scholarly journals Purified hybrid insulin/insulin-like growth factor-I receptors bind insulin-like growth factor-I, but not insulin, with high affinity

1993 ◽  
Vol 290 (2) ◽  
pp. 419-426 ◽  
Author(s):  
M A Soos ◽  
C E Field ◽  
K Siddle
Keyword(s):  
Monoclonal Antibody ◽  
Growth Factor ◽  
Insulin Receptors ◽  
Beta Subunit ◽  
Type I ◽  
Insulin Like Growth Factor ◽  
Factor I ◽  
Igf Receptors ◽  
Igf I ◽  
Growth Factor I

Hybrid insulin/insulin-like growth factor-I (IGF-I) receptors have previously been described in human placenta, but it has not been possible to study their properties in the presence of classical insulin receptors and type I IGF receptors. To facilitate the purification of hybrids, we produced an anti-peptide monoclonal antibody IGFR 1-2, directed against the C-terminal peptide of the type I IGF receptor beta-subunit. The antibody bound native human and rat type I IGF receptors, and reacted specifically with the beta-subunit on immunoblots. Solubilized placental microsomal membranes were depleted of classical type I IGF receptors by incubation with an immobilized monoclonal antibody IGFR 24-55, which reacts well with type I receptors but very poorly with hybrid receptors. Residual hybrid receptors were then isolated by incubation with immobilized antibody IGFR 1-2, and recovered by elution with excess of synthetic peptide antigen. Binding properties of hybrids were compared with those of immuno-affinity-purified insulin receptors and type I IGF receptors, by using the radioligands 125I-IGF-I and 125I-insulin. Hybrids bound approx. 20 times as much 125I-IGF-I as 125I-insulin at tracer concentrations (approx. 0.1 nM). The binding of 125I-insulin, but not 125I-IGF-I, to hybrids increased after treatment with dithiothreitol to reduce disulphide bonds between the alpha-subunits. Hybrids behaved very similarly to type I receptors with respect to the inhibition of 125I-IGF-I binding by unlabelled IGF-I and insulin. By contrast, the affinity of hybrids for insulin was approx. 10-fold lower than that of classical insulin receptors, as assessed by inhibition of 125I-insulin binding by unlabelled hormone. It is concluded that the properties of insulin receptors, but not IGF receptors, are markedly affected by assembly as hybrid compared with classical structures, and that hybrids are more likely to be responsive to IGF-I than insulin under physiological conditions.

A monoclonal antibody to human insulin-like growth factor-I: characterization, use in radioimmunoassay and effect on the biological activities of the growth factor

1989 ◽  
Vol 2 (3) ◽  
pp. 201-206 ◽  
Author(s):  
D. J. Morrell ◽  
H. Dadi ◽  
J. More ◽  
A. M. Taylor ◽  
A. Dabestani ◽  
...  
Keyword(s):  
Monoclonal Antibody ◽  
Growth Factor ◽  
Binding Site ◽  
Biological Activities ◽  
Rabbit Antiserum ◽  
Affinity Constant ◽  
Insulin Like Growth Factor ◽  
Factor I ◽  
Igf I ◽  
Growth Factor I

ABSTRACT A monoclonal antibody (BPL-M23) to insulin-like growth factor-I (IGF-I) was obtained following immunization of BALB/c mice with human IGF-I conjugated to ovalbumin. The affinity constant of BPL-M23 for IGF-I was 10·5 litres/nmol and the cross-reactivities of IGF-II, multiplication-stimulating activity III-2 and insulin were 08, 003 and less than 0·0001 % respectively. Porcine, bovine, ovine and rabbit sera, but not rat or mouse sera, showed substantial reactivity with the antibody. Comparison of radioimmunoassay analyses of 54 human serum samples from normal subjects and acromegalic and GH-deficient patients using BPL-M23 and a polyclonal rabbit antiserum (R557A) to human IGF-I showed a high correlation, indicating the usefulness of the monoclonal antibody in radioimmunoassay. Monoclonal antibody BPL-M23 was capable of abolishing the sulphation, mitogenic and insulin-like activities of IGF-I in in-vitro bioassays, suggesting that these activities may rely upon the same receptor-binding site which is near to the antibody-binding site.

scholarly journals Effects of Short-Term Insulin-Like Growth Factor-I (IGF-I) or Growth Hormone (GH) Treatment on Bone Metabolism and on Production of 1,25-Dihydroxycholecalciferol in GH-Deficient Adults1

1998 ◽  
Vol 83 (1) ◽  
pp. 81-87 ◽  
Author(s):  
Tarcisio Bianda ◽  
Yvonne Glatz ◽  
Roger Bouillon ◽  
Ernst Rudolf Froesch ◽  
Christoph Schmid
Keyword(s):  
Growth Hormone ◽  
Growth Factor ◽  
Bone Formation ◽  
Bone Turnover ◽  
Type I ◽  
Insulin Like Growth Factor ◽  
Gh Treatment ◽  
Factor I ◽  
Igf I ◽  
Growth Factor I

Administration of insulin-like growth factor-I (IGF-I) or growth hormone (GH) is known to stimulate bone turnover and kidney function. To investigate the effects of IGF-I and GH on markers of bone turnover, eight adult GH-deficient patients (48 ± 14 yr of age) were treated with IGF-I (5 μg/kg/h in a continuous sc infusion) and GH (0.03 IU/kg/daily sc injection at 2000 h) in a randomized cross-over study. We monitored baseline values for three consecutive days before initiating the five-day treatment period, as well as the wash-out period of ten weeks. Serum osteocalcin, carboxyterminal and aminoterminal propeptide of type I procollagen (PICP and PINP, respectively) increased significantly within 2–3 days of both treatments (P < 0.02) and returned to baseline levels within one week after the treatment end. The changes in resorption markers were less marked as compared with formation markers. Total 1,25-dihydroxycholecalciferol (1,25-(OH)2D3) rose significantly, whereas PTH and calcium levels remained unchanged during either treatment. Conclusions: Because the rapid increase in markers of bone formation was not preceded by an increase in resorption markers, IGF-I is likely to stimulate bone formation by a direct effect on osteoblasts. Moreover, because PTH, calcium, and phosphate remained unchanged, IGF-I appears to stimulate renal 1α-hydroxylase activity in vivo.

Insulin-like growth factor I and II in 14 animal species and man as determined by three radioligand assays and two bioassays

1987 ◽  
Vol 114 (1) ◽  
pp. 107-112 ◽  
Author(s):  
Ines Zangger ◽  
Jürgen Zapf ◽  
E. Rudolf Froesch
Keyword(s):  
Growth Factor ◽  
Animal Species ◽  
Mammalian Species ◽  
Cross Reactivity ◽  
Type I ◽  
Insulin Like Growth Factor ◽  
Fat Cell ◽  
Factor I ◽  
Igf I ◽  
Growth Factor I

Abstract. Insulin-like growth factor I and II (IGF I and II) were determined by five different assays in human serum, in the sera of ten mammalian species and in chicken, turtle, and frog serum. Sera of all tested mammals contain two different IGFs corresponding to human immunoreactive IGF I and receptor reactive IGF II. Receptor reactive IGF II of most animal species does not show significant cross-reactivity in the RIA for human IGF II. IGF activity was also detected in sera of non-mammals, such as chicken and turtles, but not in frog serum. The IGF values obtained with the different assay system corresponded rather well: there is a good correlation between the values obtained in the protein binding and the fat cell assay, and between the results of the latter assays and the sum of immunoreactive IGF I and receptor reactive IGF II. The results suggest that those regions in the IGF I and II molecules which are responsible for reactivity with the type I IGF and the insulin receptor have not essentially changed during evolution. Similarly, the C-region, which mainly determines the immunological properties of IGFs, appears to have remained relatively constant in the IGF I, but not in the IGF II molecule.

Effects of passive immunization of growing guinea-pigs with an insulin-like growth factor-I monoclonal antibody

1990 ◽  
Vol 124 (3) ◽  
pp. 403-415 ◽  
Author(s):  
D. E. Kerr ◽  
B. Laarveld ◽  
J. G. Manns
Keyword(s):  
Monoclonal Antibody ◽  
Growth Factor ◽  
Guinea Pigs ◽  
Treated Group ◽  
Insulin Like Growth Factor ◽  
Local Production ◽  
Factor I ◽  
Igf I ◽  
Animal Growth ◽  
Growth Factor I

ABSTRACT The physiological importance of circulating as opposed to locally produced insulin-like growth factor-I (IGF-I) has not been determined. By using a passive immunoneutralization technique, our objectives were to evaluate the role of circulating IGF-I in the regulation of animal growth and pituitary GH content. A monoclonal antibody (MAb) to IGF-I, generated in our laboratory, has an affinity (Ka) of 0·13 litres/pmol for recombinant human IGF-I (rhIGF-I). Cross-reactivities of recombinant des-tripeptide IGF-I and recombinant bovine IGF-II were approximately 40 and 8% respectively. This MAb inhibited binding of purified hIGF-I to human placental membranes. In a radioimmunoassay based on displacement of 125I-labelled rhIGF-I from the MAb, displacement curves generated with dilutions of acid–gel chromatography extracts of guinea-pig serum and rhIGF-I standards were parallel. Twenty-four, 3-week-old male guinea-pigs were treated with the IGF-I MAb, a bovine herpes virus-I (BHV-I) MAb (control MAb) or vehicle (phosphate-buffered saline) (n = 8 per group). Treatments were administered i.p. every 3 days for 24 days at a dose of 20 mg/kg body weight. Blood was obtained on day 23 (48 h after treatment) and on day 25 (24 h after treatment). In a liquid-phase assay, serum from the IGF-I MAb-treated group bound 38 ± 8% (mean ± s.e.m.) (day 23) and 56 ± 7% (day 25) of an 125I-labelled rhIGF-I trace at a final dilution of 1:10 000. Because of the development of an anti-mouse immune response in the guinea-pigs, these parameters would probably have been much greater during the first 2 weeks of the trial. Of the total IGF-I in serum, 50 ± 5% and 61±4% could be immunoprecipitated with an excess of rabbit anti-mouse immunoglobulin in samples from days 23 and 25 respectively. Comparisons between the groups treated with IGF-I MAb and BHV-I MAb revealed no significant differences in whole animal growth rate, growth of individual tissues, or pituitary GH content. Mean serum concentrations of IGF-I were 69 and 99% greater in IGF-I MAb-treated group than in the BHV-I MAb-treated group on days 23 and 25 respectively. These differences probably resulted from an extension of the half-life of IGF-I in serum of animals treated with the IGF-I MAb. The lack of effect of treatment with the IGF-I MAb suggests that local production of IGF-I is generally sufficient to maintain normal growth or that local production or activity of IGF-I is increased in a compensatory fashion. Journal of Endocrinology (1990) 124, 403–415

scholarly journals Insulin and insulin-like-growth-factor-I (IGF-I) receptors in Xenopus laevis oocytes. Comparison with insulin receptors from liver and muscle

1991 ◽  
Vol 273 (3) ◽  
pp. 673-678 ◽  
Author(s):  
P Hainaut ◽  
A Kowalski ◽  
S Giorgetti ◽  
V Baron ◽  
E Van Obberghen
Keyword(s):  
Growth Factor ◽  
Xenopus Laevis ◽  
Insulin Receptors ◽  
Beta Subunit ◽  
Beta Subunits ◽  
Xenopus Laevis Oocytes ◽  
Insulin Like Growth Factor ◽  
Factor I ◽  
Alpha Subunits ◽  
Igf I

Insulin and insulin-like-growth-factor-I (IGF-I) receptors were partially purified from full-grown (stages V-VI) Xenopus laevis oocytes by affinity chromatography on wheat-germ agglutinin-agarose. Competitive-binding assays revealed high-affinity binding sites for both insulin and IGF-I (Kd = 2.5 x 10(-10) M and 8 x 10(-10) M respectively). However, IGF-I receptors were about 15 times more abundant than insulin receptors (22.5 x 10(11) versus 1.5 x 10(11)/mg of protein). Moreover, comparison of intact and collagenase-treated oocytes showed that most of the insulin receptors were in the oocyte envelopes, whereas IGF-I receptors were essentially at the oocyte surface. Oocyte receptors were composed of alpha-subunits of approximately 130 kDa and a doublet of beta-subunits of 95 and 105 kDa, which both had ligand-induced phosphorylation patterns compatible with IGF-I receptor beta-subunits. Accordingly, the receptor tyrosine kinase was stimulated at low IGF-I concentrations [half-maximally effective concentration (EC50) approximately 0.5-1 nM], and at higher insulin concentrations (EC50 approximately 20-50 nM). Partially purified glycoproteins from Xenopus liver and muscle contained mainly receptors of the insulin-receptor type, with alpha-subunits of 140 kDa in liver and 125 kDa in muscle, and doublets of beta-subunits of 92-98 kDa in liver and 85-94 kDa in muscle. Immunoprecipitation of receptors from oocytes, liver and muscle by receptor-specific anti-peptide antibodies suggested that the beta-subunit heterogeneity resulted from the existence of two distinct IGF-I receptors in oocytes and of two distinct insulin receptors in both liver and muscle. In the different tissues, the two receptor subtypes differed at least by their beta-subunit C-terminal region.

scholarly journals Age-related changes in effects of insulin-like growth factor I on human osteoblast-like cells

1997 ◽  
Vol 324 (3) ◽  
pp. 753-760 ◽  
Author(s):  
Patricia Y. d'AVIS ◽  
Chester R. FRAZIER ◽  
Jay R. SHAPIRO ◽  
Neal S. FEDARKO
Keyword(s):  
Extracellular Matrix ◽  
Steady State ◽  
Growth Factor ◽  
Type I ◽  
Insulin Like Growth Factor ◽  
Human Osteoblast ◽  
Factor I ◽  
Igf I ◽  
Age Dependent ◽  
Growth Factor I

The role of insulin-like growth factor I (IGF-I) in extracellular matrix metabolism was studied in both proliferating and confluent human osteoblast-like cultures derived from donors of different ages. In proliferating cultures, recombinant human (rh)IGF-I was found to increase the incorporation of [3H]thymidine in a dose- and age-dependent manner. To study cell proliferation dynamically, continuous growth curves with and without rhIGF-I were modelled by a modified logistic function. Increasing doses of rhIGF-I decreased the lag time and maximal growth rates, whereas plateau values decreased only at the highest dose (100 ng/ml). In post-proliferative cell strains, rhIGF-I (0.1–100 ng/ml) increased levels of type I collagen, biglycan and decorin, and to a smaller extent fibronectin and thrombospondin, whereas it decreased the levels of hyaluronan and a versican-like proteoglycan when protein and proteoglycan metabolism were followed by steady-state radiolabelling with [3H]proline, [3H]glucosamine or [35S]sulphate. These responses to rhIGF-I were found to be age-dependent, with osteoblast-like cells derived from younger patients being more responsive to rhIGF-I. When extracellular matrix turnover was analysed by pulse–chase experiments, rhIGF-I had no effect. The steady-state levels of collagen, decorin, hyaluronan and a versican-like proteoglycan for bone cells treated with rhIGF-I on day 7 in culture were equivalent to levels of these matrix components in untreated osteoblasts grown for 14 days. These results are consistent with rhIGF-I's altering cellular proliferative capacity and matrix synthesis, causing a change in the osteoblast differentiated state.

scholarly journals The B domain of Insulin-like Growth Factor I (IGF-I) is recognized by IGF carrier proteins but not by type II IGF receptors

1984 ◽  
Vol 18 (11) ◽  
pp. 1210-1210
Author(s):  
M A De Vroede ◽  
S Joshi ◽  
P G Katsoyannis ◽  
S P Nissley ◽  
M M Rechler
Keyword(s):  
Growth Factor ◽  
Insulin Like Growth Factor ◽  
Type Ii ◽  
Carrier Proteins ◽  
Factor I ◽  
Igf Receptors ◽  
Igf I ◽  
Growth Factor I
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