scholarly journals Cysteine [2,4] Disulfide Bond as a New Modifiable Site of α-Conotoxin TxIB

Marine Drugs ◽  
2021 ◽  
Vol 19 (2) ◽  
pp. 119
Author(s):  
Baojian Zhang ◽  
Maomao Ren ◽  
Yang Xiong ◽  
Haonan Li ◽  
Yong Wu ◽  
...  
Keyword(s):  
Disulfide Bond ◽  
Nicotinic Acetylcholine Receptors ◽  
Acetylcholine Receptors ◽  
Therapeutic Agent ◽  
Inhibitory Effect ◽  
The Other ◽  
Nicotinic Acetylcholine ◽  
Exploitation And Utilization ◽  
Orthogonal Protection ◽  
Activity Loss

α-Conotoxin TxIB, a selective antagonist of α6/α3β2β3 nicotinic acetylcholine receptor, could be a potential therapeutic agent for addiction and Parkinson’s disease. As a peptide with a complex pharmacophoric conformation, it is important and difficult to find a modifiable site which can be modified effectively and efficiently without activity loss. In this study, three xylene scaffolds were individually reacted with one pair of the cysteine residues ([1,3] or [2,4]), and iodine oxidation was used to form a disulfide bond between the other pair. Overall, six analogs were synthesized with moderate isolated yields from 55% to 65%, which is four times higher than the traditional two-step oxidation with orthogonal protection on cysteines. The cysteine [2,4] modified analogs, with higher stability in human serum than native TxIB, showed obvious inhibitory effect and selectivity on α6/α3β2β3 nicotinic acetylcholine receptors (nAChRs), which was 100 times more than the cysteine [1,3] modified ones. This result demonstrated that the cysteine [2,4] disulfide bond is a new modifiable site of TxIB, and further modification can be a simple and feasible strategy for the exploitation and utilization of α-Conotoxin TxIB in drug discovery.

scholarly journals Interactions of Nereistoxin and Its Analogs with Vertebrate Nicotinic Acetylcholine Receptors and Molluscan ACh Binding Proteins

Marine Drugs ◽  
2022 ◽  
Vol 20 (1) ◽  
pp. 49
Author(s):  
William Kem ◽  
Kristin Andrud ◽  
Galen Bruno ◽  
Hong Xing ◽  
Ferenc Soti ◽  
...  
Keyword(s):  
Disulfide Bond ◽  
Nicotinic Acetylcholine Receptors ◽  
Acetylcholine Receptors ◽  
Specific Radioactivity ◽  
Electric Organ ◽  
Binding Affinities ◽  
Nicotinic Acetylcholine ◽  
High Affinity ◽  
High Specific Radioactivity ◽  
Alpha Bungarotoxin

Nereistoxin (NTX) is a marine toxin isolated from an annelid worm that lives along the coasts of Japan. Its insecticidal properties were discovered decades ago and this stimulated the development of a variety of insecticides such as Cartap that are readily transformed into NTX. One unusual feature of NTX is that it is a small cyclic molecule that contains a disulfide bond. In spite of its size, it acts as an antagonist at insect and mammalian nicotinic acetylcholine receptors (nAChRs). The functional importance of the disulfide bond was assessed by determining the effects of inserting a methylene group between the two sulfur atoms, creating dimethylaminodithiane (DMA-DT). We also assessed the effect of methylating the NTX and DMA-DT dimethylamino groups on binding to three vertebrate nAChRs. Radioligand receptor binding experiments were carried out using washed membranes from rat brain and fish (Torpedo) electric organ; [3H]-cytisine displacement was used to assess binding to the predominantly high affinity alpha4beta2 nAChRs and [125I]-alpha-bungarotoxin displacement was used to measure binding of NTX and analogs to the alpha7 and skeletal muscle type nAChRs. While the two quaternary nitrogen analogs, relative to their respective tertiary amines, displayed lower α4β2 nAChR binding affinities, both displayed much higher affinities for the Torpedo muscle nAChR and rat alpha7 brain receptors than their respective tertiary amine forms. The binding affinities of DMA-DT for the three nAChRs were lower than those of NTX and MeNTX. An AChBP mutant lacking the C loop disulfide bond that would potentially react with the NTX disulfide bond displayed an NTX affinity very similar to the parent AChBP. Inhibition of [3H]-epibatidine binding to the AChBPs was not affected by exposure to NTX or MeNTX for up to 24 hr prior to addition of the radioligand. Thus, the disulfide bond of NTX is not required to react with the vicinal disulfide in the AChBP C loop for inhibition of [3H]-epibatidine binding. However, a reversible disulfide interchange reaction of NTX with nAChRs might still occur, especially under reducing conditions. Labeled MeNTX, because it can be readily prepared with high specific radioactivity and possesses relatively high affinity for the nAChR-rich Torpedo nAChR, would be a useful probe to detect and identify any nereistoxin adducts.

scholarly journals Identification of Crucial Residues in α-Conotoxin EI Inhibiting Muscle Nicotinic Acetylcholine Receptor

Toxins ◽  
2019 ◽  
Vol 11 (10) ◽  
pp. 603 ◽  
Author(s):  
Jiong Ning ◽  
Jie Ren ◽  
Yang Xiong ◽  
Yong Wu ◽  
Manqi Zhangsun ◽  
...  
Keyword(s):  
Nicotinic Acetylcholine Receptors ◽  
Acetylcholine Receptors ◽  
Fold Increase ◽  
Cd Spectroscopy ◽  
Xenopus Laevis Oocytes ◽  
Muscle Type ◽  
Nicotinic Acetylcholine ◽  
Activity Loss ◽  
Spectroscopy Studies ◽  
Key Residues

α-Conotoxins (α-CTxs) are small disulfide-rich peptides from venom of Conus species that target nicotinic acetylcholine receptors (nAChRs). The muscle-type nAChRs have been recognized as a potential target for several diseases, such as myogenic disorders, muscle dystrophies, and myasthenia gravis. EI, an α4/7-CTx, mainly blocks α1β1δε nAChRs and has an extra N-terminal extension of three amino acids. In this study, the alanine scanning (Ala-scan) mutagenesis was applied in order to identify key residues of EI for binding with mouse α1β1δε nAChR. The Ala-substituted analogues were tested for their abilities of modulating muscle and neuronal nAChRs in Xenopus laevis oocytes using two-electrode voltage clamp (TEVC) recordings. Electrophysiological results indicated that the vital residues for functional activity of EI were His-7, Pro-8, Met-12, and Pro-15. These changes exhibited a significant decrease in potency of EI against mouse α1β1δε nAChR. Interestingly, replacing the critical serine (Ser) at position 13 with an alanine (Ala) residue resulted in a 2-fold increase in potency at the α1β1δε nAChR, and showed loss of activity on α3β2 and α3β4 nAChRs. Selectivity and potency of [S13A] EI was improved compared with wild-type EI (WT EI). In addition, the structure–activity relationship (SAR) of EI revealed that the “Arg1–Asn2–Hyp3” residues at the N-terminus conferred potency at the muscle-type nAChRs, and the deletion analogue △1–3 EI caused a total loss of activity at the α1β1δε nAChR. Circular dichroism (CD) spectroscopy studies demonstrated that activity loss of truncated analogue △1–3 EI for α1β1δε nAChR is attributed to disturbance of the secondary structure. In this report, an Ala-scan mutagenesis strategy is presented to identify crucial residues that are significantly affecting potency of E1 for mouse α1β1δε nAChR. It may also be important in remodeling of some novel ligands for inhibiting muscle-type nAChRs.

scholarly journals Molecular Regulation of α3β4 Nicotinic Acetylcholine Receptors by Lupeol in Cardiovascular System

2020 ◽  
Vol 21 (12) ◽  
pp. 4329
Author(s):  
Sanung Eom ◽  
Chaelin Kim ◽  
Hye Duck Yeom ◽  
Jaeeun Lee ◽  
Shinhui Lee ◽  
...  
Keyword(s):  
Natural Products ◽  
Nicotinic Acetylcholine Receptors ◽  
Acetylcholine Receptors ◽  
Animal Experiments ◽  
Inhibitory Effect ◽  
Inhibitory Effects ◽  
Nicotinic Acetylcholine ◽  
Electrode Voltage ◽  
Treatment Of Hypertension ◽  
Nicotine Acetylcholine Receptor

Cardiovascular disease (CVD) occurs globally and has a high mortality rate. The highest risk factor for developing CVD is high blood pressure. Currently, natural products are emerging for the treatment of hypertension to avoid the side effects of drugs. Among existing natural products, lupeol is known to be effective against hypertension in animal experiments. However, there exists no study regarding the molecular physiological evidence against the effects of lupeol. Consequently, we investigated the interaction of lupeol with α3β4 nicotinic acetylcholine receptors (nAChRs). In this study, we performed a two-electrode voltage-clamp technique to investigate the effect of lupeol on the α3β4 nicotine acetylcholine receptor using the oocytes of Xenopus laevis. Coapplication of acetylcholine and lupeol inhibited the activity of α3β4 nAChRs in a concentration-dependent, voltage-independent, and reversible manner. We also conducted a mutational experiment to investigate the influence of residues of the α3 and β4 subunits on lupeol binding with nAChRs. Double mutants of α3β4 (I37A/N132A), nAChRs significantly attenuated the inhibitory effects of lupeol compared to wild-type α3β4 nAChRs. A characteristic of α3β4 nAChRs is their effect on transmission in the cardiac sympathetic ganglion. Overall, it is hypothesized that lupeol lowers hypertension by mediating its effects on α3β4 nAChRs. The interaction between lupeol and α3β4 nAChRs provides evidence against its effect on hypertension at the molecular-cell level. In conclusion, the inhibitory effect of lupeol is proposed as a novel therapeutic approach involving the antihypertensive targeting of α3β4 nAChRs. Furthermore, it is proposed that the molecular basis of the interaction between lupeol and α3β4 nAChRs would be helpful in cardiac-pharmacology research and therapeutics.

scholarly journals The 3/4- and 3/6-Subfamily Variants of α-Conotoxins GI and MI Exhibit Potent Inhibitory Activity against Muscular Nicotinic Acetylcholine Receptors

Marine Drugs ◽  
2021 ◽  
Vol 19 (12) ◽  
pp. 705
Author(s):  
Xiaoli Ma ◽  
Qiuyuan Huang ◽  
Shuo Yu ◽  
Shujing Xu ◽  
Yue Huang ◽  
...  
Keyword(s):  
Disulfide Bond ◽  
Nicotinic Acetylcholine Receptors ◽  
Disulfide Bonds ◽  
Acetylcholine Receptors ◽  
Basic Amino Acid ◽  
Wild Type ◽  
Nicotinic Acetylcholine ◽  
Potent Inhibition ◽  
Potent Inhibitory Activity

α-Conotoxins GI and MI belong to the 3/5 subfamily of α-conotoxins and potently inhibit muscular nicotinic acetylcholine receptors (nAChRs). To date, no 3/4- or 3/6-subfamily α-conotoxins have been reported to inhibit muscular nAChRs. In the present study, a series of new 3/4-, 3/6-, and 3/7-subfamily GI and MI variants were synthesized and functionally characterized by modifications of loop2. The results show that the 3/4-subfamily GI variant GI[∆8G]-II and the 3/6-subfamily variants GI[+13A], GI[+13R], and GI[+13K] displayed potent inhibition of muscular nAChRs expressed in Xenopus oocytes, with an IC50 of 45.4–73.4 nM, similar to or slightly lower than that of wild-type GI (42.0 nM). The toxicity of these GI variants in mice appeared to be about a half to a quarter of that of wild-type GI. At the same time, the 3/7-subfamily GI variants showed significantly lower in vitro potency and toxicity. On the other hand, similar to the 3/6-subfamily GI variants, the 3/6-subfamily MI variants MI[+14R] and MI[+14K] were also active after the addition of a basic amino acid, Arg or Lys, in loop2, but the activity was not maintained for the 3/4-subfamily MI variant MI [∆9G]. Interestingly, the disulfide bond connectivity “C1–C4, C2–C3” in the 3/4-subfamily variant GI[∆8G]-II was significantly more potent than the “C1–C3, C2–C4” connectivity found in wild-type GI and MI, suggesting that disulfide bond connectivity is easily affected in the rigid 3/4-subfamily α-conotoxins and that the disulfide bonds significantly impact the variants’ function. This work is the first to demonstrate that 3/4- and 3/6-subfamily α-conotoxins potently inhibit muscular nAChRs, expanding our knowledge of α-conotoxins and providing new motifs for their further modifications.

Nicotinic acetylcholine receptors in the patients with Parkinson's disease: 5IA-SPECT

2005 ◽  
Vol 25 (1_suppl) ◽  
pp. S586-S586 ◽  
Author(s):  
Kazuo Hashikawa ◽  
Hidefumi Yoshida ◽  
Nobukatsu Sawamoto ◽  
Shigetoshi Takaya ◽  
Chihiro Namiki ◽  
...  
Keyword(s):  
Parkinson’S Disease ◽  
Parkinson's Disease ◽  
Nicotinic Acetylcholine Receptors ◽  
Acetylcholine Receptors ◽  
Nicotinic Acetylcholine
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