[show abstract][hide abstract] ABSTRACT: We recently found a novel cell-cell adhesion system at cadherin-based adherens junctions (AJs), consisting at least of nectin, a Ca(2+)-independent homophilic immunoglobulin-like adhesion molecule, and afadin, an actin filament-binding protein that connects nectin to the actin cytoskeleton. Nectin is associated with cadherin through afadin and alpha-catenin. The cadherin-catenin system increases the concentration of nectin at AJs in an afadin-dependent manner. Nectin constitutes a family consisting of three members: nectin-1, -2, and -3. Nectin-1 serves as an entry and cell-cell spread mediator of herpes simplex virus type 1 (HSV-1). We studied here a role of the interaction of nectin-1alpha with afadin in entry and/or cell-cell spread of HSV-1. By the use of cadherin-deficient L cells overexpressing the full length of nectin-1alpha capable of interacting with afadin and L cells overexpressing a truncated form of nectin-1alpha incapable of interacting with afadin, we found that the interaction of nectin-1alpha with afadin increased the efficiency of cell-cell spread, but not entry, of HSV-1. This interaction did not affect the binding to nectin-1alpha of glycoprotein D, a viral component mediating entry of HSV-1 into host cells. Furthermore, the cadherin-catenin system increased the efficiency of cell-cell spread of HSV-1, although it also increased the efficiency of entry of HSV-1. It is likely that efficient cell-cell spread of HSV-1 is caused by afadin-dependent concentrated localization of nectin-1alpha at cadherin-based AJs.
Journal of Virology 06/2001; 75(10):4734-43. · 5.08 Impact Factor
[show abstract][hide abstract] ABSTRACT: Actin cytoskeleton structures are essential for a wide variety of cell functions, including cell shape change, cell motility, cell adhesion, cell polarity and cytokinesis. Many actin filament (F-actin)-binding proteins have been isolated and implicated in the maintenance and reorganization of actin cytoskeleton structures.
We purified here a novel protein with a molecular mass of about 125 kDa (p125) from rat liver. We cloned its cDNA from a mouse kidney cDNA library and determined its nucleotide and deduced amino acid sequences. p125 was a protein of 979 amino acids with a calculated Mr of 108 847. p125 contained six ankyrin repeats in the N-terminal region and a domain predicted to form a coiled-coil structure in the C-terminal region. We named p125 ankycorbin (ankyrin repeat- and coiled-coil structure-containing protein). Northern blot analysis indicated that ankycorbin was ubiquitously expressed in all the tissues examined. Immunofluorescence and immunoelectron microscope analyses revealed that ankycorbin was associated with the cortical actin cytoskeleton structures in terminal web and cell-cell adhesion sites and stress fibres. However, ankycorbin did not directly bind to F-actin as estimated by the F-actin co-sedimentation assay.
These results indicate that ankycorbin is indirectly associated with the actin cytoskeleton structures, presumably through an unidentified factor and suggest that it is involved in their maintenance and/or reorganization.
Genes to Cells 01/2001; 5(12):1001-8. · 2.73 Impact Factor
[show abstract][hide abstract] ABSTRACT: Both E-cadherin, a cell-cell adhesion molecule, and c-Met, the hepatocyte growth factor (HGF)/scatter factor (SF) receptor, were colocalized at cell-cell adhesion sites of MDCK cells. HGF/SF or a phorbol ester, 12-O-tetradecanoylphorbol-13-acetate (TPA), induced disruption of cell-cell adhesion, which was accompanied by endocytosis of both E-cadherin and c-Met. Reduction of medium Ca2+ to a micromolar range showed the same effects. Re-increase in medium Ca2+ to a millimolar range formed cell-cell adhesion, which was accompanied by exocytosis of E-cadherin and c-Met, followed by their re-colocalization at the cell-cell adhesion sites. These results suggest that E-cadherin and c-Met are colocalized at cell-cell adhesion sites and undergo co-endo-exocytosis. We have previously shown that TPA does not induce disruption of cell-cell adhesion and subsequent scattering of MDCK cells stably expressing a dominant active mutant of RhoA or Rac1 small G protein or a dominant negative mutant of Rab5 small G protein. In these cell lines, the HGF- or TPA-induced coendocytosis of E-cadherin and c-Met was inhibited, but the coendocytosis of E-cadherin and c-Met in response to reduction of medium Ca2+ was not affected. Wortmannin, an inhibitor of phosphoinositide (PI) 3-kinase, inhibited the HGF-induced disruption of cell-cell junction and endocytosis of E-cadherin and c-Met, but not the TPA-induced ones. These results suggest that disruption of cell-cell adhesion is involved in the HGF- or TPA-induced coendocytosis of E-cadherin and c-Met in MDCK cells, and that the Rho and Rab family members indirectly regulate this coendocytosis. In addition, coendocytosis of E-cadherin and c-Met in response to HGF is partly mediated by PI 3-kinase. The cross-talk between cell-cell and cell-matrix adherens junctions is discussed.