scholarly journals Insulin-Like Growth Factor (IGF)-Binding Protein-4 Proteolytic Degradation in Bovine, Equine, and Porcine Preovulatory Follicles: Regulation by IGFs and Heparin-Binding Domain-Containing Peptides1

2000 ◽  
Vol 63 (2) ◽  
pp. 390-400 ◽  
Author(s):  
Sabine Mazerbourg ◽  
Jürgen Zapf ◽  
Robert S. Bar ◽  
David R. Brigstock ◽  
Philippe Monget
Keyword(s):  
Growth Factor ◽  
Binding Protein ◽  
Binding Domain ◽  
Proteolytic Degradation ◽  
Insulin Like Growth Factor ◽  
Heparin Binding ◽  
Preovulatory Follicles ◽  
Heparin Binding Domain ◽  
Igf Binding ◽  
Igf Binding Protein

Insulin-like growth factor (IGF)-binding protein-5-(201—218) region regulates hydroxyapatite and IGF-I binding

1997 ◽  
Vol 273 (5) ◽  
pp. E1005-E1013 ◽  
Author(s):  
Phil G. Campbell ◽  
Dennis L. Andress
Keyword(s):  
Growth Factor ◽  
Binding Protein ◽  
Fluid Phase ◽  
Binding Domain ◽  
Free Fluid ◽  
Insulin Like Growth Factor ◽  
Heparin Binding ◽  
Igf I ◽  
Heparin Binding Domain ◽  
Igf Binding

Insulin-like growth factor-binding protein-5 (IGFBP-5), the major bone IGFBP, modifies the biological activity of IGFs within the osteoblastic pericellular environment. Because glycosaminoglycans modulate IGFBP-5 binding to osteoblast organic extracellular matrix (ECM), we assessed whether the heparin binding domain of IGFBP-5, IGFBP-5-(102—218), modifies the interaction of IGFBP-5 with the inorganic bone ECM hydroxyapatite (HA). Synthetic IGFBP-5-(201—218) peptide increased the binding of IGFBP-5 to HA as well as the binding of IGF-I to HA-bound IGFBP-5. This action was specific for the heparin-binding domain, because IGFBP-5-(130—138), IGFBP-5-(138—152), and IGFBP-5-(1—169) were without effect. IGFBP-5-(201—218) was found to bind directly to IGFBP-5 and cause a threefold enhancement of the IGF-I binding affinity for IGFBP-5, whether IGFBP-5 was bound to HA or was in a matrix-free fluid phase. Heparin inhibited the binding of IGFBP-5 to HA and blocked the interaction of IGFBP-5 with IGFBP-5-(201—218) in the fluid phase, suggesting that the primary heparin-binding domain of IGFBP-5 specifically enhances the binding of IGFBP-5 to HA and increases IGF-I binding to IGFBP-5.

scholarly journals Proteolytic degradation of IGF-binding protein (IGFBP)-2 in equine ovarian follicles: involvement of pregnancy-associated plasma protein-A (PAPP-A) and association with dominant but not subordinated follicles

2004 ◽  
Vol 182 (3) ◽  
pp. 457-466 ◽  
Author(s):  
N Gerard ◽  
T Delpuech ◽  
C Oxvig ◽  
MT Overgaard ◽  
P Monget
Keyword(s):  
Proteolytic Activity ◽  
Plasma Protein ◽  
Follicular Fluid ◽  
Protein A ◽  
Binding Domain ◽  
Proteolytic Degradation ◽  
Heparin Binding ◽  
Heparin Binding Domain ◽  
Igf Binding ◽  
Igf Binding Protein

In the ovary of mammalian species, terminal follicular growth is accompanied by a decrease in intrafollicular levels of IGF-binding protein-2 (IGFBP-2) and IGFBP-4. The decrease in IGFBP-4 levels is essentially due to an increase in proteolytic cleavage by intrafollicular pregnancy-associated plasma protein-A (PAPP-A) in growing healthy follicles. The decrease in IGFBP-2 levels is partly due to a decrease in mRNA expression by follicular cells. In addition, we have recently shown that IGFBP-2 is also proteolytically cleaved by PAPP-A in bovine and porcine growing follicles. In the present work, we showed that follicular fluid from late dominant equine follicles (35 mm diameter) contains a proteolytic activity against IGFBP-2. First follicular fluid from dominant follicles contained lower levels of native IGFBP-2 than the corresponding serum, as assessed by Western ligand blotting. In contrast, immunoblotting experiments showed much higher levels of a 12 kDa proteolytic fragment in dominant follicular fluid than in the serum. Moreover, equine dominant follicular fluid was able to induce proteolysis of exogenous recombinant bovine (rb)IGFBP-2, this degradation being dose-dependently enhanced by IGFs. The proteolytic activity against IGFBP-2 in equine follicles was partially immunoneutralized by a polyclonal antibody raised against human PAPP-A. Moreover, cleavage of rbIGFBP-2 by equine follicular fluid was dose-dependently inhibited by a peptide derived from the heparin-binding domain of IGFBP-5, as well as by peptides derived from other heparin-binding domain-containing proteins such as connective tissue growth factor, vitronectin and heparin-interacting protein, previously shown to inhibit PAPP-A. Finally, the proteolytic activity was very low in subordinate follicles, was high in both early (25 mm diameter) and late (35 mm diameter) dominant follicles, and was slightly lower in preovulatory follicles recovered 35 h after human chorionic gonadotropin (hCG) treatment.Overall, these data show that in the equine ovary, the selection of dominant follicles is associated with an increase of the proteolytic degradation of IGFBP-2 by PAPP-A, as for IGFBP-4, and potentially other protease(s), probably contributing to the increase in IGF bioavailability. In atretic subordinate follicles, the decrease in the proteolytic degradation of IGFBP-2, probably due in part to a direct inhibition by peptides containing heparin-binding domains, contributes to the increase in IGFBP-2 levels and the decrease in IGF bioavailability. The expression of PAPP-A and IGFBP-2 mRNA during folliculogenesis remain to be investigated in the mare.

Plasminogen binds the heparin-binding domain of insulin-like growth factor-binding protein-3

1998 ◽  
Vol 275 (2) ◽  
pp. E321-E331 ◽  
Author(s):  
Phil G. Campbell ◽  
Susan K. Durham ◽  
Adisak Suwanichkul ◽  
James D. Hayes ◽  
David R. Powell
Keyword(s):  
Growth Factor ◽  
Binding Protein ◽  
Binding Domain ◽  
Insulin Like Growth Factor ◽  
Heparin Binding ◽  
Binding Studies ◽  
Igf I ◽  
Heparin Binding Domain ◽  
Igfbp 3

Limited proteolysis lowers affinity of insulin-like growth factor (IGF)-binding protein (IGFBP)-3 for bound IGFs, resulting in greater IGF bioavailability. Plasmin is one of many proteases that cleave IGFBP-3, and the plasmin system may regulate IGFBP-3 proteolysis and IGF bioavailability in cultured cells in vitro. A role for the plasmin system in IGFBP-3 proteolysis in vivo is suggested by data presented here showing that IGFBP-3 binds plasminogen (Pg; Glu-Pg) with a dissociation constant ( Kd) ranging from 1.43 to 3.12 nM. IGF-I and Glu-Pg do not compete for IGFBP-3 binding; instead, the binary IGFBP-3/Glu-Pg complex binds IGF-I with high affinity ( Kd= 0.47 nM) to form a ternary complex. Competitive binding studies suggest that the kringle 1, 4, and 5 domains of Glu-Pg and the heparin-binding domain of IGFBP-3 participate in forming the IGFBP-3/Glu-Pg complex, and other studies show that Glu-Pg in this complex is activated at a normal rate by tissue Pg activator. Importantly, IGFBP-3/Glu-Pg complexes were detected in both human citrate plasma and serum, indicating that these complexes exist in vivo. Binding of IGFBP-3 to Glu-Pg in vivo suggests how Glu-Pg activation can specifically lead to IGFBP-3 proteolysis with subsequent release of IGFs to local target tissues.

Plasmin degradation of insulin-like growth factor-binding protein-5 (IGFBP-5): regulation by IGFBP-5-(201—218)

1997 ◽  
Vol 273 (5) ◽  
pp. E996-E1004 ◽  
Author(s):  
Phil G. Campbell ◽  
Dennis L. Andress
Keyword(s):  
Growth Factor ◽  
Solid Phase ◽  
Binding Protein ◽  
Competitive Inhibitor ◽  
Binding Domain ◽  
Tissue Type ◽  
Insulin Like Growth Factor ◽  
Heparin Binding ◽  
Factor Binding ◽  
Heparin Binding Domain

Using the major bone insulin-like growth factor-binding protein (IGFBP) IGFBP-5, we took a mechanistic approach in evaluating the role of the heparin-binding domain of IGFBP-5 in regulating plasmin (Pm) proteolysis of IGFBP-5. Using synthetic IGFBP-5 peptide fragments, we determined that the heparin-binding domain, IGFBP-5-(208—218), inhibits Pm proteolysis of intact IGFBP-5. The mechanism of action of IGFBP-5-(201—218) was by inhibiting Pm binding to substrate IGFBP-5. IGFBP-5-(201—218) action was independent of site of proteolysis, fluid, or solid phase interaction. In addition, IGFBP-5-(201—218) was found to inhibit plasminogen (Pg) activation to Pm. IGFBP-5-(201—218) did not directly inhibit the activity of Pm, urokinase Pg activator (PA), or tissue-type PA but acted as a competitive inhibitor of Pg activation by PA, which is in contrast to the stimulating effect of heparin on Pg activation. These data indicate that the heparin-binding domain contains the serine protease (Pg-to-Pm) binding site region of IGFBP-5, and that this region, which is presumed to represent a Pm-induced proteolytic product of IGFBP-5, is capable of regulating Pm action.

scholarly journals Heparin Modulates the Binding of Insulin-like Growth Factor (IGF) Binding Protein-5 to a Membrane Protein in Osteoblastic Cells

1995 ◽  
Vol 270 (47) ◽  
pp. 28289-28296 ◽  
Author(s):  
Dennis L. Andress
Keyword(s):  
Growth Factor ◽  
Membrane Protein ◽  
Dissociation Constants ◽  
Binding Protein ◽  
Insulin Like Growth Factor ◽  
Heparin Binding ◽  
Heparin Treatment ◽  
Igf Binding ◽  
Mouse Osteoblast ◽  
Igf Binding Protein

Osteoblast-like cells secrete insulin-like growth factor (IGF) binding protein-5 (IGFBP-5), which may act to enhance IGF-stimulated osteoblast function. We recently demonstrated that carboxyl-truncated IGFBP-5 (IGFBP-5) binds to the osteoblast surface and stimulates mitogenesis by a pathway that is independent of IGF action. The present study was conducted to determine the mechanism of osteoblast binding of IGFBP-5, beginning with the assumption that cell surface glycosaminoglycans may mediate the binding of this heparin binding protein. Intact I-IGFBP-5 and I-IGFBP-5 exhibited one-site binding to mouse osteoblast monolayers with dissociation constants of 28 and 6 nM for intact I-IGFBP-5 and I-IGFBP-5, respectively. Osteoblast binding of intact I-IGFBP-5 was inhibited by low heparin concentrations, while I-IGFBP-5 binding was stimulated by heparin. Treatment of cells with heparinase or chlorate to decrease surface glycosaminoglycan density failed to reduce the binding of either form of IGFBP-5. In contrast, pretreatment of cells with IGFBP-5 caused down-regulation of I-IGFBP-5 binding. Cross-linking studies revealed that both intact I-IGFBP-5 and I-IGFBP-5 bind to proteins in Triton extracts of osteoblast membranes, which were absent in osteoblast-derived matrix. Purification of membrane extracts by IGFBP-5 affinity chromatography revealed a 420-kDa band on reduced SDS-polyacrylamide gels. While the membrane protein internalized both forms of IGFBP-5, heparin treatment inhibited the internalization of intact I-IGFBP-5 but stimulated I-IGFBP-5 internalization. These data indicate that IGFBP-5 binds to and is internalized by an osteoblast membrane protein, which does not appear to be a proteoglycan. Glycosaminoglycans, however, modulate the binding and internalization of IGFBP-5 in a way that may preferentially favor the intracellular accumulation of the carboxyl-truncated form.

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