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Biomedical subjects

S Tsukita

Publications and source records attributed to S Tsukita.

At least 19 recordsLinked to original sources
PubMed1992

Cadherin dysfunction in a human cancer cell line: possible involvement of loss of alpha-catenin expression in reduced cell-cell adhesiveness.

A human lung cancer cell line, PC 9, was analyzed to elucidate the molecular mechanisms of dysfunction of cadherin-mediated cell-cell adhesion in cancer. Although PC 9 cells strongly expressed E-cadherin at the cell membrane, which was indistinguishable immunochemically from functional E-cadherin, they did not show tight cell-cell adhesion and had reduced E-cadherin-mediated aggregation activity. Immunoprecipitation with E-cadherin and Western blot analysis revealed that PC 9 cells did not express alpha-catenin, a cadherin-associated protein, suggesting that this was the cause of the cadherin dysfunction in the cell line. In addition, Northern and Southern blot analyses disclosed homozygous deletion of part of the alpha-catenin gene, which might have resulted in the loss of alpha-catenin expression in PC 9 cells.

Blotting, Northern↗
PubMed1992

Ca(2+)-regulated actin and phospholipid binding protein (68 kD-protein) from bovine liver: identification as a homologue for annexin VI and intracellular localization.

An F-actin binding protein was purified from bovine liver by means of DNase I affinity, hydroxylapatite and DEAE-cellulose column chromatographies. It consisted of a single polypeptide chain having an apparent molecular weight of 68,000 with a Stokes radius of 35 A. Electron microscopy of rotary shadowed specimens showed that the 68 kD protein is a globular protein. This protein showed a higher affinity for F-actin in the presence of Ca2+ than in its absence, which is opposite to the actin-binding property shown by nonmuscle alpha-actinin or fimbrin. The 68 kD protein had no F-actin severing and capping activity. Interestingly, the 68 kD protein was found to aggregate liposomes at micromolar Ca2+ concentrations. Immunoblot analysis and partial protein sequence data identified the 68 kD protein as an annexin VI (p68) homologue. Immunocytochemical studies showed that the 68 kD protein was localized along stress fibers as well as membrane ruffles, microspikes and focal contacts, raising the possibility that annexin VI may contribute to control membrane-microfilament interaction in the cell.

Actins↗
PubMed1992

Molecular linkage between cadherins and actin filaments in cell-cell adherens junctions.

The cell-cell adherens junction is a site for cadherin-mediated cell adhesion where actin filaments are densely associated with the plasma membrane through its well-developed plasmalemmal undercoat. Recent research has focused on the molecular linkage between cadherins and actin filaments in the undercoat of adherens junctions in order to understand the functions of these undercoat-constitutive proteins in the regulation and signal transduction of cadherin-based cell adhesion.

Actins↗
PubMed1992

Cadherin-mediated cell-cell adhesion is perturbed by v-src tyrosine phosphorylation in metastatic fibroblasts.

Rat 3Y1 cells acquire metastatic potential when transformed with v-src, and this potential is enhanced by double transformation with v-src and v-fos (Taniguchi, S., T. Kawano, T. Mitsudomi, G. Kimura, and T. Baba. 1986. Jpn. J. Cancer Res. 77:1193-1197). We compared the activity of cadherin cell adhesion molecules of normal 3Y1 cells with that of v-src transformed (SR3Y1) and v-src and v-fos double transformed (fosSR3Y1) 3Y1 cells. These cells expressed similar amounts of P-cadherin, and showed similar rates of cadherin-mediated aggregation under suspended conditions. However, the aggregates or colonies of these cells were morphologically distinct. Normal 3Y1 cells formed compacted aggregates in which cells are firmly connected with each other, whereas the transformed cells were more loosely associated, and could freely migrate out of the colonies. Overexpression of exogenous E-cadherin in these transformed cells had no significant effect on their adhesive properties. We then found that herbimycin A, a tyrosine kinase inhibitor, induced tighter cell-cell associations in the aggregates of the transformed cells. In contrast, vanadate, a tyrosine phosphatase inhibitor, inhibited the cadherin-mediated aggregation of SR3Y1 and fosSR3Y1 cells but had little effect on that of normal 3Y1 cells. These results suggest that v-src-mediated tyrosine phosphorylation perturbs cadherin function directly or indirectly, and the inhibition of tyrosine phosphorylation restores cadherin action to the normal state. We next studied tyrosine phosphorylation on cadherins and the cadherin-associated proteins, catenins. While similar amounts of catenins were expressed in all of these cells, the 98-kD catenin was strongly tyrosine phosphorylated only in SR3Y1 and fosSR3Y1 cells. Cadherins were also weakly tyrosine phosphorylated only in the transformed cells. The tyrosine phosphorylation of these proteins was enhanced by vanadate, and inhibited by herbimycin A. Thus, the tyrosine phosphorylation of the cadherin-catenin system itself might affect its function, causing instable cell-cell adhesion.

Animals↗
PubMed1992

A case of subepidermal blister disease associated with autoantibody against 450 kD protein.

We report a case of subepidermal blister disease with eruptions distributed on the trunk and extremities. The blisters regressed after administration of corticosteroid and cyclophosphamide. An immunoblot analysis revealed that the patient's serum reacted exclusively with a 450-kD epidermal polypeptide. It did not react with a 230-kD or a 180-kD bullous pemphigoid antigen. The immunofluorescence study showed the patient's serum reacted with the basement membrane zone of human skin.

Aged↗
PubMed1992

A gene family consisting of ezrin, radixin and moesin. Its specific localization at actin filament/plasma membrane association sites.

Radixin is a barbed end-capping actin-modulating protein which was previously reported to be concentrated at cell-to-cell adherens junctions (AJ) and cleavage furrows. Recently, cDNA encoding mouse radixin was isolated, showing that radixin is highly homologous to but distinct from ezrin. From mouse teratocarcinoma cells we isolated and analyzed cDNA encoding another radixin-related protein. Sequence analysis has demonstrated that this protein is a mouse homologue of human moesin (98.3% identity) and that it shares 71.7% and 80.1% identity with ezrin and radixin, respectively. Translation experiments in vitro combined with immunoblot analyses led us to conclude that there is a gene family consisting of ezrin, radixin and moesin. These members are coexpressed in various types of cells. Then, by immunofluorescence microscopy, we closely analyzed their distribution using polyclonal and monoclonal antibodies, which could recognize all three members. In addition to cell-to-cell AJ and cleavage furrows, it was shown that they were concentrated at microvilli and ruffling membranes in various types of cells. Furthermore, the cell-to-substrate AJ (focal contacts) were clearly stained by anti-radixin pAb only after the apical/lateral membranes and cytoplasm were removed by the zinc method. We conclude that at least one of the members of the ezrin-radixin-moesin family is concentrated at specific regions where actin filaments are densely associated with plasma membranes.

Actins↗
PubMed1991

The 102 kd cadherin-associated protein: similarity to vinculin and posttranscriptional regulation of expression.

The E-cadherin cell adhesion molecule is associated with cytoplasmic polypeptides, and this association is essential for its cell-binding function. Using isolated adherens junctions of the liver, we purified a 102 kd protein that can associate with E-cadherin (CAP102) and isolated cDNAs encoding this protein. Sequence analysis of the cDNAs revealed that this protein has a similarity to vinculin. L cells not expressing endogenous cadherin express the mRNA for CAP102 but have only a trace amount of CAP102 protein. Introducing exogenous E-cadherin into these cells, however, induced a high expression of CAP102 protein without affecting the amount of its mRNA, suggesting that there is a posttranscriptional regulatory mechanism for this molecule. The same effect was observed by introducing N- or P-cadherin into L cells.

Amino Acid Sequence↗
PubMed1991

Radixin, a barbed end-capping actin-modulating protein, is concentrated at the cleavage furrow during cytokinesis.

Radixin is a barbed end-capping actin-modulating protein which was first identified in isolated cell-to-cell adherens junctions from rat liver (Tsukita, Sa., Y. Hieda, and Sh. Tsukita, 1989. J. Cell Biol. 108:2369-2382). In the present study, we have analyzed the distribution of radixin in dividing cells. For this purpose, an mAb specific for radixin was obtained using chicken gizzard radixin as an antigen. By immunofluorescence microscopy with this mAb and a polyclonal antibody obtained previously, it was clearly shown in rat fibroblastic cells (3Y1 cells) that radixin was highly concentrated at the cleavage furrow during cytokinesis. Radixin appeared to accumulate rapidly at the cleavage furrow at the onset of furrowing, continued to be concentrated at the furrow during anaphase and telophase, and was finally enriched at the midbody. This concentration of radixin at the cleavage furrow was detected in all other cultured cells we examined: bovine epithelial cells (MDBK cells), mouse myeloma cells (P3 cells), rat kangaroo Ptk2 cells, mouse teratocarcinoma cells, and chicken fibroblasts. Furthermore, it became clear that the epitope for the mAb was immunofluorescently masked in the cell-to-cell adherens junctions. Together, these results lead us to conclude that radixin is present in the undercoat of the cell-to-cell adherens junctions and that of the cleavage furrow, although their respective molecular architectures are distinct. The possible roles of radixin at the cleavage furrow are discussed with special reference to the molecular mechanism of the actin filament-plasma membrane interaction at the furrow.

Animals↗
PubMed1991

Specific proto-oncogenic tyrosine kinases of src family are enriched in cell-to-cell adherens junctions where the level of tyrosine phosphorylation is elevated.

To approach the transmembrane signaling pathway in the cell-to-cell adherens junctions (AJ), AJ-specific tyrosine phosphorylation was analyzed. When various types of rat adult tissues were pretreated with sodium orthovanadate, a potent inhibitor of tyrosine phosphatase, immunofluorescence microscopy showed that anti-phosphotyrosine polyclonal antibody specifically stained the undercoat of the cell-to-cell AJ. This indicates that the tyrosine kinase activity is elevated at the undercoat of the cell-to-cell AJ of adult tissues. To identify tyrosine kinases responsible for the high level of tyrosine phosphorylation at AJ, we have performed in vitro phosphorylation experiments with cell-to-cell AJ isolated from rat liver (Tsukita, Sh. and Sa. Tsukita. 1989. J. Cell Biol. 108:31-41) and immunoblotting analyses with specific antibodies for tyrosine kinases. As a result, three proto-oncogenic tyrosine kinases of src family, c-yes, c-src, and lyn kinases, were identified as major tyrosine kinases in the cell-to-cell AJ of hepatocytes. Furthermore, it was immunofluorescently shown that at least two of these kinases, c-yes and c-src kinases, were enriched at the cell-to-cell AJ of various types of cells including hepatocytes. Based on these findings, it is concluded that, in various types of cells, specific proto-oncogenic tyrosine kinases of src-family (c-yes and c-src) are enriched to work as signal mediators in the cell-to-cell AJ where the level of tyrosine phosphorylation is elevated.

Age Factors↗
PubMed1991

Radixin is a novel member of the band 4.1 family.

Radixin is an actin barbed-end capping protein which is highly concentrated in the undercoat of the cell-to-cell adherens junction and the cleavage furrow in the interphase and mitotic phase, respectively (Tsukita, Sa., Y. Hieda, and Sh. Tsukita. 1989 a.J. Cell Biol. 108:2369-2382; Sato, N., S. Yonemura, T. Obinata, Sa. Tsukita, and Sh. Tsukita. 1991. J. Cell Biol. 113:321-330). To further understand the structure and functions of the radixin molecule, we isolated and sequenced the cDNA clones encoding mouse radixin. Direct peptide sequencing of radixin and immunological analysis with antiserum to a fusion protein were performed to confirm that the protein encoded by these clones is identical to radixin. The composite cDNA is 4,241 nucleotides long and codes for a 583-amino acid polypeptide with a calculated molecular mass of 68.5 kD. Sequence analysis has demonstrated that mouse radixin shares 75.3% identity with human ezrin, which was reported to be a member of the band 4.1 family. We then isolated the cDNA encoding mouse ezrin. Sequence analysis and Northern blot analysis revealed that radixin and ezrin are similar but distinct (74.9% identity), leading us to conclude that radixin is a novel member of the band 4.1 family. In erythrocytes the band 4.1 protein acts as a key protein in the association of short actin filaments with a plasma membrane protein (glycophorin), together with spectrin. Therefore, the sequence similarity between radixin and band 4.1 protein described in this study favors the idea that radixin plays a crucial role in the association of the barbed ends of actin filaments with the plasma membrane in the cell-to-cell adherens junction and the cleavage furrow.

Amino Acid Sequence↗
PubMed1991

A 220-kD undercoat-constitutive protein: its specific localization at cadherin-based cell-cell adhesion sites.

Recently we developed an isolation procedure for the cell-to-cell adherens junctions (AJ; cadherin-based junctions) from rat liver (Tsukita, Sh. and Sa. Tsukita. 1989. J. Cell Biol. 108:31-41). In this study, using the isolated AJ, we have obtained two mAbs specific to the 220-kD undercoat-constitutive protein. Immunofluorescence and immunoelectron microscopy with these mAbs showed that this 220-kD protein was highly concentrated at the undercoat of cell-to-cell AJ in various types of tissues and that this protein was located in the immediate vicinity of the plasma membrane in the undercoat of AJ. In the cells lacking typical cell-to-cell AJ, such as fibroblasts, the 220-kD protein was immunofluorescently shown to be coconcentrated with cadherin molecules at cell-cell adhesion sites. These localization analyses appeared to indicate the possible direct or indirect association of the 220-kD protein with cadherin molecules. Furthermore, it was revealed that the 220-kD protein and alpha-spectrin were coimmunoprecipitated with the above mAbs in both the isolated AJ and the brain. The affinity-purified 220-kD protein molecule looked like a spherical particle, and its binding site on the spectrin molecule was shown to be in the position approximately 10-20 nm from the midpoint of spectrin tetramer by low-angle rotary-shadowing electron microscopy. Taking all these results together with biochemical and immunological comparisons, we are persuaded to speculate that the 220-kD protein is a novel member of the ankyrin family. However, the possibility cannot be excluded that the 220-kD protein is an isoform of beta-spectrin. The possible roles of this 220-kD protein in the association of cadherin molecules with the spectrin-based membrane skeletons at the cadherin-based cell-cell adhesion sites are discussed.

3T3 Cells↗
PubMed1990

Localization of adhesive proteins in two newly subdivided zones in electron-lucent matrix of human platelet alpha-granules.

Platelet alpha-granules have been reported to consist of two zones, nucleoid and electron-lucent matrix, with different densities under electron microscopy. When washed human platelets were prepared by a rapid freeze-substitution method using liquid helium, we found that the electron-lucent matrix could be further subclassified into two zones having different densities: the intermediate and the light zones. The light zone was located at the periphery opposite the most dense nucleoid and contained several tubular structures with diameters of about 20 nm. The intermediate zone often laid between the nucleoid and light zone. By careful inspection, intermediate and light zones could even be identified in the platelets embedded in Lowicryl K4M, which where then used to localize several adhesive proteins in these two zone by immunocytochemical studies using the respective polyclonal antibodies. Fibrinogen, thrombospondin, and fibronectin were detected only in the intermediate zone. In contrast, von Willebrand factor (vWF) was localized only in the light zone, suggesting an association between vWF and the tubular structures in the light zone. In the nucleoid, none of these adhesive proteins were detected. Glycoprotein IIb/IIIa, a receptor for these adhesive proteins on the platelet surface, was detected not only on the outer surface of the cell membranes but also on the inner surface of the alpha-granule membrane. These data indicate that two zones with different densities in electron-lucent matrix and functions exist in the platelet alpha-granules.

Blood Coagulation Factors↗
PubMed1990

Localization of adherens junction proteins along the possible sliding interface between secretory ameloblasts of the rat incisor.

Localization of junctions between inner enamel-secretory ameloblasts was examined by immunofluorescence microscopy using antibodies against adherens junction proteins, radixin, vinculin, and A-CAM. All antibodies used stained the boundary between the ameloblasts exclusively in the plane where F-actin was abundant. This suggests that the adherens junctions in the ameloblasts are involved in cell-to-cell movement with actin-based microfilament bundles.

Actins↗
PubMed1989

Isolation of cell-to-cell adherens junctions from rat liver.

A new isolation procedure for cell-to-cell adherens junctions has been developed using rat liver. From the bile canaliculi-enriched fraction obtained by homogenization of the liver and sucrose gradient centrifugation, the fraction rich in adherens junction was recovered by detergent treatment followed by sucrose gradient centrifugation. Light and electron microscopy revealed that this final fraction was mainly composed of the belt-like adherens junctions with their associated short actin filaments. Biochemical and immunological analyses have shown that vinculin is highly enriched in this fraction. Considering that vinculin is known to be localized in the cell-to-cell adherens junctions, we can conclude that we have succeeded in isolating the cell-to-cell adherens junctions. Furthermore, the constituents of the undercoat (dense layer underlying the membrane) of adherens junctions were selectively extracted from the fraction rich in junctions. Upon SDS electrophoresis of this extract, 10 polypeptides including vinculin, alpha-actinin, and actin were dominant. The results obtained are discussed with special reference to the molecular organization of the undercoats of cell-to-cell adherens junctions.

Actinin↗
PubMed1989

A new 82-kD barbed end-capping protein (radixin) localized in the cell-to-cell adherens junction: purification and characterization.

An 82-kD protein has been purified from the undercoat of the adherens junction isolated from the rat liver. The purification scheme includes low salt extraction followed by DEAE-cellulose ion exchange, DNase I-actin affinity, and carboxyl methyl-cellulose ion exchange chromatographies. The purified 82-kD protein was essentially free of contaminants as judged by SDS-PAGE combined with silver staining. The substoichiometric 82-kD protein largely inhibited the actin filament assembly; when the molar ratio of the 82-kD protein to G-actin was 1:1,000, the viscosity was reduced to 28% of the control value. Direct electron microscopic studies revealed that the 82-kD protein selectively inhibited monomer addition at the barbed ends of actin filaments. By use of the antibody raised against the 82-kD protein, this protein was shown by immunofluorescence microscopy to be localized at the cell-to-cell adherens junction in various types of cells. In contrast, the 82-kD protein was not concentrated at the cell-to-substrate adherens junctions (focal contacts). These findings have led us to conclude that the 82-kD protein is a barbed end-capping protein which is associated with the undercoat of the cell-to-cell adherens junction. Hence, we have tentatively designated the 82-kD protein as radixin (from the Latin word radix meaning root).

Acrosome↗