I. Protein Polymers, Crawling Cells and Comet Tails
II. Mechanics and Dynamics of Rapid Cell Motility
III. Evolution of a Dynamic Cytoskeleton
Part II: Mechanics and Dynamics of Rapid Cell Motility
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|iBiology Archives: Julie Theriot iBioSeminar (2006)|
In Part 1 of her video, Dr. Theriot explains how tiny, nanometer sized actin molecules can self-assemble into filaments that are hundreds of microns in length. These actin filaments are constantly growing and shrinking and this dynamic behavior allows a network of actin to generate enough force to move a cell forward. The intracellular bacterial pathogen Listeria monocytogenes uses actin polymerization to propel itself through the cytoplasm and to invade other cells. Many years of studies using Listeria have allowed Theriot and others to dissect the regulation of actin network growth in Listeria “comet tails” and at the leading edge of crawling cells.
In her second lecture, Theriot explains that fish keratocytes are an excellent system to study rapid cell motility. By labeling actin and myosin in keratocytes, Theriot and her colleagues were able to follow turnover of actin in the lamellipodium. Unexpectedly, they found that myosin II plays in important role in actin disassembly at the rear of the cell and asymmetric localization of myosin at the back of the cell appears to govern cell turning. Similar mechanisms of actin and myosin cooperation seem to drive rapid movement in both fish keratinocytes and human neutrophils.
It has been known since the early 1990s that bacteria have homologues of both actin and tubulin. In general, however, bacteria are much simpler than eukaryotes. In her final lecture, Theriot speculates about the factors that have evolved to allow eukaryotes to modify their cytoskeletons and build bigger, morphologically complex, multicellular organisms.
Julie Theriot attended college at the Massachusetts Institute of Technology, graduating with degrees in Physics and Biology. She pursued graduate training at the University of California, San Francisco, earning her Ph.D. in Cell Biology in 1993. After four years as a Fellow at the Whitehead Institute for Biomedical Research, Theriot moved to Stanford University School of Medicine where she is currently a Professor of Biochemistry and of Microbiology and Immunology. Since 2008, Theriot has also been an Investigator of the Howard Hughes Medical Institute.
Theriot's research focuses on how interactions at the molecular level determine cell behavior, in particular, how cells change their shape or direction of movement. Theriot has received numerous awards for her work including fellowships from both the David and Lucile Packard Foundation and the John D. and Catherine T. MacArthur Foundation. She has also been recognized for her exceptional teaching.
- Carlos Bustamante iBioSeminar: Biochemistry in Singulo: When Less Means More
- Pascale Cossart iBioSeminar: The Bacterial Pathogen Listeria Monocytogenes
- Hugh Huxley iBioMagazine: How Muscle Contracts
- Anthony Hyman iBioSeminar: Building a Polymer: Microtubule Dynamics
- Christine Jacobs-Wagner iBioSeminar: The Spatial Organization of Bacterial Cells
- Tim Mitchison iBioSeminar: Self Organization of Microtubule Assemblies
- Thomas Pollard iBioSeminar: Cell Motility and Cytokinesis
- Michael Rosen iBioMagazine: Physical Mechanisms of Cell Organization on Micron Length Scales
- Julie Theriot iBioMagazine: Discovering Design Principles for Cells and Organisms
- Ron Vale iBioSeminar: Cytoskeletal Motor Proteins
Alberts B, Johnson A, Lewis J, Raff M, Roberts K, and Walter P. (2002) Molecular Biology of the Cell 4th Edition, New York: Garland Science. Chapter 16.
Cameron LA, Giardini PA, Soo FS, Theriot JA. (2000) Secrets of actin-based motility revealed by a bacterial pathogen. Nat. Rev. Mol. Cell Biol. 1:110-9.
Pollard TD, Blanchoin L, Mullins RD. (2001) Actin dynamics. J Cell Sci. 114(Pt 1):3-4.
Mogilner A, Oster G. (2003) Force generation by actin polymerization II: the elastic ratchet and tethered filaments. Biophys J. 84:1591-605.
Hamon M, Bierne H, Cossart P. (2006) Listeria monocytogenes: a multifaceted model. Nature Rev. Microbiol. 4:423-34.
Wilson CA, Tsuchida MA, Allen GM, Barnhart EL, Applegate KT, Yam PT, Ji L, Keren K, Danuser G, Theriot JA. (2010) Myosin II contributes to cell-scale actin network treadmilling through network disassembly. Nature. 465(7296):373-7.
Keren K, Pincus Z, Allen GM, Barnhart EL, Marriott G, Mogilner A, Theriot JA. (2008) Mechanism of shape determination in motile cells. Nature. 453(7194):475-80.
Yam PT, Wilson CA, Ji L, Hebert B, Barnhart EL, Dye NA, Wiseman PW, Danuser G, Theriot JA. (2007) Actin-myosin network reorganization breaks symmetry at the cell rear to spontaneously initiate polarized cell motility. J Cell Biol. 178(7):1207-21.
Garner EC, Campbell CS, Mullins RD. (2004) Dynamic instability in a DNA-segregating prokaryotic actin homolog. Science. 306:987-9.
Cabeen MT, Jacobs-Wagner C. (2010) The bacterial cytoskeleton. Annu Rev Genet; 44: 365-92.
Marshall WF, Young KD, Swaffer M, Wood E, Nurse P, Kimura A, Frankel J, Wallingford J, Walbot V, Qu X, Roeder AH. (2012) What determines cell size? BMC Biol.10:101.
Theriot JA. (2013) Why are bacteria different from eukaryotes? BMC Biol.11:119.