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Biomedical subjects

A Wohlwend

Publications and source records attributed to A Wohlwend.

At least 19 recordsLinked to original sources
PubMed1992

Polarized secretion of urokinase-type plasminogen activator by epithelial cells.

Numerous epithelial cell types produce and secrete plasminogen activators (PAs) and/or PA inhibitors (PAIs). When epithelial cells were grown on polycarbonate filters and their apical and basolateral secretion products analyzed, PA activity accumulated in a highly polarized fashion; depending upon the cell line, the compartment of PA accumulation was either apical (MDCK I cells and HBL-100 cells) or basolateral (LLC-PK1, CaCo-2, and HeLa cells). By contrast, PAI-1 was recovered in roughly equal amounts in both compartments. Basolateral accumulation of urokinase-type plasminogen activator (uPA), but not its apical targeting, required an acidic compartment and the integrity of the cytoskeleton. Polarity of uPA accumulation did not result from removal of the free enzyme from the opposite compartment through its binding to the cell surface. Transfection with wild-type or mutated murine uPA demonstrated that neither the "growth factor" domain nor the kringle domain is required for the appropriate sorting of the protein. We propose that polarized secretion of PAs is one mechanism whereby cells spatially control extracellular proteolysis.

Ammonium Chloride↗
PubMed1989

Characterization of the cellular binding site for the urokinase-type plasminogen activator.

Human urokinase-type plasminogen activator (uPA) binds rapidly and with high affinity to a number of human cell types; this localizes plasmin generation to the close environment of the cell surface. uPA binding to HeLa and U937 cells is mediated by a single class of sites with an affinity of 3.4 +/- 1.3 x 10(-10) M. Binding is abolished by treatment of the cells with trypsin. Chemical cross-linking of Mr 55,000 125I-uPA to the surface of HeLa and U937 cells with disuccinimidyl suberate or with formaldehyde results in the formation of a labeled complex of Mr 100,000, suggesting a Mr of 45,000 +/- 5,000 for the receptor or a subunit thereof. When cells solubilized in Triton X-114 are subjected to heat-induced phase separation, unoccupied receptor, receptor-bound 125I-uPA, and cross-linked 125I-uPA-receptor complex all partition in the detergent phase, whereas the unbound ligand remains in the aqueous phase; similar phase partitioning is observed with endogenous uPA-receptor complexes from cultured human and murine cells. Thus, uPA bound at the cell surface is tightly associated with an amphiphilic membrane protein. Interaction of uPA with this plasma membrane receptor is species-specific, since human uPA fails to bind to murine cells, and murine uPA does not bind to human cells. Finally, incubation of HeLa cells in the presence of epidermal growth factor or phorbol 12-myristate 13-acetate results, over a period of 24 h, in a progressive change in uPA binding: an approximately 10-fold increase in the number of sites is accompanied by a 10-fold decrease in their affinity. Cross-linking and phase partitioning of 125I-uPA bound to epidermal growth factor- or phorbol 12-myristate 13-acetate-treated cells indicate that, as in control conditions, it is associated with a Mr 45,000 cell surface amphiphilic polypeptide.

Cell Line↗
PubMed1989

Facultative polypeptide translocation allows a single mRNA to encode the secreted and cytosolic forms of plasminogen activators inhibitor 2.

Two forms of plasminogen activators inhibitor 2 (PAI-2) are synthesized by human and murine monocytes/macrophages: one accumulates in the cytosol, while the other is translocated into the endoplasmic reticulum, glycosylated and secreted. We show here that a single mRNA encodes both forms of PAI-2. Firstly, a single PIA-2 mRNA was detected by Northern blot hybridization and by RNase protection. Secondly, transfection of a PAI-2 cDNA led to the synthesis of both forms of PAI-2. Finally, in vitro translation of an mRNA transcript of the PAI-2 cDNA in the presence of microsomal membranes generated two topologically distinct forms of PAI-2. The cytosolic and secreted forms of PAI-2 do not result from the use of two translation start sites, since their synthesis initiates at the same AUG, in a sequence context that is conserved between the human and murine genes. Thus, the accumulation of one polypeptide into two topologically distinct cellular compartments can be achieved by facultative translocation.

Amino Acid Sequence↗
PubMed1988

A comparison of the marginal fit of three cast ceramic crown systems.

The conclusions were: 1. The Cerestore crown system produced an impressive marginal fit without technique sensitivity. However, irregularities on the crown margin due to the porosities of the fired core were noted. 2. The Dicor castable ceramic crown system in this study produced rounded marginal openings because of the shrinkage during ceramming, the treatment of the surface texture after ceramming, and damage from air abrasives. 3. The Ceplatec crown system produced a suitable marginal fit when the distortion of the foil coping during porcelain firing was controlled. The quality of the margin was ultimately determined by the skill of the technician.

Aluminum Oxide↗
PubMed1987

Plasminogen activator-specific inhibitors in mouse macrophages: in vivo and in vitro modulation of their synthesis and secretion.

Mouse resident peritoneal macrophages synthesize two plasminogen activator-specific inhibitors (PAI) that are functionally and antigenically related, but differ in their apparent Mr and oligosaccharide content. Most of the Mr 40,000 inhibitor can be recovered from the cell lysate, whereas the Mr 55,000 glycosylated PAI is preferentially secreted. The murine macrophage PAI are functionally similar and immunologically related to PAI synthesized and secreted by human monocytes-macrophages, and to a PAI from human placenta (PAI-2). PAI production by murine mononuclear phagocytes can be modulated both in vivo and in vitro. Bone marrow-derived macrophages do not produce detectable PAI, whereas inflammatory macrophages obtained from thioglycollate-induced peritoneal exudates produce only low levels of PAI. In cultures of resident peritoneal macrophages, phorbol myristate acetate and cholera toxin increase the synthesis of the Mr 55,000 secreted PAI, whereas dexamethasone decreases the synthesis of both PAI; the production of PAI is also enhanced in the presence of macrophage colony-stimulating factor (CSF-1). The overall proteolytic activity of mononuclear phagocytes thus depends in part on the controlled synthesis and secretion of PAI. The balance between the production of plasminogen activators and of their inhibitors could be critical in determining the level of plasminogen-dependent extracellular proteolysis associated with different phases of the inflammatory response.

Animals↗
PubMed1987

Plasminogen activator-specific inhibitors produced by human monocytes/macrophages.

Human monocytes/macrophages produce plasminogen activator-specific inhibitors (PAIs) that form covalent complexes with urokinase-type plasminogen activator (uPA). We have characterized two functionally and antigenically related forms of PAIs produced by resting and phorbol myristate acetate (PMA)-treated U 937 cells: an Mr 40,000 form, presumably nonglycosylated, with a pI of 5.2, that is constitutively synthetized by these cells and that remains predominantly intracellular; a PMA-induced form of heterogeneous Mr (50,000-65,000) with a pI of 4.7, that is preferentially secreted; this PAI is glycosylated with terminal sialic acid residue(s). Biosynthetic labeling experiments demonstrated that both PAIs are synthetized by U 937 cells. They are inactivated upon treatment with propanol, heat, and acid; the covalent and equimolar complexes formed between these PAIs and 125I-uPA are dissociated by ammonium hydroxide, suggesting that the PAIs are linked to uPA via an ester bond. Human peripheral blood monocytes/macrophages also produce the two forms of PAI. These PAIs are clearly different from the main plasma protease inhibitors and they are both antigenically related to the PAI-2 characterized in human placenta.

Cell Line↗