

Abaffy, T., Malhotra, A., Luetje, C.W. (2007) The molecular basis for ligand specificity in a mouse olfactory receptor: A network of functionally important residues. Journal of Biological Chemistry 282: 1216-1224.

Shiembob, D.L., Roberts, R.L., Luetje, C.W., McIntosh, J.M. (2006) Determinants of alpha-conotoxin BuIA selectivity on the nicotinic acetylcholine receptor beta subunit. Biochemistry, 45:11200-11207.

Mihalak, K.B., Carroll, F.I., Luetje, C.W. (2006) Varenicline is a partial agonist at alpha4beta2 and a full agonist at alpha7 neuronal nicotinic receptors. Molecular Pharmacology, 70:801-805.

Abaffy, T., Matsunami, H., Luetje, C.W. (2006) Functional analysis of a mammalian odorant receptor subfamily. Journal of Neurochemistry 97: 1506-1518.

Hsiao, B., Mihalak, K.B., Repicky, S.E., Everhart, D., Mederos, A., Malhotra, A., Luetje, C.W. (2006) Determinants of zinc potentiation on the alpha4 subunit of neuronal nicotinic receptors. Molecular Pharmacology 69: 27-36.

• A more complete listing of the Luetje laboratory's publications is available.
• Coordinates for receptor models are available for download.

Current Lab Members

• Tatjana Abaffy, Research Assistant Professor
• Andy Nichols, Graduate Student
• Jakub Bartkowiak, Undergraduate Student
• Ana Mederos, Research Associate
• Yegor Isakov, Research Associate
• Vanessa Santos, Research Associate

Where Are They Now?
What's Become of Former Lab Members?

Sarah E. Repicky (graduate student 2004-2007) is currently a postdoctoral
fellow in Kendal Broadie¹s lab at Vanderbilt University.

Floyd Maddox (Research Technician Extraordinaire 1993-2006) is currently a Research Scientist II at Bristol-Myers Squibb in Princeton, New Jersey.

Karla Mihalak (Graduate Student 2001-2005) is currently a postdoctoral fellow in Karl Magleby's lab in the Department of Physiology and Biophysics at the University of Miami Miller School of Medicine.

Drew Everhart (Graduate Student 2000-2005) is currently a postdoctoral fellow in Robert Barlow's lab at SUNY Upstate Medical University in Syracuse, NY. 

Jeff Krajewski (Postdoctoral Fellow 2000-2003) is currently a Senior Research Scientist at Icagen, Inc. in Durham, North Carolina.

Armen Mirzoian (Postdoctoral Fellow 1999-2003) is currently an analytical chemist with the Alcohol, Tobacco Tax and Trade Bureau of the U.S. Treasury Department.

Bernie Hsiao (Graduate Student 1999-2002) is currently Chief Resident, Radiology/Nuclear Medicine, University of Miami.

Gilma Marimon (Undergraduate Student 1998-2000) is currently completing her medical residency.

Mike Parker (Graduate Student 1993-1999) is currently Chairman of Pharmacology at NOVA Southeastern University.

Ed Reiller (Graduate Student 1997-1999) is currently a Veterinarian in New York state.

Kevin Poth (Graduate Student 1991-1997) is currently a Research Biologist with the CDC and the San Diego County Health Department in San Diego, California.

Scott Harvey (Graduate Student 1991-1996) is currently a Pharmacist at the VA Hospital in San Diego, CA.

Javier Cuevas (Postdoctoral Fellow, 1995) is currently an Associate Professor in the Department of Pharmacology and Molecular Therapeutics, University of South Florida.