Intracellular signalling Flashcards
What are the key points of steroid signalling?
The signalling molecules are small and hydrophobic so can pass through the plasma membrane, they then bind to receptors in the cytosol forming an activated complex. The complex then moves into the nucleus and binds to the regulatory region of DNA activating transcription.
What are the key points of peptide signalling?
The signalling molecules are large and hydrophilic so cannot pass through the plasma membrane. They bind to receptors on the plasma membrane and activate intracellular pathways.
What are 5 points in the intracellular pathway activated by peptide signalling molecules?
- Relay and transduce the signal
- Amplify the signal (one signalling molecule can activate lots of pathways)
- Distribute the signal to different cells
- integrate the signal to target
- regulate
What are the types of signalling?
Intracellular - Steroid hormones and thyroid hormones
Extracellular - Ion channel linked receptors, G-protein coupled receptors (GPCR), enzyme-linked receptors.
What is the purpose of ion-channel linked receptors?
They regulate the exchange of ions that will generally cause an action potential in excitable cells. They are normally closed, when the signalling molecule binds it will open the channel and allow the exchange of ions.
What is the process of G-protein coupled receptors?
Signalling molecule binds to a receptor on the plasma membrane, this causes a conformational change and allows the G protein to bind (bound to GDP), the GDP will be released and replaced with GTP, the G-protein is now active. This causes a conformational change and allows an enzyme to bind this will start the intracellular signalling pathway.
What are the consequences of GPRC activation?
- Activation of membrane bound enzymes in the plasma membrane. e.g. Adenylyl cyclase will convert AMP-cAMP leading to changes in gene transcription.
- Activation of other proteins that can cause changes in intracellular Ca2+ which activates pKA - activate other proteins
- Regulation of ion channels - signalling pathways are integrated with and regulated by other pathways.
What is an example of a rapid response and the process?
Adrenaline - it has a direct effect on enzyme activity.
Adrenaline binds to a receptor on the plasma membrane and activates a G-protein this activates adenylyl cyclase which will convert AMP-cAMP (second messenger), cAMP will activate pKA this will activate more proteins in a protein cascade and will end up causing glycogen breakdown.
What is an example of a slower response and the process?
The production of hormones - it effects gene transcription. TF activated by pKA and then binds to DNA at promoter region and will either activate of inhibit transcription.
How to enzyme-linked receptors work?
The receptor is directly linked to the enzyme it will activate. They are very important in developmental regulation. It mediates a growth factor response and often causes permanent changes.
How to proteins act as switches?
GTPases - a specific GTPase is RAS
When “off” the RAS is complexed with GDP. When switched “on” the protein will release GDP and bind GTP.
