The Villin Family

Villin belongs to the gelsolin/villin group of actin binding proteins that are typified by the possession of three or more gelsolin-like domains.  The tyoical villins have six of these (Matsudaira et al, 1985; Arpin et al, 1988) and in addition they have a so called "head piece" at the C-terminus that is the largest single difference between gelsolin and villins.

Click here for a diagram of the domain structure of the Gelsolin/Villin family.

In vertebrates, villin expression tends to limited to the brush border.  Surprisingly, perhaps villins or villin-like proteins are expressed in protists and plants (Vidali et al, 1999)and do not seem to be associated with microvilli-like structures. 

Advillin

(Marks et al, 1998)

Protovillin

Curiously, a protein from Dictyostelium has been isolated that despite having gross domain structure similarity to vertebrate villin (Hofmann et al, 1993) including the head piece, appartently caps filaments but neither severs nor bundles filaments (Hofmann et al, 1992). Filament capping is regulated by polyphosphoinositide lipids but it is far from clear as to why this protein needs to be so large and complex since the same cell also produces a much smaller protein (cap 32/34) that has similar properties.  It was suggested that protovillin is a villin precursor, possessing a rudimentary capping activity but has not yet evolved the full severing, bundling activity.  This view assumes a rather predictive nature of molecular evolution and it seems more probable that protovillin may be a degenerate villin that has lost the properties that once it had.  Even more likely is the possibility that we have not yet fully understood the true function of protovillin and this will provide a solution.  

Supervillin

Another villin-like protein "supervillin" has been isolated from neutrophils (Pestonjamasp et al, 1997; Wulfkuhle et al, 1999), a membrane and actin binding protein with nuclear signal that drive it into the nucleus. 

Arpin, M., Pringault, E., Finidori, J., Garcia, A., Jeltsch, J., Vandekerckhove, J. & Louvard, D. (1988) Sequence of human villin: a large duplicated domain homologous with other actin-severing proteins and a unique small carboxy-terminal domain related to villin specificity., J. Cell Biol. 107, 1759-1766.

Hofmann, A., Noegel, A. A., Bomblies, L., Lottspeich, F. & Schleicher, M. (1993) The 100 kDa F-actin capping protein of Dictyostelium amoebae is a villin prototype ('protovillin'), FEBS. 328, 71-76.

Marks, P. W., Arai, M., Bandura, J. L. & Kwiatkowski, D. J. (1998) Advillin (p92): a new member of the gelsolin/villin family of actin regulatory proteins, J.Cell Sci. 111, 2129-2136.

Matsudaira, P., Jakes, R. & Walker, J. E. (1985) A gelsolin-like calcium-dependent actin-binding domain in villin., Nature. 315, 248-250.

Pestonjamasp, K. N., Pope, R. K., Wulfkuhle, J. D. & Luna, E. J. (1997) Supervillin (p205): A novel membrane-associated, F-actin-binding protein in the villin/gelsolin superfamily, J.Cell Biol. 139, 1228-1253.

Wulfkuhle, J. D., Donina, I. E., Stark, N. H., Pope, R. K., Pestonjamasp, K. N., Niswonger, M. L. & Luna, E. J. (1999) Domain analysis of supervillin, an F-actin bundling plasma membrane protein with functional nuclear localization signals., J.Cell Sci. 112, 2125-2136.