scholarly journals Expression and function of insulin/insulin-like growth factor I hybrid receptors during differentiation of 3T3-L1 preadipocytes

1998 ◽  
Vol 333 (3) ◽  
pp. 825-831 ◽  
Author(s):  
Dalit MODAN-MOSES ◽  
Michel JANICOT ◽  
John C. McLENITHAN ◽  
M. Daniel LANE ◽  
Samuel J. CASELLA
Keyword(s):  
Growth Factor ◽  
Cell Surface ◽  
Fold Increase ◽  
Insulin Binding ◽  
Cell Surface Expression ◽  
Insulin Like Growth Factor ◽  
Hybrid Form ◽  
Igf Receptors ◽  
Igf I ◽  
Igf Receptor

During the assembly of cell surface receptors, insulin proreceptors are sometimes joined to insulin-like growth factor (IGF) receptor precursors to form covalently linked hybrid receptors. To address the biological consequences of hybrid receptor formation, we studied 3T3-L1 cells known to undergo a 50–70-fold increase in insulin binding while maintaining nearly constant levels of IGF-I binding during differentiation from preadipocytes into adipocytes. The presence of insulin/IGF receptor hybrids in 3T3-L1 adipocytes was demonstrated by the immunoprecipitation of phosphorylated receptors and a novel enzyme-linked immunoassay. Hybrid receptor levels were very low in the early stages of differentiation and increased rapidly between days 4 and 6, reaching a level about 100-fold higher in the mature adipocyte. Coincident with the hybrid assembly, the formation of archetypal (α2,β2) IGF receptors decreased. In fully differentiated adipocytes, virtually all of the IGF receptors were in hybrid form. Stimulation by IGF-I of receptors isolated from mature adipocytes caused autophosphorylation of IGF receptor β subunits in hybrid complexes, whereas autophosphorylated IGF holoreceptors were not demonstrable. Insulin and IGF-I were equipotent in stimulating glucose uptake in the differentiated adipocytes, leading to the conclusion that hybrid insulin/IGF receptors can transduce a transmembrane signal when activated by IGF-I. We conclude that hybrid formation constitutes a novel post-translational mechanism whereby increased synthesis of insulin receptors limits the cell surface expression of the homologous IGF receptor. Furthermore, biological actions in 3T3-L1 adipocytes, previously attributed to archetypal IGF receptors, are in fact mediated through hybrid receptors.

scholarly journals Insulin-like growth factor binding to the atypical insulin receptors of a human lymphoid-derived cell line (IM-9)

1990 ◽  
Vol 266 (3) ◽  
pp. 737-742 ◽  
Author(s):  
H A Jonas ◽  
A J Cox
Keyword(s):  
Growth Factor ◽  
Affinity Chromatography ◽  
Insulin Receptor ◽  
Binding Sites ◽  
Insulin Binding ◽  
Type I ◽  
Insulin Like Growth Factor ◽  
Igf Receptors ◽  
Type I Igf Receptor ◽  
Igf I

The cells of the IM-9 human lymphocyte-derived line contain a sub-population of insulin-binding sites whose immunological and hormone-binding characteristics closely resemble those of the atypical insulin-binding sites of human placenta. These binding sites, which have moderately high affinity for multiplication-stimulating activity [MSA, the rat homologue of insulin-like growth factor (IGF) II] and IGF-I, are identified on IM-9 cells by 125I-MSA binding. They account for approximately 30% of the total insulin-receptor population, and do not react with a monoclonal antibody to the type I IGF receptor (alpha IR-3). The relative concentrations of unlabelled insulin, MSA and IGF-I required to displace 50% of 125I-MSA from these binding sites (1:4.7:29 respectively) are maintained for cells, particulate membranes, Triton-solubilized membranes precipitated either by poly(ethylene glycol) or a polyclonal antibody (B-10) to the insulin receptor, and receptors purified by insulin affinity chromatography. Because the atypical insulin/MSA-binding sites outnumber the type I IGF receptors in IM-9 cells by approximately 10-fold, they also compete with the latter receptors for 125I-IGF-I binding. Thus 125I-IGF-I binding to IM-9 cells is inhibited by moderately low concentrations of insulin (relative potency ratios for insulin compared with IGF-I are approx. 1/14 to 1/4) and is partially displaced (65-80%) by alpha IR-3. When type I IGF receptors are blocked by alpha IR-3 or removed by B-10 immunoprecipitation or insulin affinity chromatography, the hormone-displacement patterns for 125I-IGF-I binding resemble those of the atypical insulin/MSA-binding sites.

scholarly journals The C Region of Human Insulin-like Growth Factor (IGF) I Is Required for High Affinity Binding to the Type 1 IGF Receptor

1989 ◽  
Vol 264 (19) ◽  
pp. 11004-11008 ◽  
Author(s):  
M L Bayne ◽  
J Applebaum ◽  
D Underwood ◽  
G G Chicchi ◽  
B G Green ◽  
...  
Keyword(s):  
Growth Factor ◽  
Human Insulin ◽  
Affinity Binding ◽  
Insulin Like Growth Factor ◽  
High Affinity Binding ◽  
High Affinity ◽  
Igf I ◽  
Igf Receptor

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.

scholarly journals RAT C6 GLIAL CELLS EXPRESS INSULIN-LIKE GROWTH FACTOR (IGF) RECEPTORS AND SYNTHESIZE AND SECRETE IGF-I

1988 ◽  
Vol 23 (1) ◽  
pp. 107-107
Author(s):  
W Kiess ◽  
L Lee ◽  
D E Graham ◽  
L Greenstein ◽  
M M Reehler
Keyword(s):  
Growth Factor ◽  
Glial Cells ◽  
Insulin Like Growth Factor ◽  
Igf Receptors ◽  
Igf I

The ovine pancreatic protein which binds insulin-like growth factor binding protein-3 is procarboxypeptidase A

1996 ◽  
Vol 150 (1) ◽  
pp. 51-56 ◽  
Author(s):  
P J Fowke ◽  
S C Hodgkinson
Keyword(s):  
Growth Factor ◽  
Cell Surface ◽  
Binding Protein ◽  
Binding Activity ◽  
Insulin Like Growth Factor ◽  
Surface Binding ◽  
Factor Binding ◽  
Amino Terminal ◽  
Igf I ◽  
Igfbp 3

Abstract Insulin-like growth factor binding protein-3 (IGFBP-3) is known to modulate the actions of insulin-like growth factors (IGF)-I and -II at the level of the cell. Proposed mechanisms include association of IGFBP-3 with cell surface proteoglycan, with cell surface binding proteins, proteolysis and/or internalization of IGFBP-3. In previous studies we have characterized a protein of 40 kDa in extracts of ovine pancreas and muscle which binds IGFBP-3 on ligand blot analyses. This paper reports the identity of the pancreatic species as procarboxypeptidase A (peptidyl-l-amino acid hydrolase, E.C. 3.4.17.1; proCPA). Identity was established by amino terminal sequence analysis, binding studies with pure bovine carboxypeptidase A (CPA) and observations that the binding activity was present in pancreatic secretions consistent with the role of proCPA as a secretory zymogen. The binding activity was inhibited by unlabelled IGFBP-3 at high doses (10 μg/ml) and reduced but not abolished by preincubation of 125I-IGFBP-3 with excess IGF-I. Digestion of 125I-IGFBP-3 with mature CPA produced a 26 kDa product. Modification of IGFBP-3 by CPA or binding to proCPA may provide a mechanism for modulation of IGFBP activity and hence IGF action. Journal of Endocrinology (1996) 150, 51–56

scholarly journals Insulin receptor is phosphorylated in response to treatment of HepG2 cells with insulin-like growth factor I

1990 ◽  
Vol 270 (1) ◽  
pp. 27-32 ◽  
Author(s):  
V Duronio
Keyword(s):  
Growth Factor ◽  
Insulin Receptor ◽  
Hepg2 Cells ◽  
Insulin Binding ◽  
Response To Treatment ◽  
Insulin Like Growth Factor ◽  
Factor I ◽  
Igf I ◽  
Growth Factor I ◽  
In Cells

1. Binding of insulin and insulin-like growth factor I (IGF-I) to HepG2 cells was analysed with regard to competition by both insulin and IGF-I. At concentrations of insulin that caused maximal phosphorylation of the insulin receptor, virtually no displacement of IGF-I binding was observed. Similarly, at concentrations of IGF-I that caused maximal phosphorylation of the IGF-I receptor, no displacement of insulin binding was observed. 2. When the phosphorylation of both receptors was examined individually by using specific monoclonal antibodies to immunoprecipitate the receptors, phosphorylation of the insulin receptor was found to increase on both serine and tyrosine residues in cells treated with 100 ng of IGF-I/ml. In contrast, no increased phosphorylation of IGF-I receptor was observed in cells treated with 100 ng of insulin/ml. 3. The increase in phosphorylation of insulin receptor in response to IGF-I correlated with the dose-response of IGF-I-stimulated phosphorylation of the IGF-I receptor. 4. The IGF-I-stimulated phosphorylation of the insulin receptor could be blocked by preincubation with a monoclonal antibody that blocks IGF-I binding to the IGF-I receptor.

scholarly journals Insulin-like growth factor (IGF) receptor, IGF-I, interleukin-1 beta (IL-1 beta), and IL-6 mRNA expression in osteoarthritic and normal human cartilage.

1996 ◽  
Vol 44 (2) ◽  
pp. 133-141 ◽  
Author(s):  
J Middleton ◽  
A Manthey ◽  
J Tyler
Keyword(s):  
Extracellular Matrix ◽  
Growth Factor ◽  
Interleukin 1 ◽  
Insulin Like Growth Factor ◽  
Interleukin 1 Beta ◽  
Normal Cartilage ◽  
Igf I ◽  
Cartilage Cells ◽  
Igf Receptor

Insulin-like growth factor-I (IGF-I) stimulates the production of extracellular matrix by cartilage cells and this action is mediated through the Type 1 IGF receptor. Expression of the genes for the IGF receptor and for IGF-I was examined in normal and osteoarthritic (OA) human articular cartilage by in situ hybridization. RNA transcripts for Type 1 receptor were detected in all 73 tissue samples and in 80-100% of chondrocytes per section. Signal for the receptor was present in normal and OA cells, and the highest message levels were in the tissues exhibiting advanced pathology. Strong message signals in the cells of the more advanced lesions were also noted for IGF-I, whereas little or no IGF-I mRNA was detected in normal samples. Interleukin-1 beta (IL-1 beta) induces degradation of extracellular matrix by cartilage cells, and expression of this gene was examined with digoxygenin-labeled oligonucleotide probes. mRNA transcripts were detected in only one in five of the cartilage samples taken from OA joints. Unlike IGF-I, expression did not correlate with the degree of OA pathology and positive cells were demonstrated also in samples from young normal cartilage. IL-6 mRNA was present both in surface and deep cells of fibrillated OA cartilage, but no signal was evident in histologically normal cartilage from OA tissue or in normal young joints.

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