Contact Information
| Postal |
Email |
Phone |
Dorothy
A. Schafer, Ph.D.
Department of Biology
University of Virginia
Gilmer Hall, Room 059A
McCormick Rd.
P.O. Box 400328
Charlottesville, VA 22904-4328
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das9w@virginia.edu
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Office: 434-243-5297
Lab: 434-243-5302
Fax: 434-982-5626
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Research Interests
Our research is focused on
understanding how cells maintain the dynamic actin filament cytoskeleton
required for numerous cellular processes, including, cell migration,
determination and maintenance of shape, and intracellular protein trafficking.
To investigate molecular mechanisms of actin assembly that contribute
to these different functions, we developed a system to visualize actin
assembly in living cells using GFP-tagged probes for dynamic actin.
We also use biochemical analyses to probe the regulation of actin assembly
by individual components, with the ultimate goal of understanding how
they contribute to cell dynamics and membrane homeostasis. Initial observations
of actin assembly in living cells revealed some surprising new roles
for actin dynamics during cellular processes. A pool of dynamic actin
was observed at the cell periphery, as expected for extension of lamellipodia
during the initial steps of cell migration. However, dynamic actin was
also observed at other sites on the plasma membrane and in association
with intracellular endosomal compartments. We are testing the hypothesis
that these sites of actin assembly provide filaments that facilitate
endocytosis and post-endocytic traffic.
Dynamin and actin assembly. A survey of proteins that biochemically
link the endocytic and actin machineries reveals that the GTPase dynamin
may play a key role. We found that GTPase-defective mutant forms of
dynamin inhibit actin assembly when expressed in cells. Dynamin interacts
directly with several proteins that regulate actin assembly, including
profilin and cortactin. In addition, GTP hydrolysis by dynamin alters
the organization of actin filaments formed in vitro by Arp2/3 complex
and cortactin. We are studying the mechanisms by which dynamin regulates
actin filament dynamics for endocytosis and for cell motility.
Actin dynamics and post-endocytic traffic. Dynamic actin associated
with endosomal compartments appears to facilitate protein traffic through
the endosomal system. Movies of living cells revealed foci of dynamic
actin associated with vesicular compartments that can be loaded with
endocytic tracers. Inhibition of actin assembly leads to the accumulation
of the endocytic tracer. The function actin filaments during intracellular
protein trafficking, and the mechanism for regulation of the actin assembly
on endocytic compartments is currently being investigated.
Regulation of actin assembly during cell motility. A long-standing
interest is to understand the mechanisms of actin assembly that provides
for cell motility. For many years, one focus has been on capping protein,
a ubiquitous actin-binding protein that regulates polymerization by
binding to and thereby "capping", the fast-growing end of
actin filaments. We recently showed that proteins of the Ena/VASP family
antagonize capping activity in vitro. We are continuing these studies
to determine the mechanism whereby VASP inhibits capping of barbed ends
by capping protein.
Recent
Publications:
1. Schafer, D.A., Welch,
M.D., Machesky, L.M., Bridgman, P.D., Meyer, S.M. and Cooper, J.A. (1998)
Visualization and molecular analysis of actin assembly in living cells.
J. Cell Biol. 143:1919-1930 (PDF)
2. Huang, M., Yang, C., Schafer, D.A., Cooper, J.A., Higgs, H.N. and
Zigmond, S.H. (1999) Cdc42-induced filaments are protected from capping
protein. Curr. Biol. 9:979-982 (PDF)
3. Schafer, D.A. and T.A. Schroer. (1999) Actin-related proteins. Ann.
Rev. Cell Dev. Biol. 15:341-363 (PDF)
4. Steffen, P., Schafer, D.A., David, V., Gouin, E., Cooper, J.A. and
Cossart, P. (2000) Listeria monocytogenes ActA protein interacts with
phosphatidylinositol 4,5-bisphosphate in vitro. Cell Motil. Cytoskeleton
45:58-66 (PDF)
5. Weed, S.A., Karginov, A.V., Schafer, D.A, Weaver, A.M., Kinley, A.W.,
Cooper, J.A. Parsons, J.T. (2000) Cortactin localization to sites of
actin assembly in lamellipodia requires interactions with F-actin and
the Arp2/3 complex. J. Cell Biol. 151:29-40 (PDF)
6. Cooper, J.A. and D.A. Schafer (2000) Control of actin assembly and
disassembly at filament ends. Curr. Opin. Cell Biol. 12:97-103 (PDF)
7. Wear, M.A., Schafer, D.A. and J. A. Cooper (2000) Arp2/3 complex:
control of assembly and disassembly of actin filament networks. Curr.
Biol. 10: R891-R895
(PDF)
8. Schafer, D.A., D'Souza-Schorey, C. and Cooper, J.A. (2000) Actin
assembly at membranes controlled by ARF6. Traffic 1:892-903 (PDF)
9. Schafer, D.A. (2002) Coupling actin dynamics and membrane dynamics
during endocytosis. Curr. Opin. Cell Biol. 14:76-81 (PDF)
10. Bear, J.E., Svitkina, T. M., Krause, M., Schafer, D.A., Loureiro,
J.J., Strasser, G.A., Cooper, J.A., Borisy, G.G. and Gertler, F.B. (2002)
Antagonism between Ena/VASP proteins and actin filament capping regulates
fibroblast migration. Cell, 109:509-521 (PDF)
11. Schafer, D.A. (2003)
Actin puts on the squeeze. Nature Cell Biol. 5:693-694
(PDF)
12. Schafer,
D.A. (2004) Regulating actin assembly at membranes: a focus on dynamin.
Traffic 5:463-469
13. Schafer, D.A. (2004)
Barbed ends rule. Nature 430:734-735
Barzik, M., Kotova, T.I., Higgs, H.N., Larnele Hazelwood, Dorit Hanien,
Gertler, F.B. and Schafer, D.A. (2005) Ena/VASP proteins enhance actin
polymerization in the presence of barbed end capping proteins. J. Biol.
Chem., in press
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