Janus Kinase–Signal Transducer and Activator of Transcription (JAK–STAT) Pathway
Hormone Receptors and Molecular Signaling
Janus Kinase–Signal Transducer and Activator of Transcription (JAK–STAT) Pathway
JAK–STAT signaling connects selected cytokine and hormone receptors with changes in transcription. These receptors commonly lack intrinsic tyrosine kinase activity and instead associate with Janus kinases on their intracellular side.
The signaling sequence
Ligand binding changes receptor organization, allowing JAK activation and phosphorylation of receptor-associated sites. STAT proteins are recruited, phosphorylated and organized into complexes that influence nuclear gene regulation.
Endocrine examples
Growth hormone and prolactin prominently use JAK2–STAT5-related signaling. Receptor identity and cellular cofactors help determine the specific transcriptional response.
Limits and feedback
SOCS proteins, phosphatases and receptor trafficking help restrain the pathway. An increase in a STAT phosphorylation signal should therefore be interpreted with timing, target genes and functional outcomes. It is not equivalent to a universal increase in tissue growth.
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