Regulated, but not constitutive, secretory proteins bind porcine chymotrypsinogen.
Endocrine and exocrine cells exhibit both a constitutive and a regulated secretory pathway. In the latter pathway, secretory proteins are stored at a high concentration in secretory granules and are released by exocytosis in response to appropriate external stimuli. Sorting between the two secretory pathways is believed to take place in the trans-Golgi tubular network. To account for experimental data, it has been proposed that sorting receptors exist which bind a variety of regulated secretory proteins, including foreign secretory proteins introduced into the cells by transfection. In support of the sorting receptor hypothesis Chung et al. (Chung, K.-N., Walter, P., Aponte, G. W., and Moore, H.-P.H. (1989) Science 243, 192-197) isolated a group of 25-kDa canine pancreatic "hormone-binding proteins" that bound regulated but not constitutive secretory proteins. To determine if similar proteins are present in other species and tissues, we have screened porcine pancreas, parathyroid, adrenal medulla, and pituitary glands. A 31-kDa protein, similar to that identified by Chung et al. (1989), which binds to regulated but not to constitutive secretory proteins was identified in porcine pancreas. This protein was not detected in the parathyroid, adrenal medulla, or pituitary glands, however, which argues against it serving as a general sorting receptor. NH2-terminal sequencing, immunoreactivity, and proteolytic activity data indicate that the porcine 31-kDa protein is similar if not identical to porcine chymotrypsinogen A or B.
Gorr
S U
SU
Endocrine Cell Biology Laboratory, University of Louisville School of Dentistry, Kentucky 40292.
Hamilton
J W
JW
Cohn
D V
DV
D000313:Adrenal Medulla / Q000378:metabolism; D000595:Amino Acid Sequence; D000818:Animals; D015153:Blotting, Western; D002846:Chromatography, Affinity; D002919:Chymotrypsinogen / Q000378:metabolism*; D004591:Electrophoresis, Polyacrylamide Gel; D006056:Golgi Apparatus / Q000378:metabolism; D008969:Molecular Sequence Data; D010179:Pancreas / Q000378:metabolism; D010280:Parathyroid Glands / Q000378:metabolism; D010902:Pituitary Gland / Q000378:metabolism; D011506:Proteins / Q000378:metabolism*; D017386:Sequence Homology, Amino Acid; D013552:Swine; D014362:Trypsinogen / Q000378:metabolism
D011506:Proteins; D014362:Trypsinogen; D002919:Chymotrypsinogen