Biosynthesis and secretion of M- and Z-type alpha 1-proteinase inhibitor by human monocytes. Effect of inhibitors of glycosylation and of oligosaccharide processing on secretion and function.
The biosynthesis and secretion of M-type and Z-type alpha 1-antitrypsin was studied in human monocytes. In monocytes of PiMM individuals alpha 1-antitrypsin represented 0.08% of the newly synthesized proteins and 0.44% of the secreted proteins. Two molecular forms of alpha 1-antitrypsin could be identified: a 51-kDa intracellular form, susceptible to endoglucosaminidase H, thus representing the high-mannose type precursor form and a 56-kDa form resistant to endoglucosaminidase H which was secreted into the medium. Inhibition of de novo glycosylation by tunicamycin impaired the secretion of M-type alpha 1-antitrypsin by about 75% whereas inhibition of oligosaccharide processing by the mannosidase II inhibitor swainsonine did not alter the secretion of M-type alpha 1-antitrypsin. alpha 1-Antitrypsin secreted by human monocytes was functionally active as measured by complex formation with porcine pancreatic elastase. Even unglycosylated alpha 1-antitrypsin secreted by human monocytes treated with tunicamycin formed a complex with elastase. In monocytes of PiZZ individuals the secretion of alpha 1-antitrypsin was decreased. 72% of newly synthesized M-type alpha 1-antitrypsin, but only 35% of newly synthesized Z-type alpha 1-antitrypsin were secreted during a labeling period of 3 h with [35S]methionine. The 51-kDa form of Z-type alpha 1-antitrypsin accumulated intracellularly, whereas the 56-kDa form was secreted. Inhibition of oligosaccharide processing by swainsonine did not alter the decreased secretion of Z-type alpha 1-antitrypsin, whereas inhibition of de novo glycosylation by tunicamycin blocked the secretion of Z-type alpha 1-antitrypsin completely.
Gross
V
V
Medizinische Universitätsklinik, Freiburg.
vom Berg
D
D
Kreuzkamp
J
J
Ganter
U
U
Bauer
J
J
Würtemberger
G
G
Schulz-Huotari
C
C
Beeser
H
H
Gerok
W
W
D000470:Alkaloids / Q000494:pharmacology*; D002478:Cells, Cultured; D006031:Glycosylation; D006801:Humans; D066298:In Vitro Techniques; D046911:Macromolecular Substances; D008361:Mannosidases / Q000037:antagonists & inhibitors*; D009000:Monocytes / Q000187:drug effects / Q000378:metabolism*; D010196:Pancreatic Elastase / Q000378:metabolism; D010641:Phenotype; D017026:Swainsonine; D014415:Tunicamycin / Q000494:pharmacology*; D000515:alpha 1-Antitrypsin / Q000096:biosynthesis* / Q000378:metabolism; D019896:alpha 1-Antitrypsin Deficiency
D000470:Alkaloids; D046911:Macromolecular Substances; D000515:alpha 1-Antitrypsin; D014415:Tunicamycin; D008361:Mannosidases; D010196:Pancreatic Elastase; D017026:Swainsonine