Click here for an Introduction for the Non-Biologist
The Mission of the lab is to understand the way in which actin polymerization is recruited for motility of bacterial pathogens.
Medical studies of bacterial diseases have traditionally focused on the behavior of the bacteria themselves and on the response of the host immune system to infection. However, recent advances in our understanding of the cell biology of host-pathogen relationships indicate that disease-causing bacteria have developed extraordinarily complex and subtle ways of communicating with the host. It is clear that infection is not a process performed solely by a bacterium, but rather an elaborately choreographed interaction between the bacterium and the host cell. Using a combination of videomicroscopy, biochemistry, and molecular genetics, we study the interactions between infectious bacteria and the human host cell cytoskeleton. By examining the mechanisms these bacteria use to communicate with the host cell cytoskeleton, we hope to identify new ways to interfere with the infection process, and arrive at a deeper understanding of the normal regulation of cytoskeletal shape changes and cell movement, which is important in a plethora of cellular processes, from development to metastasis to immune responses.
Listeria monocytogenes is a ubiquitous gram-positive bacterium that can cause serious food-borne infections in pregnant women, newborns, and immunocompromised adults. Shigella flexneri is an unrelated Gram-negative bacterium, a causative agent of bacillary dysentery. Both grow directly in the cytoplasm of infected host cells, and move rapidly throughout the infected cell using a remarkable form of actin-based motility. Within a few hours after infection, host cell actin filaments initially form a dense cloud around the intracytoplasmic bacteria, and then rearrange to form a polarized "comet tail," which is associated with all moving bacteria. The comet tail is made up of short actin filaments crosslinked into a meshwork in which the majority of filaments have their barbed (rapidly growing) ends oriented toward the bacterium. We have demonstrated that new actin filament polymerization occurs only at the front of the tail, adjacent to the surface of the bacterium, and that polymerization occurs at the same rate as bacterial propulsion. Bacteria spread from cell to cell by moving into long membrane-bound protrusions that are phagocytosed by neighboring cells. We have found that a single bacterial surface protein is necessary and sufficient for motility in each organism; ActA in L. monocytogenes and IcsA in Shigella flexneri. Surprisingly, these two proteins share no primary sequence similarity, though their functions are essentially identical. Neither bacterial protein exerts any direct influence on polymerization of pure actin; both must induce comet tail formation and actin-based motility through interactions with other host cell factors.
We have reconstituted motility of both pathogens in cell-free cytoplasmic extracts. We are currently attempting to identify host cell factors that interact with the bacterial proteins so that we can reconstitute motility in a defined biochemical system. Since ActA and IcsA appear to act through distinct biochemical mechanisms, we hope to learn more about the motility process by exploring the behaviors of both pathogens than we would by studying either one alone. Though many have looked, there is no evidence for a myosin or any other known motor protein involved in this form of actin-based motility. Instead, the force for bacterial movement is derived from actin polymerization itself. We are using biophysical, biochemical, mathematical and cell biological techniques to better understand how actin generates force, and hope to determine how actin polymerization contributes to force generation at the leading edge of motile eukaryotic cells.
Some Recent Work (click on picture for more information):
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Necessary and sufficient: ActA-coated beads with comet tails |
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Why pathogens move: Intercellular spread and actin-based motility |
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Fearful Symmetry: from symmetric actin cloud to asymmetric actin tail |
Selected Publications
* Yam PT and Theriot JA 2004. "Repeated Cycles of Rapid Actin Assembly and Disassembly on Epithelial Cell Phagosomes" Molecular Biology of the Cell.
15:5647. 
* Gibbs KA, Isaac DD, Xu J, Hednrix RW, Silhavy TJ, and
Theriot JA. 2004. "Complex spatial distribution and
dynamics of an abundant Escherichia coli outer membrane
protein, LamB." Molecular Microbiology.
53(6):1771.
* Harrison SC, Alberts B, Ehrenfeld E, Enquist L, Fineberg
H, McKnight SL, Moss B, O'Donnell M, Ploegh H, Schmid SL, Walter KP,
and Theriot J. 2004. "Perspective: Discovery of
antivirals against smallpox." Proceedings of the National
Academy of Sciences USA .
101(31):11178.
* Rafelski SM and Theriot JA. 2004. "Crawling
toward a unified model of cell motility: spatial and temporal
regulaton of actin dynamics." Annural Review of
Biochemistry. 73:209.
* Fiebig A and Theriot JA. 2004. "Bacteria make
tracks to the pole." Proceedings of the National Academy of
Sciences USA. 101(23):8510.
* Cameron LA, Robbins JR, Footer MJ, and Theriot JA.
2004. "Biophysical parameters influence actin-based movement,
trajectory, and initiation in a cell-free system."
Molecular Biology of the Cell.
15(5):2312.
* Lacayo CI and Theriot JA. 2004. "Listeria
monocytogenes actin-based motility varies depending on
subcellular location: a kinematic probe for cytoarchitecture."
Molecular Biology of the Cell.
15(5):2164.
* Karlin S, Theriot J, and Mrazek J. 2004.
"Comparative analysis of gene expression among low G+C gram-positive
organisms." Proceedings of the National Academy of Sciences
USA. 101(16):6182.
* Justice SS, Hung C, Theriot JA, Fletcher DA, Anderson GG,
Footer MJ, and Hultgren SJ. 2004. "Differentiation and
developmental pathways of uropathogenic Escherichia coli in
urinary tract pathogenesis." Proceedings of the National
Academy of Sciences USA.
101(5):1333.
* Golemi-Kotra D, Mahaffy R, Footer MJ, Holtzmann JH,
Pollard TD, Theriot JA, and Schepartz A. 2004. "High
affinity, paralog-specific recognition of the Mena EVH1 domain by a
miniature protein." Journal of the American Chemical
Society. 126(1):4.
* Ream RA, Theriot JA, and Somero GN. 2003.
"Influences of thermal acclimation and acute temperature change on
the motility of epithelial wound-healing cells (keratocytes) of
tropical, temperate and Antarctic fish." Journal of
Experimental Biology.
206(Pt 24):4539.
* Robbins JR and Theriot JA. 2003. "Listeria
monocytogenes rotates around its
long axis during actin-based motility." Current
Biology. 13(19):R754.
* Auerbuch V, Loureiro JJ, Gertler FB, Theriot JA, and
Portnoy DA. 2003. "ENA/VASP proteins contribute to
Listeria monocytogenes
pathogenesis by controlling temporal and spatial persistence of
bacterial actin-based motility." Molecular
Microbiology. 49(5):1361.
* Giardini PA, Fletcher DA, and Theriot JA.
2003. "Compression forces generated by actin comet tails on
lipid vesicles." Proceedings of the National Academy of
Sciences USA. 100(11):6493.
* Baldwin DN, Vanchinathan V, Brown PO, and Theriot
JA. 2003. "A gene-expression program reflecting the
innate immune response of cultured intestinal epithelial cells to
infection by Listeria monocytogenes."
Genome Biology.
4(1):R2.
* Rafelski SM and Theriot JA. 2001. "A hitchhiker's
guide to cell biology: exploitation of host-cell functions by
intracellular pathogens." Genome Biology.
3(3):REPORTS4006.
* Lauer P, Theriot JA, Skoble J, Welch MD, and Portnoy
DA. 2001. "Systematic mutational analysis of the
amino-terminal domain of the Listeria monocytogenes
ActA protein reveals novel functions in actin-based motility."
Molecular Microbiology.
42(5):1163-77.
* Giardini, P.A. and Theriot, J.A. 2001. "Effects
of intermediate filaments on actin-based motility of Listeria
monocytogenes." Biophysical Journal. 81(6):3193-203.
* Monack, D. and Theriot, J.A. 2001. "Actin-based
motility is sufficient for bacterial membrane protrusion and host
cell uptake." Cellular Microbiology.
3(9):633-47.
* Robbins, J.R., Monack, D., McCallum, S.J., Vegas, A., Pham,
E., Goldberg, M.B., and Theriot, J.A. 2001. "The making
of a gradient: IcsA (VirG) polarity in Shigella flexneri." Molecular
Microbiology. 41(4):861-72.
* Cameron, L.A., Svitkina, T.M., Vignjevic, D., Theriot, J.A. and
Borisey, G.G. 2001. "Dendritic organization of actin comet
tails." Current Biology.
11(2):130 - 135.
* Cameron, L.A., Giardinia, P.A., Soo, F.S. and Theriot, J.A.
2000. "Secrets of actin-based motility revealed by a bacterial
pathogen." Nature Reviews in Molecular and Cell
Biology. 1(2):110 - 119.
* Theriot, J.A. 2000. "The polymerization motor. "
Traffic. 1(1):19 - 2.
* van Oudenaarden, A. and Theriot, J.A. 1999. "Cooperative
symmetry-breaking by actin filament polymerization in a model for
cell motility. " Nature Cell Biology.
1(8):493-499.
* Robbins, J.R., Barth, A.I., Marquis H., de Hostos, E., Nelson, W.J.
and Theriot, J.A. 1999. "Listeria monocytogenes exploits natural host processes and
structure to spread from cell to cell." Journal of Cell
Biology. 146(6):1333-49.
* Cameron, L.A., Footer, M.J., van Oudenaarden, A., and Theriot, J.A.
1999. "Motility of ActA protein-coated microspheres driven by actin
polymerization." Proceedings of the National Academy of
Sciences. 96: 4908-13.
* Fung, D. C. and Theriot, J. A. 1998. "Movement of bacterial
pathogens driven by actin polymerization." In Motion Analysis of
Living Cells, (John Wiley & Sons), D. Soll, ed.,
pp. 157-176.
* Smith, G. A., Theriot, J. A., and Portnoy, D. A. 1996. "The tandem
repeat domain in the Listeria monocytogenes ActA protein controls the
rate of actin-based motility, the percentage of moving bacteria, and
the localization of vasodilator-stimulated phosphoprotein and
profilin." Journal of Cell Biology,
135: 647-660.
* Goldberg, M. B. and Theriot,J. A. 1995. "Shigella flexneri surface protein IcsA is sufficient to
direct actin-based motility." Proceedings of the National
Academy of Sciences USA,
92: 6572-6576.
* Smith, G. A., Portnoy, D. A., and Theriot, J. A. 1995. "Asymmetric
distribution of the Listeria monocytogenes
ActA protein is required and sufficient to direct actin-based
motility." Molecular Microbiology,
17: 945-951.
* Theriot, J. A. 1995. "The cell biology of infection by
intracellular bacterial pathogens." Annual Review of Cell and
Developmental Biology,11: 213-239.
* Theriot, J. A., Rosenblatt, J., Portnoy, D. A.,
Goldschmidt-Clermont, P. J. and Mitchison, T. J. 1994. "Involvement
of profilin in the actin-based motility of Listeria
monocytogenes in cells and in
cell-free extracts." Cell, 76: 505-517.
* Theriot, J. A., Mitchison, T. J., Tilney, L. G. and Portnoy, D. A.
1992. "The rate of actin-based motility of intracellular Listeria
monocytogenes is equal to the
rate of actin polymerization." Nature,
357: 257-260.
* Theriot, J. A. and Mitchison, T. J. 1991. "Actin microfilament dynamics
in locomoting cells" Nature,
352: 126-131.