L17 Regulation of Cell Signalling Flashcards
Different cells respond differently to…
The same signals
Different responses to the same signal may result from (2):
- Presence of a different receptor
* Activation of different intercellular machinery
An example of the same signal and different results due to different receptor
Acetylcholine (Ach) causes skeletal muscle contraction via nicotinic ion-channel linked receptors, but reduces contraction rate in heart muscles via G-Protein linked receptors which induce hyperpolarisation
Signalling pathways can…
Interact
A lack of signals often results in…
Cell death
Signalling pathways often overlap with one another. This is known as…
Crosstalk
Crosstalk allows…
Fine tuning of response
The cost of pathway crosstalk is the…
Possible generation of wrong signals
Signals may combine to alter the levels…
Of a signalling protein
Signalling complexes may be either (2)…
1) Stable type (components linked by scaffold protein)
2) Transient type (assembly occurs only after receptor activation, may be trans membrane or on inside)
Scaffold proteins link the…
Components of stable signalling complexes
Activated proteins may be inactivated by…
1) Phosphorylation
2) Hydrolysis of GTP to GDP
3) Allosteric inactivation (conformational change is reversed)
4) Removal of secondary messengers (i.e. cAMP or cGMP hydrolysis, catalysed by phosphodiesterase)
Sildenafil (Viagra) inhibits…
cGMP phosphodiesterase via competitive inhibition
