Kostopoulou Eirini, Rojas-Gil Andrea Paola, Karvela Alexia, Spiliotis Bessie E
J Pediatr Endocrinol Metab. 2017 Feb 1;30(2):221-230. doi: 10.1515/jpem-2016-0189.
Growth hormone (GH) transduction defect (GHTD) is a growth disorder with impaired signal transducer and activator of transcription 3 (STAT3) phosphorylation mediated by overexpression of cytokine-inducible SH2-containing protein (CIS), which causes increased growth hormone receptor (GHR) degradation. This study investigated the role of epidermal growth factor (EGF) in the restoration of normal GH signaling in GHTD.
Protein expression, cellular localization and physical contact of proteins of the GH and EGF signaling pathways were studied by Western immunoblotting, immunofluorescence and co-immunoprecipitation, respectively. These were performed in fibroblasts of one GHTD patient (P) and one control child (C) at the basal state and after induction with human GH (hGH) 200 μg/L (GH200), either with or without silencing of CIS mRNA, and after induction with hGH 1000 μg/L (GH1000) or 50 ng/mL EGF.
The membrane availability of the EGF receptor (EGFR) and the activated EGFR (pEGFR) was increased in P only after simultaneous GH200 and silencing of CIS mRNA or with GH1000, whereas this occurred in C after GH200 alone. After EGF induction, the membrane localization of GHR, STAT3 and that of EGFR were increased in P more than in C.
In conclusion, in GHTD, the EGFR seems to participate in successful GH signaling, but induction of GHTD fibroblasts with a higher dose of hGH is needed. The EGF/EGFR pathway, in contrast to the GH/GHR pathway, seems to function normally in P and is more primed compared to C. The involvement of the EGFR in successful GH signaling may explain the catch-up growth seen in the Ps when exogenous hGH is administered.
生长激素（GH）转导缺陷（GHTD）是一种生长障碍，由细胞因子诱导含SH2蛋白（CIS）过表达介导的信号转导及转录激活因子3（STAT3）磷酸化受损所致，这会导致生长激素受体（GHR）降解增加。本研究调查了表皮生长因子（EGF）在恢复GHTD中正常GH信号传导的作用。
分别通过蛋白质免疫印迹、免疫荧光和免疫共沉淀研究GH和EGF信号通路蛋白的表达、细胞定位及蛋白间的物理接触。这些实验在一名GHTD患者（P）和一名对照儿童（C）的成纤维细胞中进行，基础状态下以及分别用200μg/L人GH（hGH）（GH200）诱导后（无论有无CIS mRNA沉默），还有用1000μg/L hGH（GH1000）或50ng/mL EGF诱导后。
仅在同时给予GH200和CIS mRNA沉默或给予GH1000后，P中表皮生长因子受体（EGFR）和活化的EGFR（pEGFR）的膜可用性增加，而在C中单独给予GH200后即出现这种情况。EGF诱导后，P中GHR、STAT3和EGFR的膜定位增加程度超过C。
总之，在GHTD中，EGFR似乎参与了成功的GH信号传导，但需要用更高剂量的hGH诱导GHTD成纤维细胞。与GH/GHR途径相反，EGF/EGFR途径在P中似乎功能正常，且相比于C更易被激活。EGFR参与成功的GH信号传导可能解释了给予外源性hGH时P患者出现的追赶生长现象。
