Joseph T. Barbieri, PhD
Professor
Microbiology and Molecular Genetics
Medical College of Wisconsin
Research Focus: Microbial Pathogenesis
PhD: University of Massachusetts, Amherst (1980) Microbiology
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I am interested in understanding the molecular basis of microbial pathogenesis in an area of study termed Cellular Microbiology where components of both the pathogen and host are analyzed to understand the pathogenic process. My research involves the study of bacterial toxins. Currently two families of toxins are under investigation in my laboratory: the botulinum neurotoxins and ExoS, a type III cytotoxin of Pseudomonas aeruginosa. Studies on bacterial toxins have evolved from understanding their mechanism of action to develop novel strategies to produce vaccines and therapies against their action.
ExoS is a bi-functional type III cytotoxin and includes a RhoGAP domain and an ADP-ribosyltransferase domain that inactive Rho GTPases and Ras GTPases, respectively. The outcome of ExoS action on mammalian cells is to inactivate the actin cytoskeleton to interfere with host cells phagocytosis of P. aeruginosa. Our current research involves the study of two aspects of ExoS. First, we are interested in understanding how ExoS traffics within the host cells. We have recently determined that ExoS possesses a localization domain that allows the toxin to usurp the host endocytic machinery to traffic to both Rho- and Ras- GTPases. Without this trafficking, ExoS can not locate these targets within the cell. A model for how ExoS traffics on vesicles in mammalian cells is shown in Figure 1. We are also interested in understanding how ExoS and a related toxin, ExoT, recognize their specific substrates. Although ExoS and ExoT share 76% primary amino acid homology, the two protein target completely different host proteins.
The Clostridium neurotoxins (BoNTs) are the most potent protein toxins for humans and are Category A toxins. There are seven serotypes of BoNTs, termed A-G, with serotypes A, B, E, and F responsible for most natural human disease. BoNTs are single chain A-B toxins that are organized into three specific domains. The N-terminal zinc protease domain is link by a disulfide bond to the C-terminal domain heavy chain which comprises a translocation domain and a C-terminal receptor binding domain. BoNT toxicity for neurons is due to toxin's affinity for neuron specific receptors and for the substrates that the toxin cleaves either v- or t- SNAREs. Cleavage of v- or t- SNAREs yields flaccid paralysis that is observed in botulism. We are interested in understanding how BoNT interacts with neurons and how the BoNT recognize their specific substrates. These studies use biochemical and cell biological approaches. We are studying how BoNTs bind peripheral neurons and have observed that BoNTs bind to a neuronal synaptic vesicle protein complex, which included SV2, synaptotagmin, synaptophysin, VAMP, and a vacuolar proton pump. We are characterizing the interaction of the BoNTs with these neuronal proteins. We are also studying how BoNTs recognize and cleave their v- and t- SNARE substrates. We have identified a pocket model for the recognition of BoNT/A for SNAP25. A model for the recognition steps of BoNT/A for SNAP25 is shown in Figure 2. We are currently refining this model and addressing how other BoNT serotypes recognize their substrates. These studies will develop novel strategies for vaccine and therapies against botulism.
Figure 1. Trafficking of ExoS in mammalian cells (from Deng, Zhang, and Barbieri, Traffic, 2007 In Press).
Figure 2. How BoNT/A recognizes SNAP25 (from Chen, Kim, and Barbieri, Journal of Biological Chemistry, 2006).
Recent Publications
Chen S, Hall C, Barbieri JT. Substrate Recognition of VAMP-2 by Botulinum Neurotoxin B and Tetanus Neurotoxin. J Biol Chem. 2008 Jul 25;283(30):21153-9. Epub 2008 May 29.
Abstract
Chen C, Baldwin MR, Barbieri JT. Molecular basis for tetanus toxin coreceptor interactions. Biochemistry. 2008 Jul 8;47(27):7179-86. Epub 2008 Jun 11.
Abstract
Baldwin MR, Tepp WH, Przedpelski A, Pier CL, Bradshaw M, Johnson EA, Barbieri JT. Subunit vaccine against the seven serotypes of botulism. Infect Immun. 2008 Mar;76(3):1314-8. Epub 2007 Dec 10.
Abstract
Pier CL, Tepp WH, Bradshaw M, Johnson EA, Barbieri JT, Baldwin MR. Recombinant holotoxoid vaccine against botulism. Infect Immun. 2008 Jan;76(1):437-42. Epub 2007 Oct 29.
Abstract
Deng Q, Zhang Y, Barbieri JT. Intracellular Trafficking of Pseudomonas ExoS, a Type III Cytotoxin. Traffic. 2007 Oct;8(10):1331-45. Epub 2007 Aug 20.
Abstract
Chen S, Barbieri JT. Multi-pocket recognition of SNAP25 by botulinum neurotoxin serotype E. J Biol Chem. 2007 Aug 31;282(35):25540-7. Epub 2007 Jul 3.
Abstract
Zhang Y, Deng Q, Porath JA, Williams CL, Pederson-Gulrud KJ, Barbieri JT. Plasma membrane localization affects the RhoGAP specificity of Pseudomonas ExoS. Cell Microbiol. 2007 Sep;9(9):2192-201. Epub 2007 May 8.
Abstract
Zhang Y, Deng Q, Barbieri JT. Intracellular localization of type III-delivered Pseudomonas ExoS with endosome
vesicles. J Biol Chem. 2007 Apr 27;282(17):13022-32. Epub 2007 Feb 20.
Abstract
Chen S, Kim JJ, Barbieri JT. Mechanism of substrate recognition by botulinum neurotoxin serotype A. J Biol Chem. 2007 Mar 30;282(13):9621-7. Epub 2007 Jan 23.
Abstract
Baldwin MR, Barbieri JT. Association of botulinum neurotoxin serotypes a and B with synaptic vesicle
protein complexes. Biochemistry. 2007 Mar 20;46(11):3200-10. Epub 2007 Feb 21.
Abstract
Eubanks LM, Hixon MS, Jin W, Hong S, Clancy CM, Tepp WH, Baldwin MR, Malizio CJ, Goodnough MC, Barbieri JT, Johnson EA, Boger DL, Dickerson TJ, Janda KD. An in vitro and in vivo disconnect uncovered through high-throughput identification of botulinum neurotoxin A antagonists. Proc Natl Acad Sci U S A. 2007 Feb 20;104(8):2602-7. Epub 2007 Feb 9.
Abstract
Baldwin MR, Kim JJ, Barbieri JT. Botulinum neurotoxin B-host receptor recognition: it takes two receptors to tango. Nat Struct Mol Biol. 2007 Jan;14(1):9-10.
Abstract
Maresso AW, Deng Q, Pereckas MS, Wakim BT, Barbieri JT. Pseudomonas aeruginosa ExoS ADP-ribosyltransferase inhibits ERM phosphorylation. Cell Microbiol. 2007 Jan;9(1):97-105. Epub 2006 Aug 2.
Abstract
Fu Z, Chen S, Baldwin MR, Boldt GE, Crawford A, Janda KD, Barbieri JT, Kim
JJ. Light chain of botulinum neurotoxin serotype A: structural resolution of a catalytic intermediate. Biochemistry. 2006 Jul 25;45(29):8903-11.
Abstract
Boldt GE, Kennedy JP, Hixon MS, McAllister LA, Barbieri JT, Tzipori S, Janda KD. Synthesis, characterization and development of a high-throughput methodology for the discovery of botulinum neurotoxin a inhibitors. J Comb Chem. 2006 Jul-Aug;8(4):513-21.
Abstract
Chen S, Barbieri JT. Unique substrate recognition by botulinum neurotoxins serotypes A and E. J Biol Chem. 2006 Apr 21;281(16):10906-11. Epub 2006 Feb 14.
Abstract
Zhang Y, Barbieri JT. A leucine-rich motif targets Pseudomonas aeruginosa ExoS within mammalian cells. Infect Immun. 2005 Dec;73(12):7938-45.
Abstract
Baldwin MR, Tepp WH, Pier CL, Bradshaw M, Ho M, Wilson BA, Fritz RB, Johnson EA, Barbieri JT. Characterization of the antibody response to the receptor binding domain of botulinum neurotoxin serotypes A and E. Infect Immun. 2005 Oct;73(10):6998-7005.
Abstract
Deng Q, Sun J, Barbieri JT. Uncoupling crk signal transduction by pseudomonas exoenzyme T. J Biol Chem. 2005 Oct 28;280(43):35953-60. Epub 2005 Aug 25.
Abstract
Corech R, Rao A, Laxova A, Moss J, Rock MJ, Li Z, Kosorok MR, Splaingard ML, Farrell PM, Barbieri JT. Early immune response to the components of the type III system of Pseudomonas aeruginosa in children with cystic fibrosis. J Clin Microbiol. 2005 Aug;43(8):3956-62.
Abstract
Baldwin MR, Barbieri JT. The type III cytotoxins of Yersinia and Pseudomonas aeruginosa that modulate the actin cytoskeleton. Curr Top Microbiol Immunol. 2005;291:147-66. Review.
Abstract
Aktories K, Barbieri JT. Bacterial cytotoxins: targeting eukaryotic switches. Nat Rev Microbiol. 2005 May;3(5):397-410. Review.
Abstract
Contact Information
Email: jtb01@mcw.edu
Phone: 414-456-8412
Room: BSB-256