Secretion, Surface Localization, Turnover, and Steady State Expression of Protein Disulfide Isomerase in Rat Hepatocytes

Abstract

Protein disulfide isomerase in isolated rat hepatocytes was present at a concentration of 7 micrograms/mg cell protein, representing a approximately 2-fold enrichment compared to isolated hepatic non-parenchymal cells. Though localized mainly in microsomal fractions of hepatocytes, direct immunofluorescence and cell surface radioiodination followed by immunoprecipitation revealed the presence of M(r) 57,000 disulfide isomerase at the cell surface. Electrostatic interaction of the protein with the cell surface was suggested by susceptibility to carbonate washing. Metabolic radiolabeling and immunoprecipitation studies also indicated that some of the newly synthesized M(r) 57,000 disulfide isomerase was secreted. Treatment of cells with colchicine markedly reduced the recovery of disulfide isomerase from the media, indicating microtubular-directed secretion of the protein. Partial staphlococcal V8 proteolytic digestion of the secreted protein revealed a peptide pattern similar to that of the cellular protein. Immunoprecipitation with antibody specific to the -KDEL peptide retention sequence confirmed the presence of this sequence in the secreted protein. Studies of the turnover of disulfide isomerase revealed a half-life of approximately 96 h. Treatment of cells with tunicamycin or heat shock resulted in an increased recovery of newly synthesized disulfide isomerase from cell lysates but diminished recovery from the media. The secretion and cell surface distribution of disulfide isomerase in hepatocytes may be important for the pathogenesis of immune mediated liver injury.

The protein disulphide-isomerase family: unravelling a string of folds

“…There have been several reports on the possible extracellular localization of PDI in some cell types, despite the integrity of the KDEL signal [118][119][120]. Of these, perhaps the most noteworthy is the cell-adhesion protein retina cognin [121], a 50 kDa retinaspecific protein which is probably a truncated version of PDI lacking the a domain and the C-terminal KDEL tetrapeptide [122,123].…”

Purification and Cloning of an Apoptosis-Inducing Protein Derived from Fish Infected with Anisakis simplex, a Causative Nematode of Human Anisakiasis

“…retained there by continuous retrieval from a post-ER compartment, which relies on a pH-dependent interaction of the retention signal with a specific receptor (15,16). Some proteins with the KDEL retention signal were reported to be exported from the ER to plasma membranes or extracellular medium under normal conditions or by an activation-dependent mechanism (17)(18)(19). To investigate whether AIP can be secreted as a functional molecule, we constructed pSecAIP, which contained the murine Ig -chain leader sequence in place of the signal sequence of AIP, to fully function for translocation into ER of mammalian cells.…”

Characterization of the S-Denitrosation Activity of Protein Disulfide Isomerase

“…Although large levels of this enzyme are found in the endoplasmic reticulum, PDI is secreted from cells in which it associates electrostatically with the cell surface (2,3). One of the most studied functions of PDI is its ability to catalyze isomerization and rearrangement of disulfide bonds in the endoplasmic reticulum, contributing to a proper folding of nascent proteins (4).…”