A developmentally regulated form of insulin-like growth factor receptor beta-subunit in C2 myoblasts exhibiting altered requirements for differentiation.

Barenton, Bruno; Domeyne, Anne; Garandel, Véronique; Garofalo, Robert S.

doi:10.1210/endo.133.2.8344204

Cited by 13 publications

(14 citation statements)

References 35 publications

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“…The presence of two P-subunit moieties (one of low Mr: 95-97 kDa; and one of high Mr: 101 -105 kDa) has already been reported in several tissues or cell lines (Garofalo and Rosen, 1989;Garofalo and Barenton, 1992;Moxham et al, 1989). In C2 myoblasts, we found two psubunits of Mr 95 and 101 kDa in permissive cells, and a single p-subunit of Mr 106 kDa in inducible cells (Barenton et al, 1993). We demonstrate here for the first time two high molecular weight (Mr > 100 kDa) p-subunit subtypes in the same cells.…”

Section: Discussionsupporting

confidence: 53%

“…Microsomal membranes were solubilized and IGF receptors were purified using a wheat germ agglutinin (WGA)-Sepharose column as previously described (Barenton et al, 1993). WGA-purified receptors (25 pg protein) were activated following incubation for 30 rnin at 4°C with either 1 nM IGF-I, IGF-11, or insulin.…”

Section: Autophosphorylation Of Igf Receptorsmentioning

confidence: 99%

“…As in SSM and FSM cultures, the expression of the myogenic transcription factors in C2 cells is temporally related to the course of terminal differentiation (Montarras e t al., 1991). We also described modifications in the equilibrium of several components of the IGF system between inducible and permissive C2 cells at quiescent myoblast stage (Domeyne et al, 1992a,b;Barenton et al, 1993). Since both IGF-I and IGF-I1 are actively involved in the control of myoblasts proliferation and differentiation (Ewton and Florini, 1990), we attempted to determine whether ex vivo adult satellite myoblasts derived from rabbit slowtwitch and fast-twitch muscles exhibit comparable alterations of the IGF system to permissive and inducible C2 myoblasts.…”

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confidence: 99%

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Rabbit slow and fast skeletal muscle-derived satellite myoblast phenotypes do not involve constitutive differences in the components of the insulin-like growth factor system

Barjot¹,

Navarro²,

Cotten³

et al. 1996

J. Cell. Physiol.

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The insulin-like growth factor (IGF) system is actively involved in the control of proliferation and differentiation of several myogenic cell lines, and phenotypic differences between myoblasts are associated with modifications of the equilibrium of the components of the IGF system. To determine whether this observation is a physiologic feature that also concerns the phenotypes of ex vivo adult satellite myoblasts in primary cell culture, we investigated the IGF system in rabbit slow-twitch muscle-derived satellite myoblasts (SSM), which differ phenotypically from fast-twitch muscle-derived satellite myoblasts (FSM) by their proliferation and differentiation kinetics in vitro. The expression of IGF-I and IGF-II were similar in SSM and FSM as well as their concentrations measured in cell-conditioned media. Ligand blotting of conditioned media samples indicated the presence of five IGF binding protein (IGFBP) species of Mr 37-40, 32, 30-31, 28, and 24 kDa. The 30-31 kDa doublet was visible in SSM-conditioned medium only and associated with the presence of a 22-kDa protein, which may represent a proteolytic fragment. In contrast, the 32-kDa band was observed in FSM conditioned medium only. The other IGFBP moieties were present in both SSM- and FSM-conditioned media. Cross-linking experiments revealed the presence of the M6P/IGF-II receptor on both SSM and FSM membranes. We also observed an IGF-I receptor form bearing unusual high affinity for IGF-II: the binding of [125I]IGF-I on this receptor was preferentially displaced by IGF-I but that of [125I]IGF-II was mostly inhibited by IGF-II, suggesting that the two tracers did not bind on the same epitopes. [125I]IGF-II binding to this receptor was greater on SSM than on FSM membranes. Autophosphorylation of WGA-purified receptors revealed an approximately 400-kDa band after SDS-PAGE under nonreducing conditions, which corresponded to the alpha 2 beta 2 form of the IGF-I receptor, and two beta subunit moieties of Mr 101 and 105 kDa under reducing conditions in both SSM and FSM extracts. Phosphorylation of the 105-kDa moiety was more intensively increased than that of the 101-kDa protein after growth factor stimulation. Basal phosphorylation state of the two beta subunits was similarly stimulated by IGF-I and IGF-II and less by insulin. Since both insulin and IGF-I receptors were expressed in FSM and SSM, one of the two beta subunits may actually correspond to that of the insulin receptor. We conclude that the IGF system is not considerably affected by the phenotypes of SSM and FSM. The differences observed, which mostly concern IGFBP species, more likely appear as regulatory adaptations than as phenotypic changes targeting the components of the IGF system.

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Section: Discussionsupporting

confidence: 53%

Section: Autophosphorylation Of Igf Receptorsmentioning

confidence: 99%

mentioning

confidence: 99%

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Rabbit slow and fast skeletal muscle-derived satellite myoblast phenotypes do not involve constitutive differences in the components of the insulin-like growth factor system

Barjot¹,

Navarro²,

Cotten³

et al. 1996

J. Cell. Physiol.

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“…Interestingly, in the same Western blot it can be observed that the LP8 -3 cell line (NIH-3T3 expressing activated Ha-ras) predominantly displayed the same receptor isoform. This 105-kDa variant seems to be tissue-specific and, according to some investigators, expressed during fetal development (32)(33)(34)(35) or even in leukemic cells (36). A functional analysis of the IGF-1␤ receptor showed that again in as-LOX cells there was no autophosphorylation upon IGF-1 challenging (Fig.…”

Section: Resultsmentioning

confidence: 77%

Down-regulation of Lysyl Oxidase-induced Tumorigenic Transformation in NRK-49F Cells Characterized by Constitutive Activation of Ras Proto-oncogene

Giampuzzi

Botti

Cilli³

et al. 2001

Journal of Biological Chemistry

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Several investigations have suggested a putative tumor suppressor role for lysyl oxidase because it is downregulated in many human and oncogene-induced tumors. To address this issue we down-regulated the enzyme in normal rat kidney fibroblasts by stable transfection of its cDNA in an antisense orientation. The selected clones revealed an absence of lysyl oxidase and dramatic phenotypic changes, interpretable as signs of transformation. The antisense lysyl oxidase clones showed, indeed, loose attachment to the plate and anchorage-independent growth and were highly tumorigenic in nude mice. Moreover, we found an impaired response of the PDGF and IGF-1 receptors to their ligands. In particular, the transformed cells showed a down-regulation of both PDGF receptors and expressed the 105-kDa isoform of the IGF-1␤ receptor, which was not present in the normal control cells. The lack of response to PDGF-BB has been described as a feature of many ras-transformed phenotypes. Therefore, we looked at the status of the p21 ras . Indeed, we found a significantly higher level of active p21 ras both during steady-state growth and prolonged starvation. Our data reveal new evidence for a tumor suppressor activity of lysyl oxidase, highlighting its particular role in controlling Ras activation and growth factor dependence. Lysyl oxidase (LOX)1 (protein-6-oxidase; EC 1.4.3.13) is the key enzyme that controls collagen and elastin maturation (1, 2). Indeed, it catalyzes the oxidative deamination of peptidyl lysine and hydroxylysine to peptidyl-␣-aminoadipic-␦-semialdehyde into elastin and collagen chains. The consequent aldehydes lead to a spontaneous condensation forming inter-and intrachain cross-links. This post-translational modification of extracellular matrix molecules seems to have a very important role both for collagen and elastin structural aspects and for triggering still unknown signal transduction pathways. Several reports have suggested a clear association between organ fibrosis and increased LOX activity (3-9).The most intriguing aspect regarding LOX activity refers to its putative cell phenotype control and/or tumor suppressor activity. In many naturally occurring and oncogene-induced tumors, LOX is down-regulated, while, in contrast, LOX is one of the main genes induced in concomitance with the reversion process (10 -14). In particular it seems that LOX was downregulated in cells transformed by ras or ras-dependent oncogenes, so that it was first identified as a "ras recision gene" (rrg) (10,11,13). In particular, Friedman and co-workers (10, 11) showed that H-ras-transfected NIH-3T3, induced to revert by interferon ␤/␥, would return to their transformed phenotype upon transfection with an antisense LOX vector. The reversion or the re-transformation did not affect the level of p21 ras although other possible mechanisms or parameters were not studied (10).The localization of the enzyme is mainly extracellular, although recently it has been confirmed that processed LOX is localized intracellularly and inside the nucleu...

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“…Thus, the Type I1 receptor does not appear to be involved in the stimulation of L6A1 muscle differentiation, in spite of its high abundance on these cells (Beguinot et al, 1985). However, we cannot rule out the possible involvement of other IGF-I or insulin receptor variants (Alexandrides and Smith, 1989;Casella et al, 1986;Jonas et al, 1989), IGF-I: insulin receptor hybrids (Moxham and Jacobs, 1993) or a putative aaPa IGF-I1 receptor subtype which has recently been described in C2 mouse muscle cells (Domeyne et al, 1992;Barenton et al, 1993). In their studies with human myoblasts, Shimizu et al (1986) also could not rule out the involvement of a receptor other than the Type I receptor; the monoclonal antibody, a-IR3, that specifically recognizes the IGF-I receptor, was found to only partially inhibit the response of the myoblasts to either IGF-I or IGF-11.…”

Section: Igf-iimentioning

confidence: 96%

IGF‐II is more active than IGF‐I in stimulating L6A1 myogenesis: Greater mitogenic actions of IGF‐I delay differentiation

Ewton

Roof

Magri

et al. 1994

Journal Cellular Physiology

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Mitogens are generally thought to inhibit myogenesis, and many cell biologists have found it hard to interpret observations that the insulin-like growth factors (IGFs) stimulate both proliferation and differentiation of muscle cells in culture. Our previous studies suggested that the Type I IGF receptor mediates these actions. However, IGF-II and insulin treatment caused myoblasts to differentiate much more extensively, suggesting that more complex mechanisms may be involved. Here we present evidence that the greater mitogenic activity of IGF-I (compared to IGF-II and insulin) delays L6A1 myoblast differentiation. Under conditions in which the mitogenic actions of IGF-I are suppressed, the stimulation of myogenesis by IGF-I approached that by IGF-II: (1) in L6A1 cultures plated at a higher cell density; (2) in L6A1 cultures in which cell proliferation was inhibited by cytosine arabinoside or aphidicolin; and (3) in cultures of primary human muscle cells, which exhibit a smaller mitogenic response to IGF-I. Further evidence that the Type I receptor plays a major role in relaying the signal for differentiation was obtained by using IGF-I and IGF-II analogs. Analogs which have reduced affinity for the Type I receptor showed a dramatic decrease in activity, while an analog with increased affinity for the Type II receptor was no more active than native IGF-I. Our results indicate that both mitogenic and myogenic actions of IGF-I are mediated by the Type I receptor. We conclude that IGF-I delays the onset of myogenesis as a result of its mitogenic actions, and only subsequently stimulates myogenesis. These observations reconcile the apparent conflict between our results with the IGFs and other investigators' reports of effects of other mitogens.

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A developmentally regulated form of insulin-like growth factor receptor beta-subunit in C2 myoblasts exhibiting altered requirements for differentiation.

Cited by 13 publications

References 35 publications

Rabbit slow and fast skeletal muscle-derived satellite myoblast phenotypes do not involve constitutive differences in the components of the insulin-like growth factor system

Rabbit slow and fast skeletal muscle-derived satellite myoblast phenotypes do not involve constitutive differences in the components of the insulin-like growth factor system

Down-regulation of Lysyl Oxidase-induced Tumorigenic Transformation in NRK-49F Cells Characterized by Constitutive Activation of Ras Proto-oncogene

IGF‐II is more active than IGF‐I in stimulating L6A1 myogenesis: Greater mitogenic actions of IGF‐I delay differentiation

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