Search results for "exocytosis"
showing 10 items of 56 documents
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…
Direct evidence that FK506 inhibition of FcεRI-mediated exocytosis from RBL mast cells involves calcineurin
1998
eRI-mediated exocytosis of preformed mediators from mast cells and basophils (e.g. histamine, serotonin, beta-hexosaminidase) is sensitive to the immunosuppressants cyclosporin A and FK506 (IC 50 200 and 4 n M , respectively) but not rapamycin. The mechanism of inhibition does not appear to involve tyrosine phosphorylation, hydrolysis of inositol phosphates or calcium flux. Here we report experiments using a molecular approach to assess the role of calcineurin, a serine/threonine phosphatase thought to be the primary pharmacological target of these drugs. Calcineurin’s activity requires association of its catalytic (A) subunit with an intrinsic regulatory (B) subunit. We hypothesized that c…
Distinct endocytic recycling of myelin proteins promotes oligodendroglial membrane remodeling.
2008
The central nervous system myelin sheath is a multilayered specialized membrane with compacted and non-compacted domains of defined protein composition. How oligodendrocytes regulate myelin membrane trafficking and establish membrane domains during myelination is largely unknown. Oligodendroglial cells respond to neuronal signals by adjusting the relative levels of endocytosis and exocytosis of the major myelin protein, proteolipid protein (PLP). We investigated whether endocytic trafficking is common to myelin proteins and analyzed the endocytic fates of proteins with distinct myelin subdomain localization. Interestingly, we found that PLP, myelin-associated glycoprotein (MAG) and myelin-o…
Production of biologically active light chain of tetanus toxin inEscherichia coli
1993
AbstractThe activity of the light (L) chain of tetanus toxin, and of mutants constructed by site-directed mutagenesis, was studied by expression and purification of the proteins from E. coli. Wild-type recombinant L chain (pTet87) was active in the inhibition of exocytosis from cultured bovine adrenal chromaffin cells, although at a level 5–15% of that of L chain purified from tetanus toxin. L chain mutants which terminated at Leu-438 (pTet89), or which contained a Cys-to-Ser mutation at residue 439 (pTet88) were equally as active as the full-length recombinant protein. The reduced activity of pTet87 L chain correlated with C-terminal proteolysis of the protein upon purification. A tryptic …
Phosphorylation of the Usher syndrome 1G protein SANS controls Magi2-mediated endocytosis.
2014
Item does not contain fulltext The human Usher syndrome (USH) is a complex ciliopathy with at least 12 chromosomal loci assigned to three clinical subtypes, USH1-3. The heterogeneous USH proteins are organized into protein networks. Here, we identified Magi2 (membrane-associated guanylate kinase inverted-2) as a new component of the USH protein interactome, binding to the multifunctional scaffold protein SANS (USH1G). We showed that the SANS-Magi2 complex assembly is regulated by the phosphorylation of an internal PDZ-binding motif in the sterile alpha motif domain of SANS by the protein kinase CK2. We affirmed Magi2's role in receptor-mediated, clathrin-dependent endocytosis and showed tha…
Extracellular Vesicles: Delivery Vehicles of Myokines
2019
Movement and regular physical activity are two important factors that help the human body prevent, reduce and treat different chronic diseases such as obesity, type 2 diabetes, heart diseases, hypertension, sarcopenia, cachexia and cancer. During exercise, several tissues release molecules into the blood stream, and are able to mediate beneficial effects throughout the whole body. In particular, contracting skeletal muscle cells have the capacity to communicate with other organs through the release of humoral factors that play an important role in the mechanisms of adaptation to physical exercise. These muscle-derived factors, today recognized as myokines, act as endocrine and paracrine hor…
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…
Elimination of a bacterial pore-forming toxin by sequential endocytosis and exocytosis
2008
Staphylococcus aureus alpha-toxin is the archetype of bacterial pore forming toxins and a key virulence factor secreted by the majority of clinical isolates of S. aureus. Toxin monomers bind to target cells and oligomerize to form small beta-barrel pores in the plasma membrane. Many nucleated cells are able to repair a limited number of lesions by unknown, calcium-independent mechanisms. Here we show that cells can internalize alpha-toxin, that uptake is essential for cellular survival, and that pore-complexes are not proteolytically degraded, but returned to the extracellular milieu in the context of exosome-like structures, which we term toxosomes.
A subunit of eukaryotic translation initiation factor 2α-phosphatase (CreP/PPP1R15B) regulates membrane traffic.
2012
The constitutive reverter of eIF2α phosphorylation (CReP)/PPP1r15B targets the catalytic subunit of protein phosphatase 1 (PP1c) to phosphorylated eIF2α (p-eIF2α) to promote its dephosphorylation and translation initiation. Here, we report a novel role and mode of action of CReP. We found that CReP regulates uptake of the pore-forming Staphylococcus aureus α-toxin by epithelial cells. This function was independent of PP1c and translation, although p-eIF2α was involved. The latter accumulated at sites of toxin attack and appeared conjointly with α-toxin in early endosomes. CReP localized to membranes, interacted with phosphomimetic eIF2α, and, upon overexpression, induced and decorated a pop…
Synaptobrevin cleavage by the tetanus toxin light chain is linked to the inhibition of exocytosis in chromaffin cells
1994
AbstractExocytosis of secretory granules by adrenal chromaffin cells is blocked by the tetanus toxin light chain in a zinc specific manner. Here we show that cellular synaptobrevin is almost completely degraded by the tetanus toxin light chain within 15 min. We used highly purified adrenal secretory granules to show that synaptobrevin, which can be cleaved by the tetanus toxin light chain, is localized in the vesicular membrane. Proteolysis of synaptobrevin in cells and in secretory granules is reversibly inhibited by the zinc chelating agent dipicolinic acid. Moreover, cleavage of synaptobrevin present in secretory granules by the tetanus toxin light chain is blocked by the zinc peptidase …