Topic 3: Signal transductions Flashcards
What does differential regulation (regulated by multiple molecules) allow a cell to do?
it allows for cell specific responses to extra cellular signals (depends on what AC iosforms are present)
there is cross talk with other signalling pathways
what effctors can cAMP mediate
Cyclic nucleiotde gated channels
cyclic nucelotide regulated GEFs
cAMP-dependent protein kinase A - PKA
What do protein kinases do?
Phasperalte proteins that have a specific consensus recognition sequence.
How many cAMP binding sites are on the PKA holoenzyme
4 on the regulatory subunit dimer.
how many isofroms are there of the regulatory subunit of PKA holoenzyme
4
R1a, R1B and R2a and R2B
how many catylic PKA isoforms are there?
3
Ca CB CY
are the regulatory subunits for PKA homo or hetromultimers?
both
what is the mechism of action for activation of PKA?
PKA exists in an inactive holoenzyme
4 cAMP binds to the regulatory dimer, reguatory and catalytic subunits dissociate
catalytic subunit is now active
what is an AKAP? what class of PKA enzymes are they associated with?
A-kinase anchoring protein - binds PKA II to cellular targets
What are the two main classes of PKA
PKA I
PKA II
What is an EPAC?
Exchange protein directly activated by cAMP
Functions as a GEF for the Ras like gtpases Rap1 and Rap2
What is a phosphodiesterase?
Proteins that hydrolyse cyclic nucleotides.
three main types
cGMP and cAMP selective
cAMP preference
cGMP preference
How do we achieve cAMP microdomains
AKAPs - bind to R subunits of PKA can have subcellular localisation
Caveolae - (little caves in membranes) activities regulated by signalling proteins present or by calveolin.
Localisation of Phosphodiesterises - limits sphere of influence of cAMP.
isoforms if AC and PDE each differentially regulated by proteins found in that particular sub compartment.
what is a particulate guanylyl cyclase?
A enzyme homodimeric that produces cGMP , is membrane bound and is activated by ligands
what are cytosolic GC
a GC that is activtated by NO and CO as it cointians a heme group
how long does NO last in the body
seconds, made as an when needed. also readly diffuses into surrounding cells
how is NO synthesises
By NOS which is controlled by Ca2+
What can cGMP effect
PKG, modulation of phosphodiesterase activity and cyclic nucleotide gated channels.
What class of molecules do phospholipases act on?
they act on gycerophospholipids
what does phospholipase produce from PIP2
DAG and IP3
how many isoforms of PLC is there? why is this important
13, it allows for a large number of persise control
what molecules can IP3 stimulate
inositol phopatases multiple kinases transcription and RNA processing
what molecules can DAG stimulate
enzyumes and structural proteins with C1 domin eg PKC
phosphatidic acid.
what do phosphatidylinositol 3- kinases phosphorylate?
the 3 prime position of the innosital ring in phosphatidylinositol
what activates PI3Ks?
cell surface receptors particularly those with intrinsic tyrosine kinase activity eg RTK
what is PI3Ks preferred substrate invivo ?
PtdIns(4,5)P2 (PIP2)
what is the mechism of activation of Class 1a PI3Ks check
has alot of SH2 domoins so activated RTK will allivated inhibiation by regutory subunit (P85) and bring catalytic subunit close to PIP2 to make PIP3
What does PIP3 act on
Acts as a anchor for various signalling proteins with PH (pleckstrin-homology) that accumulate at sites of PI3K activation by binding to PIP3 such as
Rho GTPases
PLCy
PKB
how is PIP3 signalling terminated?
SHIP - removes binding site for PH domain but generates PtdIns(3,4)P2 which can bind to PKB (PKB binds PtdIns(3,4)P2 and PtdIns(3,4,5)P2 with the same affinity) .
PTEN removes both PtdIns(3,4,5)P2 and PtdIns(3,4)P2 and so inhibits PKB
