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Atomic basis for therapeutic activation of neuronal potassium channels.

Kim RY, Yau MC, Galpin JD, Seebohm G, Ahern CA, Pless SA, Kurata HT - Nat Commun (2015)

Bottom Line: Introduction of a non-natural isosteric H-bond-deficient Trp analogue abolishes channel potentiation, indicating that retigabine effects rely strongly on formation of a H-bond with the conserved pore Trp.In addition, potency of numerous retigabine analogues correlates with the negative electrostatic surface potential of a carbonyl/carbamate oxygen atom present in most KCNQ activators.These findings functionally pinpoint an atomic-scale interaction essential for effects of retigabine and provide stringent constraints that may guide rational improvement of the emerging drug class of KCNQ channel activators.

View Article: PubMed Central - PubMed

Affiliation: Department of Anesthesiology, Pharmacology, and Therapeutics, University of British Columbia, 2176 Health Sciences Mall, Vancouver, British Columbia, Canada V6T 1Z3.

ABSTRACT
Retigabine is a recently approved anticonvulsant that acts by potentiating neuronal M-current generated by KCNQ2-5 channels, interacting with a conserved Trp residue in the channel pore domain. Using unnatural amino-acid mutagenesis, we subtly altered the properties of this Trp to reveal specific chemical interactions required for retigabine action. Introduction of a non-natural isosteric H-bond-deficient Trp analogue abolishes channel potentiation, indicating that retigabine effects rely strongly on formation of a H-bond with the conserved pore Trp. Supporting this model, substitution with fluorinated Trp analogues, with increased H-bonding propensity, strengthens retigabine potency. In addition, potency of numerous retigabine analogues correlates with the negative electrostatic surface potential of a carbonyl/carbamate oxygen atom present in most KCNQ activators. These findings functionally pinpoint an atomic-scale interaction essential for effects of retigabine and provide stringent constraints that may guide rational improvement of the emerging drug class of KCNQ channel activators.

No MeSH data available.


Effects of retigabine analogues correlate with electrostatic surface potential.(a) Chemical structures and electrostatic surface potentials for a series of retigabine analogues. All structures and surface potential maps have been aligned on the basis of the location of the conserved amide-ester bond—note the gradient of the intensity of the negative surface potential around the carbonyl oxygen atom (scaling is the same as in Fig. 6). (b) Summary illustrating the EC50 of each drug on Trp-rescued, F3-Trp-rescued and Ind-rescued KCNQ3*[Trp265TAG] channels (n=4–9 per data point), and the maximal efficacy (ΔV1/2) of each drug in F3-Trp and Trp-rescued channels (effects on Ind-rescued channels are minimal and thus have been omitted). Error bars represent s.e.m.
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f7: Effects of retigabine analogues correlate with electrostatic surface potential.(a) Chemical structures and electrostatic surface potentials for a series of retigabine analogues. All structures and surface potential maps have been aligned on the basis of the location of the conserved amide-ester bond—note the gradient of the intensity of the negative surface potential around the carbonyl oxygen atom (scaling is the same as in Fig. 6). (b) Summary illustrating the EC50 of each drug on Trp-rescued, F3-Trp-rescued and Ind-rescued KCNQ3*[Trp265TAG] channels (n=4–9 per data point), and the maximal efficacy (ΔV1/2) of each drug in F3-Trp and Trp-rescued channels (effects on Ind-rescued channels are minimal and thus have been omitted). Error bars represent s.e.m.

Mentions: Expanding on these observations, we examined a spectrum of KCNQ channel activators with varying potency in KCNQ3* channels (Fig. 7). We have depicted all of the drugs tested and colorimetric representations of their calculated electrostatic surface potentials, along with the observed EC50 for the shift of activation V1/2 of KCNQ3*[Trp265TAG] channels (rescued with Trp, F3-Trp or Ind). For all drugs tested, effects were abolished by the Trp265Ind substitution, indicating a common mechanism via H-bond formation with Trp265. In addition, F3-Trp substitution generally resulted in higher drug potency, although this effect was not as pronounced with the less polar analogues ICA-110381 and ICA-069673. Importantly, all of the activator compounds contain a carbonyl oxygen (either in the carbamate moiety of retigabine and flupirtine, or in the amide linker in ML-213 or the ICA compounds), and it is noteworthy that the strength of the negative surface potential correlates well with the potency of the drug for KCNQ3* activation—drugs with a weaker electrostatic surface potential trend towards weaker potency (Fig. 7). The ICA compounds are very weakly potent activators of KCNQ3* channels within our typical experimental concentration range (up to 300 μM), and notably ICA-110381 caused considerably more activation in F3-Trp-substituted channels, demonstrating that effects of an otherwise weak channel activator can be strengthened by targeting the chemical properties of Trp265. Taken together, these findings illustrate the importance of the H-bonding propensity of Trp265, likely involved in the formation of a H-bond with a carbonyl oxygen present in retigabine and its analogues.


Atomic basis for therapeutic activation of neuronal potassium channels.

Kim RY, Yau MC, Galpin JD, Seebohm G, Ahern CA, Pless SA, Kurata HT - Nat Commun (2015)

Effects of retigabine analogues correlate with electrostatic surface potential.(a) Chemical structures and electrostatic surface potentials for a series of retigabine analogues. All structures and surface potential maps have been aligned on the basis of the location of the conserved amide-ester bond—note the gradient of the intensity of the negative surface potential around the carbonyl oxygen atom (scaling is the same as in Fig. 6). (b) Summary illustrating the EC50 of each drug on Trp-rescued, F3-Trp-rescued and Ind-rescued KCNQ3*[Trp265TAG] channels (n=4–9 per data point), and the maximal efficacy (ΔV1/2) of each drug in F3-Trp and Trp-rescued channels (effects on Ind-rescued channels are minimal and thus have been omitted). Error bars represent s.e.m.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4561856&req=5

f7: Effects of retigabine analogues correlate with electrostatic surface potential.(a) Chemical structures and electrostatic surface potentials for a series of retigabine analogues. All structures and surface potential maps have been aligned on the basis of the location of the conserved amide-ester bond—note the gradient of the intensity of the negative surface potential around the carbonyl oxygen atom (scaling is the same as in Fig. 6). (b) Summary illustrating the EC50 of each drug on Trp-rescued, F3-Trp-rescued and Ind-rescued KCNQ3*[Trp265TAG] channels (n=4–9 per data point), and the maximal efficacy (ΔV1/2) of each drug in F3-Trp and Trp-rescued channels (effects on Ind-rescued channels are minimal and thus have been omitted). Error bars represent s.e.m.
Mentions: Expanding on these observations, we examined a spectrum of KCNQ channel activators with varying potency in KCNQ3* channels (Fig. 7). We have depicted all of the drugs tested and colorimetric representations of their calculated electrostatic surface potentials, along with the observed EC50 for the shift of activation V1/2 of KCNQ3*[Trp265TAG] channels (rescued with Trp, F3-Trp or Ind). For all drugs tested, effects were abolished by the Trp265Ind substitution, indicating a common mechanism via H-bond formation with Trp265. In addition, F3-Trp substitution generally resulted in higher drug potency, although this effect was not as pronounced with the less polar analogues ICA-110381 and ICA-069673. Importantly, all of the activator compounds contain a carbonyl oxygen (either in the carbamate moiety of retigabine and flupirtine, or in the amide linker in ML-213 or the ICA compounds), and it is noteworthy that the strength of the negative surface potential correlates well with the potency of the drug for KCNQ3* activation—drugs with a weaker electrostatic surface potential trend towards weaker potency (Fig. 7). The ICA compounds are very weakly potent activators of KCNQ3* channels within our typical experimental concentration range (up to 300 μM), and notably ICA-110381 caused considerably more activation in F3-Trp-substituted channels, demonstrating that effects of an otherwise weak channel activator can be strengthened by targeting the chemical properties of Trp265. Taken together, these findings illustrate the importance of the H-bonding propensity of Trp265, likely involved in the formation of a H-bond with a carbonyl oxygen present in retigabine and its analogues.

Bottom Line: Introduction of a non-natural isosteric H-bond-deficient Trp analogue abolishes channel potentiation, indicating that retigabine effects rely strongly on formation of a H-bond with the conserved pore Trp.In addition, potency of numerous retigabine analogues correlates with the negative electrostatic surface potential of a carbonyl/carbamate oxygen atom present in most KCNQ activators.These findings functionally pinpoint an atomic-scale interaction essential for effects of retigabine and provide stringent constraints that may guide rational improvement of the emerging drug class of KCNQ channel activators.

View Article: PubMed Central - PubMed

Affiliation: Department of Anesthesiology, Pharmacology, and Therapeutics, University of British Columbia, 2176 Health Sciences Mall, Vancouver, British Columbia, Canada V6T 1Z3.

ABSTRACT
Retigabine is a recently approved anticonvulsant that acts by potentiating neuronal M-current generated by KCNQ2-5 channels, interacting with a conserved Trp residue in the channel pore domain. Using unnatural amino-acid mutagenesis, we subtly altered the properties of this Trp to reveal specific chemical interactions required for retigabine action. Introduction of a non-natural isosteric H-bond-deficient Trp analogue abolishes channel potentiation, indicating that retigabine effects rely strongly on formation of a H-bond with the conserved pore Trp. Supporting this model, substitution with fluorinated Trp analogues, with increased H-bonding propensity, strengthens retigabine potency. In addition, potency of numerous retigabine analogues correlates with the negative electrostatic surface potential of a carbonyl/carbamate oxygen atom present in most KCNQ activators. These findings functionally pinpoint an atomic-scale interaction essential for effects of retigabine and provide stringent constraints that may guide rational improvement of the emerging drug class of KCNQ channel activators.

No MeSH data available.