A C-terminal domain, which prevents secretion of the neuroendocrine protein 7B2 in Saccharomyces cerevisiae, inhibits Kex2 yet is processed by the Yap3 protease.
Recent reports reveal that the C-terminal half of the neuroendocrine polypeptide 7B2 selectively inhibits and binds PC2, a mammalian prohormone converting enzyme that is homologous to the yeast pro-alpha-factor processing protease Kex2. During attempted secretion of the 185 amino-acid human 7B2 in Saccharomyces cerevisiae, we observe that the protein is mostly retained inside the cell. However a mutant polypeptide (7B2 delta 1), where the C-terminal 48 amino acids of 7B2 are deleted, is efficiently secreted. Two shorter C-terminal truncations either permit poor secretion or no secretion at all. Surprisingly, full-length 7B2 but not 7B2 delta 1 abolishes the catalytic activity of Kex2, indicating that C-terminal residues of 7B2 might also be important for inhibition of the yeast protease. When the KEX2 gene is disrupted, yeast cells unexpectedly secrete a 7B2 variant similar in size to 7B2 delta 1, suggesting involvement of the alternate yeast prohormone convertase Yap3 in processing. Secretion is enhanced by overexpression of Yap3 and by the presence of a Lys-Arg residue at the processing site of precursor 7B2. These results purport that, in neuroendocrine cells too, secretion of 7B2 could be mediated by a homologue of Yap3.
Chaudhuri
B
B
Department of Core Drug Discovery Technologies, Ciba-Geigy Ltd., Basel, Switzerland.
Stephan
C
C
D016282:Aspartic Acid Endopeptidases / Q000378:metabolism; D001483:Base Sequence; D004252:DNA Mutational Analysis; D010450:Endopeptidases / Q000378:metabolism*; D006801:Humans; D008969:Molecular Sequence Data; D009154:Mutation; D009419:Nerve Tissue Proteins / Q000235:genetics / Q000378:metabolism* / Q000494:pharmacology; D051859:Neuroendocrine Secretory Protein 7B2; D010446:Peptide Fragments / Q000494:pharmacology*; D010907:Pituitary Hormones / Q000235:genetics / Q000378:metabolism* / Q000494:pharmacology; D043484:Proprotein Convertases; D011480:Protease Inhibitors / Q000494:pharmacology*; D011499:Protein Processing, Post-Translational / Q000187:drug effects*; D021382:Protein Sorting Signals / Q000235:genetics / Q000378:metabolism; D011994:Recombinant Proteins / Q000378:metabolism / Q000494:pharmacology; D012441:Saccharomyces cerevisiae / Q000235:genetics; D029701:Saccharomyces cerevisiae Proteins; D017384:Sequence Deletion; D013329:Structure-Activity Relationship; D013381:Subtilisins / Q000037:antagonists & inhibitors / Q000378:metabolism
D009419:Nerve Tissue Proteins; D051859:Neuroendocrine Secretory Protein 7B2; D010446:Peptide Fragments; D010907:Pituitary Hormones; D011480:Protease Inhibitors; D021382:Protein Sorting Signals; D011994:Recombinant Proteins; C497678:SCG5 protein, human; D029701:Saccharomyces cerevisiae Proteins; D010450:Endopeptidases; D043484:Proprotein Convertases; D013381:Subtilisins; C058751:KEX2 protein, S cerevisiae; D016282:Aspartic Acid Endopeptidases