Chemistry Faculty:
Timothy M. Dore, Ph.D.

Associate Professor

E-mail: tdore@chem.uga.edu

Biographical Information

B.S., University of North Carolina at Chapel Hill, 1990
Ph.D., Stanford University, 1998
Postdoctoral Associate, Howard Hughes Medical Institute, University of California, San Diego, 1998-2000

Research Interests

The overall objective of my laboratory's research is to develop new methods of studying cellular function. The research embraces chemistry and biology, using organic synthesis as a tool for understanding, controlling, and manipulating cell physiology. In an approach that is complementary to genetic techniques, small organic molecules can be designed and synthesized to probe biological systems, thereby providing information about how they work. Understanding the mechanisms of cellular function appends our knowledge of the diversity and complexity of life and is necessary for medical intervention in disease states. The work is multidisciplinary in nature, involving organic synthesis, biochemistry, photophysics applied in a biological context, and some molecular and cellular biology. The research program has thrusts in three major areas: photochemistry, kinesin motor proteins, and CaaX proteins.

The photochemistry research program seeks to develop new technology that will enable less invasive methods of studying cellular function. My laboratory is interested in synthesizing, studying, and developing applications for photochemically active molecules, particularly ones with sensitivity to multiphoton excitation (MPE). One approach to controlling and manipulating cell chemistry is through the use of a photolabile protecting group to "cage" a physiologically active messenger, then release it with a flash of light. MPE of a photolabile protecting group provides exquisite spatial and temporal control of the uncaging event, because the active messenger is released only at the focus of the laser beam (~1 (µm)³). It is a particularly non-invasive method because it utilizes low energy infrared light, which minimizes tissue destruction, light absorption, and scattering, allowing much deeper and more accurate penetration into complex tissue samples than can be achieved with UV light. We have invented 8-bromo-7-hydroxyquinoline (BHQ), an MPE-sensitive caging group for use in vivo, and shown that Bhc-diol can be used as an MPE-sensitive caging group for ketones and aldehydes. These molecules will fuel efforts to answer questions about the temporal and spatial relevance of signaling by physiological messengers. For example, we have created Bhc-Anisomycin, which can be utilized to photo-regulate ribosomal protein synthesis in mammalian cell culture. Other applications include the precise delivery of neurotransmitters, signaling peptides, proteins, DNA, RNA, drugs, and other biological effectors into cells, tissue samples, and whole animals with exquisite temporal and spatial selectivity. There are many chemical applications for this research, especially in the area of combinatorial chemistry. Because of the spatial selectivity of the reaction, it represents a potential technology for microarraying oligonucleotide, peptide, oligosaccharide, and small organic molecule libraries onto "chips" for diagnostic applications.

The kinesin motor proteins are critical for many cellular functions, including cell division, vesicle and organelle transport, and motility. Kinesin motors consist of two identical ~960 amino-acid chains that contain an N-terminal globular motor domain, a central alpha-helical region, and a C-terminal tail that binds light chains, which mediate binding to the cargo. An ATP binding site on the motor domain is the source of ATPase activity, which is used to convert chemical energy into mechanical motion. Kinesin walks along microtubules processively, where the motor domains make alternate contact with the microtubules. There are many questions related to the function of individual members of these families of proteins that could be answered if there existed specific membrane permeant small molecule inhibitors. For example, selectively abolishing activity in vivo to a family of kinesins while retaining function in other families would provide insight into enzyme mechanism that cannot be obtained from genetic approaches utilizing transgenic or knockout organisms and mutant proteins. Outside of nucleotide analogs, which are nonspecific, very few molecules exist that specifically inhibit motor proteins at low concentrations. Adociasulfate-2 (AS-2) from the Haliclona sp. sea sponge inhibits microtubule-stimulated kinesin ATPase activity (IC₅₀ = 2.7 µM) by mimicking microtubules. Through computational and biochemical studies of AS-2 and kinesin, my laboratory has developed an understand of how AS-2 inhibits the ATPase activity of kinesin. Ultimately, we want to design and synthesize potent and specific, small-molecule inhibitors of kinesins.

CaaX proteins have important functions in diverse cellular processes, such as signaling (Ras, Rac, RhoB), protein folding (Hsp chaperones), and fungal mating (Saccharomyces cerevisiae a-factor). This motif is also found in some nuclear proteins (CENP-E, CENP-F, and nuclear lamins). They all possess the CaaX structural motif: a C-terminal tetrapeptide sequence with the amino acid cysteine (C), two aliphatic amino acids (aa), followed by any amino acid (X). Activation of CaaX proteins occurs by three post-translational modifications: attachment of an isoprenoid or lipid to the cysteine thiol, proteolytic cleavage of the last three amino acids, and addition of a methoxy group to the C-terminal cysteine. The Ras signaling molecule is an important CaaX protein because activating mutations of it are common in cancerous cells (30% of all cancers, 70% of all solid tumors, and 90% of pancreatic tumors). Ras converting enzyme (Rce1p) is an ER-localized membrane protein, involved in the activation of Ras, that cleaves the peptide bond between the cysteine and aaX portion of the motif by an unknown mechanism. The structure of Rce1p is also unknown. In collaboration with the laboratory of Walter Schmidt in the Department of Biochemistry and Molecular Biology at UGA, we are formulating an inhibitor profile of Rcelp. We aim to use this profile to design and synthesize compounds that will potentially act as leads for the development of new anti-cancer therapeutics.

Publications

Porter, S. B.; Hildebrandt, E. R.; Breevoort, S. R.; Dore, T. M.; Schmidt, W. K. "Inhibition of the CaaX proteases Rce1p and Ste24p by peptidyl (acyloxy)methyl ketones." Biochim. Biophys. Acta Mol. Cell Res. 2007. In press.

Reddie, K. G.; Roberts, D. R.; Dore, T. M. "Inhibition of Kinesin Motor Proteins by Adociasulfate-2" J. Med. Chem. 2006, 49, 4857-4860.

Zhu, Y.; Pavlos, C. M.; Toscano, J. P.; Dore, T. M. "8-Bromo-7-hydroxyquinoline as a Photoremovable Protecting Group for Physiological Use: Mechanism and Scope." J. Am. Chem. Soc. 2006, 128, 4267-4276.

Goard, M. P.; Aakalu, G.; Fedoryak, O. D.; Quinonez, C.; St. Julien, J.; Poteet, S. J.; Schuman, E.M.; Dore, T. M. "Light Mediated Inhibition of Protein Synthesis." Chem. Biol. 2005, 12, 685-693.

Dore, T. M. "Multiphoton Phototriggers for Exploring Cell Physiology." In Dynamic Studies in Biology: Phototriggers, Photoswitches, and Caged Biomolecules; Goeldner, M.; Givens, R. S., Eds.; Wiley-VCH: Weinheim, Germany, 2005; pp 435-459.

Lu, M.; Fedoryak, O.D.; Moister, B.R.; Dore, T.M. "Bhc-diol as a Photolabile Protecting Group for Aldehydes and Ketones." Org. Lett. 2003, 5, 2119-2122.

Fedoryak, O.D.; Dore, T.M. "Brominated Hydroxyquinoline as a Photolabile Protecting Group with Sensitivity to Multiphoton Excitation." Org. Lett. 2002, 4, 3419-3422.

Golde, C. M; Dore, T. M. "The Survey of Doctoral Education and Career Preparation: The Importance of Disciplinary Contexts." In Paths to the Professoriate: Strategies for Enriching the Preparation of Future Faculty; Wulff, D. H.; Austin, A. E., Eds.; Jossey-Bass: San Francisco, 2003; pp 19-45.

Golde, C. M.; Dore, T. M. (2001) "At Cross Purposes: What the experiences of today's doctoral students reveal about doctoral education." http://www.phd-survey.org/

Furuta, T.; Takeuchi, H.; Takahashi, Y.; Sugimoto, M.; Dore, T. M.; Kanehara, M.; Watanabe, T.; Kurahashi, T.; Iwamura, M.; Tsien, R. Y. "Bhc-cNMPs as Either Water-Soluble or Membrane-Permeant Caged Cyclic Nucleotides." ChemBioChem 2004, 5, 1119-1128.

Dooley, C. T.; Dore, T. M.; Hanson, G. T.; Jackson, W. C.; Remington, S. J.; Tsien, R. Y. "Imaging Dynamic Redox Changes in Mammalian Cells with Green Fluorescent Protein Indicators." J. Biol. Chem. 2004, 279, 22284-22293.

Furuta, T.; Wang, S. S.-H.; Dantzker, J. L.; Dore, T. M.; Bybee, W. J.; Callaway, E. M.; Denk, W.; Tsien, R. Y. "Brominated 7-Hydroxycoumarin-4-ylmethyls: Novel Photolabile Protecting Groups with Biologically Useful Cross-sections for Two Photon Photolysis." Proc. Natl. Acad. Sci. U.S.A. 1999, 96, 1193-1200.

Wender, P. A.; Dore, T. M. "A Formal Synthesis of Crinipellin B Based on the Arene-Alkene meta-Photocycloaddition Reaction." Tetrahedron Lett. 1998, 39, 8589-8592.

Wender, P. A.; Dore, T. M.; deLong, M. A. "An Arene-Alkene Photocycloaddition-Radical Cyclization Cascade: The First Syntheses of cis,cis,cis,trans-[5.5.5.5]-Fenestranes." Tetrahedron Lett. 1996, 37, 7687-7690.

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