Conopeptide Vt3.1 Preferentially Inhibits BK Potassium Channels Containing β4 Subunits via Electrostatic Interactions

BK channel β subunits (β1–β4) modulate the function of channels formed by slo1 subunits to produce tissue-specific phenotypes. The molecular mechanism of how the homologous β subunits differentially alter BK channel functions and the role of different BK channel functions in various physiologic processes remain unclear. By studying channels expressed in Xenopus laevis oocytes, we show a novel disulfide-cross-linked dimer conopeptide, Vt3.1 that preferentially inhibits BK channels containing the β4 subunit, which is most abundantly expressed in brain and important for neuronal functions. Vt3.1 inhibits the currents by a maximum of 71%, shifts the G-V relation by 45 mV approximately half-saturation concentrations, and alters both open and closed time of single channel activities, indicating that the toxin alters voltage dependence of the channel. Vt3.1 contains basic residues and inhibits voltage-dependent activation by electrostatic interactions with acidic residues in the extracellular loops of the slo1 and β4 subunits. These results suggest a large interaction surface between the slo1 subunit of BK channels and the β4 subunit, providing structural insight into the molecular interactions between slo1 and β4 subunits. The results also suggest that Vt3.1 is an excellent tool for studying β subunit modulation of BK channels and for understanding the physiological roles of BK channels in neurophysiology.     

A helical conotoxin from Conus imperialis has a novel cysteine framework and defines a new superfamily

Cone snail venoms are a rich source of peptides, many of which are potent and selective modulators of ion channels and receptors. Here we report the isolation and characterization of two novel conotoxins from the venom of Conus imperialis. These two toxins contain a novel cysteine framework, C-C-C-CC-C, which has not been found in other conotoxins described to date. We name it framework XXIII and designate the two toxins im23a and im23b; cDNAs of these toxins exhibit a novel signal peptide sequence, which defines a new K-superfamily. The disulfide connectivity of im23a has been mapped by chemical mapping of partially reduced intermediates and by NMR structure calculations, both of which establish a I-II, III-IV, V-VI pattern of disulfide bridges. This pattern was also confirmed by synthesis of im23a with orthogonal protection of individual cysteine residues. The solution structure of im23a reveals that im23a adopts a novel helical hairpin fold. A cluster of acidic residues on the surface of the molecule is able to bind calcium. The biological activity of the native and recombinant peptides was tested by injection into mice intracranially and intravenously to assess the effects on the central and peripheral nervous systems, respectively. Intracranial injection of im23a or im23b into mice induced excitatory symptoms; however, the biological target of these new toxins has yet to be identified.     

豆科植物SHR-SCR模块——根瘤“奠基细胞”的命运推手

豆科植物-根瘤菌共生固氮是可持续性农业氮肥的最重要来源。根瘤作为豆科植物共生固氮的一种特化植物侧生器官, 提供了根瘤菌生物固氮必需的微环境, 是根瘤菌的安身之本, 因此, 根瘤的正常发育是实现豆科植物-根瘤菌共生固氮的结构基础。根瘤器官的从头发生主要起始于根瘤菌诱导的根皮层细胞分裂。通常认为豆科植物的根皮层具备有别于非豆科植物根皮层的某种特异属性, 从而响应根瘤菌并与之建立固氮共生, 但长期以来该属性决定的分子机制一直不明确。近日, 中国科学院分子植物科学卓越创新中心王二涛团队以蒺藜苜蓿(Medicago truncatula)等豆科植物和拟南芥(Arabidopsis thaliana)等非豆科植物为研究对象, 发现豆科植物中保守的SHR-SCR干细胞模块决定了其皮层细胞分裂潜能从而赋予根瘤器官发生的命运。该研究揭示了豆科植物根瘤发育的全新机制, 提供了研究和理解植物-根瘤菌固氮共生进化的重要线索, 对提高豆科作物固氮效率和非豆科作物固氮工程具有重要意义。     

3种荒漠植物光合及叶绿素荧光对干旱胁迫的响应及抗旱性评价

利用盆栽试验结合人工浇水后自然耗水的方法测定干旱胁迫对梭梭、白刺、沙蒿3种荒漠植物叶片水分、光合及叶绿素荧光参数的影响,探讨各指标在干旱胁迫过程中的变化特征、响应机制及其与土壤水分的定量关系,并用隶属函数法对其进行抗旱性排序。结果表明：(1)3种植物叶片相对含水量(RWC)随干旱胁迫天数增加持续降低,最大水分亏缺(RWD)呈波动式上升趋势。(2)3种植物总叶绿素含量(Chl)和叶绿素a(Chla)、叶绿素b(Chlb)含量,以及梭梭、白刺类胡萝卜素含量均随胁迫天数增加而降低;沙蒿类胡萝卜素随土壤含水率降低逐渐升高。(3)梭梭、白刺、沙蒿叶片净光合速率(P_n)、蒸腾速率(T_r)、水分利用效率(WUE)等主要光合气体交换参数对土壤水分表现出明显的阈值响应,适宜的土壤含水率分别为8.04%～19.33%、4.17%～19.10%、6.48%～17.51%。(4)3种植物 PSⅡ最大光化学效率(Fv/F_m)、实际光化学效率(F_v′/F_m′)及光化学淬灭系数(qP)均随干旱胁迫天数增加和光照强度增大而降低,非光化学淬灭系数(NPQ)则呈逐渐上升趋势;干旱胁迫中后期,梭梭、沙蒿的F_v/F_m及F_v′/F_m′均下降,光合机构光合活性遭到破坏,电子传递受阻,PSⅡ反应中心受损,表现出光抑制,而白刺调节自身PSⅡ反应中心免受伤害的能力较强。(5)隶属函数法综合分析表明,3种植物耐旱能力大小依次为白刺>梭梭>沙蒿。研究发现,3种荒漠植物均可通过调节 PSⅡ反应中心开放程度与活性,对干旱胁迫表现出较强的耐性,胁迫后期植物PSⅡ反应中心关闭或不可逆失活,表现出光抑制。     

Molecular characterization of Giardia duodenalis isolates from police and farm dogs in China

To assess the potential zoonotic transmission of giardiasis from dogs in China, a total of 205 fecal specimens from dogs were screened for Giardia duodenalis using PCR and sequence analysis of the triosephosphate isomerase gene. The prevalence of G. duodenalis in dogs was 13.2% (27/205). The potentially zoonotic assemblage A and the dog-specific assemblage C was identified in 25 (12.2%) and two (1.0%) dogs, respectively. All assemblage A isolates belonged to sub-assemblage AI, genotype AI-1. Likewise, one subtype was found in assemblage C. The high occurrence of potentially zoonotic G. duodenalis subtype AI-1 in dogs that are in close contact with humans is of public health concern.     

Deciphering the effects of PYCR1 on cell function and its associated mechanism in hepatocellular carcinoma

Overexpression of pyrroline-5-carboxylate reductase 1 (PYCR1) has been associated with the development of certain cancers; however, no studies have specifically examined the role of PYCR1 in hepatocellular carcinoma (HCC). Based on The Cancer Genome Atlas expression array and meta-analysis conducted using the Gene Expression Omnibus database, we determined that PYCR1 was upregulated in HCC compared to adjacent nontumor tissues (P < 0.05). These data were verified using quantitative real-time polymerase chain reaction, western blotting, and immunohistochemistry analysis. Additionally, patients with low PYCR1 expression showed a higher overall survival rate than patients with high PYCR1 expression. Furthermore, PYCR1 overexpression was associated with the female sex, higher levels of alpha-fetoprotein, advanced clinical stages (III and IV), and a younger age (< 45 years old). Silencing of PYCR1 inhibited cell proliferation, invasive migration, epithelial-mesenchymal transition, and metastatic properties in HCC in vitro and in vivo. Using RNA sequencing and bioinformatics tools for data-dependent network analysis, we found binary relationships among PYCR1 and its interacting proteins in defined pathway modules. These findings indicated that PYCR1 played a multifunctional role in coordinating a variety of biological pathways involved in cell communication, cell proliferation and growth, cell migration, a mitogen-activated protein kinase cascade, ion binding, etc. The structural characteristics of key pathway components and PYCR1-interacting proteins were evaluated by molecular docking, and hotspot analysis showed that better affinities between PYCR1 and its interacting molecules were associated with the presence of arginine in the binding site. Finally, a candidate regulatory microRNA, miR-2355-5p, for PYCR1 mRNA was discovered in HCC. Overall, our study suggests that PYCR1 plays a vital role in HCC pathogenesis and may potentially serve as a molecular target for HCC treatment.     

Profiling of carotenoids in six microalgae (Eustigmatophyceae) and assessment of their β-carotene productions in bubble column photobioreactor

The profiles of carotenoids and production of β-carotene by six eustigmatophytes, Eustigmatos magnus, Eustigmatos polyphem, Eustigmatos vischeri, Vischeria helvetica, Vischeria punctata and Vischeria stellata, grown in a bubble column photobioreactor were measured. All eustigmatophytes contained β-carotene, violaxanthin and vaucheriaxanthin as their major carotenoids and accumulated large amount of β-carotene, which accounted for over 50?% of total carotenoids. Maximum intracellular β-carotene contents ranged 1.5–3.5?% of dry wt and in V. stellata it reached 5.9?% dry wt, accompanied by a biomass dry wt >7.3?g/l, with the highest up to 9.8?g/l. These eustigmatophytes are thus promising producers of β-carotene.     

我国沿海四爿藻的室内培养

在水产养殖中,四爿藻是一种重要的饵料资源,从我国沿海(包括广东、浙江、山东等省)采集到的海洋单细胞绿藻四爿藻,用毛细管法挑取进行单种培养,然后在固体培养基中稀释划线分离得到无菌纯培养物,利用改良的Guillard &; Ryther(Guillard F)培养基、海洋Ⅲ号培养基和改良的海洋Ⅲ号培养基对四爿藻进行了实验室培养。结果发现,改良的海洋Ⅲ号培养基中四爿藻的生长速率最快,最适pH范围为7．0～8．0,加入维生素B12(10μg·L^-1),也可以适当增加四爿藻的生长速率。这种改良的海洋Ⅲ号培养基配制简单,适合于水产养殖中四爿藻的规模生产。