monensin and lucifer-yellow

Trafficking pathways underlying the assembly of connexins into gap junctions were examined using living COS-7 cells expressing a range of connexin-aequorin (Cx-Aeq) chimeras. By measuring the chemiluminescence of the aequorin fusion partner, the translocation of oligomerized connexins from intracellular stores to the plasma membrane was shown to occur at different rates that depended on the connexin isoform. Treatment of COS-7 cells expressing Cx32-Aeq and Cx43-Aeq with brefeldin A inhibited the movement of these chimera to the plasma membrane by 84 +/- 4 and 88 +/- 4%, respectively. Nocodazole treatment of the cells expressing Cx32-Aeq and Cx43-Aeq produced 29 +/- 16 and 4 +/- 7% inhibition, respectively. In contrast, the transport of Cx26 to the plasma membrane, studied using a construct (Cx26/43T-Aeq) in which the short cytoplasmic carboxyl-terminal tail of Cx26 was replaced with the extended carboxyl terminus of Cx43, was inhibited 89 +/- 5% by nocodazole and was minimally affected by exposure of cells to brefeldin A (17 +/-11%). The transfer of Lucifer yellow across gap junctions between cells expressing wild-type Cx32, Cx43, and the corresponding Cx32-Aeq and Cx43-Aeq chimeras was reduced by nocodazole treatment and abolished by brefeldin A treatment. However, the extent of dye coupling between cells expressing wild-type Cx26 or the Cx26/43T-Aeq chimeras was not significantly affected by brefeldin A treatment, but after nocodazole treatment, transfer of dye to neighboring cells was greatly reduced. These contrasting effects of brefeldin A and nocodazole on the trafficking properties and intercellular dye transfer are interpreted to suggest that two pathways contribute to the routing of connexins to the gap junction.

Topics: Aequorin; Animals; Brefeldin A; Calcium; Cell Membrane; Connexin 26; Connexins; COS Cells; Gap Junction beta-1 Protein; Gap Junctions; Isoquinolines; Kinetics; Luminescent Measurements; Monensin; Nocodazole; Recombinant Fusion Proteins; Transfection

Extensive internalization into endothelial cells has been found for a water soluble amphipathic 26-mer beta-sheet peptide (FLUOS-DPKGDPKGVTVTVTVTVTGKGDPKPD-NH2; VT5). With the D-Val13,D-Thr14 di-D-amino acid analog of VT5 (DD-VT5), exhibiting an identical primary structure but no propensity to adopt a beta-sheet conformation, only about 5% of the cellular uptake of VT5 was found. The mechanism of entry of VT5 into the cells remained unclear, but proved to be energy, temperature and pH dependent and, therefore, clearly distinct from that reported for helical amphipathic peptides. No detectable cytotoxicity, high solubility in water and the found extensive entry into endothelial cells make VT5 appear a good lead for developing new types of vectors for delivering oligonucleotides and peptides into intact cells.

Topics: Amino Acid Sequence; Animals; Aorta; Biological Transport; Brefeldin A; Cattle; Cell Survival; Cells, Cultured; Cyclopentanes; Deoxyglucose; Endothelium, Vascular; Fluoresceins; Fluorescent Dyes; Hydrogen-Ion Concentration; Isoquinolines; Molecular Sequence Data; Monensin; Peptides; Protein Structure, Secondary; Proteins; Solubility; Temperature; Vincristine

Lucifer yellow (LY) accumulation was used to measure macrophage pinocytosis. The hematopoietic growth factors, macrophage colony-stimulating factor (CSF-1), granulocyte-macrophage CSF (GM-CSF), and interleukin 3, and the macrophage activators, lipopolysaccharide and zymosan, all stimulated LY uptake in both murine bone marrow-derived macrophages (BMMs) and resident peritoneal macrophages (RPMs) without affecting LY efflux. The stimulation of pinocytosis in the poorly cycling RPMs and in BMMs by nonmitogens dissociates stimulation of pinocytosis from subsequent DNA synthesis. Regulation of pinocytosis in BMMs appears to be independent of that of urokinase-type plasminogen activator expression. The increases in CSF-mediated BMM pinocytosis were not inhibited by pertussis toxin, by elevations in intracellular cAMP, or by glucocorticoids and were only partially inhibited by inhibitors of Na+/H+ antiport and Na+/K(+)-ATPase activities. Protein kinase C activation could be involved in regulating BMM pinocytosis because phorbol myristate acetate, oleoylacyglycerol, and exogenously added phospholipase C can all stimulate it. Ca2+ ionophores were inactive, whereas the Na+/H+ ionophore monensin potently inhibited BMM pinocytosis.

Topics: Animals; Bone Marrow Cells; Calcium; Colony-Stimulating Factors; Cyclic AMP; Dexamethasone; Granulocyte-Macrophage Colony-Stimulating Factor; Interleukin-3; Isoquinolines; Macrophage Colony-Stimulating Factor; Macrophages; Mice; Mice, Inbred Strains; Monensin; Peritoneal Cavity; Pertussis Toxin; Pinocytosis; Protein Kinase C; Sodium; Type C Phospholipases; Urokinase-Type Plasminogen Activator; Virulence Factors, Bordetella