title: IGF dependent modulation of IGF binding protein (IGFBP) proteolysis by pregnancy-associated plasma protein-A (PAPP-A): multiple PAPP-A-IGFBP interaction sites.
abstract: BACKGROUND
  Pregnancy-associated plasma protein-A (PAPP-A) is a local regulator of insulin-like growth factor (IGF) bioavailability in physiological systems, but many structural and functional aspects of the metzincin metalloproteinase remain to be elucidated. PAPP-A cleaves IGF binding protein (IGFBP)-4 and IGFBP-5. Cleavage of IGFBP-4, but not IGFBP-5, depends on the binding of IGF before proteolysis by PAPP-A can occur. The paralogue PAPP-A2 has two substrates among the six IGFBPs: IGFBP-3 and IGFBP-5.
  
  
  METHODS
  Sets of chimeric proteins between IGFBP-4 and -5, and IGFBP-3 and -5 were constructed to investigate the structural requirements for IGF modulation. At the proteinase level, we investigated the importance of individual acidic amino acids positioned in the proteolytic domain of PAPP-A for proteolytic activity against IGFBP-4 and -5. Interaction between PAPP-A and its substrates was analyzed by surface plasmon resonance.
  
  
  CONCLUSIONS
  We provide data suggesting that the C-terminal domain of the IGFBPs is responsible for IGF-dependent modulation of access to the scissile bond. Loss or reduction of IGFBP proteolysis by PAPP-A was observed upon mutation of residues positioned in the unique 63-residue stretch separating the zinc and Met-turn motifs, and in the short sequence following the Met-turn methionine. A model of the proteolytic domain of PAPP-A suggests the presence of structural calcium ions in the C-terminal subdomain, implicated in IGFBP substrate interactions.
  
  
  CONCLUSIONS
  Detailed knowledge of interactions between PAPP-A and its substrates is required to understand the modulatory role of PAPP-A on IGF receptor stimulation.
authors.affiliation: Department of Molecular Biology and Genetics, University of Aarhus, DK-8000 Aarhus, Denmark.
authors.forename: Ervinas
authors.initials: E
authors.lastname: Gaidamauskas
authors.forename: Claus
authors.initials: C
authors.lastname: Gyrup
authors.forename: Henning B
authors.initials: HB
authors.lastname: Boldt
authors.forename: Vivien R
authors.initials: VR
authors.lastname: Schack
authors.forename: Michael T
authors.initials: MT
authors.lastname: Overgaard
authors.forename: Lisbeth S
authors.initials: LS
authors.lastname: Laursen
authors.forename: Claus
authors.initials: C
authors.lastname: Oxvig
mesh_terms: D000595:Amino Acid Sequence; D001665:Binding Sites; D005260:Female; D057809:HEK293 Cells; D006801:Humans; D018972:Insulin-Like Growth Factor Binding Protein 3 / Q000737:chemistry* / Q000235:genetics; D018975:Insulin-Like Growth Factor Binding Protein 5 / Q000737:chemistry* / Q000235:genetics; D008958:Models, Molecular; D008969:Molecular Sequence Data; D011247:Pregnancy; D011266:Pregnancy-Associated Plasma Protein-A / Q000737:chemistry* / Q000235:genetics; D011485:Protein Binding; D054730:Protein Interaction Domains and Motifs; D059748:Proteolysis; D011993:Recombinant Fusion Proteins / Q000737:chemistry / Q000235:genetics; D013002:Somatomedins / Q000737:chemistry* / Q000235:genetics; D013379:Substrate Specificity; D014162:Transfection
chemical_list: C515497:IGFBP3 protein, human; D018972:Insulin-Like Growth Factor Binding Protein 3; D018975:Insulin-Like Growth Factor Binding Protein 5; D011993:Recombinant Fusion Proteins; D013002:Somatomedins; D011266:Pregnancy-Associated Plasma Protein-A; C579283:PAPPA protein, human