Vinculin is a highly conserved protein that plays essential roles in directing the proper assembly of the actin cytoskeleton following the formation of focal (cell-matrix) and adherens (cell-cell) junctions. Vinculin orchestrates changes in the cytoskeleton by binding to key scaffold proteins, including talin, which binds to integrin receptors in focal adhesions, and to a-actinin and a-catenin, which bind to cadherins in adherens junctions. Previous biochemical studies have suggested that activation of vinculin is largely accomplished through severing the intramolecular association of vinculin's head (Vh) and tail (Vt) domains. This was thought to occur through the binding of acidic phospholipids to the Vt domain, which would unfurl Vt, leaving a rigid Vh domain free to associate with its binding partners. To establish the underlying principles governing vinculin activation in our Preliminary Studies we solved the crystal structures of the inactive human Vh:Vt complex, and of a talin vinculin binding site (talin VBS3) bound to Vh. The crystal structure of the Vh:Vt complex reveals that, in its resting state, vinculin is held in a closed conformation through interactions of amphipathic a-helical bundles present in Vh and Vt. More importantly, the crystal structure of talin-bound Vh has demonstrated a novel and unexpected level of control, whereby binding of talin to Vh triggers striking alterations in Vh, creating an entirely new helical bundle structure that abolishes the binding site for Vt. These findings support a model in which: 1. Talin plays a direct and active role in vinculin activation; and 2. Vh is a dynamic, flexible, domain that functions as a molecular switch which controls cytoskeletal rearrangements in adherens versus focal adhesion junctions. In support of this model, experiments in Specific Aim #1 will define the crystal structure of native, full-length vinculin and of Vh bound to vinculin binding sites present in talin. The vinculin binding domains of talin and of other vinculin-binding proteins are highly related and are predicted to bind Vh in a mutually exclusive manner. Therefore in Specific Aim #2 we will test the model that the Vh domain functions as a molecular switch that directs focal adhesions versus adherens junctions, by solving the structure of the Vh domain, and of vinculin, in complex with other vinculin binding proteins. Finally, the successful crystallization of full-length human vinculin now allows us to also determine the crystal structures of other key binding partners that interact with vinculin. Thus in Specific Aim #3 we will determine the crystal structures of vinculin bound to proteins that bind to its Proline-rich domain that links Vh and Vt. It is hoped that the proposed experiments will pinpoint the interactions that are required for proper cytoskeletal assembly in normal cells, and how these interactions may be disrupted in cancer or other disease states. ? ?

Agency
National Institute of Health (NIH)
Institute
National Institute of General Medical Sciences (NIGMS)
Type
Research Project (R01)
Project #
1R01GM071596-01
Application #
6811901
Study Section
Biophysical Chemistry Study Section (BBCB)
Program Officer
Flicker, Paula F
Project Start
2004-08-01
Project End
2008-07-31
Budget Start
2004-08-01
Budget End
2005-07-31
Support Year
1
Fiscal Year
2004
Total Cost
$270,000
Indirect Cost
Name
St. Jude Children's Research Hospital
Department
Type
DUNS #
067717892
City
Memphis
State
TN
Country
United States
Zip Code
38105
Rangarajan, Erumbi S; Izard, Tina (2013) Dimer asymmetry defines ?-catenin interactions. Nat Struct Mol Biol 20:188-93
Lee, Jun Hyuck; Rangarajan, Erumbi S; Vonrhein, Clemens et al. (2012) The metavinculin tail domain directs constitutive interactions with raver1 and vinculin RNA. J Mol Biol 422:697-704
Rangarajan, Erumbi S; Lee, Jun Hyuck; Izard, Tina (2011) Apo raver1 structure reveals distinct RRM domain orientations. Protein Sci :
Pilati, Camilla; Amessou, Mohamed; Bihl, Michel P et al. (2011) Somatic mutations activating STAT3 in human inflammatory hepatocellular adenomas. J Exp Med 208:1359-66
Rangarajan, Erumbi S; Lee, Jun Hyuck; Yogesha, S D et al. (2010) A helix replacement mechanism directs metavinculin functions. PLoS One 5:e10679
Rangarajan, Erumbi S; Izard, Tina (2010) Improving the diffraction of full-length human selenomethionyl metavinculin crystals by streak-seeding. Acta Crystallogr Sect F Struct Biol Cryst Commun 66:1617-20
Lee, Jun Hyuck; Rangarajan, Erumbi S; Yogesha, S D et al. (2009) Raver1 interactions with vinculin and RNA suggest a feed-forward pathway in directing mRNA to focal adhesions. Structure 17:833-42
Rebouissou, Sandra; Amessou, Mohamed; Couchy, Gabrielle et al. (2009) Frequent in-frame somatic deletions activate gp130 in inflammatory hepatocellular tumours. Nature 457:200-4
Nhieu, Guy Tran Van; Izard, Tina (2007) Vinculin binding in its closed conformation by a helix addition mechanism. EMBO J 26:4588-96
St-Jean, Miguel; Izard, Tina; Sygusch, Jurgen (2007) A hydrophobic pocket in the active site of glycolytic aldolase mediates interactions with Wiskott-Aldrich syndrome protein. J Biol Chem 282:14309-15

Showing the most recent 10 out of 14 publications