Lecture 18: RTKs Flashcards
How many families of RTKs are there?
16
What are the functions of EGF?
promote:
- cell growth
- cell survival
- proliferation
What is the structure of RTKs?
- extracellular domain varies depending on the receptor e.g. cysteine rich domains, Ig-like domains, repeat sequences = ligand binding sites
- intracellular domain has kinase activity
- single transmembrane domain
What is the purpose of ligand dimerisation during canonical RTK activation?
- facilitates receptor dimerisation/oligomerisation - receptors in close proximity so the receptors can interact with each other
- reorientates receptor oligomers so their active domains are face to face
- increased kinase activity
- autophosphorylation of tyrosines creating docking sites
- kinase domains phosphorylate each other. stabilises receptor in active state.
Creating dominant negative RTK
- normal receptor with mutated tyrosine kinase domain overexpressed
- blocks activity of functional RTK during dimerisation - won’t phosphorylate to activate it
Creating constitutively active RTK
- receptor with homodimerisation domain instead of ligand binding domain expressed at normal levels
- ligand independent
- cells rapidly divide
HSPG with transmembrane protein core
Syndecan
HSPG with tethered protein core
Glypican
Secreted HSPG
Perlecan
Structure of HSPGs
long chain of sugars on a protein core. the sugars are modified by sulphation, resulting in specific binding sites for specific proteins (confers specificity)
Function of HSPGs
co-receptor facilitating e.g. FGF ligand dimerisation
What phosphopeptide does the Src SH2 domain recognise?
phosphotyrosine- glutamic acid - glutamic acid - isoleucine
Which intracellular signalling protein in the RTK pathway activates RAS/MAP kinase pathway?
GAPs e.g. GRB2
Which intracellular signalling protein in the RTK pathway activates inositol lipid pathway?
PI3K and PLC-gamma
How does the Ras signalling cascade become activated?
- inactive Ras is tethered to the membrane
- GRB2 binds to docking sites on receptor
- Sos binds to GRB2, coupling inactive Ras to the receptor
- Sos promotes dissociation of GDP from Ras
- GTP binds to Ras - Ras activated
- Sos dissociates from inactive Ras
- Ras initiates signalling cascade