The rapid assembly and disassembly of the actin cytoskeleton is central to many cellular functions, including mitosis, cell division, intracellular transport, and the control of cell shape and polarity. Alterations of cytoskeletal proteins are linked to diseases, including cardiovascular and neurodegenerative disorders. The hydrolysis of ATP by actin drives the transition between its monomeric form (G-actin) and filamentous form (F-actin). F-actin is asymmetric, undergoing net association of ATP-actin to the """"""""barbed"""""""" end and dissociation of ADP-actin from the """"""""pointed"""""""" end. This dynamic process, known as actin filament treadmilling, is regulated in vivo by a plethora of actin-binding proteins (ABPs). ABPs have evolved relatively few actin-binding motifs, including the WASP homology domain-2 (WH2), actin-depolymerizing factor-homology (ADF-H), and calponin-homology (CH) motifs. The long-term goal of this proposal is to understand the structural basis for the interactions of these motifs with G- and F-actin and their role in the regulation of the cytoskeleton. A unifying hypothesis is proposed that holds that ADF-H, WH2, gelsolin, and actin itself, which are generally unrelated, present common structural features that allow them to share a common binding site on actin, consisting of a hydrophobic pocket at the interface between subdomains 1 and 3. In contrast, the CH domain, which is a classical F-actin-binding motif, is not expected to bind in this pocket.
Specific aim 1 studies the X-ray structures of complexes of WH2 domains from various disease-related proteins with actin.
Specific aim 2 deals with the study of twinfilin, which is composed of two ADF-H domains in tandem.
Specific aim 3 focuses on the study of the crystal structure of the CH pair from alpha-actinin, its regulation by PIP2, and its interaction with F-actin. Crystals are available in aims 1 and 3, and micro-crystals are also available in aim 2. The crystallographic and biochemical studies are being complemented by EM studies of twinfilin and a-actinin decorated F-actin, in collaboration with W.J. Lehman at BU. This proposal offers a comprehensive approach to study three of the most important actin-binding motifs in nature. By studying these motifs in parallel we will establish common and distinctive features of their structures and interactions with G- and F-actin that determine their functions in the regulation of the cytoskeleton.

Agency
National Institute of Health (NIH)
Institute
National Institute of General Medical Sciences (NIGMS)
Type
Research Project (R01)
Project #
5R01GM073791-05
Application #
7392289
Study Section
Biophysical Chemistry Study Section (BBCB)
Program Officer
Deatherage, James F
Project Start
2005-04-01
Project End
2010-03-31
Budget Start
2008-04-01
Budget End
2010-03-31
Support Year
5
Fiscal Year
2008
Total Cost
$316,102
Indirect Cost
Name
University of Pennsylvania
Department
Physiology
Type
Schools of Medicine
DUNS #
042250712
City
Philadelphia
State
PA
Country
United States
Zip Code
19104
Arnesen, Thomas; Marmorstein, Ronen; Dominguez, Roberto (2018) Actin's N-terminal acetyltransferase uncovered. Cytoskeleton (Hoboken) 75:318-322
Lee, In-Gyun; Olenick, Mara A; Boczkowska, Malgorzata et al. (2018) A conserved interaction of the dynein light intermediate chain with dynein-dynactin effectors necessary for processivity. Nat Commun 9:986
Mentes, Ahmet; Huehn, Andrew; Liu, Xueqi et al. (2018) High-resolution cryo-EM structures of actin-bound myosin states reveal the mechanism of myosin force sensing. Proc Natl Acad Sci U S A 115:1292-1297
Turegun, Bengi; Baker, Richard W; Leschziner, Andres E et al. (2018) Actin-related proteins regulate the RSC chromatin remodeler by weakening intramolecular interactions of the Sth1 ATPase. Commun Biol 1:
Drazic, Adrian; Aksnes, Henriette; Marie, Michaƫl et al. (2018) NAA80 is actin's N-terminal acetyltransferase and regulates cytoskeleton assembly and cell motility. Proc Natl Acad Sci U S A 115:4399-4404
Burke, Thomas A; Harker, Alyssa J; Dominguez, Roberto et al. (2017) The bacterial virulence factors VopL and VopF nucleate actin from the pointed end. J Cell Biol 216:1267-1276
Boczkowska, Malgorzata; Yurtsever, Zeynep; Rebowski, Grzegorz et al. (2017) Crystal Structure of Leiomodin 2 in Complex with Actin: A Structural and Functional Reexamination. Biophys J 113:889-899
Fowler, Velia M; Dominguez, Roberto (2017) Tropomodulins and Leiomodins: Actin Pointed End Caps and Nucleators in Muscles. Biophys J 112:1742-1760
Dominguez, Roberto (2016) The WH2 Domain and Actin Nucleation: Necessary but Insufficient. Trends Biochem Sci 41:478-490
Boczkowska, Malgorzata; Rebowski, Grzegorz; Kremneva, Elena et al. (2015) How Leiomodin and Tropomodulin use a common fold for different actin assembly functions. Nat Commun 6:8314

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