Increased degradation of newly synthesized interferon-gamma (IFN-gamma) in anti CD3-stimulated lymphocytes treated with glycoprotein processing inhibitors.
As described previously (Kosuge T., Toyoshima S., Biol. Pharm. Bull., 23, 1-5 (2000)), inhibitors of the glycoprotein processing enzymes, glucosidase I and II, induce decreased secretion of interferon-gamma (IFN-gamma) into culture supernatants of anti CD3-stimulated lymphocytes, and in the present study the mechanism has been investigated in further detail. The processing inhibitors did not affect intracellular levels of IFN-gamma but enhanced the degradation of newly synthesized IFN-gamma in anti CD3-stimulated lymphocytes. Furthermore, since the stability of N-glycosylated proteins is known to be regulated by lectin family chaperones, such as calnexin, a type I transmembrane protein located in the endoplasmic reticulum (ER), and calreticulin, a soluble protein in the ER lumen, the effect of the processing inhibitors on the interaction of IFN-gamma with calnexin and calreticulin was investigated. It was found that IFN-gamma formed complexes with calnexin and calreticulin in anti CD3-stimulated lymphocytes. Total binding of IFN-gamma to calnexin was not affected but that to calreticulin was increased in anti CD3-stimulated lymphocytes treated with the processing inhibitors. However, binding of newly synthesized IFN-gamma to calreticulin was decreased in the lymphocytes under the same conditions as above. These results suggest that these glycoprotein processing inhibitors block the release of IFN-gamma from already formed calreticulin complexes, which prevents the binding of newly synthesized IFN-gamma to calreticulin and results in the enhancement of IFN-gamma degradation.
Kosuge
T
T
Department of Biochemistry, Faculty of Pharmaceutical Sciences, Hoshi University, Tokyo, Japan.
Toyoshima
S
S
D000818:Animals; D001692:Biological Transport; D017252:CD3 Complex / Q000276:immunology*; D002135:Calcium-Binding Proteins / Q000378:metabolism; D037281:Calnexin; D037282:Calreticulin; D015550:Cell Degranulation; D004721:Endoplasmic Reticulum / Q000378:metabolism; D004791:Enzyme Inhibitors / Q000494:pharmacology; D005260:Female; D005959:Glucosidases / Q000037:antagonists & inhibitors; D006023:Glycoproteins / Q000378:metabolism*; D006031:Glycosylation; D007371:Interferon-gamma / Q000276:immunology / Q000378:metabolism*; D037102:Lectins / Q000737:chemistry; D008214:Lymphocytes / Q000187:drug effects / Q000276:immunology*; D051379:Mice; D008810:Mice, Inbred C57BL; D018832:Molecular Chaperones / Q000378:metabolism; D011499:Protein Processing, Post-Translational / Q000187:drug effects; D012261:Ribonucleoproteins / Q000378:metabolism
D017252:CD3 Complex; D002135:Calcium-Binding Proteins; D037282:Calreticulin; D004791:Enzyme Inhibitors; D006023:Glycoproteins; D037102:Lectins; D018832:Molecular Chaperones; D012261:Ribonucleoproteins; D037281:Calnexin; D007371:Interferon-gamma; D005959:Glucosidases