QSAR features for inhibitors of mitochondrial bioenergetics.
description
Transcript of QSAR features for inhibitors of mitochondrial bioenergetics.
QSAR features for inhibitors of mitochondrial QSAR features for inhibitors of mitochondrial
bioenergetics.bioenergetics.
Anatoly A. StarkovAnatoly A. Starkov
HH++HH++
Oxygen
C-III
SDH
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C-IV
C-I
FMN
IM
NADH
NAD+
Succinate
Fumarate
Water
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CoQ CoQ
Fuel Fuel Supply Supply SystemSystem
Electron transfer in the respiratory chainElectron transfer in the respiratory chain
NADH Oxygen, CoQH2
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HH++ p.m.f. = p.m.f. = + + pHpH
1. What is “uncoupling”?
2. What are “uncouplers”?
3. What are the mechanisms of uncoupling?
4. How much uncoupling is toxic?
5. Is a class-independent QSAR model for uncouplers
possible? What descriptors should be selected?
6. What models should be used to test the uncouplers?
A. UNCOUPLING.
Classical definitions:
Uncoupling of oxidative phosphorylation is a process de-coupling oxygen consumption from ATP production.
Uncouplers:
1.Stimulate resting respiration. 2.Decrease ATP yield (P:O ratio).3.Activate latent ATPase.
any energy-dissipating process competing for energy with routinemitochondrial functions, thus inducing a metabolically futile wasting of energy.
Wallace KB, Starkov AA. Mitochondrial targets of drug toxicity. Annu Rev Pharmacol Toxicol. 2000;40:353-88.
UNCOUPLING:.
Respiratorychain
H+
H+
AH
AH A-
A-
H+
H+
IM
Matrix
A-
AHRespiratory
chain
H+
H+
AH
AH A-
H+
H+
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pH
HA2-
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Proton shuttling by lipophilic weak acids.
substituted phenols trifluoromethylbenzimidazolessalicylanilidescarbonylcyanide phenylhydrazones
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+
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+
pH
1. 2.
Blaikie FH, Brown SE, Samuelsson LM, Brand MD, Smith RA, Murphy MP. Targeting dinitrophenol to mitochondria: limitations to the development of a self-limiting mitochondrial protonophore. Biosci Rep. 2006 Jun;26(3):231-43.
Terada H. Uncouplers of oxidative phosphorylation. Environ Health Perspect. 1990 Jul;87:213-8.
[uncoupler], M
Sta
te 4
, nm
ol O
2/m
in/m
gState 3 respiration rate
[Uncoupler] max
Respiratorychain
H+
H+
RN+
RN+ RN
RN
H+
H+
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pH
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Respiratorychain
H+
H+
RNA-H+
RNA-H+ RN
H+
H+
IM
Matrix
pH
A-
RN
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+
Proton shuttling by lipophilic weak bases and ion pairs.
amine local anesthetics
3. 4.
Respiratorychain
H+
H+
AH
AH A-
A-
H+
H+
IM
Matrix
P
Protein –mediated uncoupling by non-permeating anions and protein modifying reagents.
P: ATP/ADP translocator, Glutamate transporter
Long-chain fatty acids, SDS, 2,4-DNP
Respiratorychain
H+
H+H+
H+
IM
Matrix
P
P: Uncoupling Protein 1 (UCP1), anion carriers, membrane-active peptides, Permeability transition Pore (mPTP).
Long-chain fatty acids, SH-modifying reagents.
pH
pH
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5. 6.
Respiratorychain
H+
H+2H+
2H+
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EU
pH
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Ca2+
Ca2+
U: Ca2+ uniporter.
E: Ca2+ ionophores.
7.
Ion cycling.
(Variant : U=valinomycin, Ca2+ =K+, E=nigericine)
RCRC
H+
H+
Ca2+
Ca2+
2H+
IM
MatrixMatrix
pH
Ca2+
Ca2+
2H+
UU
EE
precipitateprecipitate
++CypDCypD
++++
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PTPPTP
CytosolCytosolCaCa2+ 2+ signalsignal
ER storageER storage
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1. Normal Ca1. Normal Ca2+2+ signaling: signaling:
Uncoupling due to the permeability transition pore (mPTP).8.
RCRC
H+
H+
Ca2+
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2H+
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MatrixMatrix
pH
Ca2+
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2H+
UU
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precipitateprecipitate
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CytosolCytosol
CaCa2+ 2+ floodingflooding ER storageER storage
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2. Pathological Ca2. Pathological Ca2+2+ flooding opens mPTP: flooding opens mPTP:
McLaughlin SG, Dilger JP. Transport of protons across membranes by weak acids. Physiol Rev. 1980 Jul;60(3):825-63.
Classical efficient uncoupler: 4<pKa<7.2, 3<logP<8
McLaughlin SG, Dilger JP. Transport of protons across membranes by weak acids. Physiol Rev. 1980 Jul;60(3):825-63.
Steps: Mechanism type descriptorsAcquire H+ 1-5, 7 pKaAdsorb to the membrane 1-5, 7, (6) D(water-membrane) (partition coefficient)Partition into the membrane 1-7, (6) K,K’(surface-core) (species partition coefficient)Cross the membrane 1-5, 7 k,k’(species) (translocation rate constant)Release H+ inside matrix 1-5, 7 pKaCross the membrane 1-5, 7 k’(species) (translocation rate constant)Acquire H+ 1-5, 7 pKa’
Information on the surrounding: pH out and in, lipid phase volume, lipid phase(s) dielectric constants and viscosity, gradient of the electrical membrane potential across the membrane, total amount of a compound.
Minimum reasonable set of parameters to consider:
Classical: 4<pKa<7.2, 3<logP<8
Spycher S, Smejtek P, Netzeva TI, Escher BI. Toward a class-independent quantitative structure--activity relationship model for uncouplers of oxidative phosphorylation. Chem Res Toxicol. 2008 Apr;21(4):911-27.
Spycher S, Smejtek P, Netzeva TI, Escher BI. Toward a class-independent quantitative structure--activity relationship model for uncouplers of oxidative phosphorylation. Chem Res Toxicol. 2008 Apr;21(4):911-27.
McLaughlin SG, Dilger JP. Transport of protons across membranes by weak acids. Physiol Rev. 1980 Jul;60(3):825-63.
Black lipid membranes as a model to test the intrinsic efficiency of uncouplers:
Ilivicky J, Casida JE. Uncoupling action of 2,4-dinitrophenols, 2-trifluoromethylbenzimidazoles and certain other pesticide chemicals upon mitochondria from different sources and its relation to toxicity. Biochem Pharmacol. 1969 Jun;18(6):1389-401.
Isolated mammalian mitochondria as a model to test the toxicity of uncouplers
1. What do they do? – inhibit electron transport thereby suppressing H+ generation and stimulating ROS production.
2. How many are known? – a few hundreds of natural compounds and a gazillion of synthetic chemicals.
3. Are there some common chemical features in these compounds? – yes and no.
4. Is their MOA similar? – yes and no.
5. Is a class-independent QSAR model for the RC inhibitors possible? – Perhaps, but not there yet.
6. Why it is so? – insufficient knowledge of RC complexes and their structural diversity.
7. What models should be used to test the RC inhibitors? – isolated mammalian mitochondria.
B. Inhibitors of the respiratory chain complexes.
Oxygen
C-III
SDH C-I
FMN
C
C-IVIM
NADH
NAD+
Water
e
ee
e
e
CoQ CoQ
ROSROSROSROS ROSROSROSROS ROSROS
Succinate
Fumarate
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Fuel Fuel Supply Supply SystemSystem
Qi site
Qo site
blow
bhighe
e
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eeISP
Cyt.c1Cyt.c
Myxothiazol
Antimycin
Stigmatellin
Qi
Qo QH2
Q
Matrix side-
+
IM
AQH2
CoQ:Cytochrome c reductase (RC Complex III)
Antimycin A
Myxothiazol
Stigmatellin
Classical inhibitors of CoQ:Cytochrome c reductase (RC Complex III)
N3FMN
N1bN4N5N7
N2
N6aN6b
N1a
Complexity of mammalian NADH:CoQ reductase (RC Complex I)
Schuler F, Casida JE. The insecticide target in the PSST subunit of complex I. Pest Manag Sci. 2001 Oct;57(10):932-40
PSST subunit of Complex I is a common target for many and various inhibitors.
Inhibitor binding site
Different classes of the Q site Complex I inhibitors.
Degli Esposti M. Inhibitors of NADH-ubiquinone reductase: an overview. Biochim Biophys Acta. 1998 May 6;1364(2):222-35.
Future developments toward QSAR model of mitochondrial poisons:
1. Create a realistic biophysical model of the inner mitochondrial membrane;
2. Obtain more detailed information on the molecular structure of mitochondrial proteins targeted by toxins;
3. Create a unified database of mitochondrial toxins and analyze it toward both their molecular properties and the mechanisms of intrinsic activity;
4. Create a good team of researchers with proper expertise (and funding) to develop and validate QSAR models in a relevant biological model (isolated mitochondria) under physiologically meaningful conditions.
[O2]=0
Coupled respiration
ADP
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O2
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0 n
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~2
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Uncoupled respiration
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0 n
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V)
2,4-DNP
V(u) state 3
V(u) state 4,4’
ADP:O(u)
<
>
=
UncoupledCoupled
Uncoupling: less ATP for the same O2 and substrates
V state 3
V state 4,4’
ADP:O
V(u) state 3
V(u) state 4,4’
ADP:O(u)
Ilivicky J, Casida JE. Uncoupling action of 2,4-dinitrophenols, 2-trifluoromethylbenzimidazoles and certain other pesticide chemicals upon mitochondria from different sources and its relation to toxicity. Biochem Pharmacol. 1969 Jun;18(6):1389-401.
ROS production is regulated by ROS production is regulated by
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-Ketoglutarate…+ ADP
Glutamate + malate…+ ADP
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olx m
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-Ketoglutarate…+ ADP-Ketoglutarate…+ ADP
Glutamate + malate…+ ADPGlutamate + malate…+ ADP
succinate
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