Somatomedin (Insulin-Like Growth Factors)-Binding Proteins

Binoux, M; Hossenlopp, Paul; Hardouin, S; Seurin, Danielle; Lassarre, Claudine; Gourmelen, M

doi:10.1159/000180553

Cited by 89 publications

(35 citation statements)

References 22 publications

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“…In these animals, intravenously injected IGF has a much shorter half-life than in normal rats [8] and the animals are more susceptible to acute insulin-like effects of IGF I and II than normal rats [8]. Other studies suggest that truncated IGFBPs bind IGFs with lower affinity than the intact forms [14,26,27], although this has been challenged [28]. Thus, intravenously injected IGF I has a longer serum elimination half-life in non-pregnant as compared to pregnant rats, in which intact IGFBP-3 is dramatically reduced [15].…”

Section: Discussionmentioning

confidence: 99%

“…Our data provide evidence that proteolysis of IGFBP-3 is under hormonal control. Thus, GH may augment concentrations of IGFs both systemically and locally: (i) directly by inducing all components of the ternary serum complex (IGF, IGFBP-3, and the acidlabile subunit, ALS) and increasing IGF synthesis in certain tissues; (ii) indirectly by inducing an IGFBP-3 proteolytic activity, thereby facilitating the dissociation of IGF from IGFBP-3, which is a constituent of the ternary complex both in its intact and truncated form [26,29,30]. Our study does not address the question to which extent ALS may protect IGFBP-3 from proteolysis.…”

Section: Discussionmentioning

confidence: 99%

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Growth hormone, but not insulin‐like growth factor I, induces a serum protease activity for insulin‐like growth factor binding protein‐3 in hypophysectomized rats in vivo

Rutishauser¹,

Schmid²,

Hauri³

et al. 1993

FEBS Letters

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Insulin-like growth factor binding proteins (IGFBPs) modulate IGF action. Proteolytic cleavage of IGFBPs yields lower molecular forms with reduced ability to bind IGFs, thereby increasing IGF bioavailability. In serum from normal adult rats, we found a proteolytic activity for IGFBP-3, presumably a cation-dependent serine protease. It is lacking in serum from hypophysectomized rats and restored by infusion of growth hormone (GH), but not IGF I. Thus, IGF I does not appear to mediate the GH effect on IGFBP-3 proteolysis. Rather, GH seems to modulate IGF action indirectly via alteration of IGFBP-3 structure.Growth hormone; Insulin-like growth factor; Insulin-like growth factor binding protein; Proteolysis; Insulin-like growth factor bioavailability

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Section: Discussionmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

Growth hormone, but not insulin‐like growth factor I, induces a serum protease activity for insulin‐like growth factor binding protein‐3 in hypophysectomized rats in vivo

Rutishauser¹,

Schmid²,

Hauri³

et al. 1993

FEBS Letters

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“…The methods used have been described in detail elsewhere [13,181. Samples were gel-filtered on Ultrogel AcA 54 (1.5 x 30 cm) in 1 M CH,COOH, 0.15 M NaCl, 0.1% bovine serum albumin.…”

Section: H) Binding Protein and Igf Assaysmentioning

confidence: 99%

“…These were used as tracers and for the competitive binding studies. Iodination of the IGFs by the chloramine-T method and their subsequent purification were performed as described elsewhere [13]. A partially purified preparation (350 ng/mg protein) containing a 1 : 1 (w/w) mixture of IGF I and IGF I1 was used in demonstrating the specificity of labelled IGF binding to the binding proteins.…”

mentioning

confidence: 99%

Heterogeneity of insulin‐like growth factor binding proteins and relationships between structure and affinity

Hardouin

Hossenlopp

Segovia

et al. 1987

European Journal of Biochemistry

175

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Circulating insulin‐like growth factors (IGFs) are bound to specific, high‐affinity binding proteins (BPs), and form complexes with relative molecular masses of about 150000 (‘large’ complex) and 40000 (‘small’ complex). The large complex appears to be under growth‐hormone control and its proportions vary with those of the IGFs. Molecular heterogeneity among the binding proteins was revealed by polydcrylamide gel electrophoresis (SDS‐PAGE) of serum in which they were cross‐linked to 125I‐labelled IGF I or II. Out of the six specific bands observed, of 150000, 120000, 49000, 46000, 40000 and 37000 Mr, the last three appeared in both complexes, whereas the first three were visible only in the large complex. Some or all of the 49000–37000‐Mr species may constitute the subunits of 150000‐Mr and/or 120000‐Mr IGF‐BP complexes. With electrophoresis followed by transfer onto nitrocellulose and incubation with either 125I‐labelled IGF I or II (western blot), the different binding proteins were identified per se. There were five molecular forms with Mr of 41 500, 38 500, 34000, 30000 and 24000. In normal serum the 41 500 and 38 500‐Mr forms were the major binding proteins. They appeared in both complexes, but were predominant in the large complex where they constitute the elementary binding units. These two proteins therefore bind to IGFs to form both ‘monomeric’ IGF‐BP and ‘oligomeric’ (IGF‐BP)n complexes. The 34000, 30000 and 24000‐Mr forms, by contrast, were visible only in the small complex. Different mechanisms appear to regulate the different binding proteins: in acromegalic serum the 41 500 and 38 500‐Mr forms were augmented and the 34000‐Mr form diminished, whereas in hypopituitary serum the reverse was true and, in addition, the 30000‐Mr form was augmented. With chromatofocusing, the 34000, 30000 and 24000‐Mr forms eluted in three peaks between pH 6.0 and 4.0, whereas the 41 500 and 38 500‐Mr forms eluted throughout the gradient, principally at pH 7.5 and 7.0. Competitive binding studies, done on binding proteins separated either by chromatofocusing or by SDS‐PAGE and transfer onto nitrocellulose, revealed different affinities for the IGFs among the different molecular forms. The 41 500 and 24 000‐Mr binding proteins preferentially bound IGF I and the 38 500, 34 000 and 30 000‐Mr proteins preferentially bound IGF II. Our findings demonstrate the molecular heterogeneity of the binding proteins and the existence of a relationship between their structure and their affinities for the IGFs. They also suggest that, apart from their function as IGF carriers, the binding proteins also play a modulating role in the interaction between IGFs and their target cells.

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“…The mol. wts range from 24 to 150 kd (Wilkins and D'Ercole, 1985;Binoux et al, 1986). Some of these proteins are related to the 150-kd BP (Baxter et al, 1986a), some are thought to be derived from the low mol.…”

Section: Introductionmentioning

confidence: 99%

Isolation and characterization of a cDNA encoding the low molecular weight insulin-like growth factor binding protein (IBP-1).

et al. 1988

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IGF‐I and IGF‐II are growth‐stimulating peptides with strong mitogenic properties. These polypeptide growth factors circulate in serum bound to specific binding proteins. We report the cloning and complete sequence of a cDNA encoding a low mol. wt IGF‐binding protein from a human placenta cDNA library. We propose the designation IGF‐binding protein 1 (IBP‐1) for the gene and corresponding protein. Expression of the cDNA encoding IBP‐1 in COS cells resulted in the synthesis of a 30‐kd protein which binds IGF‐I and is immunologically indistinguishable from the IGF‐binding protein isolated from amniotic fluid or human serum. Northern blotting analysis demonstrated that expression of the IBP‐1 gene is highly tissue specific and limited to placental membranes and fetal liver suggesting a rigid control. The IBP‐1 gene is a single copy gene, located on chromosome 7. The results obtained suggest that most, if not all, lower mol. wt IGF‐binding proteins originate from this gene.

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Somatomedin (Insulin-Like Growth Factors)-Binding Proteins

Cited by 89 publications

References 22 publications

Growth hormone, but not insulin‐like growth factor I, induces a serum protease activity for insulin‐like growth factor binding protein‐3 in hypophysectomized rats in vivo

Growth hormone, but not insulin‐like growth factor I, induces a serum protease activity for insulin‐like growth factor binding protein‐3 in hypophysectomized rats in vivo

Heterogeneity of insulin‐like growth factor binding proteins and relationships between structure and affinity

Isolation and characterization of a cDNA encoding the low molecular weight insulin-like growth factor binding protein (IBP-1).

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