High impact information on VIL1

• We have studied the mechanism of Ca++-dependent restriction of actin filament length by villin, one of the major actin-associated proteins of intestinal microvilli microfilament bundles [1].
• Regulation of actin polymerization by villin, a 95,000 dalton cytoskeletal component of intestinal brush borders [2].
• A 95,000 dalton actin-binding polypeptide, villin, has been purified to 98% homogeneity from brush border cytoskeletons of chicken intestinal epithelial cells [2].
• In view of these striking properties, villin is likely to be an important in vivo regulator of cytoskeletal structure and, by implication, of cell shape and motility [2].
• Role of fimbrin and villin in determining the interfilament distances of actin bundles [3].

Biological context of VIL1

• The protein sequence of villin deduced from a single cDNA clone contains a conserved sequence that is repeated six times and is found in each domain of the villin core [4].
• In addition, chemical shift changes for residues Lys70-Phe76 in the C-terminal subdomain suggest that the HP67 actin binding site is disrupted upon unfolding of the N-terminal subdomain, providing a potential mechanism for regulating the villin-dependent bundling of actin filaments [5].
• Calcium-binding proteins of this system include intestinal calcium binding protein (CaBP), calmodulin (CaM), villin, and a 36,000-mol-wt protein substrate of tyrosine kinases [6].
• Gel-sol transformation of actin filaments, a process essential for cell motility, can be reconstituted in vitro and regulated in a predictable fashion by the combined action of villin and filamin [7].
• We have investigated the structure, equilibria, and folding kinetics of an engineered 35-residue subdomain of the chicken villin headpiece, an ultrafast-folding protein [8].

Anatomical context of VIL1

• Six are contained in the amino-terminal Mr 87,000 villin core, a Ca2+-regulated actin-severing fragment, whereas the carboxyl-terminal domain includes the villin "headpiece," a fragment involved in bundling of actin filaments [4].
• Villin, a Ca2+-modulated F-actin-binding protein (95,000 daltons) present in microvillus core filament bundles, has been shown to contain multiple Ca2+-binding sites [9].
• The headpiece domain of villin, a protein found in the actin bundles of the brush border epithelium, is of interest both as a compact F-actin binding domain and as a model folded protein [10].
• Villin is a member of a family of actin-severing proteins that regulate the organization of actin in the eukaryotic cytoskeleton [11].
• This study would suggest that as the Ca++ rises in the intestinal epithelial cell an ordered sequence of Ca++ saturation of intracellular receptors occurs with the order from the lowest to highest Ca++ requirements being CaBP less than CaM less than villin less than P-36 [6].

Associations of VIL1 with chemical compounds

• Protein sequence analysis documents that the core comprises the NH2-terminal portion of intact villin, whereas the headpiece covers the COOH-terminal 76 amino acids [12].
• The contribution of interactions involving the imidazole ring of His41 to the pH-dependent stability of the villin headpiece (HP67) N-terminal subdomain has been investigated by nuclear magnetic resonance (NMR) spin relaxation [5].
• In reconstitution experiments, actin filaments incubated in EGTA with purified fimbrin and villin form smooth-sided bundles containing an apparently random number of filaments [13].
• Maps constructed from the cleavage pattern suggest that villin contains six cysteine residues, two located in its amino-terminal peptide of Mr 44,000, and four located in the carboxyl-terminal peptide of Mr 51,000 [14].
• Peptide antisera specific for either the amino- or carboxyl-terminal regions of villin were used to locate the position of cysteine residues in immunoblots of villin cleaved with 2-nitro-5-thiocyanobenzoic acid [14].

Regulatory relationships of VIL1

• Villin inhibits filamin-induced F-actin gelation, but the effect can be overcome by increasing the amount of filamin [7].

Other interactions of VIL1

• Moreover a significant within-sire effect of VIL1, a marker gene for NRAMP1, was observed in 117 progeny resulting from 25 informative matings [15].
• Actin, villin, myosin, tropomyosin and spectrin, but not myosin I (previously called 110 kD; see Mooseker and Coleman, J. Cell Biol. 108, 2395-2400, 1989) are already concentrated in the luminal cytoplasm of crypt cells, as seen by immunofluorescence [16].
• Sedimentation assays show that villin does not inhibit gelation of actin by preventing filamin from binding to F-actin [7].

Analytical, diagnostic and therapeutic context of VIL1

• Using quantitative densitometry of cDNA-hybridized RNA blots from cells isolated from crypts, villus middle (mid), or villus tip (tip), we found a 2- to 3-fold increase in villin, calmodulin and tropomyosin steady-state mRNA levels; an increase parallel to morphological brush border development [16].
• The physical structure of villin, a Ca2+-modulated regulator protein of actin filament organization, has been studied in the absence and presence of Ca2+ using analytical ultracentrifugation, gel chromatography, ultraviolet difference spectroscopy, and circular dichroism [17].
• A procedure is described for the immobilization of monomeric actin so that about 30% of the immobilized protein is competent to bind the monomeric-actin-binding proteins bovine pancreatic deoxyribonuclease I and chicken villin [18].
• Villin, a 95,000 dalton polypeptide of intestinal brush border which is known to bundle or sever actin filaments in a Ca++-dependent manner, was localized in rat and chicken intestinal epithelium by means of immunocytochemistry at the light- and electron-microscopic levels [19].
• PvuII PCR polymorphism at the chicken VIL locus [20].

References