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Mol. Cells 2009; 27(5): 591-599

Published online May 31, 2009

https://doi.org/10.1007/s10059-009-0073-4

© The Korean Society for Molecular and Cellular Biology

A Role for Leu247 Residue within Transmem-brane Domain 2 in Ginsenoside-Mediated alpha Nicotinic Acetylcholine Receptor Regulation

Byung-Hwan Lee, Sun-Hye Choi, Mi Kyung Pyo, Tae-Joon Shin, Sung-Hee Hwang, Bo-Ra Kim, Sang-MoK Lee, Jun-Ho Lee, Joon-Hee Lee, Hui Sun Lee , Han Choe, Kyou-Hoon Han, Hyoung-Chun Kim, Hyewhon Rhim, Joon-Hwan Yong, and Seung-Yeol Nah

Received: February 20, 2009; Revised: March 18, 2009; Accepted: March 19, 2009

Abstract

Nicotinic acetylcholine receptors (nAChRs) play important roles in nervous system functions and are involved in a variety of diseases. We previously demonstrated that ginsenosides, the active ingredients of Panax ginseng, inhibit subsets of nAChR channel currents, but not ?7, expressed in Xenopus laevis oocytes. Mutation of the highly conserved Leu247 to Thr247 in the transmembrane domain 2 (TM2) channel pore region of ?7 nAChR induces alterations in channel gating properties and converts ?7 nAChR antagonists into agonists. In the present study, we assessed how point mutations in the Leu247 residue leading to various amino acids affect 20(S)-ginsenoside Rg3 (Rg3) activity against the ?7 nAChR. Mutation of L247 to L247A, L247D, L247E, L247I, L247S, and L247T, but not L247K, rendered mutant receptors sensitive to Rg3. We further character-ized Rg3 regulation of L247T receptors. We found that Rg3 inhibition of mutant ?7 nAChR channel currents was reversible and concentration-dependent. Rg3 inhibition was strongly voltage-dependent and noncompetitive manner. These results indicate that the interaction between Rg3 and mutant receptors might differ from its interaction with the wild-type receptor. To identify differences in Rg3 interactions between wild-type and L247T receptors, we utilized docked modeling. This modeling revealed that Rg3 forms hydrogen bonds with amino acids, such as Ser240 of subunit I and Thr244 of subunit II and V at the channel pore, whereas Rg3 localizes at the interface of the two wild-type receptor subunits. These results indicate that mutation of Leu247 to Thr247 induces conformational changes in the wild-type receptor and provides a binding pocket for Rg3 at the channel pore.

Keywords ginsenoside Rg3, interaction sites, mutant ?7 nAChR, Panax ginseng

Article

Research Article

Mol. Cells 2009; 27(5): 591-599

Published online May 31, 2009 https://doi.org/10.1007/s10059-009-0073-4

Copyright © The Korean Society for Molecular and Cellular Biology.

A Role for Leu247 Residue within Transmem-brane Domain 2 in Ginsenoside-Mediated alpha Nicotinic Acetylcholine Receptor Regulation

Byung-Hwan Lee, Sun-Hye Choi, Mi Kyung Pyo, Tae-Joon Shin, Sung-Hee Hwang, Bo-Ra Kim, Sang-MoK Lee, Jun-Ho Lee, Joon-Hee Lee, Hui Sun Lee , Han Choe, Kyou-Hoon Han, Hyoung-Chun Kim, Hyewhon Rhim, Joon-Hwan Yong, and Seung-Yeol Nah

Received: February 20, 2009; Revised: March 18, 2009; Accepted: March 19, 2009

Abstract

Nicotinic acetylcholine receptors (nAChRs) play important roles in nervous system functions and are involved in a variety of diseases. We previously demonstrated that ginsenosides, the active ingredients of Panax ginseng, inhibit subsets of nAChR channel currents, but not ?7, expressed in Xenopus laevis oocytes. Mutation of the highly conserved Leu247 to Thr247 in the transmembrane domain 2 (TM2) channel pore region of ?7 nAChR induces alterations in channel gating properties and converts ?7 nAChR antagonists into agonists. In the present study, we assessed how point mutations in the Leu247 residue leading to various amino acids affect 20(S)-ginsenoside Rg3 (Rg3) activity against the ?7 nAChR. Mutation of L247 to L247A, L247D, L247E, L247I, L247S, and L247T, but not L247K, rendered mutant receptors sensitive to Rg3. We further character-ized Rg3 regulation of L247T receptors. We found that Rg3 inhibition of mutant ?7 nAChR channel currents was reversible and concentration-dependent. Rg3 inhibition was strongly voltage-dependent and noncompetitive manner. These results indicate that the interaction between Rg3 and mutant receptors might differ from its interaction with the wild-type receptor. To identify differences in Rg3 interactions between wild-type and L247T receptors, we utilized docked modeling. This modeling revealed that Rg3 forms hydrogen bonds with amino acids, such as Ser240 of subunit I and Thr244 of subunit II and V at the channel pore, whereas Rg3 localizes at the interface of the two wild-type receptor subunits. These results indicate that mutation of Leu247 to Thr247 induces conformational changes in the wild-type receptor and provides a binding pocket for Rg3 at the channel pore.

Keywords: ginsenoside Rg3, interaction sites, mutant ?7 nAChR, Panax ginseng

Mol. Cells
Nov 30, 2022 Vol.45 No.11, pp. 763~867
COVER PICTURE
Naive (cyan) and axotomized (magenta) retinal ganglion cell axons in Xenopus tropicalis (Choi et al., pp. 846-854).

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