Mammalian protein secretion without signal peptide removal. Biosynthesis of plasminogen activator inhibitor-2 in U-937 cells

Journal Article · Tue Apr 05 04:00:00 EDT 1988 · J. Biol. Chem.; (United States)

OSTI ID:7242320

Ye, R D; Wun, T C; Sadler, J E

Plasminogen activator inhibitor-2 (PAI-2) is a serine protease inhibitor that regulates plasmin generation by inhibiting urokinase and tissue plasminogen activator. The primary structure of PAI-2 suggests that it may be secreted without cleavage of a single peptide. To confirm this hypothesis we have studied the glycosylation and secretion of PAI-2 in human monocytic U-937 cells by metabolic labeling, immunoprecipitation, glycosidase digestion, and protein sequencing. PAI-2 is variably glycosylated on asparagine residues to yield intracellular intermediates with zero, one, two, or three high mannose-type oligosaccharide units. Secretion of the N-glycosylated species began by 1 h of chase and the secreted molecules contained both complex-type N-linked and O-linked oligosaccharides. Enzymatically deglycosylated PAI-2 had an electrophoretic mobility identical to that of the nonglycosylated precursor and also to that of PAI-2 synthesized in vitro in a rabbit reticulocyte lysate from synthetic mRNA derived from full length PAI-2 cDNA. The amino-terminal protein sequence of secreted PAI-2 began with the initiator methionine residue. These results indicate that PAI-2 is glycosylated and secreted efficiently without the cleavage of a signal peptide. PAI-2 shares this property with its nearest homologue in the serine protease inhibitor family, chicken ovalbumin, and appears to be the first well characterized example of this phenomenon among natural mammalian proteins.

• Research Organization: Washington Univ. School of Medicine, St. Louis, MO (USA)
• OSTI ID: 7242320
• Journal Information: J. Biol. Chem.; (United States), Journal Name: J. Biol. Chem.; (United States) Vol. 263:10; ISSN JBCHA
• Country of Publication: United States
• Language: English

Related Subjects

550201* -- Biochemistry-- Tracer Techniques
59 BASIC BIOLOGICAL SCIENCES
ALDEHYDES
ANIMAL CELLS
ANIMALS
BIOCHEMICAL REACTION KINETICS
BIOLOGICAL MATERIALS
BIOSYNTHESIS
BLOOD
BLOOD CELLS
BODY FLUIDS
CARBOHYDRATES
DRUGS
ENZYME INHIBITORS
ERYTHROCYTES
FIBRINOLYTIC AGENTS
HEMATOLOGIC AGENTS
HEXOSES
IMMUNOASSAY
IMMUNOLOGY
ISOTOPE APPLICATIONS
KINETICS
LABELLED COMPOUNDS
MAMMALS
MANNOSE
MATERIALS
MONOSACCHARIDES
ORGANIC COMPOUNDS
PLASMINOGEN
RABBITS
RADIOASSAY
RADIOIMMUNOASSAY
RADIOIMMUNOLOGY
REACTION KINETICS
RETICULOCYTES
SACCHARIDES
SECRETION
SYNTHESIS
TRACER TECHNIQUES
TRITIUM COMPOUNDS
VERTEBRATES