An antibody against secretogranin I (chromogranin B) is packaged into secretory granules.
We have investigated the sorting and packaging of secretory proteins into secretory granules by an immunological approach. An mAb against secretogranin I (chromogranin B), a secretory protein costored with various peptide hormones and neuropeptides in secretory granules of many endocrine cells and neurons, was expressed by microinjection of its mRNA into the secretogranin I-producing cell line PC12. An mAb against the G protein of vesicular stomatitis virus--i.e., against an antigen not present in PC12 cells--was expressed as a control. The intracellular localization and the secretion of the antibodies was studied by double-labeling immunofluorescence using the conventional and the confocal microscope, as well as by pulse-chase experiments. The secretogranin I antibody, like the control antibody, was transported along the secretory pathway to the Golgi complex. However, in contrast to the control antibody, which was secreted via the constitutive pathway, the secretogranin I antibody formed an immunocomplex with secretogranin I, was packaged into secretory granules, and was released by regulated exocytosis. Our results show that a constitutive secretory protein, unaltered by genetic engineering, can be diverted to the regulated pathway of secretion by its protein-protein interaction with a regulated secretory protein. The data also provide the basis for immunologically studying the role of luminally exposed protein domains in the biogenesis and function of regulated secretory vesicles.
Rosa
P
P
Cell Biology Programme, European Molecular Biology Laboratory, Heidelberg, Federal Republic of Germany.
Weiss
U
U
Pepperkok
R
R
Ansorge
W
W
Niehrs
C
C
Stelzer
E H
EH
Huttner
W B
WB
D000643:Ammonium Chloride / Q000494:pharmacology; D000818:Animals; D000911:Antibodies, Monoclonal / Q000378:metabolism; D000936:Antigen-Antibody Complex / Q000378:metabolism*; D015153:Blotting, Western; D002451:Cell Compartmentation / Q000187:drug effects; D002460:Cell Line; D053378:Chromogranin B; D002864:Chromogranins; D003594:Cytoplasmic Granules / Q000378:metabolism*; D005455:Fluorescent Antibody Technique; D008845:Microinjections; D010673:Pheochromocytoma; D011233:Precipitin Tests; D011506:Proteins / Q000276:immunology* / Q000378:metabolism; D051381:Rats; D013111:Spider Venoms / Q000494:pharmacology
D000911:Antibodies, Monoclonal; D000936:Antigen-Antibody Complex; D053378:Chromogranin B; D002864:Chromogranins; D011506:Proteins; D013111:Spider Venoms; C506140:chromogranin B, rat; D000643:Ammonium Chloride; C020763:alpha-latrotoxin