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Growth hormone as a cytokine
M J Waters1, C A Shang, S N Behncken
1Department of Physiology and Pharmacology, University of Queensland, St Lucia, Australia. m.waters@mailbox.uq.edu.au
Clinical and Experimental Pharmacology & Physiology
|November 5, 1999
Summary
Growth hormone (GH) receptors, part of the class 1 cytokine receptor family, are activated by GH-induced dimerization. New research reveals novel physiological roles for GH beyond its traditional functions.
Area of Science:
- Endocrinology
- Molecular Biology
- Cell Signaling
Background:
- The growth hormone (GH) receptor, a class 1 cytokine receptor, shares structural and signaling similarities with family members, notably utilizing Janus kinase 2 (JAK2).
- GH receptor activation involves GH-induced homodimerization, a process targeted by specific hormone antagonists.
Purpose of the Study:
- To explore the detailed mechanisms of GH receptor signaling, including transcription factor involvement.
- To investigate and highlight novel physiological roles of GH, expanding beyond the established insulin-like growth factor-1 (IGF-1) pathway.
- To emphasize the diverse tissue-specific functions of GH.
Main Methods:
- Promoter analyses and electrophoretic mobility gel shift assays were employed to identify transcription factors activated by the GH receptor.
- Literature review and synthesis of existing research to identify and discuss novel GH functions.
Main Results:
- The study details the transcription factors engaged by the activated GH receptor.
- Novel roles for GH were identified in the brain GH axis, vitamin B12 metabolism, early embryonic development, and tooth development.
- GH receptor signaling is widespread, with newly discovered paracrine and local functions.
Conclusions:
- The established view of GH action solely through IGF-1 is an oversimplification.
- GH induces a complex array of growth factors and receptors, with tissue- and developmental stage-specific variations.
- Understanding GH receptor signaling and its diverse roles is crucial for comprehending its broad physiological impact.