Search results for "cytoskeleton"

2021

Primary cilia are sensory organelles vital for developmental and physiological processes. Their dysfunction causes a range of phenotypes including retinopathies. Although primary cilia have been described in the retinal pigment epithelium (RPE), little is known about their contribution to biological processes within this tissue. Ciliary proteins are increasingly being identified in non-ciliary locations and might carry out additional functions, disruption of which possibly contributes to pathology. The RPE is essential for maintaining photoreceptor cells and visual function. We demonstrate that upon loss of Bbs8, predominantly thought to be a ciliary gene, the RPE shows changes in gene and …

Rhodopsin transport in the membrane of the connecting cilium of mammalian photoreceptor cells

2000

The transport of the photopigment rhodopsin from the inner segment to the photosensitive outer segment of vertebrate photoreceptor cells has been one of the main remaining mysteries in photoreceptor cell biology. Because of the lack of any direct evidence for the pathway through the photoreceptor cilium, alternative extracellular pathways have been proposed. Our primary aim in the present study was to resolve rhodopsin trafficking from the inner to the outer segment. We demonstrate, predominantly by high-sensitive immunoelectron microscopy, that rhodopsin is also densely packed in the membrane of the photoreceptor connecting cilium. Present prominent labeling of rhodopsin in the ciliary mem…

Arginine deficiency leads to impaired cofilin dephosphorylation in activated human T lymphocytes

2012

The amino acid arginine is fundamentally involved in the regulation of the immune response during infection, inflammatory diseases and tumor growth. Arginine deficiency (e.g. due to the myeloid cell enzyme arginase) inhibits proliferation and effector functions of activated T lymphocytes. Here, we studied intracellular mechanisms mediating this suppression of human T lymphocytes. Our proteomic analysis revealed an impaired dephosphorylation of the actin-binding protein cofilin upon T-cell activation in the absence of arginine. We show that this correlates with alteration of actin polymerization and impaired accumulation of CD2 and CD3 in the evolving immunological synapse in T cell-antigen …

Yeast karyopherins Kap123 and Kap95 are related to the function of the cell integrity pathway

2009

The characterization of mutant strains in the gene encoding karyopherin Kap123 has revealed several morphogenetic defects. Inactivation of KAP123 caused alterations in the actin cytoskeleton, resulting in hyperpolarization and resistance to the actin polymerization inhibitor latrunculin B. In fact, the level of actin filaments is increased in kap123 mutant cells. In addition to the defect in actin cytoskeleton, the kap123 mutant cells showed a weakened cell wall, cell lysis and a growth defect in either the presence of sodium dodecyl sulfate or at high temperatures, which is alleviated by osmotic stabilizers. These defects in cell integrity and the actin cytoskeleton suggested a relationshi…

Rot1 plays an antagonistic role to Clb2 in actin cytoskeleton dynamics throughout the cell cycle.

2007

ROT1 is an essential gene whose inactivation causes defects in cell cycle progression and morphogenesis in budding yeast. Rot1 affects the actin cytoskeleton during the cell cycle at two levels. First, it is required for the maintenance of apical growth during bud growth. Second, Rot1 is necessary to polarize actin cytoskeleton to the neck region at the end of mitosis; because of this defect, rot1 cells do not properly form a septum to complete cell division. The inability to polarize the actin cytoskeleton at the end of mitosis is not due to a defect in the recruitment of the polarisome scaffold protein Spa2 or the actin cytoskeleton regulators Cdc42 and Cdc24 in the neck region. Previous …

Proprotein convertase 5/6 is critical for embryo implantation in women: regulating receptivity by cleaving ebp50, modulating ezrin binding, and membr…

2011

Establishment of endometrial receptivity is vital for successful embryo implantation; its failure causes infertility. Epithelial receptivity acquisition involves dramatic structural changes in the plasma membrane and cytoskeleton. Proprotein convertase 5/6 (PC6), a serine protease of the proprotein convertase (PC) family, is up-regulated in the human endometrium specifically at the time of epithelial receptivity and stromal cell decidualization. PC6 is the only PC member tightly regulated in this manner. The current study addressed the importance and mechanisms of PC6 action in regulating receptivity in women. PC6 was dysregulated in the endometrial epithelium during the window of implantat…

Macroporous Scaffolds Based on Chitosan and Bioactive Molecules†

2007

Chitosan-based macroporous scaffolds for tissue engineering applications are developed by cryogelation in aqueous media. The cryogels obtained are modified using a new RGD-containing peptide developed in this laboratory. A RGD-containing peptide is chemically attached to the surface of the cryogels to improve cell adhesion to the 3D-structure chitosan-based scaffolds. The synthesis, physico-chemical, and biological evaluations of the system are described, and the optimization of the formulations is carried out by varying the reaction parameters. Fibroblasts and endothelial cells are used in cell cultures to determine cell behavior and the cytocompatibility of the macroporous cryogels. Cell …

Inhibition of FcεRI-mediated Activation of Rat Basophilic Leukemia Cells by Clostridium difficile Toxin B (Monoglucosyltransferase)

1996

Abstract Treatment of rat basophilic leukemia (RBL) 2H3-hm1 cells with Clostridium difficile toxin B (2 ng/ml), which reportedly depolymerizes the actin cytoskeleton, blocked [3H]serotonin release induced by 2,4-dinitrophenyl-bovine serum albumin, carbachol, mastoparan, and reduced ionophore A23187-stimulated degranulation by about 55-60%. In lysates of RBL cells, toxin B 14C-glucosylated two major and one minor protein. By using two-dimensional gel electrophoresis and immunoblotting, RhoA and Cdc42 were identified as protein substrates of toxin B. In contrast to toxin B, Clostridium botulinum transferase C3 that selectively inactivates RhoA by ADP-ribosylation did not inhibit degranulation…

3D Morphology, ultrastructure and development of Ceratomyxa puntazzi stages: first insights into the mechanisms of motility and budding in the Myxozo…

2012

Free, amoeboid movement of organisms within media as well as substrate-dependent cellular crawling processes of cells and organisms require an actin cytoskeleton. This system is also involved in the cytokinetic processes of all eukaryotic cells. Myxozoan parasites are known for the disease they cause in economical important fishes. Usually, their pathology is related to rapid proliferation in the host. However, the sequences of their development are still poorly understood, especially with regard to pre-sporogonic proliferation mechanisms. The present work employs light microscopy (LM), electron microscopy (SEM, TEM) and confocal laser scanning microscopy (CLSM) in combination with specific…

An Extended Filament Based Lamellipodium Model Produces Various Moving Cell Shapes in the Presence of Chemotactic Signals

2015

The Filament Based Lamellipodium Model (FBLM) is a two-phase two-dimensional continuum model, describing the dynamcis of two interacting families of locally parallel actin filaments (C.Schmeiser and D.Oelz, How do cells move? Mathematical modeling of cytoskeleton dynamics and cell migration. Cell mechanics: from single scale-based models to multiscale modeling. Chapman and Hall, 2010). It contains accounts of the filaments' bending stiffness, of adhesion to the substrate, and of cross-links connecting the two families. An extension of the model is presented with contributions from nucleation of filaments by branching, from capping, from contraction by actin-myosin interaction, and from a pr…