L9 Flashcards
what type of molecules are PDGF-beta and Insulin receptor
RTK
2 different way that PI3K can bind an RTK
binding to PDGF-beta, PI3K binds directly to receptor
with insulin, PI3K needs adapter protein
what is the adaptor protein for PI3K binding to insulin receptor
IRS1
3 key domains of IRS-1 protein
N terminal has PH domain which binds to PIP2
N terminal also has SH2 domain
both of these domains anchor IRS-1 to Insulin receptor
also YXXM sequence
PIP2 and PIP3 bind what type of domains
PH domain
what does PH domain stand for
plekstrin homology domain
3 components of pip2
lipid, phosphate, inositol
SH2 stands for
Src homology domain 2
what happens at YXXM sequence
tyrosine is phosphorylated - this is substrate for the tyrosine kinase domain of the insulin receptor
what happens to IRS when tyrosine is phosphorylated to phosphotyrosine
IRS serves as adaptor protein, linking insulin receptor to downstream signalling events
difference between pip2 and pip3
PIP3 has one extra phosphate group at carbon 1 - phosphate instead of hydroxyl
what molecule is responsible for the pip2 to pip3 transition
pi3k
what kind of family is PI3K in
lipid kinases
structure of PI3k molecule
heterodimer of 2 subunits of 110 kDa and 85kD
what are the 2 monomers in PI3K
catalytic monomer called p110, and regulatory monomer called P85
what 2 things mediate the activation of PI3K
SH2 domain of P85 interacting with phosphorylated RTK
P110 subunit associating with Ras-GTP
2 other key domains of PI3K
ABD, RBD, Kinase
ABD domain of PI3K
adapter protein binding domain - this is responsible for binding the regulatory domain (p85)
RBD domain of PI3K
receptor binding domain of PI3K - binds to Ras
3 domains of p85 (PI3K)
cSH2 domain, I, and N
I means inter-SH2
state of p110 and p85 when inactive
bound together
carboxyl side of sh2 domain blocks kinase domain - making it inactive
how is PI3K activated
when RTK is activated and tyrosine is phosphorylated, the N-sh2 and C-sh2 bind to the phosphorylated tyrosine
means cSH2 is no longer blocking the active site, and active site is available
what does active PI3K target
PIP2 (inositol)
what is PTEN
PTEN catalyses reverse reaction of PIP3-> PIP2
what kind of molecule is PTEN
phosphatase
what does pip3 actiate
PDK1
what special domain does PDK1 have
pleckstrin homology domain which is specific for pip3
what happens once you have a lot of PIP3
you’ll draw other proteins that bind PIP3
what are PIP3 binding proteins
Akt/PKB, also PDK1,
where do PDK1 and AKT bind to PIP3
on membrane
what happens once PDK1 and AKT bind PIP3
Activated PDK phosphorylates AKT at Thr308
what 2 residues on AKT need to be phosphorylated to be active
thr308 and serine 473
what molecule phosphorylates AKT at Sea 473
other proteins like MTORC2
what happens once AKT is phosphorylated on both residues
it leaves the membrane -> goes to activate other substrates
