title: The neuroendocrine protein 7B2 acts as a molecular chaperone in the in vitro folding of human insulin-like growth factor-1 secreted from yeast.
abstract: The neuroendocrine protein 7B2 prevents premature activation of PC2, an enzyme involved in the processing of prohormones in the secretory pathway. We inquired if this chaperone-like function encompasses a broader role for 7B2 in the folding of hormone-like proteins. As a test, the fate of misfolded human insulin-like growth factor-1 (IGF1) was assessed, in the presence and absence of 7B2. Most of the recombinant IGF1 molecules, secreted from yeast, are a conglomeration of inactive multimers which are either disulfide-linked or mere physical aggregates. We find that yeast-produced 7B2 influences the in vitro conversion of inactive molecules into active monomers. However, the amounts of disulfide-linked dimers remain unaffected during this conversion. Interestingly, both 7B2 and the molecular chaperone DnaK interact with IGF1 in the yeast two-hybrid system. Like DnaK, 7B2 also binds the tumor suppressor protein p53. Binding of DnaK to exposed epitopes of aggregated proteins is known to be a prerequisite for deaggregation. It is conceivable that 7B2 participates in an analogous manner in the dissociation of non-covalently linked multimers of IGF1. Our results indicate that 7B2 might find an application in the deaggregation of potentially useful therapeutic proteins.
authors.affiliation: Department of Core Drug Discovery Technologies, Ciba-Geigy AG, Basel, Switzerland.
authors.forename: B
authors.initials: B
authors.lastname: Chaudhuri
authors.forename: C
authors.initials: C
authors.lastname: Stephan
authors.forename: R P
authors.initials: RP
authors.lastname: Huijbregts
authors.forename: G J
authors.initials: GJ
authors.lastname: Martens
mesh_terms: D001483:Base Sequence; D018833:Chaperonins / Q000378:metabolism*; D002851:Chromatography, High Pressure Liquid; D003001:Cloning, Molecular; D017931:DNA Primers; D006801:Humans; D007334:Insulin-Like Growth Factor I / Q000096:biosynthesis* / Q000737:chemistry*; D008668:Metallothionein / Q000096:biosynthesis; D008969:Molecular Sequence Data; D009419:Nerve Tissue Proteins / Q000096:biosynthesis / Q000378:metabolism*; D051859:Neuroendocrine Secretory Protein 7B2; D009490:Neurosecretory Systems / Q000502:physiology; D010907:Pituitary Hormones / Q000096:biosynthesis / Q000378:metabolism*; D010957:Plasmids; D017510:Protein Folding; D011993:Recombinant Fusion Proteins / Q000096:biosynthesis; D011994:Recombinant Proteins / Q000096:biosynthesis / Q000737:chemistry; D015183:Restriction Mapping; D012441:Saccharomyces cerevisiae; D001616:beta-Galactosidase / Q000032:analysis / Q000096:biosynthesis
chemical_list: D017931:DNA Primers; D009419:Nerve Tissue Proteins; D051859:Neuroendocrine Secretory Protein 7B2; D010907:Pituitary Hormones; D011993:Recombinant Fusion Proteins; D011994:Recombinant Proteins; C497678:SCG5 protein, human; D007334:Insulin-Like Growth Factor I; D008668:Metallothionein; D001616:beta-Galactosidase; D018833:Chaperonins