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Query: UNIPROT:P06889 (Mol)
 630,302 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Insulin gene expression has been demonstrated in nonpancreatic tissues early in development, suggesting that this hormone might have actions significant for the differentiating embryo. Because such actions imply ligand-receptor binding, we quantified mRNAs encoding the two known forms of insulin receptor in rat liver and yolk sac, two endodermally derived tissues shown to express insulin genes, between gestation days (E) 13 and E21 (mid-organogenesis to parturition). Because of its presumed importance for fetal growth, we estimated the abundance of mRNA encoding insulin-like growth factor 1 (IGF 1) receptor in the same samples for comparison. The abundance of insulin receptor mRNA exceeded that for IGF 1 receptor mRNA in liver and yolk sac at all times studied. This difference was greater in liver, where insulin receptor mRNAs were three to more than 50 times more abundant than IGF 1 receptor mRNA on gestation days E13-E16, times which antedate the development of significant hepatic metabolic actions of insulin. The marked abundance of mRNAs encoding insulin receptors is consistent with the hypothesis that insulin has significant actions in specific tissues during the organogenic period.
Mol Endocrinol 1992 Oct
PMID:Insulin receptor gene expression during development: developmental regulation of insulin receptor mRNA abundance in embryonic rat liver and yolk sac, developmental regulation of insulin receptor gene splicing, and comparison to abundance of insulin-like growth factor 1 receptor mRNA. 144 16

In organ culture of pregnant rabbit mammary gland, a low casein synthesis occurs with prolactin (PRL) alone. Insulin markedly potentiates the effect of PRL. Only pharmacological concentrations of insulin (5 micrograms/ml) exert the maximal enhancement, suggesting a possible interaction with the insulin-like growth factor 1 (IGF1) receptor. The presence of IGF1 and insulin binding sites was analyzed and the biological effects of both peptides were compared. Binding of iodinated human IGF1 or porcine insulin to mammary microsomes prepared from mid-pregnant rabbits revealed distinct high affinity binding sites for both peptides (Kd approximately 2 nM). In rabbit mammary explants, we confirmed that only non-physiological concentrations of insulin (greater than or equal to 100 ng/ml) exerted a significant stimulation of the PRL effect. Surprisingly, IGF1 was not found to be more potent than insulin on a molar basis, which did not provide evidence for the exclusive involvement of the IGF1 receptor. Near-physiological concentrations of IGF1 (approximately 100 ng/ml), however, exerted a significant enhancement which suggested a possible action for IGF1 on PRL-induced lactogenesis in vivo.
Mol Cell Endocrinol 1989 Aug
PMID:Comparison of insulin-like growth factor 1 and insulin effects on prolactin-induced lactogenesis in the rabbit mammary gland in vitro. 255 Feb 95

We have recently shown that epithelial cells from a high proportion of benign human thyroid tumours (follicular adenomas) have escaped from the requirement of the normal cell for an exogenous source of insulin-like growth factor 1 (IGF-1), suggesting either autocrine production or intracellular generation of an IGF-1-induced growth signal. We show here that conditioned medium from these adenoma cells can confer IGF-1 independence on normal thyroid epithelial cells and that this activity is abolished by immunoadsorption with an anti-IGF-1 antibody. In addition, tumour but not normal cells contain immunoreactive IGF-1. Our data provide the first evidence for autocrine production of IGF-1 (or a related factor) in a benign epithelial tumour and suggest that this may be a key early step in thyroid tumorigenesis.
Mol Cell Endocrinol 1989 Jan
PMID:Evidence for autocrine production of IGF-1 in human thyroid adenomas. 274 15

By using immature porcine Sertoli cells cultured in serum-free defined medium, we report that Sertoli cell-conditioned medium (SCCM) contains immunoreactive somatomedin C/insulin-like growth factor 1 (ir-SmC/IGF 1) which dilutes in parallel with purified human SmC/IGF 1. The release of ir-SmC/IGF 1 in the culture medium was dependent on the exposure time to Sertoli cells: no measurable ir-SmC/IGF 1 at 8 h, 12.1 +/- 1.2 ng/10(6) cells at 24 h and 33.9 +/- 5.3 ng/10(6) cells at 48 h of incubation. Moreover, ir-SmC/IGF 1 was also evidenced in SCCM following high performance liquid chromatography using a muC18 Bondapak column; ir-SmC/IGF 1 Sertoli cell-conditioned medium co-eluted with pure human SmC/IGF, suggesting a high homology between the two peptides. The effects of SmC/IGF 1 on testicular steroidogenesis were studied by incubating immature porcine Leydig cells with a biosynthetic human SmC/IGF 1. SmC/IGF 1 exerted a dose- and time-dependent stimulating effect on Leydig cell function with a maximal response at 50 ng/ml after 48 h of treatment. SmC/IGF 1 increased both LH/hCG binding (4.3-fold), basal testosterone (4-fold) and DHAS- and hCG-stimulated testosterone and DHAS (dehydroepiandrosterone sulfate) production (15.5- and 6.4-fold respectively). The slight effect of SmC/IGF 1 (100 ng for 48 h) on cell number (1.3-fold) and incorporation of [3H]thymidine into DNA (1.5-fold) in comparison with the high steroidogenic effect, supports the concept that SmC/IGF 1 acts as a cytodifferentiative factor rather than as a growth factor.(ABSTRACT TRUNCATED AT 250 WORDS)
Mol Cell Endocrinol 1987 Mar
PMID:Somatomedin C/insulin-like growth factor 1 as a possible intratesticular regulator of Leydig cell activity. 295 35

Insulin receptor substrate 1 (IRS-1) mediates the activation of a variety of signaling pathways by the insulin and insulin-like growth factor 1 receptors by serving as a docking protein for signaling molecules with SH2 domains. We and others have shown that in response to insulin stimulation IRS-1 binds GRB2/Sos and have proposed that this interaction is important in mediating Ras activation by the insulin receptor. Recently, it has been shown that the interleukin (IL)-4 receptor also phosphorylates IRS-1 and an IRS-1-related molecule, 4PS. Unlike insulin, however, IL-4 fails to activate Ras, extracellular signal-regulated kinases (ERKs), or mitogen-activated protein kinases. We have reconstituted the IL-4 receptor into an insulin-responsive L6 myoblast cell line and have shown that IRS-1 is tyrosine phosphorylated to similar degrees in response to insulin and IL-4 stimulation in this cell line. In agreement with previous findings, IL-4 failed to activate the ERKs in this cell line or to stimulate DNA synthesis, whereas the same responses were activated by insulin. Surprisingly, IL-4's failure to activate ERKs was not due to a failure to stimulate the association of tyrosine-phosphorylated IRS-1 with GRB2/Sos; the amounts of GRB2/Sos associated with IRS-1 were similar in insulin- and IL-4-stimulated cells. Moreover, the amounts of phosphatidylinositol 3-kinase activity associated with IRS-1 were similar in insulin- and IL-4-stimulated cells. In contrast to insulin, however, IL-4 failed to induce tyrosine phosphorylation of Shc or association of Shc with GRB2. Thus, ERK activation correlates with Shc tyrosine phosphorylation and formation of an Shc/GRB2 complex. Thus, ERK activation correlates with Shc tyrosine phosphorylation and formation of an Shc/GRB2 complex. Previous studies have indicated that activation of ERks in this cell line is dependent upon Ras since a dominant-negative Ras (Asn-17) blocks ERK activation by insulin. Our findings, taken in the context of previous work, suggest that binding of GRB2/Sos to Shc may be the predominant mechanism whereby insulin as well as cytokine receptors activate Ras.
Mol Cell Biol 1995 Mar
PMID:Association between GRB2/Sos and insulin receptor substrate 1 is not sufficient for activation of extracellular signal-regulated kinases by interleukin-4: implications for Ras activation by insulin. 786 67

The controlling mechanism for adrenal androgen production has not been elucidated. The presence of receptors for prolactin, human chorionic gonadotropin (hCG), insulin and insulin-like growth factor 1 (IGF-1) in the adrenal cortex raises the possibility of their involvement in the control of adrenal steroidogenesis. This study was undertaken to investigate the effects of prolactin, hCG, insulin and IGF-1 in the presence and absence of ACTH on cortisol and androgen production using isolated guinea-pig adrenal cells. hCG 10(-7) and 10(-6) M significantly increased cortisol (P < 0.05) production. hCG 10(-6) M significantly increased androstenedione (A4) (P < 0.05) production. In the presence of ACTH, 10(-12) M, hCG 10(-6) M significantly increased the cortisol (P < 0.01) and A4 (P < 0.01) responses. Although the mean cortisol and A4 response to ACTH 10(-9) M was reduced in the presence of hCG 10(-6) M, this was not statistically significant. Prolactin 10(-8) M increased cortisol (P < 0.01), A4, and dehydroepiandrosterone (P < 0.05) production. In the presence of ACTH 10(-12) M, prolactin 10(-8) M increased the cortisol and A4 (P < 0.05) responses. However, the maximally ACTH-stimulated cortisol and A4 responses were not significantly altered in the presence of prolactin 10(-8) M. Insulin 10(-11)-10(-8) M and IGF-1 10(-10)-10(-7) M resulted in no significant increase in cortisol, A4 or dehydroepiandrosterone production. This study suggests that prolactin and hCG could play a role in modulation of adrenal steroidogenesis, particularly when ACTH levels are low. However, there was no evidence that prolactin or hCG is the specific cortical androgen stimulating hormone.
J Steroid Biochem Mol Biol 1994 Feb
PMID:The effect of prolactin, human chorionic gonadotropin, insulin and insulin-like growth factor 1 on adrenal steroidogenesis in isolated guinea-pig adrenal cells. 814

Insulin receptors have been characterized in a cell line recently isolated from a chicken hepatoma (LMH). The binding of 125I-insulin to LMH cells or membranes displayed the expected criteria for insulin receptors: affinity, temperature dependency, curvilinearity of Scatchard plot, rank order of potency for insulin analogs and insulin induced down-regulation. The alpha-subunit of LMH cell insulin receptors exhibited a normal size of 135 kDa. Following autophosphorylation, LMH WGA-purified receptors revealed a 95 kDa beta-subunit and a 72 kDa protein (pp72). Both proteins were phosphorylated in a time-, insulin- (and insulin-like growth factor 1; IGF-1) and manganese-dependent manner, and were precipitated by antiphosphotyrosine and two anti-insulin receptor antibodies. The 72 kDa protein was not present under non-reducing condition PAGE or in normal chicken liver. These results strongly suggest that pp72 is either a truncated form of the insulin receptor beta-subunit specific to LMH cells or a degradation product. Lectin-purified insulin receptors from LMH cells or chicken liver membranes exhibited similar tyrosine kinase activity, using artificial substrate poly(Glu-Tyr) 4:1. Finally, amino acid uptake by LMH cells was insulin stimulatable.
Mol Cell Endocrinol 1993 Oct
PMID:Insulin receptor and insulin sensitivity in a chicken hepatoma cell line. 827 26

The mechanism or mechanisms by which ras oncogenes induce morphological transformation and anchorage-independent growth are poorly understood but are thought to involve stable alterations in gene expression. We previously described a genetically dominant, mutant rat fibroblast cell line (ER-1-2) that is resistant to ras-induced anchorage-independent growth. We now describe a cell line derived from ER-1-2 cells, termed ER-1-2T, that has apparently sustained a second, dominant mutation that conferred on these cells the ability to form colonies in soft agar. Analysis of these and control cell lines demonstrated that deregulation of many of the genes commonly associated with the transformed phenotype could be dissociated from anchorage-independent growth. After infection with a ras-expressing retrovirus, both control and ER-1-2 cell lines constitutively expressed elevated levels of the c-jun, junB, fosB, c-myc, collagenase, ornithine decarboxylase, osteopontin, stromelysin, cathepsin L, and insulin-like growth factor 1 genes. These data indicate that signaling events downstream of ras were largely intact in ER-1-2 cells and that the defect in these cells lies either on a pathway separate from those that control stable, ras-mediated expression of these genes or at a point in the cell-division cycle distinct from those that control expression of the genes. In contrast, only c-jun, junB, c-myc, and ornithine decarboxylase were expressed at a significantly elevated level in ER-1-2T cells. Thus, deregulated expression of the genes analyzed was not sufficient for anchorage-independent growth. Furthermore, deregulation of most of them was also not necessary.
Mol Carcinog 1996 Jul
PMID:Dissociation of ras oncogene-induced gene expression and anchorage-independent growth in a series of somatic cell mutants. 868 49

Both sexes of adult mice homozygous for a targeted mutation of the Igf1 gene, encoding insulin-like growth factor 1, are infertile dwarfs (approximately 30% of normal size). The testes are reduced in size less than expected from the degree of dwarfism but sustain spermatogenesis only at 18% of the normal level. The epididymides are overall nearly allometric to the reduced body weight, but the distal regions of the duct, vas deferens, seminal vesicles, and prostate are vestigial. Despite the mutational impact on the epididymis, capacitated sperm are able to fertilize wild type eggs in vitro. It is hypothesized that the infertility of male mutants is caused by failure of androgenization resulting in absence of mating behavior, due to drastically reduced levels of serum testosterone (18% of normal). This hormonal deficiency was correlated with an ultrastructural analysis of mutant Leydig cells revealing a significant developmental delay, while assays in organ culture showed that the basal and LH-stimulated production of testosterone by testicular parenchyma is reduced in comparison with wild type controls. The female mutants fail to ovulate even after administration of gonadotropins, which is apparently the primary cause of their infertility, and possess an infantile uterus that exhibits a dramatic hypoplasia especially in the myometrium. The phenotypic manifestations of the mutation were correlated with the localization of transcripts for insulin-like growth factor I and its cognate receptor in wild type reproductive tissues by in situ hybridization.
Mol Endocrinol 1996 Jul
PMID:Effects of an Igf1 gene null mutation on mouse reproduction. 881 30

It is now well-recognized that the mitogen-activated protein (MAP) kinase cascade facilitates signaling from an activated tyrosine kinase receptor to the nucleus. In fact, an increasing number of extracellular effectors have been reported to activate the MAP kinase cascade, with a significant number of cellular responses attributed to this activation. We set out to explore how two extracellular effectors, basic fibroblast growth factor (bFGF) and insulin-like growth factor 1 (IGF-1), which have both been reported to activate MAP kinase, generate quite distinct cellular responses in C2C12 myoblasts. We demonstrate here that bFGF, which is both a potent mitogen and inhibitor of myogenic differentiation, is a strong MAP kinase agonist. By contrast, IGF-1, which is equally mitogenic for C2C12 cells but ultimately enhances the differentiated phenotype, is a weak activator of the MAP kinase cascade. We further demonstrate that IGF-1 is a potent activator of both insulin receptor substrate IRS-1 tyrosyl phosphorylation and association of IRS-1 with activated phosphatidylinositol 3-kinase (PI 3-kinase). Finally, use of the specific MAP kinase kinase inhibitor, PD098059, and wortmannin, a PI 3-kinase inhibitor, suggests the existence of an IGF-1-induced, MAP kinase-independent signaling event which contributes to the mitogenic response of this factor, whereas bFGF-induced mitogenesis appears to strongly correlate with activation of the MAP kinase cascade.
Mol Cell Biol 1996 Nov
PMID:Stimulation of C2C12 myoblast growth by basic fibroblast growth factor and insulin-like growth factor 1 can occur via mitogen-activated protein kinase-dependent and -independent pathways. 888 26


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