Biomedical subjects
Publications and source records attributed to Masahiro Yanagisawa.
We present quantum feedback control for deterministic entanglement generation at the single-photon level. The protocol of controlling both total photon number and phase difference is based on the cascade structure of cavities placed in an optical closed loop, quantum nondemolition measurement with cross-Kerr interactions, and Lyapunov stability for feedback design.
During epithelial tumor progression, the loss of E-cadherin expression and inappropriate expression of mesenchymal cadherins coincide with increased invasiveness. Reexpression experiments have established E-cadherin as an invasion suppressor. However, the mechanism by which E-cadherin suppresses invasiveness and the role of mesenchymal cadherins are poorly understood. We show that both p120 catenin and mesenchymal cadherins are required for the invasiveness of E-cadherin-deficient cells. p120 binding promotes the up-regulation of mesenchymal cadherins and the activation of Rac1, which are essential for cell migration and invasiveness. p120 also promotes invasiveness by inhibiting RhoA activity, independently of cadherin association. Furthermore, association of endogenous p120 with E-cadherin is required for E-cadherin-mediated suppression of invasiveness and is accompanied by a reduction in mesenchymal cadherin levels. The data indicate that p120 acts as a rheostat, promoting a sessile cellular phenotype when associated with E-cadherin or a motile phenotype when associated with mesenchymal cadherins.
Peroxisome proliferator-activated receptor gamma (PPARgamma) causes epithelial to mesenchymal transformation (EMT) in intestinal epithelial cells, as evidenced by reorganization of the actin cytoskeleton, acquisition of a polarized, mesenchymal cellular morphology, increased cellular motility, and colony scattering. This response is due to activation of Cdc42, resulting in p21-activated kinase-dependent phosphorylation and activation of MEK1 Ser(298) and activation of ERK1/2. Dominant negative MEK1, MEK2, and ERK2 block PPARgamma-induced EMT, whereas constitutively active MEK1 and MEK2 induce a mesenchymal phenotype similar to that evoked by PPARgamma. PPARgamma also stimulates ERK1/2 phosphorylation in the intestinal epithelium in vivo. PPARgamma induces the p110alpha subunit of phosphoinositide 3-kinase (PI3K), and inhibition of PI3K blocks PPARgamma-dependent phosphorylation of MEK1 Ser(298), activation of ERK1/2, and EMT. We conclude that PPARgamma regulates the motility of intestinal epithelial cells through a mitogen-activated protein kinase cascade that involves PI3K, Cdc42, p21-activated kinase, MEK1, and ERK1/2. Regulation of cellular motility through Rho family GTPases has not been previously reported for nuclear receptors, and elucidation of the mechanism that accounts for the role of PPARgamma in regulating motility of intestinal epithelial cells provides fundamental new insight into the function of this receptor during renewal of the intestinal epithelium.
Peroxisome proliferator-activated receptor-gamma (PPARgamma) is expressed in the intestinal epithelium, yet little is known about the physiological role of PPARgamma in the small bowel or the effects of PPARgamma on small intestinal epithelial cells. The present studies investigate cellular and genomic effects of PPARgamma in nontransformed rat intestinal epithelial cells (RIE). These cells were engineered to express mouse PPARgamma1, and thereby to model the molecular phenotype that obtains upon induction of PPARgamma at the crypt/villus junction in the small intestine. In these studies, we have used a novel third generation thiazolidinedione derivative, RS5444, which activates PPARgamma with an EC50 about 1/50th that of rosiglitazone and has no effect on RIE cells that do not express PPARgamma. We used Affymetrix oligonucleotide microarrays to identify potential PPARgamma-regulated processes in RIE cells, including lipid metabolism, cell proliferation and differentiation, remodeling of the extracellular matrix, cell morphology, cell-cell adhesion, and motility. The genomic profile reflects cellular events that occur following PPARgamma activation: RS5444 inhibited culture growth and caused irreversible G1 arrest, but did not induce apoptosis. In addition, RS5444 caused dramatic changes in cellular morphology which were associated with increased motility and diminished cellular adherence, but no increase in the ability of such cells to digest and invade Matrigel. Inhibition of proliferation, cell cycle arrest, increased motility, and altered adherence are aspects of the differentiated phenotype of villus epithelial cells, which withdraw from the cell cycle at the crypt/villus interface, migrate to the villus tips, and are subsequently shed by loss of contact with the epithelium and the underlying extracellular matrix. Our results are consistent with the hypothesis that PPARgamma regulates critical aspects of differentiation in the small intestinal epithelium. Many nuclear receptors regulate differentiation. However, our results point to novel effects of PPARgamma on cell-cell and cell-matrix interactions, which are not typical of other nuclear receptors.
p120-catenin exists in a membrane-associated cadherin-bound pool, a cytosolic pool that affects Rho GTPases, and a nuclear pool that is thought to associate with the methylation-relevant transcriptional repressor Kaiso. We show here that cytoplasmic p120 can also associate both directly and indirectly with the microtubule network, and that p120 traffics along microtubules toward their plus ends. The direct binding required most of the armadillo repeats and was mutually exclusive for interaction with E-cadherin. Perturbing the p120-microtubule interaction with nocodazole or taxol markedly affected both the tubulin interaction and the balance between cytoplasmic and nuclear p120. The indirect binding occurred via a novel interaction between a segment of the p120 N-terminal domain and conventional kinesin heavy chains. Selective uncoupling of the p120-kinesin interaction by overexpression of the respective p120 and kinesin-binding fragments promoted nuclear p120 accumulation. In addition, expression of full-length kinesin reduced the nuclear accumulation of p120 and blocked the branching phenotype associated with p120 overexpression. Taken together, the data suggest that kinesin affects both the targeting and activity of p120 at several cellular locations.
The SEC-MALS-QELS (size-exclusion chromatography equipped with multiangle light scattering and quasi-elastic light scattering detectors) method using lithium chloride/N,N-dimethylacetamide (LiCl/DMAc) and LiCl/1,3-dimethyl-2-imidazolidinone (LiCl/DMI) as mobile phases was applied to cellulose and cellulose tricarbanilate (CTC) samples with various average degree of polymerization (DP) values. Molecular conformations of cellulose and CTC in the solvents were then discussed and compared on the basis of the relationships between the radii of gyration (R(g,z) or S(2)(z)(1/2)), the hydrodynamic radii (R(h,z)), and weight-average DP (DP(w)) or the contour lengths (L(w)). The Benoit-Doty theory for wormlike polymer chains was applied to the R(g) vs L(w) data obtained, and the theoretical curves with Kuhn segment lengths l(K) of around 18 nm were found to fit the data of both cellulose and CTC molecules in the solvents. It was concluded from the obtained results that both cellulose and CTC molecules have conformations essentially identical to each other in the solvents; they behave as typical semiflexible chains in good solvents.