Table I:

What is Ena/VASP doing anyway?

1. Ena/VASP enhances protrusion
     and propulsion speedVASP targeted to leading edge = lamellipodia protrusion speed increases (Bear et al., 2000, 2002).
Results confirmed by CALIa against EGFP (Vitriol et al., 2007).
FAT1 knockdown to reduce VASP at leading edge = kymograph leading edge smoother (Moeller et al., 2004).
Listeria (Loisel et al., 1999).
Beads (Samarin et al., 2003; Plastino et al., 2004b).
Soft beads (Trichet et al., 2007).
2. Ena/VASP inhibits formation
     of actin branches by the
     Arp2/3 complexIn solution: fluorescence microscopy, phalloidin-stabilized (Skoble et al., 2001) (conflicting study:
     [Boujemaa-Paterski et al., 2001], see text).
In cells, electron microscopy of the leading edge (Bear et al., 2002).
Comets on beads, Arp2/3 to actin ratio (Samarin et al., 2003).
Comets on beads, electron microscopy (Plastino et al., 2004b).
3. Ena/VASP nucleates
     actin polymerizationBy pyrene assayb, high (physiological) salt
     concentration (Barzik et al., 2005).By pyrene assayb, low salt concentration (Hüttelmaier et al., 1999; Schirenbeck et al., 2006).
Listeria mutants that do not recruit the Arp2/3 complex
     do not accumulate actin (Skoble et al., 2000).On beads coated with the ActA domain that binds VASP
     (Fradelizi et al., 2001; Plastino et al., 2004a).
On mitochondria that target Ena/VASP proteins via
     the poly-proline repeats of ActA (Bear et al., 2000).In conjunction with zyxin, observed by targeting zyxin
     to mitochondria in cells (Fradelizi et al., 2001).
4. Ena/VASP enhances barbed
     end elongationBy pyrene assayb using F-actin seeds
     (Bear et al., 2002).By pyrene assayb using monomeric actin (Skoble et al., 2001).
By pyrene assayb using F-actin seeds (Barzik et al., 2005).
By pyrene assayb with actin NPFs free in solution
     (Samarin et al., 2003).By pyrene assayb with actin NPFs immobilized on beads
     (Samarin et al., 2003).
By measuring actin incorporation into comet tails
     on moving beads (Plastino et al., 2004b).
5. Ena/VASP protects filament
     barbed ends from capping
    –Anti-cappingBy pyrene assayb (Samarin et al., 2003).By pyrene assayb (Bear et al., 2002; Barzik et al., 2005).
    –UncappingBy pyrene assayb (Schirenbeck et al., 2006).
Lack of capture of capped barbed ends by beads
     coated with VASP (Bear et al., 2002)c.
  • a Chromophore-assisted laser inactivation.

  • b The pyrene assay is a method of monitoring the change in the amount of F-actin in a solution by following the fluorescence of pyrenyl-actin, which increases when pyrenyl-actin molecules are incorporated into the filament.

  • c In a similar study, Samarin et al. (2003) observed capture of capped barbed ends by beads coated with VASP. However, these authors concluded that this activity was due to VASP's F-actin binding activity and not to uncapping activity.