Abstract
We have compared the potencies of structurally distinct channel blockers at recombinant NR1/NR2A, NR1/NR2B, NR1/NR2C and NR1/NR2D receptors. The IC50 values varied with stereochemistry and subunit composition, suggesting that it may be possible to design subunit-selective channel blockers. For dizocilpine (MK-801), the differential potency of MK-801 stereoisomers determined at recombinant NMDA receptors was confirmed at native receptors in vitro and in vivo. Since the proton sensor is tightly linked both structurally and functionally to channel gating, we examined whether blocking molecules that interact in the channel pore with the gating machinery can differentially sense protonation of the receptor. Blockers capable of remaining trapped in the pore during agonist unbinding showed the strongest dependence on extracellular pH, appearing more potent at acidic pH values that promote channel closure. Determination of pKa values for channel blockers suggests that the ionization of ketamine but not of other blockers can influence its pH-dependent potency. Kinetic modelling and single channel studies suggest that the pH-dependent block of NR1/NR2A by (-)MK-801 but not (+)MK-801 reflects an increase in the MK-801 association rate even though protons reduce channel open probability and thus MK-801 access to its binding site. Allosteric modulators that alter pH sensitivity alter the potency of MK-801, supporting the interpretation that the pH sensitivity of MK-801 binding reflects the changes at the proton sensor rather than a secondary effect of pH. These data suggest a tight coupling between the proton sensor and the ion channel gate as well as unique subunit-specific mechanisms of channel block.
| Original language | English |
|---|---|
| Pages (from-to) | 107-128 |
| Number of pages | 22 |
| Journal | Journal of Physiology |
| Volume | 581 |
| Issue number | 1 |
| DOIs | |
| State | Published - May 15 2007 |
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All Science Journal Classification (ASJC) codes
- Physiology
Cite this
Subunit-specific mechanisms and proton sensitivity of NMDA receptor channel block. / Dravid, Shashank M.; Erreger, Kevin; Yuan, Hongjie; Nicholson, Katherine; Le, Phuong; Lyuboslavsky, Polina; Almonte, Antoine; Murray, Ernest; Mosely, Cara; Barber, Jeremy; French, Adam; Balster, Robert; Murray, Thomas F.; Traynelis, Stephen F.
In: Journal of Physiology, Vol. 581, No. 1, 15.05.2007, p. 107-128.Research output: Contribution to journal › Article
}
TY - JOUR
T1 - Subunit-specific mechanisms and proton sensitivity of NMDA receptor channel block
AU - Dravid, Shashank M.
AU - Erreger, Kevin
AU - Yuan, Hongjie
AU - Nicholson, Katherine
AU - Le, Phuong
AU - Lyuboslavsky, Polina
AU - Almonte, Antoine
AU - Murray, Ernest
AU - Mosely, Cara
AU - Barber, Jeremy
AU - French, Adam
AU - Balster, Robert
AU - Murray, Thomas F.
AU - Traynelis, Stephen F.
PY - 2007/5/15
Y1 - 2007/5/15
N2 - We have compared the potencies of structurally distinct channel blockers at recombinant NR1/NR2A, NR1/NR2B, NR1/NR2C and NR1/NR2D receptors. The IC50 values varied with stereochemistry and subunit composition, suggesting that it may be possible to design subunit-selective channel blockers. For dizocilpine (MK-801), the differential potency of MK-801 stereoisomers determined at recombinant NMDA receptors was confirmed at native receptors in vitro and in vivo. Since the proton sensor is tightly linked both structurally and functionally to channel gating, we examined whether blocking molecules that interact in the channel pore with the gating machinery can differentially sense protonation of the receptor. Blockers capable of remaining trapped in the pore during agonist unbinding showed the strongest dependence on extracellular pH, appearing more potent at acidic pH values that promote channel closure. Determination of pKa values for channel blockers suggests that the ionization of ketamine but not of other blockers can influence its pH-dependent potency. Kinetic modelling and single channel studies suggest that the pH-dependent block of NR1/NR2A by (-)MK-801 but not (+)MK-801 reflects an increase in the MK-801 association rate even though protons reduce channel open probability and thus MK-801 access to its binding site. Allosteric modulators that alter pH sensitivity alter the potency of MK-801, supporting the interpretation that the pH sensitivity of MK-801 binding reflects the changes at the proton sensor rather than a secondary effect of pH. These data suggest a tight coupling between the proton sensor and the ion channel gate as well as unique subunit-specific mechanisms of channel block.
AB - We have compared the potencies of structurally distinct channel blockers at recombinant NR1/NR2A, NR1/NR2B, NR1/NR2C and NR1/NR2D receptors. The IC50 values varied with stereochemistry and subunit composition, suggesting that it may be possible to design subunit-selective channel blockers. For dizocilpine (MK-801), the differential potency of MK-801 stereoisomers determined at recombinant NMDA receptors was confirmed at native receptors in vitro and in vivo. Since the proton sensor is tightly linked both structurally and functionally to channel gating, we examined whether blocking molecules that interact in the channel pore with the gating machinery can differentially sense protonation of the receptor. Blockers capable of remaining trapped in the pore during agonist unbinding showed the strongest dependence on extracellular pH, appearing more potent at acidic pH values that promote channel closure. Determination of pKa values for channel blockers suggests that the ionization of ketamine but not of other blockers can influence its pH-dependent potency. Kinetic modelling and single channel studies suggest that the pH-dependent block of NR1/NR2A by (-)MK-801 but not (+)MK-801 reflects an increase in the MK-801 association rate even though protons reduce channel open probability and thus MK-801 access to its binding site. Allosteric modulators that alter pH sensitivity alter the potency of MK-801, supporting the interpretation that the pH sensitivity of MK-801 binding reflects the changes at the proton sensor rather than a secondary effect of pH. These data suggest a tight coupling between the proton sensor and the ion channel gate as well as unique subunit-specific mechanisms of channel block.
UR - http://www.scopus.com/inward/record.url?scp=34248228746&partnerID=8YFLogxK
UR - http://www.scopus.com/inward/citedby.url?scp=34248228746&partnerID=8YFLogxK
U2 - 10.1113/jphysiol.2006.124958
DO - 10.1113/jphysiol.2006.124958
M3 - Article
C2 - 17303642
AN - SCOPUS:34248228746
VL - 581
SP - 107
EP - 128
JO - Journal of Physiology
JF - Journal of Physiology
SN - 0022-3751
IS - 1
ER -