NMDAR revision 2

Question 1

What is the EC50 of glutamate binding to GluN2?

Answer 1

2uM

Question 2

What does the addition of exon5 do to GluN2B containing receptors (and who showed this?

Answer 2

Increase deactivation rate by 3-4 fold

Rumbaugh, 2000

Question 3

How do heterotrimeric GluN1/2A/2B receptors differ in response to ifenprodil and who showed this?

Answer 3

Reduced maximal effect as evidenced by slower onset of drug action and faster offset

Tovar and Westenbroek 1999

Question 4

What does the CTD consist of?

Answer 4

Tyrosine kinase phosphorylation and binding sites

Question 5

What does the M2 form?

Answer 5

A re-entrant loop from the inside which lines the major part of the channel pore and regulates Ca2+ and Mg2+ with crucial arginine residues (Wollmouth, 1998)

Question 6

Where is the proton sensitivity site?

Answer 6

In the NTD

Question 7

What is the importance of proton sensitivity?

Answer 7

Under physiological conditions, blocks 50% NMDAR’s - Traynelis and Cull-Candy, 1990

Question 8

What is the most obvious different in transmembrane topology between subtypes?

Answer 8

Length of CTD

GluN2A/B = longest

GluN1/3B = shortest

Question 9

What position was the S residue changed to L to show subtype specific Mg2+ block in GluN2A?

Answer 9

S632 in M3

Question 10

Why might GluN3 be insensitive to Mg2+?

Answer 10

No Arginine in M2

Question 11

What is a way of measuring Ca2+ permeability?

Answer 11

Single channel conductance

Question 12

What does Mg2+ block do to the synaptic current?

Answer 12

selective block at negative potentials

As the membrane becomes depolarised, the Mg2+ is expelled from the pore allowing charge to flow into the cell, meaning that synaptic currents are prolonged when the membrane is depolarised.

Question 13

NMDAR decays with a double-exponential decay - what is the time course of the first decay and who found this?

Answer 13

200 ms , Spruston 1995

Question 14

Why might unbinding of agnonist and desensitization affect the decay time course of EPSC?

Answer 14

• prolonged activation after short period of agonist application - Lester 1990
• Desensitization in continued presence of agonsit

Question 15

What type of study was used to show that GluN2 containing subunits have different decay time course?

Answer 15

In an outside-out patch, in the presence of a brief pulse of agonist, the NMDAR-mediated current displays a characteristic decay time course that depends on the identity of the GluN2 subunit

Question 16

What is the time course decay ratio between GluN1-1b and GluN1-1a receptors?

Answer 16

tW = 1:4

Question 17

What is a use-dependent GluNC/D blocker?

Answer 17

QNZ46

a non-competitive antagonist that has a 50-fold greater selectivity for GluN2C/GluN2D than for other GluN2 subunits
but glutamate binding - use dependent

Hansen & Traynelis, 2011

Question 18

What is a non-competitive GluN2C/2D antagonist?

Answer 18

DQP-1105 inhibited GluN2C- and GluN2D-containing receptors with IC50 values that were at least 50-fold lower than those for other GluN2 recombinant receptors. Inhibition was voltage-independent and could not be surmounted by increasing concentrations of either coagonist, glutamate or glycine, consistent with a noncompetitive mechanism of action (Acker et al.,2011)

Question 19

Is ketamine subunit selective? under what conditions?

Answer 19

when acting on receptors expressing GluN1/GluN2C subunits, has a three to four times greater potency than when acting on NMDARs containing other GluN2 subunits, but only in the presence of extracellular Mg2+ (Khlestova et al., 2016)

Question 20

How do we know that GluN2B mediates the anti-depressant effect of ketamine>

Answer 20

deletion of GluN2B in vivo from principal cortical neurons imitating the anti-depressant action of Ketamine (Miller et al., 2014)

Question 21

What does ketamine and memantine block depend on?

Answer 21

Both open channel block by Ketamine and Memantine depends on the asparagine residue in M2 in GluN1/GluN2 subunits. Thus, NMDAR’s containing GluN3 subunits are less effectively blocked

Question 22

What is a GluN2A specific antagonist and how does it work?

Answer 22

TCN201 and TCN213 which produce a non-competitive block dependent on glycine concentration by increasing the rate of glycine dissociation from the GluN1 agonist-binding domain in GluN2A containing NMDAR’s (Bettini et al., 2010)