Search results for "endoplasmic reticulum"
showing 10 items of 306 documents
Paraoxonase-2 Reduces Oxidative Stress in Vascular Cells and Decreases Endoplasmic Reticulum Stress–Induced Caspase Activation
2007
Background— In the vascular system, elevated levels of reactive oxygen species (ROS) produce oxidative stress and predispose to the development of atherosclerosis. Therefore, it is important to understand the systems producing and those scavenging vascular ROS. Here, we analyzed the ROS-reducing capability of paraoxonase-2 (PON2) in different vascular cells and its involvement in the endoplasmic reticulum stress pathway known as the unfolded protein response. Methods and Results— Quantitative real-time polymerase chain reaction and Western blotting revealed that PON2 is equally expressed in vascular cells and appears in 2 distinct glycosylated isoforms. By determining intracellular ROS, we…
Dithiothreitol Treatment of Madin-Darby Canine Kidney Cells Reversibly Blocks Export from the Endoplasmic Reticulum but Does Not Affect Vectorial Tar…
1995
Addition of dithiothreitol (DTT) to the culture medium of Madin-Darby canine kidney (MDCK) cells blocks transport of newly synthesized gp80 (clusterin, apolipoprotein J), a soluble marker protein for apical exocytosis in this epithelial cell line. In cells treated with DTT during pulse labeling, gp80 is retained in the endoplasmic reticulum. After removal of the reducing agent, gp80 is posttranslationally oxidized and secreted at the apical surface of MDCK cell monolayers. This demonstrates that when folded and oxidized posttranslationally, gp80 can acquire a conformation that exhibits sorting signals for vectorial targeting. In the continuous presence of DTT, the transepithelial electrical…
Transmembrane but not soluble helices fold inside the ribosome tunnel
2018
Integral membrane proteins are assembled into the ER membrane via a continuous ribosome-translocon channel. The hydrophobicity and thickness of the core of the membrane bilayer leads to the expectation that transmembrane (TM) segments minimize the cost of harbouring polar polypeptide backbones by adopting a regular pattern of hydrogen bonds to form α-helices before integration. Co-translational folding of nascent chains into an α-helical conformation in the ribosomal tunnel has been demonstrated previously, but the features governing this folding are not well understood. In particular, little is known about what features influence the propensity to acquire α-helical structure in the ribosom…
Calcium negatively regulates meprin β activity and attenuates substrate cleavage
2015
The meprin β metalloproteinase is an important enzyme in extracellular matrix turnover, inflammation, and neurodegeneration in humans and mice. Previous studies showed a diminished cleavage of certain meprin β substrates in the presence of calcium, although the mechanism was not clear. With the help of a specific fluorogenic peptide assay and the human amyloid precursor protein as substrate, we demonstrated that the influence of calcium is most likely a direct effect on human meprin β itself. Analyzing the crystal structures of pro- and mature meprin β helped to identify a cluster of negatively charged amino acids forming a potential calcium binding site. Mutation of 2 of these residues (D2…
Perturbed interactions of mutant proteolipid protein/DM20 with cholesterol and lipid rafts in oligodendroglia: implications for dysmyelination in spa…
2006
Missense mutations in the humanPLP1gene lead to dysmyelinating diseases with a broad range of clinical severity, ranging from severe Pelizaeus–Merzbacher disease (PMD) to milder spastic paraplegia type 2 (SPG-2). The molecular pathology has been generally attributed to endoplasmic reticulum (ER) retention of misfolded proteolipid protein (PLP) (and its splice isoform DM20) and induction of the unfolded protein response. As opposed to previous studies of heterologous expression systems, we have analyzed PLP/DM20 trafficking in oligodendroglial cells, thereby revealing differences between PMD and SPG-2-associated PLP/DM20 isoforms. PLPA242Vand DM20A242V(jimpy-msdin mice), associated with seve…
Proteomic identification of the heterogeneous nuclear ribonucleoprotein K as irradiation responsive protein related to migration
2014
Abstract Irradiation resistance is a major obstacle of head and neck squamous cell carcinoma (HNSCC) therapy, limiting treatment success and patient survival. The aim of our experiments was to identify irradiation-regulated proteins as potential drug targets. Two established HNSCC cell lines (HNSCCUM-01T and HNSCCUM-02T) were treated with a single 8 Gy (Gray) fraction of irradiation. Changes in cellular protein expression were studied after 24 h by means of 2D-electrophoresis and MALDI–TOF-mass spectrometry. Ninety-four differentially expressed proteins were identified. The expression levels of four proteins were regulated similarly in both cell lines after irradiation treatment, i.e., GRP7…
Classes of non-conventional tetraspanins defined by alternative splicing
2019
AbstractTetraspanins emerge as a family of membrane proteins mediating an exceptional broad diversity of functions. The naming refers to their four transmembrane segments, which define the tetraspanins‘ typical membrane topology. In this study, we analyzed alternative splicing of tetraspanins. Besides isoforms with four transmembrane segments, most mRNA sequences are coding for isoforms with one, two or three transmembrane segments, representing structurally mono-, di- and trispanins. Moreover, alternative splicing may alter transmembrane topology, delete parts of the large extracellular loop, or generate alternative N- or C-termini. As a result, we define structure-based classes of non-con…
Role of JAK/STAT in Interstitial Lung Diseases; Molecular and Cellular Mechanisms
2021
Interstitial lung diseases (ILDs) comprise different fibrotic lung disorders characterized by cellular proliferation, interstitial inflammation, and fibrosis. The JAK/STAT molecular pathway is activated under the interaction of a broad number of profibrotic/pro-inflammatory cytokines, such as IL-6, IL-11, and IL-13, among others, which are increased in different ILDs. Similarly, several growth factors over-expressed in ILDs, such as platelet-derived growth factor (PDGF), transforming growth factor β1 (TGF-β1), and fibroblast growth factor (FGF) activate JAK/STAT by canonical or non-canonical pathways, which indicates a predominant role of JAK/STAT in ILDs. Between the different JAK/STAT iso…
The ER-Membrane Transport System Is Critical for Intercellular Trafficking of the NSm Movement Protein and Tomato Spotted Wilt Tospovirus.
2015
Plant viruses move through plasmodesmata to infect new cells. The plant endoplasmic reticulum (ER) is interconnected among cells via the ER desmotubule in the plasmodesma across the cell wall, forming a continuous ER network throughout the entire plant. This ER continuity is unique to plants and has been postulated to serve as a platform for the intercellular trafficking of macromolecules. In the present study, the contribution of the plant ER membrane transport system to the intercellular trafficking of the NSm movement protein and Tomato spotted wilt tospovirus (TSWV) is investigated. We showed that TSWV NSm is physically associated with the ER membrane in Nicotiana benthamiana plants. An…
Age-dependent regulation of antioxidant genes by p38α MAPK in the liver
2018
p38α is a redox sensitive MAPK activated by pro-inflammatory cytokines and environmental, genotoxic and endoplasmic reticulum stresses. The aim of this work was to assess whether p38α controls the antioxidant defense in the liver, and if so, to elucidate the mechanism(s) involved and the age-related changes. For this purpose, we used liver-specific p38α-deficient mice at two different ages: young-mice (4 months-old) and old-mice (24 months-old). The liver of young p38α knock-out mice exhibited a decrease in GSH levels and an increase in GSSG/GSH ratio and malondialdehyde levels. However, old mice deficient in p38α had higher hepatic GSH levels and lower GSSG/GSH ratio than young p38α knock-…