Tissue distribution of ERp61 and association of its increased expression with IgG production in hybridoma cells.
A protein of molecular weight 60 kDa was purified from the culture medium of a murine colon carcinoma cell line, colon26, and its partial amino-acid sequence determined. Extremely high homology was found with the deduced sequence from cDNA of rat ERp61, earlier found to be an endoplasmic reticulum (ER)-resident protein with redox activity and a similar structure to protein disulfide isomerase (PDI). Western blotting analysis showed that colon26 cells secrete a significant amount of ERp61 into culture medium, although most remains intracellular. The thiol:protein disulfide oxidoreductase activity of the purified mouse ERp61 was demonstrated by insulin-reduction assay. The ER location of the protein in fibroblasts was immunocytochemically confirmed by double staining for ERp61 and another ER-resident protein, PDI or Hsp47. Immunohistochemical studies of murine tissues showed a ubiquitous distribution of ERp61 in a wide variety of cell types. However, it was particularly abundant in plasma cells, mucus-secreting cells in various tissues, neuroendocrine cells including neurons, and follicular epithelia of thyroid gland that actively synthesize and secrete proteins containing cysteine residues. Furthermore, a high correlation was observed between intracellular amounts of ERp61 and immunoglobulin production by hybridoma cells. These results indicate that ERp61 may be involved in disulfide bond formation for such proteins.
Kozaki
K
K
Second Department of Pathology, Nagoya University School of Medicine, Japan.
Miyaishi
O
O
Asai
N
N
Iida
K
K
Sakata
K
K
Hayashi
M
M
Nishida
T
T
Matsuyama
M
M
Shimizu
S
S
Kaneda
T
T
D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D015153:Blotting, Western; D003110:Colonic Neoplasms; D004273:DNA, Neoplasm; D004721:Endoplasmic Reticulum / Q000276:immunology / Q000378:metabolism*; D006360:Heat-Shock Proteins / Q000276:immunology / Q000378:metabolism*; D006825:Hybridomas / Q000166:cytology / Q000276:immunology; D007074:Immunoglobulin G / Q000096:biosynthesis*; D007150:Immunohistochemistry; D007535:Isomerases; D051379:Mice; D008969:Molecular Sequence Data; D009928:Organ Specificity; D010084:Oxidation-Reduction; D019704:Protein Disulfide-Isomerases; D014407:Tumor Cells, Cultured
D004273:DNA, Neoplasm; D006360:Heat-Shock Proteins; D007074:Immunoglobulin G; D007535:Isomerases; C513196:PDIA3 protein, rat; C513195:Pdia3 protein, mouse; D019704:Protein Disulfide-Isomerases