Search results for "TRANSMEMBRANE PROTEIN"
showing 10 items of 186 documents
Type-II Transmembrane Prolyl Dipeptidases and Matrix Metalloproteinases in Membrane Vesicles of Active Endothelial Cells
2006
Endothelia cells in sparse culture are migratory and increase the production of gelatinases of serine- and metallo-classes in membrane vesicles. Collectively, proteases associated with membrane vesicles degrade extracellular matrix components including type-I and type-IV collagens, laminin and fibronectin. Inhibitor studies suggest the existence of small gelatinases that were derived from these serine- and metallo-proteases. Thus, further studies are warranted to demonstrate the cooperative action of metallo- and serine proteases on cell surfaces and in extracellular vesicles during endothelial cell migration in 3D collagenous matrices, and potential proteolytic activation mechanism for the…
mp23, a Theileria parva transmembrane protein with homology to the protein disulfide isomerase family
2002
The protozoan parasite Theileria parva (Apicomplexa) causes the bovine disease East Coast Fever in endemic areas in Subsaharan Africa. The intralymphocytic schizont stage is largely responsible for the pathogenicity and induces a transformed phenotype in host cells [1]. Current evidence supports a model in which the schizont perturbs the immune response by inducing production of cytokines and stimulating the growth of parasitized cells [2]. We were interested to identify parasite proteins involved in parasite/host interaction and have described earlier a screening procedure for identification of schizont stage-exported proteins based on cell-free expression of cDNA and testing for transloca…
Alpha-toxin of Staphylococcus aureus
1991
Alpha-toxin, the major cytotoxic agent elaborated by Staphylococcus aureus, was the first bacterial exotoxin to be identified as a pore former. The protein is secreted as a single-chain, water-soluble molecule of Mr 33,000. At low concentrations (less than 100 nM), the toxin binds to as yet unidentified, high-affinity acceptor sites that have been detected on a variety of cells including rabbit erythrocytes, human platelets, monocytes and endothelial cells. At high concentrations, the toxin additionally binds via nonspecific absorption to lipid bilayers; it can thus damage both cells lacking significant numbers of the acceptor and protein-free artificial lipid bilayers. Membrane damage occu…
Nimrod, a Putative Phagocytosis Receptor with EGF Repeats in Drosophila Plasmatocytes
2007
SummaryThe hemocytes, the blood cells of Drosophila, participate in the humoral and cellular immune defense reactions against microbes and parasites [1–8]. The plasmatocytes, one class of hemocytes, are phagocytically active and play an important role in immunity and development by removing microorganisms as well as apoptotic cells. On the surface of circulating and sessile plasmatocytes, we have now identified a protein, Nimrod C1 (NimC1), which is involved in the phagocytosis of bacteria. Suppression of NimC1 expression in plasmatocytes inhibited the phagocytosis of Staphylococcus aureus. Conversely, overexpression of NimC1 in S2 cells stimulated the phagocytosis of both S. aureus and Esc…
Recovery of human fibroblasts from attack by the pore-forming alpha-toxin of Staphylococcus aureus.
1994
When applied at low concentrations (10 micrograms/ml), staphylococcal alpha-toxin generates a small channel in keratinocyte and lymphocyte membranes that permits selective transmembrane flux of monovalent ions. Here we show that a moderate concentration (1-50 micrograms/ml) of alpha-toxin similarly produces a small pore in membranes of human fibroblasts. This process leads to rapid leakage of K+ and to a drop in cellular ATP to 10-20% of normal levels in 2 h. In the presence of medium supplemented with serum and at pH 7.4, the cells are able to recover from toxin attack, so that normal levels of K+ and ATP are reached after 6-8 h at 37 degrees C. The repair process is dependent on the prese…
Putative identification of an amphipathic alpha-helical sequence in hemolysin of Escherichia coli (HlyA) involved in transmembrane pore formation.
2008
Abstract Escherichia coli hemolysin is a pore-forming protein belonging to the RTX toxin family. Cysteine scanning mutagenesis was performed to characterize the putative pore-forming domain of the molecule. A single cysteine residue was introduced at 48 positions within the sequence spanning residues 170–400 and labeled with the polarity-sensitive dye badan. Spectrofluorimetric analyses indicated that several amino acids in this domain are inserted into the lipid bilayer during pore formation. An amphipathic α-helix spanning residues 272–298 was identified that may line the aqueous pore. The importance of this sequence was highlighted by the introduction of two prolines at positions 284 and…
Recombinant expression, in vitro refolding, and biophysical characterization of the N-terminal domain of T1R3 taste receptor
2012
Facteur d'impact (5 ans) : 1,617Notoriété à 2 ans : Acceptable (biochem.res.methods); The sweet taste receptor is a heterodimeric receptor composed of the T1R2 and T1R3 subunits, while T1R1 and T1R3 assemble to form the umami taste receptor. T1R receptors belong to the family of class C G-protein coupled receptors (GPCRs). In addition to a transmembrane heptahelical domain, class C GPCRs have a large extracellular N-terminal domain (NTD), which is the primary ligand-binding site. The T1R2 and T1R1 subunits have been shown to be responsible for ligand binding, via their NTDs. However, little is known about the contribution of T1R3-NTD to receptor functions. To enable biophysical characteriza…
NG2 regulates directional migration of oligodendrocyte precursor cells via Rho GTPases and polarity complex proteins.
2013
The transmembrane proteoglycan NG2 is expressed by oligodendrocyte precursor cells (OPC), which migrate to axons during developmental myelination and remyelinate in the adult after migration to injured sites. Highly invasive glial tumors also express NG2. Despite the fact that NG2 has been implicated in control of OPC migration, its mode of action remains unknown. Here, we show in vitro and in vivo that NG2 controls migration of OPC through the regulation of cell polarity. In stab wounds in adult mice we show that NG2 controls orientation of OPC toward the wound. NG2 stimulates RhoA activity at the cell periphery via the MUPP1/Syx1 signaling pathway, which favors the bipolar shape of migrat…
Function of DcuS from Escherichia coli as a Fumarate-stimulated Histidine Protein Kinase in Vitro
2002
The two-component regulatory system DcuSR of Escherichia coli controls the expression of genes of C(4)-dicarboxylate metabolism in response to extracellular C(4)- dicarboxylates such as fumarate or succinate. DcuS is a membrane-integral sensor kinase, and the sensory and kinase domains are located on opposite sides of the cytoplasmic membrane. The intact DcuS protein (His(6)-DcuS) was overproduced and isolated in detergent containing buffer. His(6)-DcuS was reconstituted into liposomes made from E. coli phospholipids. Reconstituted His(6)-DcuS catalyzed, in contrast to the detergent-solubilized sensor, autophosphorylation by [gamma-(33)P]ATP with an approximate K(D) of 0.16 mm for ATP. Up t…
Regulation ofMUC1Expression in Human Mammary Cell Lines by the c-ErbB2 and Ras Signaling Pathways
2001
The MUC1 protein is a highly O-glycosylated transmembrane molecule that is expressed at the luminal surface of most glandular epithelial cells and is upregulated in carcinomas. Here, we report the effect of the activation of the c-ErbB2 --Ras pathway on the expression of the MUC1 gene in the nontumorigenic mammary cell lines MTSV1-7 and HB2 and in the malignant cell lines T47D and ZR75. Endogenous levels of MUC1 mRNA and protein in HB2 clones permanently overexpressing c-ErbB2 or V12-H-Ras were markedly reduced compared with levels in the parental cell lines. Furthermore, in transient transfection assays, the transcription of a CAT reporter construct driven by the MUC1 promoter was inhibite…