摘要：
Jingzhaotoxin-XI (JZTX-XI) is a 34-residue peptide from the Chinese tarantula Chilobrachys jingzhao venom that potently inhibits both voltage-gated sodium channel Nav1.5 and voltage-gated potassium channel Kv2.1. In the present study, we further showed that JZTX-XI blocked Kv2.1 currents with the 1050 value of 0.39 +/- 0.06 M. JZTX-XI significantly shifted the current-voltage (I V) curves and normalized conductance-voltage (G V) curves of Kv2.1 channel to more depolarized voltages. Ala-scanning mutagenesis analyses demonstrated that mutants 1273A, F274A, and E277A reduced toxin binding affinity by 10-, 16-, and 18-fold, respectively, suggesting that three common residues (1273, F274, E277) in the Kv2.1 S3b segment contribute to the formation of JZTX-XI receptor site, and the acidic residue Glu at the position 277 in Kv2.1 is the most important residue for JZTX-XI sensitivity. A single replacement of E277 with Asp(D) increased toxin inhibitory activity. These results establish that JZTX-XI inhibits Kv2.1 activation by trapping the voltage sensor in the rested state through a similar mechanism to that of HaTxl, but these two toxins have small differences in the most crucial molecular determinant. Furthermore, the in-depth investigation of the subtle differences in molecular determinants may be useful for increasing our understanding of the molecular details regarding toxin-channel interactions. (C) 2016 Elsevier Ltd. All rights reserved.
关键词：
Drug reward;Dynorphin;Kappa opioid receptor;Paraventricular nucleus of thalamus
摘要：
It has been reported that kappa opioid receptor (KOR) is expressed in the paraventricular nucleus of thalamus (PVT), a brain region associated with arousal, drug reward and stress. Although intra-PVT infusion of KOR agonist was found to inhibit drug-seeking behavior, it is still unclear whether endogenous KOR agonists directly regulate PVT neuron activity. Here, we investigated the effect of the endogenous KOR agonist dynorphin-A (Dyn-A) on the excitability of mouse PVT neurons at different developmental ages. We found Dyn-A strongly inhibited PVT neurons through a direct postsynaptic hyperpolarization. Under voltage-clamp configuration, Dyn-A evoked an obvious outward current in majority of neurons tested in anterior PVT (aPVT) but only in minority of neurons in posterior PVT (pPVT). The Dyn-A current was abolished by KOR antagonist nor-BNI, Ba2+ and non-hydrolyzable GDP analogue GDP-beta-s, indicating that Dyn-A activates KOR and opens G-protein-coupled inwardly rectifying potassium channels in PVT neurons. More interestingly, by comparing Dyn-A currents in aPVT neurons of mice at various ages, we found Dyn-A evoked significant larger current in aPVT neurons from mice around prepuberty and early puberty stage. In addition, KOR activation by Dyn-A didn't produce obvious desensitization, while mu opioid receptor (MOR) activation induced obvious desensitization of mu receptor itself and also heterologous desensitization of KOR in PVT neurons. Together, our findings indicate that Dyn-A activates KOR and inhibits aPVT neurons in mice at various ages especially around puberty, suggesting a possible role of KOR in regulating aPVT-related brain function including stress response and drug-seeking behavior during adolescence. (C) 2015 Elsevier Ltd. All rights reserved.
作者机构：
[Zhou, Xi; Tang, Cheng; Chen, Ping; Zhang, Yunxiao; Liu, Zhonghua; Huang, Ying] Hunan Normal Univ, Coll Life Sci, Changsha 410081, Hunan, Peoples R China.;[Tao, Huai] Hunan Univ Chinese Med, Dept Biochem & Mol Biol, Changsha 410208, Hunan, Peoples R China.
通讯机构：
[Liu, Zhonghua] H;Hunan Normal Univ, Coll Life Sci, Changsha 410081, Hunan, Peoples R China.
关键词：
Jingzhaotoxin-II;Nav1.5;Action mechanism
摘要：
Jingzhaotoxin-II (JZTX-II) is a 32-residue peptide from the Chinese tarantula Chilobrachysjingzhao venom, and preferentially inhibits the fast inactivation of the voltage-gated sodium channels (VGSCs) in rat cardiac myocytes. In the present study, we elucidated the action mechanism of JZTX-II inhibiting hNav1.5, a VGSC subtype mainly distributed in human cardiac myocytes. Among the four VGSC subtypes tested, hNav1.5 was the most sensitive to JZTX-II (EC50 = 125 +/- 4 nM). Although JZTX-II had little or no effect on steady-state inactivation of the residual currents conducted by hNav1.5, it caused a 10 mV hyperpolarized shift of activation. Moreover, JZTX-II increased the recovery rate of hNav1.5 channels, which should lead to a shorter transition from the inactivation to closed state. JZTX-II dissociated from toxin-channel complex via extreme depolarization and subsequently rebound to the channel upon repolarization. Mutagenesis analyses showed that the domain IV (DIV) voltage-sensor domain (VSD) was critical for JZTX-II binding to hNav1.5 and some mutations located in S1-S2 and S3-S4 extracellular loops of hNav1.5 DIV additively reduced the toxin sensitivity of hNav1.5. Our data identified the mechanism underlying JZTX-II inhibiting hNav1.5, similar to scorpion a-toxins, involving binding to neurotoxin receptor site 3. (C) 2015 Elsevier Inc. All rights reserved.
摘要：
Oxytocin (OT) was reported to affect cognitive and emotional behavior by action in ventral tegmental area (VTA) and other brain areas. However, it is still unclear how OT activates VTA and related midline nucleus. Here, using patch-clamp recording, we studied the effects of OT on neuron activity in VTA and interfascicular nucleus (IF). OT dose-dependently and selectively excited small neurons located in medial VTA and the majority of IF neurons but not large neurons in lateral VIA. We found the hyperpolarization-activated current (I-h) and the membrane capacitance of OT-sensitive neuron were significantly smaller than those of OT-insensitive neurons. The action potential width of 01-sensitive neurons was about half that of OT-insensitive neurons. The OT effect was blocked by the OT receptor antagonist atosiban and WAY-267464 but not by tetrodotoxin, suggesting a direct postsynaptic activation of OT receptors. In addition, the phospholipase C (PLC) inhibitor U73122 antagonized the depolarization by OT. Both the nonselective cation channel (NSCC) antagonist SKF96365 and the Na+-Ca2+ exchanger (NCX) blocker SN-6 attenuated OT effects. These results suggested that the PLC signaling pathway coupling to NSCC and NCX contributes to the OT-mediated activation of neurons in medial VIA and IF. Taken together, our results indicate OT directly acted on medial WA and especially IF neurons to activate NSCC and NCX via PLC. The direct activation by OT of midbrain neurons may be one mechanism underlying OT effects on social behavior. (C) 2013 Elsevier Ltd. All rights reserved.
摘要：
肿瘤干细胞(Cancer stem cells, CSCs)是肿瘤组织中一小部分具有自我更新和致瘤性的细胞, 具有特殊的耐药机制, 与肿瘤的复发和治疗失败关系密切。微小RNA(microRNAs, miRNAs)是一类长度约为19~25个核苷酸的内源性非编码单链RNA, 能够通过调控相关靶基因的表达, 参与调控肿瘤干细胞增殖、凋亡、上皮-间质转化等重要的生命过程, 引起CSCs对化疗药物产生原发性多药耐药性。本论文就miRNAs在调控CSCs多药耐药性方面的研究进展作一综述。 Cancer stem cells(CSCs) are a subpopulation of tumor cells that possess self-renewal to regenerate themselves and tumor initiation capacity. CSCs possess special intrinsic mechanisms of resistance to chemotherapeutic drugs, leading to cancer recurrence and treatment failure. MicroRNAs (miRNAs) are short endogenous non-coding single-stranded RNAs that consist of 21 to 25 nucleotides. They play important roles in several cellular processes of CSCs by regulating the expression of related target genes, such as proliferation, apoptosis, and epithelial-mesenchymal transition (EMT), leading to primary CSCs drug resistance. The progress of miRNAs regulation in CSCs drug resistance was reviewed.
