Replica exchange molecular dynamics simulation of cross‐fibrillation of IAPP and PrP106‐126

Aggregation of proteins into amyloid is the central hallmark of a number of protein diseases. Most studies were carried out on the aggregation between proteins of similar species. However, it was observed that some patients with certain protein disease can easily acquire another unrelated protein disease. As such, it is also important to examine aggregation between proteins of different species. Usually aggregation between proteins of the same species can be attributed to the similarity between their respective amino acid sequences. In this article, we were motivated by an experimental study of aggregation between amylin (Islet Amyloid Polypeptide, IAPP) and prion_106‐126 (PrP106‐126) fragment (JACS, 2013, 135, 13582–9). It was found that the two non‐homologous peptides can aggregate quickly to form fibrils in the presence of negatively charged lipid bilayer. We attempted to elucidate the molecular mechanism of the early stage of dimerization of these two peptides through extensive replica exchange molecular dynamics simulations. Conformations consisting of various degrees of β‐sheets structures, both intra‐chain and inter‐chain, were found in the simulations. The conformations of the aggregated complex are very diverse, which suggests that the cross‐species fibrils formed between the two proteins are highly polymorphic. The driving forces are mainly hydrophobic interactions, including aromatic‐aliphatic interactions. The palindromic region of PrP106‐126 and SNNFGAIL region of IAPP were found to play important roles in the interaction. Our study sheds insight into the exciting research of protein cross‐fibrillation. Proteins 2016; 84:1134–1146. © 2016 Wiley Periodicals, Inc.     

MiR‐126a‐5p limits the formation of abdominal aortic aneurysm in mice and decreases ADAMTS‐4 expression

Abdominal aortic aneurysm (AAA) is a serious vascular disease featured by inflammatory infiltration in aortic wall, aortic dilatation and extracellular matrix (ECM) degradation. Dysregulation of microRNAs (miRNAs) is implicated in AAA progress. By profiling miRNA expression in mouse AAA tissues and control aortas, we noted that miR‐126a‐5p was down‐regulated by 18‐fold in AAA samples, which was further validated with real‐time qPCR. This study was performed to investigate miR‐126a‐5p's role in AAA formation. In vivo, a 28‐d infusion of 1 μg/kg/min Angiotensin (Ang) II was used to induce AAA formation in Apoe^‐/‐ mice. MiR‐126a‐5p (20 mg/kg; MIMAT0000137) or negative control (NC) agomirs were intravenously injected to mice on days 0, 7, 14 and 21 post‐Ang II infusion. Our data showed that miR‐126a‐5p overexpression significantly improved the survival and reduced aortic dilatation in Ang II‐infused mice. Elastic fragment and ECM degradation induced by Ang II were also ameliorated by miR‐126a‐5p. A strong up‐regulation of ADAM metallopeptidase with thrombospondin type 1 motif 4 (ADAMTS‐4), a secreted proteinase that regulates matrix degradation, was observed in smooth muscle cells (SMCs) of aortic tunica media, which was inhibited by miR‐126a‐5p. Dual‐luciferase results demonstrated ADAMTS‐4 as a new and valid target for miR‐126a‐5p. In vitro, human aortic SMCs (hASMCs) were stimulated by Ang II. Gain‐ and loss‐of‐function experiments further confirmed that miR‐126‐5p prevented Ang II‐induced ECM degradation, and reduced ADAMTS‐4 expression in hASMCs. In summary, our work demonstrates that miR‐126a‐5p limits experimental AAA formation and reduces ADAMTS‐4 expression in abdominal aortas.     

Protective effect of edaravone against PrP106‐126–induced PC12 cell death

The prion protein peptide PrP106‐126 induces cell apoptosis through mechanisms involving production of intracellular reactive oxygen species. The present study investigated the effects of edaravone, a potent free radical scavenger in clinical use, on cell cytotoxicity induced by PrP106‐126. Results showed that PrP106‐126 decreased PC12 cell viability in a dose‐ and time‐dependent manner. Edaravone significantly antagonized the cytotoxic effects of PrP106‐126. Mechanistically, PrP106‐126 decreased PC 12 intracellular glutathione (GSH) concentrations, decreased superoxide dismutase (SOD) enzyme activity, increased concentrations of the oxidation end product malondialdehyde (MDA), depolarized the mitochondrial membrane, and increased caspase‐3 activity. Edaravone alone did not affect GSH, SOD, or MDA but did effectively reverse all of the intracellular prooxidant effects induced by PrP106‐126 and inhibit induced apoptosis in PC12 cells. In conclusion, edaravone may be a viable candidate for the treatment of oxidative stress‐induced neurodegenerative disease. © 2010 Wiley Periodicals, Inc. J Biochem Mol Toxicol 24:235–241, 2010; View this article online at wileyonlinelibrary.com . DOI 10.1002/jbt.20330     

Activity and viability of polycyclic aromatic hydrocarbon‐degrading Sphingomonas sp. LB126 in a DC‐electrical field typical for electrobioremediation measures

There has been growing interest in employing electro‐bioremediation, a hybrid technology of bioremediation and electrokinetics for the treatment of contaminated soil. Knowledge however on the effect of weak electrokinetic conditions on the activity and viability of pollutant‐degrading microorganisms is scarce. Here we present data about the influence of direct current (DC) on the membrane integrity, adenosine triphosphate (ATP) pools, physico‐chemical cell surface properties, degradation kinetics and culturability of fluorene‐degrading Sphingomonas sp. LB126. Flow cytometry was applied to quantify the uptake of propidium iodide (PI) and the membrane potential‐related fluorescence intensities (MPRFI) of individual cells within a population. Adenosine tri‐phosphate contents and fluorene biodegradation rates of bulk cultures were determined and expressed on a per cell basis. The cells' surface hydrophobicity and electric charge were assessed by contact angle and zeta potential measurements respectively. Relative to the control, DC‐exposed cells exhibited up to 60% elevated intracellular ATP levels and yet remained unaffected on all other levels of cellular integrity and functionality tested. Our data suggest that direct current (X = 1 V cm^?1; J = 10.2 mA cm^?2) as typically used for electrobioremediation measures has no negative effect on the activity of the polycyclic aromatic hydrocarbon (PAH)‐degrading soil microorganism, thereby filling a serious gap of the current knowledge of the electrobioremediation methodology.     

Another functional frame‐shift polymorphism of DEFB126 (rs11467497) associated with male infertility

DEFB126 rs140685149 mutation was shown to cause sperm dysfunction and subfertility. Indel rs11467497 is another 4‐nucleotide frame‐shift mutation (151bp upstream of rs140685149) that leads to the premature termination of translation and the expression of peptide truncated at the carboxyl terminus. In the present study, we performed a comprehensive association study to check the contribution of rs140685149 and rs11467497 to male infertility. Our results confirmed the previous findings that there was no association between rs140685149 and sperm motility. In contrast, we found a significant association of another indel rs11467497 with male infertility. Moreover, rs11467497 was shown to be associated with higher number of round cells in the infertile males with low sperm motility. Surprisingly, the two mutations commonly existed in the sperm donors (n = 672), suggesting a potential application of the two indels in the screening for eligible sperm donors. Western blotting assays showed the sperms with rs140685149 2‐nt deletion tended to have unstable DEFB126 protein in contrast of no DEFB126 protein expressed in the sperms with rs11467497 4‐nt deletion, suggesting a more severe consequence caused by rs11467497 mutation. In conclusion, our study presented a significant contribution of another functional frame‐shift polymorphism of DEFB126 (rs11467497) to male infertility.     

MicroRNAs-126（miR-126）的生物学功能

MicroRNAs(MiRNAs)负向调控基因的表达,在细胞分化和细胞功能调节中起着重要作用,且涉及血管新生。应用克隆和测序方法,检测出miR-126在人内皮细胞高度表达。MiR-126与许多肿瘤关系密切,miR-126通过信号传导通路负向调控肿瘤细胞增殖、迁移和侵袭,并且抑制肿瘤生长延长患者存活率;相反的,在某些肿瘤中miR-126也可通过促进肿瘤细胞血管生长加速肿瘤进展,可能是未来作为相关肿瘤治疗的手段之一。本文就miR-126在生理进程和病理进程的表达及其作用进行综述。     

MicroRNA-126(miR-126)对血管调节的分子机制

脉管系统的结构,维护及重塑的精确调节对于血管的正常发育,组织损伤的应答和肿瘤的生长都是必不可少的。最近,越来越多的研究报道了非编码的RNAs,又叫做microRNAs调节内皮细胞对血管原刺激的应答反应。在体内,维持血管内皮细胞和血管的完整性方面miR-126是一种重要的血管生成信号调节因子。miR-126通过负性调控血管生长因子促进血管发生反应,这些血管因子包括血管内皮生长因子(VEGF)和碱性成纤维细胞生长因子(bFGF)。因此,miR-126表达的靶向作用也许对于血管过多或缺乏引起的相关疾病开辟了一种新的治疗方法,这些发现也证实了单一miRNA能够调节血管的完整性及血管生成,为调整血管的形态和功能提供了一个新的靶点。本文就当前miR-126对血管的调节及分子机制进行综述。     

miR-126&126* Restored Expressions Play a Tumor Suppressor Role by Directly Regulating ADAM9 and MMP7 in Melanoma

The abnormal expression of several microRNAs has a causal role in tumorigenesis with either antineoplastic or oncogenic functions. Here we demonstrated that miR-126 and miR-126* play a tumor suppressor role in human melanoma through the direct or indirect repression of several key oncogenic molecules. The expression levels of miR-126&126* were elevated in normal melanocytes and primary melanoma cell lines, whereas they markedly declined in metastatic cells. Indeed, the restored expression of miR-126&126* in two advanced melanoma cell lines was accompanied by a significant reduction of proliferation, invasion and chemotaxis in vitro as well as of growth and dissemination in vivo. In accordance, the reverse functional effects were obtained by knocking down miR-126&126* by transfecting antisense LNA oligonucleotides in melanoma cells. Looking for the effectors of these antineoplastic functions, we identified ADAM9 and MMP7, two metalloproteases playing a pivotal role in melanoma progression, as direct targets of miR-126&126*. In addition, as ADAM9 and MMP7 share a role in the proteolytic cleavage of the HB-EGF precursor, we looked for the effectiveness of this regulatory pathway in melanoma, confirming the decrease of HB-EGF activation as a consequence of miR-126&126*-dependent downmodulation of ADAM9 and MMP7. Finally, gene profile analyses showed that miR-126&126* reexpression was sufficient to inactivate other key signaling pathways involved in the oncogenic transformation, as PI3K/AKT and MAPK, and to restore melanogenesis, as indicated by KIT/MITF/TYR induction. In view of this miR-126&126* wide-ranging action, we believe that the replacement of these microRNAs might be considered a promising therapeutic approach.