Ann Pediatr Endocrinol Metab.  2018 Dec;23(4):204-209. 10.6065/apem.2018.23.4.204.

The role of p21/CIP1/WAF1 (p21) in the negative regulation of the growth hormone/growth hormone receptor and epidermal growth factor/epidermal growth factor receptor pathways, in growth hormone transduction defect

Affiliations
  • 1Paediatric Endocrine Research Laboratory, Division of Paediatric Endocrinology and Diabetes, Department of Paediatrics, University of Patras School of Medicine, Patras, Greece. eirini.kost@gmail.com
  • 2Faculty of Human Movement and Quality of Life Sciences, Department of Nursing, University of Peloponnese, Sparta, Greece.

Abstract

PURPOSE
Growth hormone transduction defect (GHTD) is characterized by severe short stature, impaired STAT3 (signal transducer and activator of transcription-3) phosphorylation and overexpression of the cytokine inducible SH2 containing protein (CIS) and p21/CIP1/WAF1. To investigate the role of p21/CIP1/WAF1 in the negative regulation of the growth hormone (GH)/GH receptor and Epidermal Growth Factor (EGF)/EGF Receptor pathways in GHTD.
METHODS
Fibroblast cultures were developed from gingival biopsies of 1 GHTD patient and 1 control. The protein expression and the cellular localization of p21/CIP1/WAF1 was studied by Western immunoblotting and immunofluorescence, respectively: at the basal state and after induction with 200-μg/L human GH (hGH) (GH200), either with or without siRNA CIS (siCIS); at the basal state and after inductions with 200-μg/L hGH (GH200), 1,000-μg/L hGH (GH1000) or 50-ng/mL EGF.
RESULTS
After GH200/siCIS, the protein expression and nuclear localization of p21 were reduced in the patient. After successful induction of GH signaling (control, GH200; patient, GH1000), the protein expression and nuclear localization of p21 were reduced. After induction with EGF, p21 translocated to the cytoplasm in the control, whereas in the GHTD patient it remained located in the nucleus.
CONCLUSIONS
In the GHTD fibroblasts, when CIS is reduced, either after siCIS or after a higher dose of hGH (GH1000), p21's antiproliferative effect (nuclear localization) is also reduced and GH signaling is activated. There also appears to be a positive relationship between the 2 inhibitors of GH signaling, CIS and p21. Finally, in GHTD, p21 seems to participate in the regulation of both the GH and EGF/EGFR pathways, depending upon its cellular location.

Keyword

Cyclin-dependent kinase inhibitor p21; Feedback signal transduction; Growth hormone; Epidermal growth factor; Cell cycle; Cyclin-dependent kinases

MeSH Terms

Biopsy
Blotting, Western
Cell Cycle
Cyclin-Dependent Kinase Inhibitor p21
Cyclin-Dependent Kinases
Cytoplasm
Epidermal Growth Factor
Fibroblasts
Fluorescent Antibody Technique
Growth Hormone*
Humans
Phosphorylation
RNA, Small Interfering
Transducers
Cyclin-Dependent Kinase Inhibitor p21
Cyclin-Dependent Kinases
Epidermal Growth Factor
Growth Hormone
RNA, Small Interfering
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