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Table 15.1 HGF-induced cell motility in primary cultures of enterocytes or MDCK cells
expressing villin
Mean velocity (mm/min)
Vil /
Vil +/+
Primary cultures of enterocytes
MDCK cells
Velocity was calculated using tracks of individual cells after videorecording for 9 h (see Figure 15.2 for
a typical experiment).
comet formed by intracellular bacteria. Together, these results indicate that
villin plays an important role in the different steps of Shigella infection
through its ability to remodel the actin cytoskeleton reorganization elicited by
the invasion process (Athman et al., submitted).
Villin as a regulator of actin dynamics
Background on actin dynamics
Actors of actin dynamics
Proteins of the gelsolin family are regulated by calcium (which activates
severing and/or capping) and certain inositol phospholipids (which cause
uncapping, the release of actin filament barbed ends, and thus allows for actin
polymerization from the barbed ends). In the case of gelsolin itself, there is
both a widely-expressed intracellular form and a higher molecular weight
extracellular form found in plasma; this latter form appears to play a role in
scavenging extracellular actin released from lysed cells. CapZ is a calcium-
independent heterodimeric protein that caps barbed ends of filaments in
platelets, which appears to be coordinated with severing and capping by
gelsolin family proteins. ADF/cofilin family proteins are calcium-independent,
and also promote actin filament disassembly; however, the activity of these
proteins differs from that of gelsolin family proteins. ADF/cofilin proteins
appear to accelerate depolymerization from the pointed ends of actin
filaments and weakly to sever filaments without capping. Arp2/3 complex
and associated factors appear to promote actin filament assembly by de novo
nucleation (or stabilization of nuclei), complementing assembly from barbed
ends of existing filaments following barbed-end uncapping. This complex
forms a cap on filament pointed ends and may also help to establish
a branched actin filament geometry by binding to the sides of existing
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