文档介绍：Unit 7: Signal Transduction
Multi-Step Regulation of Gene Expression
DNA
Primary RNA transcript
mRNA
mRNA
Degraded mRNA
Protein
Active Protein
Degraded Proteinn
Transcription control
RNA processing control
RNA transport control
nucleus
cytosol
mRNA degradation control
mRNA translation control
protein activity control
Protein degradation control
Signal Transduction Pathways
Pathways of molecular interactions that munication between the cell membrane and intracellular endpoints, leading to some change in the cell
Major themes in ST
The “plexity” of each interaction
binatorial nature of ponent molecule (may receive and send multiple signals)
The integration of pathways works
Signal source
A signaling cell produces a particular particular type of signal molecule
This is detected in another target cell, by means of a receptor protein, which recognizes and responds specifically to its ligand
We distinguish between Endocrine, paracrine and autocrine signaling. The latter often occurs in a population of homogenous cells.
Each cell responds to a limited set of signals, and in a specific way
Signaling Molecule
The signal molecule is often secreted from the signaling cell to the extracellular space
In some cases the signaling molecule is bound to the cell surface of the signaling cell. Sometimes, a signal in both cells will be initiated by such an event.
Receptors
Cell surface receptors detect hydrophilic ligands that do not enter the cell
Alternatively, a small hydrophobic ligand (. steroids) may cross the membrane, and bind to an intracellular receptor
Cells may also be linked through a gap junction, sharing small intracellular signaling molecules
GAP JUNCTIONS
Cell Surface Receptors
Ion channel linked: Binding of ligand causes channel to open or close
G-protein linked: Binding of ligand activates a G-protein which will activate a separate enzyme or ion channel
Enzyme linked receptor: Binding of ligand activates an enzyme domain on the