Molecular underpinning of intracellular pH regulation on TMEM16F

TMEM16F, a dual-function phospholipid scramblase and ion channel, is important in blood coagulation, skeleton development, HIV infection, and cell fusion. Despite advances in understanding its structure and activation mechanism, how TMEM16F is regulated by intracellular factors remains largely elusive. Here we report that TMEM16F lipid scrambling and ion channel activities are strongly influenced by intracellular pH (pH_i). We found that low pH_i attenuates, whereas high pH_i potentiates, TMEM16F channel and scramblase activation under physiological concentrations of intracellular Ca²⁺ ([Ca²⁺]_i). We further demonstrate that TMEM16F pH_i sensitivity depends on [Ca²⁺]_i and exhibits a bell-shaped relationship with [Ca²⁺]_i: TMEM16F channel activation becomes increasingly pH_i sensitive from resting [Ca²⁺]_i to micromolar [Ca²⁺]_i, but when [Ca²⁺]_i increases beyond 15 µM, pH_i sensitivity gradually diminishes. The mutation of a Ca²⁺-binding residue that markedly reduces TMEM16F Ca²⁺ sensitivity (E667Q) maintains the bell-shaped relationship between pH_i sensitivity and Ca²⁺ but causes a dramatic shift of the peak [Ca²⁺]_i from 15 µM to 3 mM. Our biophysical characterizations thus pinpoint that the pH_i regulatory effects on TMEM16F stem from the competition between Ca²⁺ and protons for the primary Ca²⁺-binding residues in the pore. Within the physiological [Ca²⁺]_i range, the protonation state of the primary Ca²⁺-binding sites influences Ca²⁺ binding and regulates TMEM16F activation. Our findings thus uncover a regulatory mechanism of TMEM16F by pH_i and shine light on our understanding of the pathophysiological roles of TMEM16F in diseases with dysregulated pH_i, including cancer.     

How competitive intransitivity and niche overlap affect spatial coexistence

Competitive intransitivity is mostly considered outside the main body of coexistence theories that rely primarily on the role of niche overlap and differentiation. How the interplay of competitive intransitivity and niche overlap jointly affects species coexistence has received little attention. Here, we consider a rock–paper–scissors competition system where interactions between species can represent the full spectra of transitive–intransitive continuum and niche overlap/differentiation under different levels of competition asymmetry. By comparing results from pair approximation that only considers interference competition between neighbouring cells in spatial lattices, with those under the mean-field assumption, we show that 1) species coexistence under transitive competition is only possible at high niche differentiation; 2) in communities with partial or pure intransitive interactions, high levels of niche overlap are not necessary to beget species extinction; and 3) strong spatial clustering can widen the condition for intransitive loops to facilitate species coexistence. The two mechanisms, competitive intransitivity and niche differentiation, can support species persistence and coexistence, either separately or in combination. Finally, the contribution of intransitive loops to species coexistence can be enhanced by strong local spatial correlations, modulated and maximised by moderate competition asymmetry. Our study, therefore, provides a bridge to link intransitive competition to other generic ecological theories of species coexistence.     

葡萄VvIQD10果形相关基因定位及其互作研究

以葡萄6个不同果形品种盛花期花序为材料,通过荧光定量PCR方法分析比较葡萄IQ67结构域(IQ67 domain, IQD)基因家族成员VvIQD10的表达;从椭圆形葡萄品种‘天山’中克隆出VvIQD10基因编码区序列,对其进行生物信息学分析,采用亚细胞定位瞬时表达载体转化烟草的方法研究VvIQD10蛋白在细胞中的分布情况,并通过酵母双杂交实验和双分子荧光互补试验进行蛋白互作研究。结果表明:(1)VvIQD10基因在长果形葡萄品种中的表达量高于近圆形葡萄品种。(2)VvIQD10基因开放阅读框长度为1 401 bp,编码466个氨基酸。(3)VvIQD10蛋白为不稳定亲水性蛋白,无信号肽和跨膜区,但含保守的IQ67结构域,主要结构为α螺旋和随机卷曲,与猕猴桃IQD家族成员(PSS09955.1)亲缘关系最为接近。(4)VvIQD10蛋白主要定位于微管和质膜,并且直接与细胞骨架组织相关蛋白——钙调素类蛋白(VvCML)相互作用。研究认为,VvIQD10基因可能参与葡萄果形调控,葡萄VvCML蛋白从胞质到微管的募集依赖于VvIQD10,推测VvIQD10蛋白可能通过和钙调素类蛋白相结合来调控细胞骨架运动,进而参与葡萄果实形状的变化。     

C19orf66 Inhibits Japanese Encephalitis Virus Replication by Targeting -1 PRF and the NS3 Protein

Virologica Sinica - The Japanese encephalitis serogroup of the neurogenic Flavivirus has a specific feature that expresses a non-structural protein NS1′ produced through a programmed -1...     

Th2 polarization in target organs is involved in the alleviation of pathological damage mediated by transplanting granulocyte colony-stimulating factor-primed donor T cells

Acute graft-versus-host disease(a GVHD) is caused by allo-activated donor T cells infiltrating target organs. As a regulator of immune function, granulocyte colony-stimulating factor(G-CSF) has been demonstrated to relieve the a GVHD reaction.However, the role of G-CSF-primed donor Tcells in specific target organs is still unknown. In this study, we employed a classical MHC-mismatched transplantation mouse model(C57BL/6 into BALB/c) and found that recipient mice transplanted with GCSF-primed T cells exhibited prolonged survival compared with that of the PBS-treated group. This protective function against GVHD mediated by G-CSF-primed donor T cells was further confirmed by decreased clinical and pathological scores in this a GVHD mouse model, especially in the lung and gut. Moreover, we found that Tcells polarized towards Th2 cells and regulatory T cells were increased in specific target organs. In addition, G-CSF treatment inhibited inducible co-stimulator(ICOS) expression and increased the expression of tolerance-related genes in recipient mice. Our study provides new insight into the immune regulatory effects of G-CSF on T cell-mediated a GVHD, especially for its precise regulation in GVHD target organs.     

The spatial variation of soil bacterial community assembly processes affects the accuracy of source tracking in ten major Chinese cities

Urban soils harbor billions of bacterial cells and millions of species. However, the distribution patterns and assembly processes of bacterial communities remain largely uncharacterized in urban soils. It is also unknown if we can use the bacteria to track soil sources to certain cities and districts. Here, Illumina MiSeq sequencing was used to survey soil bacterial communities from 529 random plots spanning 61 districts and 10 major cities in China. Over a 3,000 km range, community similarity declined with increasing geographic distance(Mantel r=0.62), and community composition was clustered by city(R~2=0.50). Within cities(100 km), the aforementioned biogeographic patterns were weakened. Process analysis showed that homogenizing dispersal and dispersal limitation dominated soil bacterial assembly at small and large spatial scales, respectively. Accordingly, the probabilities of accurately tracking random soil sources to certain cities and districts were 90.0% and 66.7%, respectively. When the tested samples originated from cities that were more than 1,265 km apart, the soil sources could be identified with nearly 100% accuracy. Overall, this study demonstrates the strong distance-decay relationship and the clear geographic zoning of urban soil bacterial communities among cities. The varied importance of different community assembly processes at multiple spatial scales strongly affects the accuracy of microbial source tracking.     

Interactions between commensal bacteria and viral infection: insights for viral disease control in farmed animals

Viral diseases cause serious economic loss in farmed animals industry. However, the efficacy of remedies for viral infection in farmed animals is limited, and treatment strategies are generally lacking for aquatic animals. Interactions of commensal microbiota and viral infection have been studied in recent years, demonstrating a third player in the interaction between hosts and viruses. Here, we discuss recent developments in the research of interactions between commensal bacteria and viral infection,including both promotion and inhibition effect of commensal bacteria on viral pathogenesis, as well as the impact of viral infection on commensal microbiota. The antiviral effect of commensal bacteria is mostly achieved through priming or regulation of the host immune responses, involving differential microbial components and host signaling pathways, and gives rise to various antiviral probiotics. Moreover, we summarize studies related to the interaction between commensal bacteria and viral infection in farmed animals, including pigs, chickens, fish and invertebrate species. Further studies in this area will deepen our understanding of antiviral immunity of farmed animals in the context of commensal microbiota, and promote the development of novel strategies for treatment of viral diseases in farmed animals.     

An inducible constitutive expression system in Bombyx mori mediated by phiC31 integrase

Inducible gene-expression systems play important roles in gene functional assays in the post-genome era. Streptomyces phage-derived phiC31 integrase, which mediates an irreversible site-specific cassette exchange between the phage attachment site (attP) and the bacterial attachment site (attB), provides a promising option for the construction of a controllable gene-expression system. Here, we report a phiC31 integrase-mediated promoter flip system (FLIP) for the inducible expression of target genes in silkworm (Bombyx mori). First, we constructed a FLIP reporter system, in which a BmAct4 promoter with enhanced translational efficiency was flanked by the attB and attP sites in a head-to-head orientation and further linked in a reverse orientation to a DsRed reporter gene. The coexpression of a C-terminal modified phiC31-NLS integrase carrying a simian virus 40 (SV40) nuclear localization signal (NLS) effectively flipped the BmAct4 promoter through an attB/attP exchange, thereby activating the downstream expression of DsRed in a silkworm embryo-derived cell line, BmE. Subsequently, the FLIP system, together with a system continuously expressing the phiC31-NLS integrase, was used to construct binary transgenic silkworm lines. Hybridization between FLIP and phiC31-NLS transgenic silkworm lines resulted in the successful flipping of the BmAct4 promoter, with an approximately 39% heritable transformation efficiency in silkworm offspring, leading to the constitutive and high-level expression of DsRed in silkworms, which accounted for approximately 0.81% of the silkworm pupal weight. Our successful development of the FLIP system offers an effective alternative for manipulating gene expression in silkworms and other lepidopteran species.