Structural requirements for intracellular processing and sorting of bactericidal/permeability-increasing protein (BPI): comparison with lipopolysaccharide-binding protein.
The bactericidal/permeability-increasing protein (BPI), which is stored in the azurophil granules of neutrophils, and the circulating lipopolysaccharide-binding protein (LBP) share the same structure. Both bind lipopolysaccharide of gram-negative bacteria through their amino-terminal domains. The carboxy-terminal domain of BPI promotes bacterial attachment to phagocytes, whereas the corresponding domain of LBP delivers lipopolysaccharide to monocytes/macrophages. Our aim was to investigate the role of the amino-and carboxy-terminal domains of BPI and LBP for sorting and storage in myeloid cells after transfection of cDNA to two rodent hematopoietic cell lines. Full-length BPI and LBP were both targeted for storage in these cells. Deletion of the carboxy-terminal half of BPI resulted in storage followed by degradation while the reciprocal deletion of the amino-terminal half led to retention in the endoplasmic reticulum for proteasomal degradation. Chimeras between halves of BPI and LBP were also targeted for storage, but those containing carboxy-terminal BPI had the highest stability, again indicating a role for the carboxy-terminal domain of BPI in protection against degradation. Therefore, we propose a critical stability function for the hydrophobic carboxy-terminal domain of BPI during intracellular sorting for storage while the amino-terminal domain may confer targeting for storage.
Bülow
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Department of Hematology, Research Department 2, University Hospital, Lund, Sweden. elinor.bulow@hematologi.lu.se
Gullberg
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Olsson
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D000209:Acute-Phase Proteins; D000818:Animals; D023181:Antimicrobial Cationic Peptides; D001798:Blood Proteins / Q000235:genetics / Q000378:metabolism*; D002352:Carrier Proteins / Q000235:genetics / Q000378:metabolism*; D002460:Cell Line; D003546:Cysteine Endopeptidases / Q000378:metabolism; D018870:Endoplasmic Reticulum, Rough / Q000378:metabolism; D006801:Humans; D008562:Membrane Glycoproteins; D008565:Membrane Proteins; D022423:Myeloid Cells / Q000378:metabolism; D015388:Organelles / Q000378:metabolism; D010446:Peptide Fragments / Q000235:genetics / Q000378:metabolism; D011499:Protein Processing, Post-Translational; D017434:Protein Structure, Tertiary; D017452:Receptors, IgG / Q000235:genetics; D011993:Recombinant Fusion Proteins / Q000235:genetics / Q000378:metabolism; D013329:Structure-Activity Relationship; D014162:Transfection; D000099231:Lipopolysaccharide-Binding Protein
D000209:Acute-Phase Proteins; D023181:Antimicrobial Cationic Peptides; D001798:Blood Proteins; D002352:Carrier Proteins; D003546:Cysteine Endopeptidases; D008562:Membrane Glycoproteins; D008565:Membrane Proteins; D010446:Peptide Fragments; D017452:Receptors, IgG; D011993:Recombinant Fusion Proteins; D000099231:Lipopolysaccharide-Binding Protein; C021623:bactericidal permeability increasing protein