iGluR 1 Flashcards
(25 cards)
What is the structure of iGluRs?
ATD (No effect if deleted)
LBD
TMD
CTD
What iGluRs is glutamate an agonist for?
AMPAR
KAR
GluN1
What iGluRs is glycine/D-serine an agonist for?
GluN1
GluN3
How can we determine the structure of iGluRs using X-ray crystallography?
- Sample crystalized
- Make an electron density map
- Make an atomic crystal structure model
What are the pros and cons of X-ray crystallography?
:) High resolution
:( Uses crystals
How can we determine the structure of iGluRs using cryo-electron microscopy?
- Sample is frozen in an electron microscope
2. Make 2D pics > 3D map > 3D model
What are the pros and cons of cryo-electron microscopy?
:) Can use single particles
:( Difficult to get high resolution
How did we work out that iGluRs are tetramers?
- Electrophoresis and sedimentation used to separate proteins from neurons
- Western blot analysis used to show AMPAR formed tetramers
What are the subunits in AMPAR, KAR and NMDAR tetramers?
AMPAR: GluA2 assembles with 1, 3 and 4
KAR: GluK 4 and 5 assembles with 1, 2 and 3
NAMDAR: 2 GluN1 with 2 GluN2 or with GluN2,3
What did they discover in 1950 and 1970 with regards to glutamate?
1950: injected into brain = convulsion
1970: injected into brain = depolarisations (thought they were ion channel)
What did they discover in 1970 and 1980 with regards to glycine?
1970: NMDAR + conditioned medium = depolarisation
1980: realised it was glycine
How did they discover that NMDA and glycine are co-agonists and when?
1988:
1. Extracted RNA from rat brains
2. Injected into frog oocytes
3. express for few days
4. measure electrophysiology of cells with NMDA and Gycine = large depol
What did they find in 1979 and how?
- Rat brain slices isolated and synaptic membranes washed
- Add kainate and glutamate serum = little radioactivity because they compete for same site
- Add kainate alone = lots of activity
- Add kainate and NMDA = lots of activity because they have different sites
What blocks NMDAR and when did they find this?
- Magnesium
- 1980
Describe ion permeability in iGluRs
- AMPAR: Na, K, Ca (least)
- KAR: Na, K, Ca
- NMDAR: Na, K, Ca (most)
Describe an experiment to test antagonists of non-NMDAR
- Stimulate synapses = depolarisation
- CNQX + YDDG antagonists given = no depolarisation.
- AP5 = depolarisation
Conclusions: CNQX and YDDG are non-NMDAR antagonists whilst AP5 isn’t
Describe an experiment to test antagonists of NMDAR
- NMDAR given tetanus = high depol (LTP)
BUT - When AP5 is given followed by tetanus = normal levels of depolarisation
Therefore, AP5 must be a selective inhibitor of NMDAR not non NMDARs.
How can we stop seizures (give an example)?
- Block glutamate receptors
e. g. block AMPAR with CNQX
Where are different AMARs found in the brain?
GluA1 = not in entorhinal cortex GluA3 = in hypothalamus and amygdala GluA4 = olfactory bulb/cerebellum/auditory pathway
What type of neurons are permeable/impermeable to Ca?
Interneurons - permeable
Principle neurons - impermeable
Where in the brain are different NMDARs found?
- GluNB (embryonic) and GluN2A (adulthood) in the hippocampus
- GluN2C (adult) and GluN2B (embryonic) in cerebellum
What is the iGluR channel conductance equation?
G = i/V
G = conductance (ability of channel to pass current) I = current V = voltage
NMDAR has higher conductance current vs AMPAR
Describe microscopic currents
- Caused by rapid transitioning of opening/closing channels
- Detected using patch clamp technque
- Difficult to record tho cos its so small
Describe macroscopic currents
- Caused by activation/deaction (when agonist binds/comes off = conform change)
- Desensitisation = when agonist binds to closed channel but it is still stable
- Resensitisation = channel stays shut but becomes unstable so agonist comes off
