Principles of Cellular Communication & Signal Transduction Flashcards
What are receptors?
Proteins which are specifically evolved to receive signals carried by molecules
How do cell-surface receptors work?
Receptors are present on the plasma membrane of the cell, extra cellular signals do not penetrate plasma membrane
How do intracellular receptors work?
Signalling molecules are freely diffusible through the plasma membrane, the receptors for these are located inside the cell
What molecules use intracellular receptors?
Small hydrophobic signal molecules and steroid hormones
What is juxtacrine signalling?
- short range signalling
- ligand is a molecule expressed by one cell surface, and the receptor is expressed by neighbouring cell
What is paracrine signalling?
- middle range signalling used by growth factors
- signal is produced by one cell which diffuses through organ/tissue
- signal is received by receptor on other cell
- cells can use autocrine signalling to signal to themselves
What is endocrine signalling?
- long range signalling used by hormones
- gland secretes soluble hormone which goes into bloodstream and spreads across the body
What is synaptic signalling?
- synaptic signalling type
- is juxtacrine so need cells to directly interact
- cells are neurons and grow long, so is long range like endocrine signalling
- relies on diffusible signal just like paracrine signalling
What happens during slow cellular responses?
Extracellular signal interacts with receptor, signal is taken to the nucleus where gene expression is altered to produce specific RNA, which alters protein synthesis, which alters cytoplasmic machinery, which leads to altered cell behaviour
What happens during fast cellular responses?
Extracellular signal interacts with receptor, which uses intracellular signalling pathway to directly alter protein function, which alters cytoplasmic machinery, leading to altered cell behaviour
What is signal transduction?
Reversible signal dependent modulation of protein-protein interaction networks in cells
What is allosteric regulation?
Protein activity can be changed via signal-dependent modification of the regulatory domain that is distinct from the functional domain
How does allosteric regulation work?
- most signalling proteins are found in the auto-inhibited conformation, where the functional domain is blocked so cannot carry out function
- input signal interacts with regulatory domain, changing the conformation and allowing function to act
How does cAMP act as an allosteric regulator
It binds to the regulatory domain, which hinges to expose and activate Epac
Why proteins carry out and undo phosphorylation?
Kinases phosphorylate, phosphatases dephosphorylate
