GHR signalling: Receptor activation and degradation mechanisms

Growth hormone (GH) actions via initiating cell signalling through the GH receptor (GHR) are important for many physiological processes, in addition to its well-known role in regulating growth. The activation of JAK-STAT signalling by GH is well characterized, however knowledge on GH activation of SRC family kinases (SFKs) is still limited. In this review we summarise the collective knowledge on the activation, regulation, and downstream signalling of GHR. We highlight studies on GH activation of SFKs and the important outcome of this signalling pathway with a focus on the different degradation mechanisms that can regulate GHR availability since this is an area that warrants further study considering its role in tumour progression.

The Growth Hormone Receptor: Mechanism of Receptor Activation, Cell Signaling, and Physiological Aspects

The growth hormone receptor (GHR), although most well known for regulating growth, has many other important biological functions including regulating metabolism and controlling physiological processes related to the hepatobiliary, cardiovascular, renal, gastrointestinal, and reproductive systems. In addition, growth hormone signaling is an important regulator of aging and plays a significant role in cancer development. Growth hormone activates the Janus kinase (JAK)-signal transducer and activator of transcription (STAT) signaling pathway, and recent studies have provided a new understanding of the mechanism of JAK2 activation by growth hormone binding to its receptor. JAK2 activation is required for growth hormone-mediated activation of STAT1, STAT3, and STAT5, and the negative regulation of JAK-STAT signaling comprises an important step in the control of this signaling pathway. The GHR also activates the Src family kinase signaling pathway independent of JAK2. This review covers the molecular mechanisms of GHR activation and signal transduction as well as the physiological consequences of growth hormone signaling.