Proteolytic processing of the Aplysia A peptide precursor in AtT-20 cells.
When the Aplysia ELH precursor is expressed in AtT-20 cells, the carboxyterminal derived peptides are packaged and stored in secretory vesicles, while the aminoterminal region of the precursor is constitutively secreted. In contrast, when the highly homologous A peptide precursor is transfected into AtT-20 cells, both aminoterminal and carboxyterminal derived peptides are packaged in storage granules. We propose that this is due to the fact that the initial cleavage of the A peptide precursor occurs more slowly, and perhaps later in the secretory pathway, than the ELH precursor. We further suggest that in the A peptide precursor, the first cleavage occurs after the sorting site resulting in co-packaging of the multiple products derived from a single precursor protein. To determine the structural features of the prohormones responsible for this differential sorting, we made chimeric precursors and determined the rates of the initial cleavage as well as the efficiency of storing the peptide products. From these studies, we conclude that the differential sorting is regulated both by the amino acid sequence of the first processing site, and by more global aspects of the precursor structure.
Paganetti
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Howard Hughes Medical Institute, Department of Molecular and Cellular Physiology, Stanford University, CA 94305.
Scheller
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RH
D000818:Animals; D001048:Aplysia / Q000378:metabolism*; D001483:Base Sequence; D002460:Cell Line; D010450:Endopeptidases / Q000378:metabolism*; D007447:Invertebrate Hormones / Q000276:immunology / Q000378:metabolism; D008969:Molecular Sequence Data; D010957:Plasmids; D011233:Precipitin Tests; D011498:Protein Precursors / Q000276:immunology / Q000378:metabolism*; D011499:Protein Processing, Post-Translational; D011993:Recombinant Fusion Proteins / Q000378:metabolism; D013347:Subcellular Fractions / Q000378:metabolism
D007447:Invertebrate Hormones; D011498:Protein Precursors; D011993:Recombinant Fusion Proteins; C026880:egg-laying hormone, Mollusca; D010450:Endopeptidases