thapsigargin and kifunensine

Lung endothelial barrier dysfunction leads to severe pathologies, including the lethal Acute Respiratory Distress Syndrome. P53 has been associated with anti-inflammatory activities. The current study employs a variety of unfolded protein response (UPR) activators and inhibitors to investigate the regulation of P53 by UPR in lung cells. The bovine cells that were exposed to the UPR inductors brefeldin A, dithiothreitol, and thapsigargin; demonstrated elevated expression levels of P53 compared to the vehicle-treated cells. On the contrary, the UPR inhibitors N-acetyl cysteine, kifunensine, and ATP-competitive IRE1α kinase-inhibiting RNase attenuator; produced the opposite effects. The outcomes of the present study reveal a positive regulation between UPR and P53. Since it has been shown that a mild induction of the unfolded protein response opposes inflammation, we suggest that P53 is involved in those protective activities in the lung.

Topics: Acetylcysteine; Alkaloids; Animals; Brefeldin A; Cattle; Cells, Cultured; Dithiothreitol; Endothelium; Genes, p53; Pulmonary Artery; Thapsigargin; Unfolded Protein Response

Quality control in the endoplasmic reticulum must discriminate nascent proteins in their folding process from terminally unfolded molecules, selectively degrading the latter. Unassembled Ig-mu and J chains, two glycoproteins with five N-linked glycans and one N-linked glycan, respectively, are degraded by cytosolic proteasomes after a lag from synthesis, during which glycan trimming occurs. Inhibitors of mannosidase I (kifunensine), but not of mannosidase II (swainsonine), prevent the degradation of mu chains. Kifunensine also inhibits J chain dislocation and degradation, without inhibiting secretion of IgM polymers. In contrast, glucosidase inhibitors do not significantly affect the kinetics of mu and J degradation. These results suggest that removal of the terminal mannose from the central branch acts as a timer in dictating the degradation of transport-incompetent, glycosylated Ig subunits in a calnexin-independent way. Kifunensine does not inhibit the degradation of an unglycosylated substrate (lambda Ig light chains) or of chimeric mu chains extended with the transmembrane region of the alpha T cell receptor chain, implying the existence of additional pathways for extracting proteins from the endoplasmic reticulum lumen for proteasomal degradation.

Topics: Alkaloids; Cysteine Endopeptidases; Cytosol; Endoplasmic Reticulum; Enzyme Inhibitors; Glycoproteins; Glycosylation; Homeostasis; Humans; Immunoglobulin J-Chains; Immunoglobulin mu-Chains; Kinetics; Mannosidases; Multienzyme Complexes; Multiple Myeloma; Proteasome Endopeptidase Complex; Protein Subunits; Receptors, Antigen, T-Cell, alpha-beta; Recombinant Fusion Proteins; Thapsigargin; Tumor Cells, Cultured