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.

Insulin-like growth factor-binding protein-5 (IGFBP-5) stimulates phosphorylation of the IGFBP-5 receptor

1998 ◽  
Vol 274 (4) ◽  
pp. E744-E750 ◽  
Author(s):  
Dennis L. Andress
Keyword(s):  
Growth Factor ◽  
Membrane Protein ◽  
Binding Protein ◽  
Serine Phosphorylation ◽  
Insulin Like Growth Factor ◽  
Kinase Activation ◽  
Igf Binding ◽  
Independent Effects ◽  
Carboxy Terminal ◽  
Igf Binding Protein

The finding that insulin-like growth factor (IGF)-binding protein-5 (IGFBP-5) binding to mouse osteoblasts was capable of being downregulated by IGFBP-5 suggested that the 420-kDa membrane protein, which interacted with IGFBP-5, may be a signaling receptor (Andress, D. L. J. Biol. Chem. 270: 28289–28296, 1995). In the current study, a carboxy-terminal IGFBP-5 peptide, IGFBP-5-(201—218), which was found to competitively inhibit125I-IGFBP-5 binding and to specifically bind to osteoblast monolayers, was used to affinity-purify the 420-kDa membrane protein. Coincubation of the affinity-purified membrane protein with [32P]ATP resulted in autophosphorylation at serine residues. Serine phosphorylation of the 420-kDa protein was enhanced by intact IGFBP-5, IGFBP-5-(1—169), and IGFBP-5-(201—218). When the IGFBP-5 receptor was incubated with dephosphorylated casein in the presence of [32P]ATP, casein became phosphorylated on serine residues. These data indicate that IGFBP-5 stimulates the phosphorylation of the IGFBP-5 receptor and suggest that serine/threonine kinase activation may be important in mediating some of the IGF-independent effects of IGFBP-5.

Specimen processing time and measurement of total insulin-like growth factor-I (IGF-I), free IGF-I, and IGF binding protein-3 (IGFBP-3)

2006 ◽  
Vol 16 (2) ◽  
pp. 86-92 ◽  
Author(s):  
Tiffany G. Harris ◽  
Howard D. Strickler ◽  
Herbert Yu ◽  
Michael N. Pollak ◽  
E. Scott Monrad ◽  
...  
Keyword(s):  
Growth Factor ◽  
Processing Time ◽  
Binding Protein ◽  
Insulin Like Growth Factor ◽  
Factor I ◽  
Igf I ◽  
Specimen Processing ◽  
Igf Binding ◽  
Igf Binding Protein ◽  
Igfbp 3

scholarly journals Genetic Determinants of Circulating Insulin-Like Growth Factor (IGF)-I, IGF Binding Protein (BP)-1, and IGFBP-3 Levels in a Multiethnic Population

2007 ◽  
Vol 92 (9) ◽  
pp. 3660-3666 ◽  
Author(s):  
Iona Cheng ◽  
Katherine DeLellis Henderson ◽  
Christopher A. Haiman ◽  
Laurence N. Kolonel ◽  
Brian E. Henderson ◽  
...  
Keyword(s):  
Growth Factor ◽  
Binding Protein ◽  
Insulin Like Growth Factor ◽  
Genetic Determinants ◽  
Igf I ◽  
Igf Binding ◽  
Multiethnic Population ◽  
Igf Binding Protein ◽  
Igfbp 3

scholarly journals Insulin-Like Growth Factor Bioactivity, Stanniocalcin-2, Pregnancy-Associated Plasma Protein-A, and IGF-Binding Protein-4 in Pleural Fluid and Serum From Patients With Pulmonary Disease

2017 ◽  
Vol 102 (9) ◽  
pp. 3526-3534 ◽  
Author(s):  
Ulrick Skipper Espelund ◽  
Mette Bjerre ◽  
Rikke Hjortebjerg ◽  
Torben Riis Rasmussen ◽  
Anders Lundby ◽  
...  
Keyword(s):  
Growth Factor ◽  
Pleural Fluid ◽  
Plasma Protein ◽  
Binding Protein ◽  
Protein A ◽  
Insulin Like Growth Factor ◽  
Igf System ◽  
Igf Binding ◽  
Stanniocalcin 2 ◽  
Igf Binding Protein

Abstract Context Members of the insulin-like growth factor (IGF) system are primarily produced in the liver and secreted into the circulation, but they are also produced, recruited, and activated locally in tissues. Objective To compare activity and concentrations of IGF system components in pleural fluid and blood. Design Pathological pleural fluid, secondary to lung cancer or nonmalignant disease, and matching blood samples were collected from 24 patients ages 66.7 to 81.9 years. Methods IGF-related proteins and cytokine levels were measured by immunoassays or immunoblotting. Bioactive IGF was measured by an IGF-1 receptor phosphorylation assay. Results Total IGF-1 concentration did not differ between the compartments, but concentrations of free IGF-1 and bioactive IGF were more than threefold higher in pleural fluid than in corresponding serum samples (P = 0.0004), regardless of etiology. Median pregnancy-associated plasma protein-A (PAPP-A) and interleukin (IL)-6 levels were increased 47-fold and 143-fold, respectively, in pleural fluid compared with plasma (P < 0.0001). PAPP-A and IL-6 concentrations correlated positively (r = 0.46; P = 0.02). In pleural fluid, levels of PAPP-A–generated IGF binding protein-4 fragments correlated inversely with that of stanniocalcin-2 (r ≤ −0.42; P ≤ 0.05), a PAPP-A inhibitor; such correlations were absent in plasma. Conclusion Pathological pleural fluid is characterized by increased in vitro IGF bioactivity and elevated concentrations of PAPP-A, an IGF-activating proteinase. Thus, the tissue activity of the IGF system may differ substantially from that of the circulating IGF system. The correlation between IL-6 and PAPP-A indicates that inflammation plays a role in promoting local tissue IGF activity.

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