Immunoglobulin-derived polypeptides enter the regulated secretory pathway in AtT-20 cells.
Constitutively secreted proteins have traditionally been believed to be excluded from the regulated secretory pathway. In this work we show that kappa light chain and Fc fragment, two markers of the constitutive pathway, are present in the regulated pathway in AtT-20 cells. They colocalize with the endogenous hormone ACTH and they exhibit stimulus-dependent secretion. The Fc fragment, which undergoes intracellular transport at the same rate as the ACTH precursor POMC, enters the forming secretory granules, however, it is partially lost during granule maturation. These observations show that classic constitutive secretory markers are not excluded from the regulated secretory pathway and that efficient sorting for regulated secretion occurs above a background of proteins which enter the granules without sorting.
Castle
A M
AM
Department of Cell Biology, University of Virginia Health Sciences Center, Charlottesville 22908, USA. amc3c@virginia.edu
Huang
A Y
AY
Castle
J D
JD
D000324:Adrenocorticotropic Hormone / Q000378:metabolism; D000818:Animals; D001692:Biological Transport; D002478:Cells, Cultured; D004723:Endorphins / Q000378:metabolism; D005455:Fluorescent Antibody Technique; D007141:Immunoglobulin Fc Fragments / Q000235:genetics / Q000378:metabolism*; D007145:Immunoglobulin kappa-Chains / Q000235:genetics / Q000378:metabolism*; D051379:Mice; D010455:Peptides / Q000378:metabolism; D010902:Pituitary Gland / Q000166:cytology / Q000378:metabolism*; D014162:Transfection
D004723:Endorphins; D007141:Immunoglobulin Fc Fragments; D007145:Immunoglobulin kappa-Chains; D010455:Peptides; D000324:Adrenocorticotropic Hormone