Objectives Acidosis has an inhibitory effect on the inactivation of Kv1.4 ΔN channel through the position H508. So in order to show the effects of glutamic acid on the mutant Kv 1.4 channel that lacks N-type inactiva...Objectives Acidosis has an inhibitory effect on the inactivation of Kv1.4 ΔN channel through the position H508. So in order to show the effects of glutamic acid on the mutant Kv 1.4 channel that lacks N-type inactivation （Kv1.4 Δ2-146）, we studied in the expression system of the Xenopus oocytes. Methods The two-electrode voltage-clamp technique （TEV） was used to record the currents. Results Acidosis increased fKv1.4 Δ2-146 C-type inactivation. After application of glutamic acid （1 mmol/L） to Kv1.4 Δ2-146 increased C-type inactivation further, changed inactivation time constants from （2.02 ± 0.39 s ） to （1.71 ± 0.23 s） （P〈 0.05） at ＋50mv, and shifted the steady-state inactivation curves of Kv1.4 ΔN to positive potential, which was from （-44.30 ± 0.59 mV） to （-39.88 ± 0.29 mV）（P〈0.05）. and slowed the rate of recovery from inactivation, which was from （1.64 ± 0.19 s） to （1.91 ± 0.23 s）（P〈 0.05）. Conclusions Together, these results suggest that 1 mmol/L glutamic acid accelerates the C-type inactivation of Kv1.4 ΔN in pH 6.8.展开更多
Nicotinic acetylcholine receptors （nAChRs） are ligand-gated ion channels, which mediate fast cholinergic synaptic transmission in insect and vertebrate nervous systems. The nAChR agonist-binding site is present at t...Nicotinic acetylcholine receptors （nAChRs） are ligand-gated ion channels, which mediate fast cholinergic synaptic transmission in insect and vertebrate nervous systems. The nAChR agonist-binding site is present at the interface of adjacent subunits and is formed by loops A-C present in α subunits together with loops D-F present in either non-α subunits or homomer-forming α subunits. Although Y151 in loop B has been identified as important in agonist binding, various residues at the 151-site are found among vertebrate and invertebrate nAChR α subunits, such as F 151. In Xenopus oocytes expressing Nlα1 or Nlα1^Y151F plus rat β2, Y151F mutation was found to significantly change the rate of receptor desensitization and altered the pharmacological properties of acetylcholine, but not imidacloprid, including the decrease Of Imax, the increase of EC50 （the concentration causing 50% of the maximum response） and the fast time-constant of decay （τf）. By comparisons of residue structure, the hydroxyl group in the side chain of Y151 was thought to be important in the interaction between Nlα1/β2 nAChRs and acetylcholine, and the phenyl group to be important between Nlα1/β2 nAChRs and imidacloprid.展开更多
本工作用电压箝记录方法研究了爪蟾卵母细胞经注射大鼠脑mRNA后表达的电压门控钙通道。钙通道的特性由通过钙通道的钡离子流(I_(Ba))来描述。本研究采用的卵母细胞均取自被鉴定的爪蟾。这些爪蟾卵母细胞内源性I_(Ba)大多为零,或小于15n...本工作用电压箝记录方法研究了爪蟾卵母细胞经注射大鼠脑mRNA后表达的电压门控钙通道。钙通道的特性由通过钙通道的钡离子流(I_(Ba))来描述。本研究采用的卵母细胞均取自被鉴定的爪蟾。这些爪蟾卵母细胞内源性I_(Ba)大多为零,或小于15nA。将从出生后10d的大鼠全脑中提取的mRNA微量注入这些卵母细胞。在注射mRNA后的5d内,I_(Ba)逐渐增大。在mRNA注射后第三天,由大鼠脑mRNA表达的电压依赖性I_(Ba)最大值一般超过100nA。作为对比,在注射从胚胎大鼠脑提取的mRNA的卵母细胞,几乎测不到电压依赖性I_(Ba)的表达。我们研究了由大鼠脑mRNA表达的I_(Ba)的电压依赖性激活及失活特性和I_(Ba)的药理。发现镧系金属离子(La^(+3),Nd^(+3),Sm^(+3),Eu^(+3),Gd^(+3),Dy^(+3),Er^(+3)在微摩尔浓度数量级即能有效抑制I_(Ba)。L-型钙通道配体nifedipine和Bay K 8644在浓度100μmmol/L时,抑制I_(Ba),而另一dihydropyridine类配体(±)-nimodipine在相同浓度却增加I_(Ba)。展开更多
文摘Objectives Acidosis has an inhibitory effect on the inactivation of Kv1.4 ΔN channel through the position H508. So in order to show the effects of glutamic acid on the mutant Kv 1.4 channel that lacks N-type inactivation （Kv1.4 Δ2-146）, we studied in the expression system of the Xenopus oocytes. Methods The two-electrode voltage-clamp technique （TEV） was used to record the currents. Results Acidosis increased fKv1.4 Δ2-146 C-type inactivation. After application of glutamic acid （1 mmol/L） to Kv1.4 Δ2-146 increased C-type inactivation further, changed inactivation time constants from （2.02 ± 0.39 s ） to （1.71 ± 0.23 s） （P〈 0.05） at ＋50mv, and shifted the steady-state inactivation curves of Kv1.4 ΔN to positive potential, which was from （-44.30 ± 0.59 mV） to （-39.88 ± 0.29 mV）（P〈0.05）. and slowed the rate of recovery from inactivation, which was from （1.64 ± 0.19 s） to （1.91 ± 0.23 s）（P〈 0.05）. Conclusions Together, these results suggest that 1 mmol/L glutamic acid accelerates the C-type inactivation of Kv1.4 ΔN in pH 6.8.
基金Acknowledgments This work was supported by the Program for New Century Excellent Talents in University （06-0494）, National Natural Science Foundation of China Program Grant （30700528） and Special Fund for Basic Expenditure for Scientific ＆ Research of Central Non-profit Scientific Research Institutions （2007RG016）.
文摘Nicotinic acetylcholine receptors （nAChRs） are ligand-gated ion channels, which mediate fast cholinergic synaptic transmission in insect and vertebrate nervous systems. The nAChR agonist-binding site is present at the interface of adjacent subunits and is formed by loops A-C present in α subunits together with loops D-F present in either non-α subunits or homomer-forming α subunits. Although Y151 in loop B has been identified as important in agonist binding, various residues at the 151-site are found among vertebrate and invertebrate nAChR α subunits, such as F 151. In Xenopus oocytes expressing Nlα1 or Nlα1^Y151F plus rat β2, Y151F mutation was found to significantly change the rate of receptor desensitization and altered the pharmacological properties of acetylcholine, but not imidacloprid, including the decrease Of Imax, the increase of EC50 （the concentration causing 50% of the maximum response） and the fast time-constant of decay （τf）. By comparisons of residue structure, the hydroxyl group in the side chain of Y151 was thought to be important in the interaction between Nlα1/β2 nAChRs and acetylcholine, and the phenyl group to be important between Nlα1/β2 nAChRs and imidacloprid.
文摘本工作用电压箝记录方法研究了爪蟾卵母细胞经注射大鼠脑mRNA后表达的电压门控钙通道。钙通道的特性由通过钙通道的钡离子流(I_(Ba))来描述。本研究采用的卵母细胞均取自被鉴定的爪蟾。这些爪蟾卵母细胞内源性I_(Ba)大多为零,或小于15nA。将从出生后10d的大鼠全脑中提取的mRNA微量注入这些卵母细胞。在注射mRNA后的5d内,I_(Ba)逐渐增大。在mRNA注射后第三天,由大鼠脑mRNA表达的电压依赖性I_(Ba)最大值一般超过100nA。作为对比,在注射从胚胎大鼠脑提取的mRNA的卵母细胞,几乎测不到电压依赖性I_(Ba)的表达。我们研究了由大鼠脑mRNA表达的I_(Ba)的电压依赖性激活及失活特性和I_(Ba)的药理。发现镧系金属离子(La^(+3),Nd^(+3),Sm^(+3),Eu^(+3),Gd^(+3),Dy^(+3),Er^(+3)在微摩尔浓度数量级即能有效抑制I_(Ba)。L-型钙通道配体nifedipine和Bay K 8644在浓度100μmmol/L时,抑制I_(Ba),而另一dihydropyridine类配体(±)-nimodipine在相同浓度却增加I_(Ba)。
