Part I: Mechanism of cell motility 1
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Pollard begins with a brief history of the proteins involved in cellular motility; actin, myosin, and the various factors involved in regulating actin filament turnover. He focuses on the role of the Arp2/3 protein complex in nucleating the growth of the branched actin filaments found at the leading edge of a motile cell. Structural and biochemical studies allowed Pollard and his colleagues to formulate a model for how actin polymerization can provide the force to push the cell membrane forward.
In his second talk, Pollard explains why the fission yeast S. pombe is an excellent model to study actin-mediated processes. Fluorescently labeled actin-binding proteins allowed Pollard and his colleagues to follow actual cellular events and compare them with their mathematical model. Adjusting the model so it matched the experimental data provided insight into how actin assembly and turnover could produce the force needed for cells to move or undergo endocytosis.
Cytokinesis is the process by which a contractile ring forms around the middle of a cell and squeezes to divide it into two daughter cells. Although it has been known since the 1970s that the contractile ring contains actin and myosin, it turns out that there are over 100 other proteins involved in cytokinesis. In fission yeast, conditional and deletion mutants of many cytokinesis genes are available, many cytokinesis proteins have been labeled with fluorescent tags so they can be followed over time in live cells, and biochemical characterization of proteins has informed computer models. In his third talk, Pollard discusses the data that have given rise to the latest model for how the contractile ring forms and is regulated.
Tom Pollard is the Sterling Professor of Molecular, Cellular and Developmental Biology at Yale University. He received his BA from Pomona College and his MD from Harvard Medical School. He was a Professor at the Johns Hopkins University School of Medicine from 1977-1996 and President of the Salk Institute in San Diego from 1996-2000. He joined Yale University in 2001.
Pollard has been an integral member of the cell biology and biophysics communities for many years. He has been President of both the Biophysical Society and the American Society for Cell Biology, Director of the Physiology course at the Marine Biological Laboratory, and a member of the ASCB Public Policy Committee for 25 years. He has organized numerous meetings, has been a member of many committees and scientific advisory boards, and has been on the editorial boards of at least 10 journals. Together with William Earnshaw, he is the author of the popular textbook Cell Biology.
Pollard is a member of the National Academy of Sciences and the Institute of Medicine and a fellow of the American Association for the Advancement of Science. He has received numerous awards including the E.B. Wilson Award from the ASCB in 2005 and the Gairdner International Award in 2006.
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Mullins RD, Heuser JA, Pollard TD. (1998) The interaction of Arp2/3 complex with actin: nucleation, high affinity pointed end capping, and formation of branching networks of filaments. Proc Natl Acad Sci U S A. 95(11):6181-6.PMID: 9600938
Robinson RC, Turbedsky K, Kaiser DA, Marchand JB, Higgs HN, Choe S, Pollard TD. (2001) Crystal structure of Arp2/3 complex. Science 294(5547):1679-84. PMID:11721045
Pollard TD, Borisy GG. (2003) Cellular motility driven by assembly and disassembly of actin filaments. Cell 112(4):453-65. Review. PMID:12600310
Wu JQ, Pollard TD. (2005) Counting cytokinesis proteins globally and locally in fission yeast. Science. 310(5746):310-4. PMID:16224022
Vavylonis D, Wu JQ, Hao S, O'Shaughnessy B, Pollard TD. (2008) Assembly mechanism of the contractile ring for cytokinesis by fission yeast. Science. 319(5859):97-100. PMID:18079366
Pollard TD. (2014) The value of mechanistic biophysical information for systems-level understanding of complex biological processes such as cytokinesis. Biophys J.107(11):2499-507. PMID: 25468329
Stachowiak MR, Laplante C, Chin HF, Guirao B, Karatekin E, Pollard TD, O'Shaughnessy B.(2014) Mechanism of cytokinetic contractile ring constriction in fission yeast. Dev Cell. 29(5):547-61. PMID: 24914559