Theodore G. Wensel, Ph.D.
Department of Biochemistry and Molecular Biology
Robert A. Welch Chair in Chemistry
Department of Biochemistry and Molecular Biology
Department of Neuroscience
Department of Ophthalmology
Department of Pharmacology
- Ph.D., Chemistry, 1984, University of California, Davis
- Postdoctoral, 1984-1988, Stanford University
Molecular Mechanisms of Signal Transduction in Healthy and Degenerating Neurons
The interests in the laboratory are broadly in the area of signal transduction mediated by heterotrimeric G proteins, with emphases on phototransduction in the vertebrate retina and on slow neurotransmission in the brain. Our interests encompass understanding these processes at the molecular and atomic levels, and using this knowledge to develop new approaches to understanding and treating human disease. Our approach is highly interdisciplinary and collaborative, spanning the range from determination of atomic structures by x-ray crystallography to electrophysiological and behavioral studies of genetically engineered animals.
Transducin interactions with photoreceptor membranes
This project is a detailed study of the structure, function, and dynamics of membrane-associated proteins that mediate the phototransduction cascade. To determine the structures of signal transducing membrane complexes, we are using: x-ray crystallography, electron crystallography and single particle analysis, molecular modeling, fluorescence resonance energy transfer, site-directed spin labeling and electron spin resonance spectroscopy, and mass spectrometry. To understand the dynamics of signal transducing membrane complexes we are using fluorescence recovery after photobleaching on intact photoreceptor cells of transgenic Xenopus laevis, and on recombinant proteins in vitro, as well as stopped-flow, flash-photolysis, and other rapid kinetic techniques. To understand the role of membrane lipids we are using reconstitution with defined lipid vesicles and chromatographic and mass spectrometric analysis of native membranes.
RGS domain function in the mammalian retina
Our laboratory was the first to discover the activity of a family of proteins known as Regulators of G Protein Signaling, or RGS proteins, which has now become a major sub-field of G protein signaling. In the retina our focus is on retinal isoforms of RGS9 and RGS7. We use mouse and frog transgenesis, mouse knockouts, x-ray crystallography, electron microscopy, biochemistry, membrane reconstitution, mutagenesis, and mass spectrometry. A increasingly important part of this project is accurate mathematical modeling of light responses based on measured biochemical properties. We believe rod cells are the first mammalian neuron for which a complete molecular description of signaling can be achieved, and that this effort will serve as a model for understanding other G protein pathways in less tractable settings.
RGS domain function in the mammalian brain
One isoform of RGS9, RGS9-2, is specific for the striatum, a part of the brain involved in dopamine signaling, the reward and reinforcement system, and movement control, and RGS9-knockouts show enhanced susceptibility to drugs of abuse. We are using biochemical, immunochemical, and proteomic approaches with our knockout and transgenic mice to unravel the signaling pathways it regulates. We are also studying the related RGS7, which is expressed throughout the brain.
ABCR function in macular degeneration
We are collaborating with Jim Lupski's lab (BCM Human & Molecular Genetics) to determine the function of the retinal ATP-binding cassette transporter, ABCR, and the functional consequences of mutations known from human genetics to cause retinal degeneration and blindness. We are using biochemistry, spectrophotometry, and transgenic Xenopus to solve this problem.
Evolution-based mutagenesis of G-protein coupled receptors
We are collaborating with Olivier Lichtarge (BCM Human & Molecular Genetics) to use his bioinformatics method, the Evolutionary Trace, to design, construct, and assay, new G protein coupled receptors with novel specificities
Gene-based therapy for hereditary retinal degeneration
Collaborating with John Wilson (BCM Biochemistry) we have developed mouse knock-in reporter models for assessing gene-based therapies for hereditary retinal degenerative disorders, and are testing them with viral and oligonucleotide therapies.
Light striking the retina activates the photon receptor, rhodopsin (R*), which in turns activates the alpha subunit of the G protein, transducin (Gt). Gt turns on a cGMP-specific phosphodiesterase (PDE), which rapidly lowers cellular cGMP. A Low concentration of cGMP causes plama membrane cation channels to close, hyperpolarizing the cell and inhibiting neurotransmitter release at the synapse.
As it transduces signals, the G protein shuttles among different membrane-bound complexes. In the dark, it is bound to beta-gamma subunits and GDP; light causes transient binding to R*, which catalyzes the exchange of GDP exchange for GTP; Gt-GTP activates the PDE, which, together with a GTPase activating protein (GAP), accelerates return of Gt to the dark GDP state.
- Gilliam, J. C. Wensel, T. G. 2011. TRP channel gene expression in the mouse retina. Vision Res. 51:2440-52.
- Price, B. A., Sandoval, I. M., Chan, F., Simons, D. L., Wu, S. M., Wensel, T. G., Wilson, J. H. 2011. Mislocalization and degradation of human P23H-rhodopsin-GFP in a knock-in mouse model of retinitis pigmentosa. Invest Ophthalmol Vis Sci. 52(13):9728-36.
- Chan, F., Hauswirth, W. W., Wensel, T. G., Wilson, J. H. 2011. Efficient mutagenesis of the rhodopsin gene in rod photoreceptor neurons in mice. Nucleic Acids Res. 39: 5955-5966.
- Moiseenkova-Bell, V., Wensel, T.G. 2011. Functional and structural studies of TRP channels heterologously expressed in budding yeast. Adv Exp Med Biol. 704:25-40.
- Mojumder, D. K., Concepcion, F. A., Patel, S. K., Barkmeier, A. J., Carvounis, P. E., Wilson, J. H., Holz, E. R., Wensel, T. G. 2010. Evaluating retinal toxicity of intravitreal caspofungin in the mouse eye. Invest. Ophthalmol. Vis. Sci. 51: 5796-5803.
- Budzynski, E, Gross, A. K., McAlear, S. D., Peachey, N. S., Shukla, M., He, F., Edwards, M., Won, J. Hicks, W. L., Wensel, T. G., Naggert, J. K., Nishina, P. M. 2010. Mutations of the opsin gene (Y102H and I307N) in mice lead to light induced degeneration of photoreceptors and constitutive activation of phototransduction. J. Biol. Chem. 285:14521-14533.
- Rodriguez, G. J., Yao, R., Lichtarge, O., Wensel, T. G. 2010. Evolution-guided discovery and recoding of allosteric pathway specificity determinants in psychoactive bioamine receptors. Proc. Nat. Acad. Sci. USA. 107:7787-792.
- Mojumder, D. K., Wensel, T. G. 2010. Topical mydriatics Topical mydriatics affect light-evoked retinal responses in anesthetized mice. Invest. Ophthalmol. Vis. Sci. 51:567-76
- Manucso, J. J., Qian, Y., Long, C. Wu, G.-Y., Wensel, T. G. 2010. Distribution of RGS9-2 in neurons of the mouse striatum J. Neurochem. 112:651-661
- Yao, C.-K., Lin, Y. Q, Ly, C. V. Ohyama, T., Haueter, C. M., Moiseenkova-Bell, V. Y., Wensel, T. G., Bellen, H. J. 2009. A synaptic vesicle- and presynaptic membrane-associated ion channel regulates resting Ca2+ levels and synaptic endocytosis. Cell, 138:947-60.