Human glycine alpha1 receptor inhibition by quercetin is abolished or inversed by alpha267 mutations in transmembrane domain 2.
Quercetin, one of the flavonoids, is a compound of low molecular weight found in fruits and vegetables. Besides its antioxidative effect, quercetin also shows a wide range of diverse neuropharmacological actions. However, the cellular mechanisms of quercetin's actions, especially on ligand-gated ion channels and synaptic transmissions, are not well studied. We investigated the effect of quercetin on the human glycine alpha1 receptor channel expressed in Xenopus oocytes using a two-electrode voltage clamp technique. Application of quercetin reversibly inhibited glycine-induced current (I(Gly)). Quercetin's inhibition depends on its dose, with an IC(50) of 21.5+/-.2 microM. The inhibition was sensitive to membrane voltages. Site-directed mutations of S267 to S267Y but not S267A, S267F, S267G, S267K, S267L and S267T at transmembrane domain 2 (TM2) nearly abolished quercetin-induced inhibition of I(Gly). In contrast, in site-directed mutant receptors such as S267 to S267I, S267R and S267V, quercetin enhanced I(Gly) compared to the wild-type receptor. The EC(50) was 22.6+/-1.4, 25.5+/-4.2, and 14.5+/-3.1 microM for S267I, S267R and S267V, respectively. These results indicate that quercetin might regulate the human glycine alpha(1) receptor via interaction with amino acid residue alpha267 and that alpha267 plays a key role in determining the regulatory consequences of the human glycine alpha1 receptor by quercetin.
Lee
Byung-Hwan
BH
Department of Physiology, College of Veterinary Medicine, Konkuk University, Seoul, Korea.
Lee
Jun-Ho
JH
Yoon
In-Soo
IS
Lee
Joon-Hee
JH
Choi
Sun-Hye
SH
Pyo
Mi Kyung
MK
Jeong
Sang Min
SM
Choi
Woo-Sung
WS
Shin
Tae-Joon
TJ
Lee
Sang-Mok
SM
Rhim
Hyewhon
H
Park
Yong-Sun
YS
Han
Ye Sun
YS
Paik
Hyun-Dong
HD
Cho
Ssang-Goo
SG
Kim
Cheon-Ho
CH
Lim
Yoong-Ho
YH
Nah
Seung-Yeol
SY
D000704:Analysis of Variance; D000818:Animals; D000975:Antioxidants / Q000494:pharmacology*; D004305:Dose-Response Relationship, Drug; D004307:Dose-Response Relationship, Radiation; D005260:Female; D005998:Glycine / Q000494:pharmacology; D006801:Humans; D015640:Ion Channel Gating / Q000187:drug effects*; D008564:Membrane Potentials / Q000187:drug effects / Q000502:physiology / Q000528:radiation effects; D008845:Microinjections / Q000379:methods; D016297:Mutagenesis, Site-Directed / Q000379:methods; D009154:Mutation / Q000502:physiology*; D009865:Oocytes; D018408:Patch-Clamp Techniques; D011794:Quercetin / Q000494:pharmacology*; D018009:Receptors, Glycine / Q000737:chemistry / Q000502:physiology*; D013329:Structure-Activity Relationship; D014982:Xenopus laevis
D000975:Antioxidants; D018009:Receptors, Glycine; D011794:Quercetin; D005998:Glycine