Disease relevance of VASP

• A novel proline-rich motif present in ActA of Listeria monocytogenes and cytoskeletal proteins is the ligand for the EVH1 domain, a protein module present in the Ena/VASP family [1].
• A cardinal feature of Listeria and Shigella actin-based motility is the involvement of vasodilator-stimulated phosphoprotein (VASP) [2].
• VASP-/- mice demonstrated hyperplasia of megakaryocytes in bone marrow and spleen but exhibited no other macroscopic or microscopic abnormalities [3].
• Immunolocalization using rabbit anti-VASP antibody revealed that VASP concentrates behind motile virions in HeLa cells [2].
• VASP mutated (Ser/Thr to Ala) at all three of its established phosphorylation sites (vesicular stomatitis virus-tagged VASP-AAA mutant) was not phosphorylated by cGK I and was resistant to detaching from HUVEC focal adhesions in response to 8-pCPT-cGMP [4].

High impact information on VASP

• Putting on the brakes: a negative regulatory function for Ena/VASP proteins in cell migration [5].
• Structure of the enabled/VASP homology 1 domain-peptide complex: a key component in the spatial control of actin assembly [6].
• Phosphorylation by these kinases appears to modulate Ena/VASP function within cells, although the mechanism underlying this regulation remains to be determined [7].
• Ena/VASP proteins are a conserved family of actin regulatory proteins made up of EVH1, EVH2 domains, and a proline-rich central region [7].
• Vertebrate Ena/VASP proteins are substrates for PKA/PKG serine/threonine kinases [7].

Chemical compound and disease context of VASP

• We found that VASP was phosphorylated after treating SW480 colon cancer cells with exisulind, CP461, or CP248 [8].
• Prostacyclin (PG-I2), prostaglandin-E1 (PG-E1) and the stable prostacyclinanalog Iloprost, all agents used for the treatment of peripheral vascular disease, induced rapid, stoichiometric and reversible phosphorylation of VASP in human platelets mediated by the cAMP-dependent protein kinase [9].
• Vasodilator-stimulated phosphoprotein (VASP) 239 phosphorylation flow cytometric assessment has been reported as a tool to evaluate the responsiveness to clopidogrel in coronary heart disease (CHD) patients [10].

Biological context of VASP

• The Ena-VASP family of proteins act as molecular adaptors linking the cytoskeletal system to signal transduction pathways [11].
• VASP-deficient mice may provide an interesting model system for diseases in which enhanced platelet activation plays a major role [3].
• Hence, phosphorylation may significantly alter the actin binding properties of VASP [12].
• Ena/VASP (enabled/vasodilator-stimulated phosphoprotein) proteins play an important role in actin and filament dynamics, whereas members of the semaphorin protein family are guidance signals in embryo- and organogenesis [13].
• Thus, our data pinpoint PREL1 as the first direct link between Ras signalling and cytoskeletal remodelling via Ena/VASP proteins during cell migration and spreading [14].

Anatomical context of VASP

• VASP is a microfilament and focal adhesion associated protein which is also concentrated in highly dynamic regions of the cell cortex [15].
• Inhibition of binding between Fyb/SLAP and Ena/VASP proteins or WASP and the Arp2/3 complex impairs TCR-dependent actin rearrangement, suggesting that these interactions play a key role in linking T cell signaling to remodeling of the actin cytoskeleton [16].
• In activated T cells, Fyb/SLAP associates with Ena/VASP family proteins and is present within biochemical complexes containing WASP, Nck, and SLP-76 [16].
• Human platelet VASP bound directly to purified profilins from human platelets, calf thymus and birch pollen [15].
• Ena/VASP proteins influence the organization of actin filament networks within lamellipodia and filopodia of migrating cells and in actin comet tails [17].

Associations of VASP with chemical compounds

• Dual epitope recognition by the VASP EVH1 domain modulates polyproline ligand specificity and binding affinity [11].
• These data support the concept that VASP is a negative modulator of platelet and integrin alphaIIbbeta3 activation [3].
• Here we demonstrate that stimulation of human umbilical vein endothelial cells (HUVECs) by both ANP and 8-(4-chlorophenylthio)guanosine 3':5'-monophosphate (8-pCPT-cGMP) activates transfected cGK I and causes detachment of VASP and its known binding partner (zyxin) from focal adhesions in >60% of cells after 30 min [4].
• Recently, the vasodilator-stimulated phosphoprotein (VASP), a substrate of cyclic AMP-dependent or cyclic GMP-dependent kinases and a component of focal adhesion sites, was shown to bind to vinculin [18].
• We propose that PIP2-dependent signalling modulates microfilament organization at cellular adhesion sites by regulating vinculin-VASP complexes [18].
• To examine the functional effects of this modification in living cells, we studied VASP phosphorylation at Ser239 by nitric oxide (NO) stimulation of cGMP-dependent protein kinase [19].
• VASP phosphorylation analysis can evaluate the individual response to clopidogrel loading dose prior to PCI and predict postprocedural MACE [20].

Physical interactions of VASP

• Here, we report that VASP also directly binds to vinculin, another component of adherens junctions [21].
• Identification, purification, and characterization of a zyxin-related protein that binds the focal adhesion and microfilament protein VASP (vasodilator-stimulated phosphoprotein) [22].
• Profilin interacts with the Gly-Pro-Pro-Pro-Pro-Pro sequences of vasodilator-stimulated phosphoprotein (VASP): implications for actin-based Listeria motility [23].
• An in vitro analysis demonstrates that the proline-rich domain of WASp binds VASP with an affinity of approximately 10(6) M(-1) [24].
• Using immobilized peptides corresponding to the two proline-rich motifs within this domain, the VASP-binding site was localized to proline-rich motif-l (residues 839-850) [25].

Enzymatic interactions of VASP

• VASP is a major substrate for cAMP- and cGMP-regulated protein kinases and it has been shown to be directly phosphorylated on Ser157 by PKC (protein kinase C) [26].

Co-localisations of VASP

• Immunofluorescence studies revealed that the two host proteins, VASP and (&agr;)-actinin colocalized with actin in the tails of Rickettsia but neither the Arp2/3 complex which we detected in the Shigella actin tails, nor N-WASP, were detected in Rickettsia actin tails [27].

Regulatory relationships of VASP

• In addition, one of the effects of VEGF and IL-8 in angiogenesis may be to induce VASP expression in a paracrine manner [28].
• These phenotypes are more severe than loss of Ena/VASP, suggesting that Lpd regulates other effectors of the actin cytoskeleton in addition to Ena/VASP [29].
• Finally, in a reconstituted motility medium, VASP enhances actin-based propulsion of WASp-coated beads in a fashion reminiscent of its effect on Listeria movement [24].
• WASP- and Ena/VASP-family proteins have been reported to regulate the cortical actin cytoskeleton as downstream effectors of the Rho-family small G-proteins Rac and Cdc42, but their functions are little understood [30].
• In cultured cells, mammalian MIG-10 promotes lamellipodial growth and Ena/VASP proteins induce filopodia [31].

Other interactions of VASP

• VASP, in turn, provides the ABM-2 sequences [XPPPPP, X = G, P, L, S, A] for binding profilin, an actin-regulatory protein that stimulates actin filament assembly [2].
• Vinculin did not colocalize with VASP on motile virions and remained in focal adhesion contacts; however, another ABM-1-containing host protein, zyxin, was concentrated at the rear of motile virions [2].
• The COOH-terminal half recruits zyxin as well as Mena and VASP from cell extracts [32].
• LPP localizes in focal adhesions as well as in cell-to-cell contacts, and it binds VASP, a protein implicated in the control of actin organization [33].
• Infections of either N-WASP- or Ena/VASP-defective cells showed that these proteins are not essential for B. pseudomallei-induced actin polymerization [34].

Analytical, diagnostic and therapeutic context of VASP

• Determination of the VASP EVH1 domain solution structure, together with peptide library screening, measurement of individual K(d)s by fluorescence titration, and NMR chemical shift mapping, revealed a second affinity-determining epitope present in all four ActA EVH1-binding motifs [11].
• VASP binding to purified p83 in solid-phase binding assays and the closely matching subcellular localization in double-label immunofluorescence analyses demonstrated that both proteins also directly interact as native proteins in vitro and possibly in living cells [22].
• Using cosmid DNA as a probe for fluorescence in situ hybridization, the human VASP gene was assigned to chromosome 19q13.2-q13.3, an extended region with homology to mouse chromosome 7 [35].
• Immunocytochemistry revealed that endogenous M10 co-localized with Mena/VASP at the tip of filopodia [36].
• Here, we demonstrate that palladin is an additional direct binding partner for VASP, by using co-immunoprecipitation and blot overlay techniques with both endogenous palladin and recombinant myc-tagged palladin [37].

References