The vasodilator‐stimulated phosphoprotein promotes actin polymerisation through direct binding to monomeric actin

Abstract

The vasodilator-stimulated phosphoprotein (VASP) functions as a cellular regulator of actin dynamics. VASP may initialise actin polymerisation, suggesting a direct interaction with monomeric actin. The present study demonstrates that VASP directly binds to actin monomers and that complex formation depends on a conserved four amino acid motif in the EVH2 domain. Point mutations within this motif drastically weaken VASP/G-actin interactions, thereby abolishing any actin-nucleating activity of VASP. Additionally, actin nucleation was found to depend on VASP oligomerisation since VASP monomers fail to induce the formation of actin filaments. Phosphorylation negatively affects VASP/G-actin interactions preventing VASP-induced actin filament formation.

TetraThymosinβ Is Required for Actin Dynamics inCaenorhabditis elegansand Acts via Functionally Different Actin-binding Repeats

“…However, the fact that all homologues of tetraThymosin␤ bind ATP-G-actin more strongly (Hertzog et al, 2002) and the notion that tetraThymosin␤ displays F-actin binding may agree with a model in which repeat 3 could putatively serve as a targeting domain to these ends. The combined presence of an F-actin interaction site and actin monomer recruitment sites is not unprecedented: it is also reported, e.g., for VASP and WASP (Bachmann et al, 1999;Walders-Harbeck et al, 2002). For these proteins, the in vivo relevance hereof is underscored by a novel model for actin-based motility .…”

“…Gelsolin is a well-known example where homologous segments have different actin-binding activities and their combined activity is responsible for severing and subsequent capping (Pope et al, 1991;Van Troys et al, 1996a). Multiple differential actin-binding units have also been reported in Ena/VASP proteins (Bachmann et al, 1999;Walders-Harbeck et al, 2002), Calponin Homology-domain containing proteins (Gimona et al, 2002), twinfilin (Ojala et al, 2002), MARCKS (Yarmola et al, 2001), and MIM (Mattila et al, 2003;Yamagishi et al, 2004).…”

A Novel Mechanism of G Protein-dependent Phosphorylation of Vasodilator-stimulated Phosphoprotein

“…As VASP localization to the membrane and focal adhesions is required for cell adhesion, motility, and formation of filopodia (35), it is likely that thrombin stimulation and G␣ 13 activation may modify VASP function by its phosphorylation and translocation. Additionally, these findings are interesting because G␣ 13 protein is known to induce cell retraction and actin stress fiber formation (29), whereas VASP phosphorylation may serve as a negative regulator of actin polymerization (55,56). We speculate that VASP phosphorylation induced by G␣ 13 activation can be an autoregulatory mechanism by which G␣ 13 limits its own responses.…”

Ena/VASP: proteins at the tip of the nervous system

“…Motifs in the EVH2 domain mediate direct binding to both monomeric (G-) and filamentous (F-) actin and, because they are tetramers, they can bundle actin filaments [12][13][14]. Ultrastructural analysis of actin filaments at the leading edge of fibroblasts and neuronal growth cones provided important clues to how Ena/VASP proteins influence cytoskeletal architecture.…”