Lecture 8: Armstrong et al. Flashcards
How many subunits make up a glutamate receptor?
4
What are channelopathies involving GluRs?
fragile X, schizophrenia, autism, neurodegeneration in ALS, parkinson’s, neurodegeneration in stroke
What are some glutamate receptor agonists?
kainate, glutamate, glycine, AMPA, NMDA, domoate, quisqualate. All have overall negative charge.
Where is the ligand binding domain of GluRs?
S1 and S2
Where is the Q/R editing site?
In the M2 re-entrant pore loop
What is the Q/R editing site?
Site within M2 where post-transcriptional modification changes a Q (GAG) –> R (GIG). This occurs in AMPA (GluA2) and kainate (GluK1 and GluK2) receptors. It makes the channel impermeable to calcium, low conductance, and the IV relationship will be approximately linear
What is the alternative splicing site?
Right after S2 domain. All APMA, kainate, and NMDA receptors are alternatively spliced at the C-terminus. Flip: desensitizes more slowly, flop: desensitizes rapidly and more profoundly.
What are the subunits that form and NMDA receptor?
2 GluN1 and 2GluN2 subunits
Why are NMDA receptors called “coincidence detectors”?
They need both depolarization and the presence of glutamate and D-serine (or glycine) to open. They have an Mg block, so depolarization pushes out the Mg block.
What does GluN1 bind to?
D-serine or glycine
What does GluN2 bind to?
glutamate
What are NMDA receptors permeable to?
Highly permeable to calcium
What is the GluR2 ‘flop’ receptor construct?
It is an engineered construct containing only the S1 S2 domain and a flop alternatively spliced site
What is the shape of the GluR2 S1S2 bound to kainate?
Has a clam shell shape with kainate bound at the crevice between each shell. The alpha helices are pointing towards the interdomain crevice, the N-terminus (slightly positive) points towards the kainate, which is negative, stabilizing and attracting the kainate towards the crevice
What are some interactions that stabilize tertiary structure?
charge-charge (electrostatic) interactions, hydrogen bonding, alpha helix-dipole interactions, cation-pi interactions (Y, W, F),
Which amino acids stabilize the carboxy groups of kainate?
S654 (H-bonding), T655 (H-bonding), R485 (electrostatic), T480 (H-bonds), F helix
Which amino acids stabilize the amine of kainate?
Tyr450 lid (cation-pi), E705 (electrostatic), P478 (H-bonds), T480
Why is the binding pocket slightly negative, even though kainate is negatively charged?
You want to make sure there is not irreversible binding, need some instability in the binding pocket
