Transduction Systems for Peptide Hormones, Growth Factors, and Cytokines
Signal Transduction Overview: Signal transduction is the process by which cells respond to external signals (such as peptide hormones, growth factors, and cytokines) and convert these signals into specific cellular responses. This process typically involves the binding of signalling molecules to cell surface receptors, which then initiate intracellular signalling cascades.
STAT Transduction Mechanism
Overview:
The STAT (Signal Transducer and Activator of Transcription) pathway is a signalling mechanism used by cytokines and some growth factors. It is crucial for mediating responses such as cell growth, differentiation, and immune functions.
STAT Transduction Mechanism
Key Components:
- Cytokines/Growth Factors: Signalling molecules that bind to specific receptors on the cell surface (e.g., Interleukins, Interferons).
- Receptors: Often receptor tyrosine kinases (RTKs) or cytokine receptors.
- Janus Kinases (JAKs): A family of tyrosine kinases that associate with cytokine receptors.
- STAT Proteins: Transcription factors that, when activated, move to the nucleus to influence gene expression.
STAT Transduction Mechanism
Mechanism:
- Ligand Binding: A cytokine or growth factor binds to its receptor on the cell surface.
- Receptor Dimerization: The receptor undergoes dimerization (pairing of two receptor molecules), bringing associated JAKs into close-proximity.
- JAK Activation: The JAKs phosphorylate each other and the receptor, creating docking sites for STAT proteins.
- STAT Recruitment and Phosphorylation: STAT proteins bind to the phosphorylated receptor and are themselves phosphorylated by JAKs.
- Dimerization of STATs: Phosphorylated STAT proteins dimerize (pair up).
- Nuclear Translocation: The STAT dimers translocate to the nucleus.
- Gene Expression: In the nucleus, STAT dimers bind to specific DNA sequences to regulate the transcription of target genes.