Growth hormone is the hormone primarily responsible for body growth. Growth hormone (GH) binds membrane-bound growth hormone receptor (GHR) to activate and enhance the binding of JAK2. This stimulates phosphorylation of JAK2 and GHR. JAK2 initiates GH signal transduction. This activation initiates multiple signalling pathways: STAT transcription factors, activation of kinases, and insulin receptor pathways. GH stimulates Signal Transducer and Activator of Transcription (STAT) and its binding to Sis-inducible elements of the c-fos promoter. C-fos expression has input from multiple pathways. The serum response element binds serum response factors and other complex transcription factors regulated by GH via the MEK/ERK pathway. STAT 5 is also involved in the synthesis of many GH-sensitive genes. STAT proteins are phosphorylated and then released from the GH/JAK2 complex. Once released, they become dimers and move to the nucleus to bind binding sites in GH-regulated genes. STAT proteins may also dimerize with other transcription factors to regulate transcription. GH can stimulate glucose transport in the cell through JAK2 stimulation of IRS proteins that recruit PI3K to regulate glucose transport.

Growth Hormone Signaling Pathway References