Flashcards in Receptor Tyrosine Kinases Deck (14)
What are the similarities and differences in RTKs?
The EC domains vary, IC domains give kinase activity
Describe how RTKs are activated
When the signal molecule (ligand) binds to the receptor it causes the two tyrosine domains to phosphorylate each other and actives the RTK
What is the outcome of the activation of the RTK?
The activity of the kinase is increased, the receptor is stabilised in the active site and it causes the kinase to phosphorylate other tyrosines in the receptor to create docking sites
How can RTK signalling be analysed?
Genetically engineer DNA that encodes for a normal receptor that is mutated in the kinase domain. The DNA is expressed at high levels and poisons the endogenous receptor
Generate DNA that encodes for receptor that lacks a ligand binding domain. It is expressed at normal levels and is ligand independent - receptor is constitutively active
How do proteins recognise the docking sites on phosphorylated tyrosine kinases?
There are pockets that recognise the surrounding amino acids, SH2 domain in Src recognises phosphotyrosine
What are the three forms of HSPGs that act as low affinity receptors?
Inserted into the membrane
Slightly tethered to the ECM
What is the heparan component of the HSPGs made up of?
A long chain of sugars
How can each sugar of the heparan component of HSPGs be modified?
What can modification of HSPGs lead to?
A code that creates binding sites for specfic proteins (e.g. FGF2). FGF and its receptor can form a complex with heparan sulphate proteoglycans where heperans act as a co-receptor to allow activation
What are the RAS protein subfamily?
A large group of GTPases
What are the only proteins of the RAS protein subfamily that are involved in signalling?
Ras and Rho
Discuss the mechanisms of the RAS signalling cascade
The SH2 component of the Grb2 adaptor protein binds to a phosphate of the activated RTK
The SH3 components bind to Sos, activating it and promoting dissociation of GDP from Ras
GTP binds and Sos dissociates from active Ras
GTP to GDP acts as a molecular switch to activate downstream signals
Discuss the MAP kinase signalling pathway
The active Ras protein activates Raf
Raf phosphorylates and activates Mek after receiving an activating signal from Ras
Mek phosphorylates and therefore activates Erk
Erk enters the nucleus and phosphorylates one or more components of the transcription regulatory complex
This activates transcription factors of a set of immediate early genes