Secretion of plasminogen activator inhibitor 2 by human peripheral blood monocytes occurs via an endoplasmic reticulum-golgi-independent pathway.
Plasminogen activator inhibitor 2 (PAI-2) is a serine protease inhibitor (serpin) that is secreted and accumulated intracellularly by monocytes. We investigated PAI-2 synthesis by isolated human peripheral blood monocytes and found that a 47-kDa nonglycosylated form of PAI-2 was abundant in conditioned medium from monocytes. Secretion of PAI-2 by monocytes was not inhibited by agents that inhibit either ER-Golgi pathway-dependent secretion, brefeldin A, or N-linked glycosylation, tunicamycin. IL-1beta served as a control for a protein that is secreted by an ER-Golgi-independent pathway, and secretion of IL-1beta was not inhibited by brefeldin A. This was in contrast to secretion of TNFalpha, which was dependent on the ER-Golgi pathway. None of the treatments was cytotoxic toward monocytes, as measured by release of the intracellular enzyme lactate dehydrogenase (LDH) into the conditioned medium. Subcellular fractionation revealed that PAI-2 and IL-1beta were colocalized. The mechanism for secretion of PAI-2 was not dependent on calcium or intracellular trafficking via the classical vesicular mechanism(s), distinguishing it from IL-1beta secretion. These studies show that PAI-2 is secreted by primary human monocytes via an ER-Golgi-independent pathway.
Department of Molecular and Cell Biology, University of Aberdeen, Foresterhill, Aberdeen, AB25 2ZD, United Kingdom.
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D000900:Anti-Bacterial Agents / Q000494:pharmacology; D000998:Antiviral Agents / Q000494:pharmacology; D020126:Brefeldin A; D002478:Cells, Cultured; D017077:Culture Media, Conditioned / Q000737:chemistry / Q000378:metabolism; D003517:Cyclopentanes / Q000494:pharmacology; D004721:Endoplasmic Reticulum / Q000737:chemistry / Q000378:metabolism*; D019085:Fluorescent Antibody Technique, Direct; D006056:Golgi Apparatus / Q000737:chemistry / Q000378:metabolism*; D006801:Humans; D018942:Macrolides; D018613:Microscopy, Confocal; D009000:Monocytes / Q000187:drug effects / Q000378:metabolism* / Q000648:ultrastructure; D017396:Plasminogen Activator Inhibitor 2 / Q000276:immunology / Q000378:metabolism*; D014407:Tumor Cells, Cultured / Q000737:chemistry / Q000378:metabolism; D014415:Tunicamycin / Q000494:pharmacology
D000900:Anti-Bacterial Agents; D000998:Antiviral Agents; D017077:Culture Media, Conditioned; D003517:Cyclopentanes; D018942:Macrolides; D017396:Plasminogen Activator Inhibitor 2; D014415:Tunicamycin; D020126:Brefeldin A