Biosynthesis and processing of the mannose receptor in human macrophages.
The biosynthesis and processing of the human mannose receptor has been studied in monocyte-derived macrophages. Adherent cells were labeled for 60 min with Trans35S (a mixture of 35S-labeled methionine and cysteine), chased, and subjected to immunoprecipitation by antibody raised against the human placental receptor. The antibody immunoprecipitated a single protein of molecular mass 162 kDa; precipitation of the labeled receptor could be inhibited by placental receptor. The results presented demonstrate that the receptor is synthesized as a 154-kDa precursor which is processed to 162 kDa in 90 min. The precursor is a glycoprotein bearing endoglycosidase H-sensitive oligosaccharides; the 162-kDa form is endoglycosidase H-resistant but peptide:N-glycanase-sensitive. Desialylation of the mannose receptor with neuraminidase generates a protein which is recognized by peanut agglutinin, a lectin that specifically binds desialylated O-linked oligosaccharides. Thus, the human macrophage mannose receptor bears both N- and O-linked oligosaccharide chains. Newly synthesized mannose receptor exhibits a half-life of 33 h as determined by pulse-chase studies. This indicates that on the average, each molecule of receptor recycles between the cell surface and endosomes hundreds of times before degradation.
Lennartz
M R
MR
Department of Cell Biology and Physiology, Washington University School of Medicine, St. Louis, Missouri.
Cole
F S
FS
Stahl
P D
PD
D000906:Antibodies; D000918:Antibody Specificity; D002478:Cells, Cultured; D005260:Female; D006023:Glycoproteins / Q000096:biosynthesis; D006801:Humans; D007700:Kinetics; D037181:Lectins, C-Type; D008264:Macrophages / Q000378:metabolism*; D008358:Mannose / Q000378:metabolism*; D000090323:Mannose Receptor; D037241:Mannose-Binding Lectins; D008970:Molecular Weight; D009844:Oligosaccharides / Q000032:analysis; D010920:Placenta / Q000378:metabolism; D011247:Pregnancy; D011499:Protein Processing, Post-Translational; D011956:Receptors, Cell Surface; D011971:Receptors, Immunologic / Q000096:biosynthesis* / Q000235:genetics / Q000302:isolation & purification
D000906:Antibodies; D006023:Glycoproteins; D037181:Lectins, C-Type; D000090323:Mannose Receptor; D037241:Mannose-Binding Lectins; D009844:Oligosaccharides; D011956:Receptors, Cell Surface; D011971:Receptors, Immunologic; D008358:Mannose