How IGF-II Binds to the Human Type 1 Insulin-like Growth Factor Receptor.
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ABSTRACT:
SUBMITTER: Xu Y
PROVIDER: S-EPMC7343240 | biostudies-literature |
REPOSITORIES: biostudies-literature
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Project description:BackgroundInsulin-like growth factor-II (IGF-II) promotes cell proliferation and survival and plays an important role in normal fetal development and placental function. IGF-II binds both the insulin-like growth factor receptor (IGF-1R) and insulin receptor isoform A (IR-A) with high affinity. Interestingly both IGF-II and the IR-A are often upregulated in cancer and IGF-II acts via both receptors to promote cancer proliferation. There is relatively little known about the mechanism of ligand induced activation of the insulin (IR) and IGF-1R. The recently solved IR structure reveals a folded over dimer with two potential ligand binding pockets arising from residues on each receptor half. Site-directed mutagenesis has mapped receptor residues important for ligand binding to two separate sites within the ligand binding pocket and we have recently shown that the IGFs have two separate binding surfaces which interact with the receptor sites 1 and 2.Methodology/principal findingsIn this study we describe a series of partial IGF-1R and IR agonists generated by mutating Glu12 of IGF-II. By comparing receptor binding affinities, abilities to induce negative cooperativity and potencies in receptor activation, we provide evidence that residue Glu12 bridges the two receptor halves leading to receptor activation.Conclusions/significanceThis study provides novel insight into the mechanism of receptor binding and activation by IGF-II, which may be important for the future development of inhibitors of its action for the treatment of cancer.
| S-EPMC3227035 | biostudies-literature
Project description:Monomers of the insulin receptor and type 1 insulin-like growth factor receptor (IGF-1R) can combine stochastically to form heterodimeric hybrid receptors. These hybrid receptors display ligand binding and signaling properties that differ from those of the homodimeric receptors. Here, we describe the cryoelectron microscopy structure of such a hybrid receptor in complex with insulin-like growth factor I (IGF-I). The structure (ca. 3.7 Å resolution) displays a single IGF-I ligand, bound in a similar fashion to that seen for IGFs in complex with IGF-1R. The IGF-I ligand engages the first leucine-rich-repeat domain and cysteine-rich region of the IGF-1R monomer (rather than those of the insulin receptor monomer), consistent with the determinants for IGF binding residing in the IGF-1R cysteine-rich region. The structure broadens our understanding of this receptor family and assists in delineating the key structural motifs involved in binding their respective ligands.
| S-EPMC9364964 | biostudies-literature
Project description:Human type 1 insulin-like growth factor receptor is a homodimeric receptor tyrosine kinase that signals into pathways directing normal cellular growth, differentiation and proliferation, with aberrant signalling implicated in cancer. Insulin-like growth factor binding is understood to relax conformational restraints within the homodimer, initiating transphosphorylation of the tyrosine kinase domains. However, no three-dimensional structures exist for the receptor ectodomain to inform atomic-level understanding of these events. Here, we present crystal structures of the ectodomain in apo form and in complex with insulin-like growth factor I, the latter obtained by crystal soaking. These structures not only provide a wealth of detail of the growth factor interaction with the receptor's primary ligand-binding site but also indicate that ligand binding separates receptor domains by a mechanism of induced fit. Our findings are of importance to the design of agents targeting IGF-1R and its partner protein, the human insulin receptor.
| S-EPMC5826941 | biostudies-literature
Project description:The mannose 6-phosphate/insulin-like growth factor II receptor (M6P/IGF2R) binds M6P-capped ligands and IGF-II at different binding sites within the ectodomain and mediates ligand internalization and trafficking to the lysosome. Multivalent M6P-based ligands can cross-bridge the M6P/IGF2R, which increases the rate of receptor internalization, permitting IGF-II binding as a passenger ligand and subsequent trafficking to the lysosome, where the IGF-II is degraded. This unique feature of the receptor may be exploited to design novel therapeutic agents against IGF-II-dependent cancers that will lead to decreased bioavailable IGF-II within the tumor microenvironment. We have designed a panel of M6P-based ligands that bind to the M6P/IGF2R with high affinity in a bivalent manner and cause decreased cell viability. We present evidence that our ligands bind through the M6P-binding sites of the receptor and facilitate internalization and degradation of IGF-II from conditioned medium to mediate this cellular response. To our knowledge, this is the first panel of synthetic bivalent ligands for the M6P/IGF2R that can take advantage of the ligand-receptor interactions of the M6P/IGF2R to provide proof-of-principle evidence for the feasibility of novel chemotherapeutic agents that decrease IGF-II-dependent growth of cancer cells.
| S-EPMC5308735 | biostudies-literature
Project description:We report an original association of complex genetic defects in a patient carrying both an 11p paternal duplication, resulting in the double expression of insulin-like growth factor 2 (IGF2), as reported in Beckwith-Wiedemann syndrome, and a 15q terminal deletion, including the type 1 IGF receptor gene (IGF1R), resulting in haploinsufficiency for this gene. The patient was born with measurements appropriate for her gestational age but experienced growth retardation in early childhood, allowing a better comprehension of the IGF system in the pathophysiology of growth. It is possible that IGF-II plays a key role in fetal growth, independently of IGF1R signaling, and that its role is less important in post-natal growth, leaving IGF-I and growth hormone as the main actors.
| S-EPMC6503735 | biostudies-literature
Project description:Type 2 insulin-like growth factor (IGF-II) levels are increased in fibrosing lung diseases such as idiopathic pulmonary fibrosis (IPF) and scleroderma/systemic sclerosis-associated pulmonary fibrosis (SSc). Our goal was to investigate the contribution of IGF receptors to IGF-II-mediated fibrosis in these diseases and identify other potential mechanisms key to the fibrotic process. Cognate receptor gene and protein expression were analyzed with qRT-PCR and immunoblot in primary fibroblasts derived from lung tissues of normal donors (NL) and patients with IPF or SSc. Compared to NL, steady-state receptor gene expression was decreased in SSc but not in IPF. IGF-II stimulation differentially decreased receptor mRNA and protein levels in NL, IPF, and SSc fibroblasts. Neutralizing antibody, siRNA, and receptor inhibition targeting endogenous IGF-II and its primary receptors, type 1 IGF receptor (IGF1R), IGF2R, and insulin receptor (IR) resulted in loss of the IGF-II response. IGF-II tipped the TIMP:MMP balance, promoting a fibrotic environment both intracellularly and extracellularly. Differentiation of fibroblasts into myofibroblasts by IGF-II was blocked with a TGFβ1 receptor inhibitor. IGF-II also increased TGFβ2 and TGFβ3 expression, with subsequent activation of canonical SMAD2/3 signaling. Therefore, IGF-II promoted fibrosis through IGF1R, IR, and IGF1R/IR, differentiated fibroblasts into myofibroblasts, decreased protease production and extracellular matrix degradation, and stimulated expression of two TGFβ isoforms, suggesting that IGF-II exerts pro-fibrotic effects via multiple mechanisms.
| S-EPMC6876936 | biostudies-literature
Project description:Insulin and insulin growth factor type 1 (IGF-1) and their receptors are closely related molecules, but both factors bind to the receptor of the other one with a weak affinity. No study has presently documented a role of insulin as a myeloma growth factor (MGF) for human multiple myeloma cells (MMCs), whereas many studies have concluded that IGF-1 is a major MGF. IGF-1 receptor (IGF-1R) is aberrantly expressed by MMCs in association with a poor prognosis. In this study we show that insulin receptor (INSR) is increased throughout normal plasma cell differentiation. INSR gene is also expressed by MMCs of 203/206 newly diagnosed patients. Insulin is an MGF as potent as IGF-1 at physiological concentrations and requires the presence of insulin/IGF-1 hybrid receptors, stimulating INSR(+)IGF-1R(+) MMCs, unlike INSR(+)IGF-1R(-) or INSR(-)IGF-1R(-) MMCs. Immunoprecipitation experiments indicate that INSR is linked with IGF-1R in MMCs and that insulin induces both IGF-1R and INSR phosphorylations and vice versa. In conclusion, we demonstrate for the first time that insulin is an MGF as potent as IGF-1 at physiological concentrations and its activity necessitates insulin/IGF-1 hybrid receptor activation. Further therapeutic strategies targeting the IGF/IGF-1R pathway have to take into account neutralizing the IGF-1R-mediated insulin MGF activity.
| S-EPMC3141222 | biostudies-literature
Project description:BackgroundSerum IGF-I and IGF-II levels decline with age. IGF-I replacement therapy reduces the impact of age in rats. We have recently reported that IGF-II is able to act, in part, as an analogous of IGF-I in aging rats reducing oxidative damage in brain and liver associated with a normalization of antioxidant enzyme activities. Since mitochondria seem to be the most important cellular target of IGF-I, the aim of this work was to investigate whether the cytoprotective actions of IGF-II therapy are mediated by mitochondrial protection.MethodsThree groups of rats were included in the experimental protocol young controls (17 weeks old); untreated old rats (103 weeks old); and aging rats (103 weeks old) treated with IGF-II (2 ?g/100 g body weight and day) for 30 days.ResultsCompared with young controls, untreated old rats showed an increase of oxidative damage in isolated mitochondria with a dysfunction characterized by: reduction of mitochondrial membrane potential (MMP) and ATP synthesis and increase of intramitochondrial free radicals production and proton leak rates. In addition, in untreated old rats mitochondrial respiration was not blocked by atractyloside. In accordance, old rats showed an overexpression of the active fragment of caspases 3 and 9 in liver homogenates. IGF-II therapy corrected all of these parameters of mitochondrial dysfunction and reduced activation of caspases.ConclusionsThe cytoprotective effects of IGF-II are related to mitochondrial protection leading to increased ATP production reducing free radical generation, oxidative damage and apoptosis.
| S-EPMC3162510 | biostudies-literature
Project description:Increased risk of cancer and other adult diseases have been associated with perinatal exposure to adverse conditions such as stress and famine. Recently, Insulin-like growth factor II (IGF-II) was identified as the first gene associated with altered expression caused by fetal exposure to poor nutrition. IGF-II regulates fetal development and breast cancer cell survival, in part, by regulating anti-apoptotic proteins through activation of the IGF-I and insulin receptors. African-American (AA) women have a lower overall breast cancer (BC) incidence, however, they present with advanced disease at diagnosis, poorer prognosis and lower survival than Caucasian (CA) women. The reasons for the BC survival disparity are not well understood. We hypothesize that IGF-II plays a role in the survival disparity observed among AA breast cancer patients by stimulating rapid tumor growth, inhibiting apoptosis, and promoting metastasis.This study examines IGF-II expression and regulation of the anti-apoptotic proteins Bcl-2, Bcl-X(L), and survivin in Hs578t (ER-), CRL 2335 (ER-), and CRL 2329 (ER+) breast cancer cells and compares with the expression of these proteins in paired breast tissue samples from AA and CA women by qRT-PCR and Western blotting.IGF-II expression was significantly higher in AA cell lines and tissue samples when compared to Caucasians. IGF-II siRNA treatment decreased anti-apoptotic protein levels in all cell lines (regardless of ER status). These effects were blocked by the addition of recombinant IGF-II. Of significance, IGF-II expression and regulation of Bcl-X(L) and survivin in cell lines correlated with their expression in paired breast tissues.IGF-II and the anti-apoptotic proteins differential expression among AA and CA patients may contribute to the breast cancer survival disparities observed between these ethnic groups.
| S-EPMC2885869 | biostudies-literature
Project description:We investigated the binding properties of the type I insulin-like growth factor (IGF) receptor expressed in NIH-3T3 fibroblasts transfected with a human type I receptor cDNA. Cell surface receptors bound IGF-I with KD = 1 nM as predicted. Although recent studies have suggested that IGF-I and IGF-II bind to type I receptors with near-equal affinity, the receptors in this system bound IGF-II with much lower affinity (KD = 15-20 nM). When type I receptors from the transfected cells were solubilized and immunopurified, however, both 125I-IGF-I and 125I-IGF-II bound to the purified receptors with extremely high and relatively similar affinities (KD = 8 and 17 pM respectively). Thus the immunopurified receptors had higher affinity but lower specificity for the two ligands. The monoclonal antibody alpha IR-3 effectively inhibited IGF-I binding to cell surface receptors (75 +/- 10%), but did not inhibit IGF-II binding. In the purified receptor assay, alpha IR-3 also inhibited IGF-I binding more effectively than IGF-II binding (38 +/- 7% versus 10 +/- 4%). We conclude that the products of this cDNA can account for the binding patterns that we previously observed in receptors immunopurified from human placenta. The differential effect of alpha IR-3 on IGF-I versus IGF-II raises the possibility that these homologous growth factors bind to immunologically distinct epitopes on the type I receptor.
| S-EPMC1130700 | biostudies-other