epidermal-growth-factor and Dwarfism

Topics: Animals; Biological Assay; Cell Cycle; Chemical Phenomena; Chemistry; Dwarfism; Epidermal Growth Factor; Fibroblast Growth Factors; Forecasting; Growth Hormone; Growth Substances; Humans; Hypophysectomy; Insulin; Insulin-Like Growth Factor II; Molecular Weight; Peptides; Pituitary Gland, Anterior; Prolactin; Receptors, Cell Surface; Receptors, Somatotropin; Somatomedins

The adaptor protein GAREM has two subtypes. Each is involved in Erk activation signaling downstream of the cell growth factor receptor in cultured cells. Regarding their role in individual animals, we have previously reported that mice deficient in GAREM2, which is highly expressed in the brain, exhibit emotional changes. In this paper, we report an amino acid substitution mutation (K291R) in GAREM1, in a patient with idiopathic short stature, which indicates that the mutant exhibits dominant-negative properties. The GAREM K291R mutant did not promote Erk activation in EGF-stimulated cultured cells. Similar features were also observed in cells in which GAREM1 expression was suppressed by genome editing; along with Erk, phosphorylation of S6 kinase and 4EBP1, whose activation is necessary for cell proliferation and biological growth, were inhibited Furthermore, we generated mice deficient in GAREM1 and showed that the mutant mice are lighter in weight. Overall, the results of this paper suggest that GAREM1 is required for normal growth and for maintaing average body size in humans and mice.

Topics: Adaptor Proteins, Signal Transducing; Animals; Body Weight; Cell Cycle Proteins; Cell Line; Dwarfism; Epidermal Growth Factor; GRB2 Adaptor Protein; Humans; MAP Kinase Signaling System; Mice; Phosphorylation; Ribosomal Protein S6 Kinases

Background Growth hormone(GH) and epidermal growth factor (EGF) stimulate cell growth and differentiation, and crosstalking between their signaling pathways is important for normal cellular development. Growth hormone transduction defect (GHTD) is characterized by excessive GH receptor (GHR) degradation, due to over-expression of the E3 ubiquitin ligase, cytokine inducible SH2-containing protein (CIS). GH induction of GHTD fibroblasts after silencing of messenger RNA (mRNA) CIS (siCIS) or with higher doses of GH restores normal GH signaling. β-Transducing-repeat-containing protein (β-TrCP), another E3 ubiquitin ligase, also plays a role in GHR endocytosis. We studied the role of β-TrCP in the regulation of the GH/GHR and EGF/EGF receptor (EGFR) pathways in normal and GHTD fibroblasts. Materials and methods Fibroblast cultures were developed from gingival biopsies of a GHTD (P) and a control child (C). Protein expression and cellular localization of β-TrCP were studied by Western immunoblotting and immunofluorescence, respectively, after: (1) GH 200 μg/L human GH (hGH) induction, either with or without silence CIS (siCIS), and (2) inductions with 200 μg/L GH or 1000 μg/L GH or 50 ng/mL EGF. Results After induction with: (1) GH200/siCIS, the protein expression and cytoplasmic-membrane localization of β-TrCP were increased in the patient, (2) GH200 in the control and GH1000 in the patient, the protein and cytoplasmic-membrane localization of β-TrCP were increased and (3) EGF, the protein expression and cytoplasmic-membrane localization of β-TrCP were increased in both the control and the patient. Conclusions (1) β-TrCP appears to be part of the negative regulatory mechanism of the GH/GHR and EGF/EGFR pathways. (2) There appears to be a negative correlation between β-TrCP and CIS. (3) In the control and GHTD patient, β-TrCP increases when CIS is suppressed, possibly as a compensatory inhibitor of the GH/GHR pathway.

Topics: beta-Transducin Repeat-Containing Proteins; Child; Dwarfism; Epidermal Growth Factor; ErbB Receptors; Fibroblasts; Gene Silencing; Human Growth Hormone; Humans; Male; Proteasome Endopeptidase Complex; Protein Processing, Post-Translational; Protein Transport; Proteolysis; Receptors, Somatotropin; RNA Interference; RNA, Messenger; RNA, Small Interfering; Signal Transduction; Suppressor of Cytokine Signaling Proteins; Ubiquitination

Leprechaunism is a rare inherited disorder characterized by severe intrauterine growth retardation and insulin resistance. Cultured skin fibroblasts from an infant with Leprechaunism were previously reported to show decreased stimulation of DNA synthesis by insulin despite apparently normal binding of [125I]insulin and [125I]somatomedin C. We have now further investigated the growth of this patient's fibroblasts and compared their metabolic responses to insulin and various peptide growth factors with responses in normal foreskin-derived fibroblasts. The doubling time of Leprechaun fibroblasts was prolonged (90 vs. 29 h), and their morphology was abnormal. Stimulation of [3H]glucose uptake was minimal with low insulin levels (1--10 ng/ml) relative to controls, but was comparable at higher insulin concentrations (1--10 micrograms/ml). Stimulation of [3H] aminoisobutyric acid uptake by insulin, epidermal growth factor (EGF), multiplication-stimulating activity, and somatomedin C (Sm-C) in Leprechaun cells was diminished relative to control cells at all concentrations tested. Furthermore, stimulation of [3H]thymidine incorporation in Leprechaum cells by EGF, Sm-C, and fibroblast growth factor was also subnormal. Binding of [125I]EGF to Leprechaun fibroblasts was not decreased. It is concluded that fibroblasts from this patient are resistant to the metabolic effects of insulin, EGF, Sm-C, and fibroblast growth factor. Since receptors for three of these peptides are apparently normal, it is likely that the defect in these cells is at the postreceptor level, perhaps involving a metabolic pathway common to the action of multiple growth factors.

Topics: Aminoisobutyric Acids; Cell Division; Cells, Cultured; Drug Resistance; Dwarfism; Epidermal Growth Factor; ErbB Receptors; Fibroblast Growth Factors; Fibroblasts; Glucose; Humans; Infant; Insulin Resistance; Insulin-Like Growth Factor I; Peptides; Receptors, Cell Surface; Somatomedins; Syndrome; Thymidine

Growth hormone is essential for sustaining longitudinal growth in man. However, during the last 20 years, it has become evident that the actions of growth hormone, at a cellular level, are mediated by specific growth promoting factors. This paper describes the nature and actions of mammalian growth factors and summarises the immense contribution that the measurement of these substances has made towards the elucidation of many problems in the science of human growth and development.

Topics: Cyclic AMP; Dwarfism; Epidermal Growth Factor; Fibroblasts; Growth Substances; Humans; Liver; Nerve Growth Factors; Nonsuppressible Insulin-Like Activity; Somatomedins