Abstract
Apigenin (4',5,7-trihydroxyflavone) is an activator of cystic fibrosis transmembrane conductance regulator (CFTR)-mediated Cl- currents across epithelia at low concentrations and a blocker at high concentrations. We determined the roles of structural components of apigenin for both stimulation and block of Cl- currents across Calu-3 epithelia. The half-maximal binding affinity of apigenin for current stimulation (K(S)) was 9.1 ± 1.3 μM, and the rank-order of molecular structures was 7-hydroxyl > pyrone = 4'-hydroxyl > 5-hydroxyl. Both the 7-hydroxyl and the 4'-hydroxyl served as H-bond acceptors, whereas the 5-hydroxyl was an H-bond donor. The half-maximal binding affinity of apigenin during current block was 74 ± 11 μM. Blocked Cl- currents were structurally determined by 7-hydroxyl = 4'-hydroxyl > pyrone > 5-hydroxyl. Prestimulation of tissues with forskolin significantly affected activation kinetics and binding characteristics. After forskolin stimulation, K(S) was 4.1 ± 0.9 μM, which was structurally determined by pyrone > all hydroxyls > single hydroxyls. In contrast, block of Cl- current by apigenin was not affected by forskolin stimulation. We conclude that apigenin binds to a stimulatory and an inhibitory binding site, which are distinguished by their affinities and the molecular interactions during binding.
| Original language | English (US) |
|---|---|
| Journal | American Journal of Physiology - Cell Physiology |
| Volume | 279 |
| Issue number | 6 48-6 |
| State | Published - 2000 |
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Keywords
- Binding site
- Chloride transport
- Cystic fibrosis transmembrane conductance regulator
- Epithelia
- Flavonoids
- Resveratrol
ASJC Scopus subject areas
- Clinical Biochemistry
- Cell Biology
- Physiology
- Physiology (medical)
Cite this
Structural determinants for activation and block of CFTR-mediated chloride currents by apigenin. / Illek, Beate; Lizarzaburu, Mike E.; Lee, Vivien; Nantz, Michael H.; Kurth, Mark J.; Fischer, Horst.
In: American Journal of Physiology - Cell Physiology, Vol. 279, No. 6 48-6, 2000.Research output: Contribution to journal › Article
}
TY - JOUR
T1 - Structural determinants for activation and block of CFTR-mediated chloride currents by apigenin
AU - Illek, Beate
AU - Lizarzaburu, Mike E.
AU - Lee, Vivien
AU - Nantz, Michael H.
AU - Kurth, Mark J.
AU - Fischer, Horst
PY - 2000
Y1 - 2000
N2 - Apigenin (4',5,7-trihydroxyflavone) is an activator of cystic fibrosis transmembrane conductance regulator (CFTR)-mediated Cl- currents across epithelia at low concentrations and a blocker at high concentrations. We determined the roles of structural components of apigenin for both stimulation and block of Cl- currents across Calu-3 epithelia. The half-maximal binding affinity of apigenin for current stimulation (K(S)) was 9.1 ± 1.3 μM, and the rank-order of molecular structures was 7-hydroxyl > pyrone = 4'-hydroxyl > 5-hydroxyl. Both the 7-hydroxyl and the 4'-hydroxyl served as H-bond acceptors, whereas the 5-hydroxyl was an H-bond donor. The half-maximal binding affinity of apigenin during current block was 74 ± 11 μM. Blocked Cl- currents were structurally determined by 7-hydroxyl = 4'-hydroxyl > pyrone > 5-hydroxyl. Prestimulation of tissues with forskolin significantly affected activation kinetics and binding characteristics. After forskolin stimulation, K(S) was 4.1 ± 0.9 μM, which was structurally determined by pyrone > all hydroxyls > single hydroxyls. In contrast, block of Cl- current by apigenin was not affected by forskolin stimulation. We conclude that apigenin binds to a stimulatory and an inhibitory binding site, which are distinguished by their affinities and the molecular interactions during binding.
AB - Apigenin (4',5,7-trihydroxyflavone) is an activator of cystic fibrosis transmembrane conductance regulator (CFTR)-mediated Cl- currents across epithelia at low concentrations and a blocker at high concentrations. We determined the roles of structural components of apigenin for both stimulation and block of Cl- currents across Calu-3 epithelia. The half-maximal binding affinity of apigenin for current stimulation (K(S)) was 9.1 ± 1.3 μM, and the rank-order of molecular structures was 7-hydroxyl > pyrone = 4'-hydroxyl > 5-hydroxyl. Both the 7-hydroxyl and the 4'-hydroxyl served as H-bond acceptors, whereas the 5-hydroxyl was an H-bond donor. The half-maximal binding affinity of apigenin during current block was 74 ± 11 μM. Blocked Cl- currents were structurally determined by 7-hydroxyl = 4'-hydroxyl > pyrone > 5-hydroxyl. Prestimulation of tissues with forskolin significantly affected activation kinetics and binding characteristics. After forskolin stimulation, K(S) was 4.1 ± 0.9 μM, which was structurally determined by pyrone > all hydroxyls > single hydroxyls. In contrast, block of Cl- current by apigenin was not affected by forskolin stimulation. We conclude that apigenin binds to a stimulatory and an inhibitory binding site, which are distinguished by their affinities and the molecular interactions during binding.
KW - Binding site
KW - Chloride transport
KW - Cystic fibrosis transmembrane conductance regulator
KW - Epithelia
KW - Flavonoids
KW - Resveratrol
UR - http://www.scopus.com/inward/record.url?scp=0033636431&partnerID=8YFLogxK
UR - http://www.scopus.com/inward/citedby.url?scp=0033636431&partnerID=8YFLogxK
M3 - Article
C2 - 11078699
AN - SCOPUS:0033636431
VL - 279
JO - American Journal of Physiology - Renal Fluid and Electrolyte Physiology
JF - American Journal of Physiology - Renal Fluid and Electrolyte Physiology
SN - 1931-857X
IS - 6 48-6
ER -