The Synapse 2 Flashcards
What does the guanylate like kinase domain of PSD-95 interact with in the PSD?
Guanylate kinase associated protein (GKAP)
What type of experiment discovered that GUK interacts with GKAP?
Yeast two hybrid
immunohistochemistry shows colocalisation
What does GKAP bind to in the PSD?
Shank
What proteins does shank bind to?
GKAP
Homer
What domains does Shank have?
Ankarin repeats SH3 PDZ Proline rich sequences SAM
What does the ankarin repeats in shank allow for?
Association with cytoskeletal proteins
SH3 domains interact with….?
Proline rich sequences
What domain on SHANK does GKAP bind to?
The PDZ domain
Which does the proline rich region on shank allow for?
Interaction with homer and therefore indirectly to mGluRs
Interaction with cortactin which links to cytoskeleton
The SAM domain of shank is important for….?
Shank mulitmerisation
Give the three examples of the important evidence of scaffolding proteins
Couple of NMDARs to nNOS(alpha)
Homer permits coupling of mGluR to the IP3 receptor complex
AMPARs and stargazin and role in LTP
Why is nNOS located in the PSD?
It can bind to psd-95
Localisation of nNOS to NMDAR’s permits signalling that is?
Specific
Rapid
Efficient
Briefly explain the significance of NMDAR localisation to nNOS
nNOS requires the calcium calmodulin complex to make NO
NMDARs are permeable to Calcium
Much NO can be produced
Why is NO incredibly hard to measure?
What can we measure instead to study NO signalling?
NO has an incredibly short life span
Measure cGMP which is a molecule made down stream to NO signalling
Who did the experiment which shows nNOS interacts with psd-95?
Brenmann et al 1996
What does impairment of psd-95 and nNOS coupling do to levels of cGMP?
Decreases levels of cGMP
Since NO is neurotoxicity these neurons also survive longer with increasing concs of NMDA given to cell
What happens to the NMDAR current with mutant psd-95 which cannot function?
NMDAR current is uneffected as psd-95 is not needed for postsynaptic localisation
What are the different types of homer subunits?
Homer 1(a,b,c) Homer 2(a,b,c)
What makes homer 1a unique
Only contains the EVH1 domain
All other isoforms contain EVH1 and the leucine zipper + coiled coil domain
What sequence of amino acids does EVH1 bind to?
PPXXFR
The c terminus if mGluRs have a proline rich motif
IP3 receptor also has a conserved protein rich motif
What does homer allows mGluR(1-5) to couple to?
The IP3 R on the SER
Allow release of calcium
mGluR 1-5 are coupled to which G protein?
Gq
When talking about homer who will we reference?
Tu et al 1998
What happens to homer 1a expression on increasing synaptic activity?
It increases
What does increasing homer 1a expression mean?
Reduced mGluR to IP3r coupling as homer1a cannot multimerise
This will decrease calcium mobilisation on subsequent synaptic stimulation
In what cells is this change in homer expression important?
Purkinje cells in the cerebellum
Important for LTD
What did Chen et al discover?
Stargazin immunoprecipitates with psd95
Did this in 2000
Prior to a high frequency stimulus, what is the difference between the EPSP between mutant psd-95 mice and WT?
Mutant mice show slightly diminished EPSPs
What construct of mutant psd-95 were used by migaud et al in there experiment?
Psd-95 with only pdz 1 and 2
Since stargazin binds to pdz 3 they do not couple together?
What was the purpose of the experiment by migaud et al 1998?
To observe is mutant psd-95 effects synaptic plasticity in a murine model?
What did migaud et al 1998 discover after HFS for mutant and WT mice?
Mutant psd-95 show greater potentiation (increased sensitivity to a potentiation stimulus)
What does an increased sensitivity for potentiation in the psd-95 mutants mean?
That there were a low number of AMPARs at the post synaptic membrane prior to the HFS.
I.E. There is greater potential for LTP in psd mutants
Stargazins interaction with psd-95 is essential for AMPAR localisation it membrane
On an stimulus (1Hz) designed to cause LTD what happened to the EPSPs of the mutant mice?
They showed LTP
In the Morris water maze what did mutant mice show? What does this mean?
They showed impaired spatial memory
Therefore, LTD is important for memory too and it is likely memory depends on bidirectional plasticity of neurons
Why is psd-95 sufficient by not necessary for AMPAR localisation to synapse?
- Even though psd-95 was non functional, mutants were still able to potentate the synapse (meaning they must have got to the post synaptic membrane in a psd-95 independent way)
- Overexpression of psd-95 increases the amount of AMPARs made from GluR1 at the synapses. This means that there is less potential for LTP as it is saturable. Seen experiemtnally
(FURTHER READING)
Name another protein which interacts with pSd-95 and state it’s importance
SynGAP which is activated by CaMKII
activates intrinsic GTPases of ras proteins making them inactive
Localisation to NMDARs important for efficient synGAP function (mediating LTP)
