企业邮箱
天下生命科学前沿动态周报（七十）
（12.12-12.18/2011）
一竞技国际集团:陶国新
主要内容：特别的GATA因子是内胚层上皮-间质转化的守旧诱导物；影响疤痕形成的物理因素；卵白亚磺�；谙赴藕磐分械闹饕骼碜饔�；HIV病毒进入细胞核的“钥匙”；确定造血干细胞的起源；葡聚糖水凝胶对三度烧伤的治疗效果。
焦点动态：影响疤痕形成的物理因素。
1. 特别的GATA因子是内胚层上皮-间质转化的守旧诱导物
【动态】
上皮-间质转化（EMT）使静止的上皮细胞转变为有移动能力的间充质细胞状态，西班牙科学家最近证实果蝇内胚层的EMT依赖GATA因子Srp。当Srp异位激活后作用类似于高效的EMT触发剂。Srp通过下调但不阻断联接卵白dE钙粘素（dE-Cad）而影响内胚层的EMT。并且，Srp通过直接抑制crumbs(crb)基因重定位dE-Cad。他们的研究还显示Srp的直接同源物人GATA-6在哺乳动物细胞中诱导类似的转变。类似于Srp，人GATA-6通过下调但不阻断E-Cad起作用，并诱导抑制Crumbs 的直接同源物crb2。总的看来，他们的研究发明一套在发育学和病理学中GATA因子是选择性的守旧的触发物抑制上皮细胞的上皮特征而付与其迁徙能力。
【点评】
该研究发明上皮-间质转化依赖GATA因子，关于深入相识生物发育以及肿瘤生长有推行动用。
【参考论文】
Developmental Cell, 2011; 21 (6): 1051 DOI: 10.1016/j.devcel.2011.10.005
Specific GATA Factors Act as Conserved Inducers of an Endodermal-EMT
The epithelial-to-mesenchymal transition (EMT) converts cells from static epithelial to migratory mesenchymal states (Hay, 1995 ). Here, we demonstrate that EMT in the Drosophila endoderm is dependent on the GATA-factor Serpent (Srp), and that Srp acts as a potent trigger for this transition when activated ectopically. We show that Srp affects endodermal-EMT through a downregulation of junctional dE-Cadherin (dE-Cad) protein, without a block in its transcription. Moreover, the relocalization of dE-Cad is achieved through the direct repression of crumbs (crb) by Srp. Finally, we show that hGATA-6, an ortholog of Srp, induces a similar transition in mammalian cells. Similar to Srp, hGATA-6 acts through the downregulation of junctional E-Cad, without blocking its transcription, and induces the repression of a Crumbs ortholog, crb2. Together, these results identify a set of GATA factors as a conserved alternative trigger to repress epithelial characteristics and confer migratory capabilities on epithelial cells in development and pathogenesis.
2. 影响疤痕形成的物理因素
【动态】
纤维增生兴旺是受伤后常见的并发症，缘故原由尚不明晰。一个常被忽视的创伤修复的要害因素是机械力，机械力通详尽胞内包括焦点粘连激酶（FAK）在内的焦点粘连因素调理细胞-基质相互作用。美国斯坦福大学的科学家最近报道了皮肤损伤后FAK被激活，这一历程被机械力负载所增强。在疤痕增生动物模子中，敲除成纤维细胞特异性的FAK的老鼠显着比比照老鼠炎症和纤维化都少。他们发明FAK通详尽胞外相关激酶（ERK）物理性的触发单核细胞化学引诱物-1（MCP-1，也叫CCL2）的渗透，这是一种与人体纤维病变有关的高效趋化因子。类似地，敲除MCP-1的老鼠形成的疤痕最小，意味着炎症趋化因子途径是FAK通过力传导诱导纤维化的主要机理。用小分子抑制FAK能够在人体细胞中阻断这些作用，并且通过调理MCP-1信号和炎症细胞的招募而镌汰实验动物的疤痕形成。这些发明合在一起批注机械力通过炎症FAK–ERK–MCP-1途径调理纤维化以及针对FAK的分子战略能够有用的扫除机械力与病理疤痕形成的关联。
【点评】
该研究剖析了机械力可以通过增强炎症反应诱导组织纤维化增生。扫除机械力的影响能够改善纤维化状态。
【参考论文】
Nature Medicine, 2011; DOI: 10.1038/nm.2574
Focal adhesion kinase links mechanical force to skin fibrosis via inflammatory signaling
Victor W Wong, Kristine C Rustad, Satoshi Akaishi, et al.
Exuberant fibroproliferation is a common complication after injury for reasons that are not well understood. One key component of wound repair that is often overlooked is mechanical force, which regulates cell-matrix interactions through intracellular focal adhesion components, including focal adhesion kinase (FAK). Here we report that FAK is activated after cutaneous injury and that this process is potentiated by mechanical loading. Fibroblast-specific FAK knockout mice have substantially less inflammation and fibrosis than control mice in a model of hypertrophic scar formation. We show that FAK acts through extracellular-related kinase (ERK) to mechanically trigger the secretion of monocyte chemoattractant protein-1 (MCP-1, also known as CCL2), a potent chemokine that is linked to human fibrotic disorders. Similarly, MCP-1 knockout mice form minimal scars, indicating that inflammatory chemokine pathways are a major mechanism by which FAK mechanotransduction induces fibrosis. Small-molecule inhibition of FAK blocks these effects in human cells and reduces scar formation in vivo through attenuated MCP-1 signaling and inflammatory cell recruitment. These findings collectively indicate that physical force regulates fibrosis through inflammatory FAK–ERK–MCP-1 pathways and that molecular strategies targeting FAK can effectively uncouple mechanical force from pathologic scar formation.
3. 卵白亚磺�；谙赴藕磐分械闹饕骼碜饔�
【动态】
卵白亚磺�；且恢址牒笮奘�，在高等真核生物中逐渐显示出其主要性。可是，研究其多样性的作用照旧很有挑战性的，尤其是在自然的细胞情形内。美国科学家最近开发使用DYn-2，一种新的化学选择性探针检测人体细胞内的亚磺�；穆寻�。他们的研究批注表皮生长因子受体介导的信号导致过氧化氢的爆发和下游卵白的氧化。另外，他们还证实DYn-2能够细胞内亚磺�；实牟畋�，这种差别与靶卵白的定位差别有关。他们还发明过氧化氢在表皮生长因子受体的要害活性位点半胱氨酸（Cys797）举行直接修饰能够增强其酪氨酸激酶活性。总起来看，他们的发明显示亚磺�；抢嗨朴诹姿峄娜中孕藕呕�，牵涉到其他受体酪氨酸激酶和针对卵白中氧化敏感的半胱氨酸的不可逆抑制剂。
【点评】
卵白亚磺�；谙赴藕诺骼碇凶饔玫奶岣�，会增进以调理卵白亚磺�；康牡囊┪镅芯亢涂�。可是更主要的意义在于，这批注卵白翻译后修饰有多种方法都很主要，生命自身的调理远比我们已知的更为重大巧妙。
【参考论文】
Nature Chemical Biology, 11 December 2011 DOI: 10.1038/nchembio.736
Peroxide-dependent sulfenylation of the EGFR catalytic site enhances kinase activity
Candice E Paulsen, Thu H Truong, Francisco J Garcia, et al.
Protein sulfenylation is a post-translational modification of emerging importance in higher eukaryotes. However, investigation of its diverse roles remains challenging, particularly within a native cellular environment. Herein we report the development and application of DYn-2, a new chemoselective probe for detecting sulfenylated proteins in human cells. These studies show that epidermal growth factor receptor–mediated signaling results in H2O2 production and oxidation of downstream proteins. In addition, we demonstrate that DYn-2 has the ability to detect differences in sulfenylation rates within the cell, which are associated with differences in target protein localization. We also show that the direct modification of epidermal growth factor receptor by H2O2 at a critical active site cysteine (Cys797) enhances its tyrosine kinase activity. Collectively, our findings reveal sulfenylation as a global signaling mechanism that is akin to phosphorylation and has regulatory implications for other receptor tyrosine kinases and irreversible inhibitors that target oxidant-sensitive cysteines in proteins.
4. HIV病毒进入细胞核的“钥匙”
【动态】
慢病毒像HIV-1横穿核膜孔复合物（NPC）并熏染终末分解的不破碎细胞，它们怎样做到的还不清晰。以前的研究已发明胞浆NPC卵白Nup358/RaBP2是HIV-1辅因子。最近英国和美国的科学家报道HIV-1病毒壳（CA）直接团结到Nup358/RaBP2的亲环素（cyclophilin, Cyp）结构域。该Cyp与三重TRIM5的融合爆发了一种新的HIV-1复制抑制剂，与体内的一种相互作用一致。与CypA团结到HIV-1 CA相反，Nup358的团结对环孢霉素的抑制不敏感，借此可以区分CypA和Nup358的影响。抑制CypA镌汰了对Nup358和核篮卵白Nup153的依赖，批注CypA调理病毒加入的核内转运机制的选择。相比野生型病毒，HIV-1 病毒壳的Cyp团结突变G89V和P90A在高密度转录单位的基因区域有更多整合和相关特征。野生型病毒在环孢霉素保存时的整合倾向性与高密度转录区域有类似的改变。相反，HIV-1 CA在使抱病毒对Nup358 或 TRN-SR2 删除（CA N74D, N57A）更不敏感的壳外貌另一区域的改变导致整合到少有转录单位的基因区域。两组CA突变在HeLa细胞和人单核细胞源巨噬细胞的复制中受到损害。他们的发明将HIV-1衔接亲环素与整合目的和复制效率联系起来，并对病毒亲环素招募的守旧性提供了新看法。
【点评】
该研究剖析了艾滋病毒HIV-1与亲环素的相互作用决议了往核内转运的途径、整合的目的以及复制的效率。关于开发新的抗艾滋病药物会有推行动用。
【参考论文】
PLoS Pathogens, 2011; 7 (12): e1002439 DOI: 10.1371/journal.ppat.1002439
HIV-1 Capsid-Cyclophilin Interactions Determine Nuclear Import Pathway, Integration Targeting and Replication Efficiency
Torsten Schaller, Karen E. Ocwieja, Jane Rasaiyaah, et al.
Lentiviruses such as HIV-1 traverse nuclear pore complexes (NPC) and infect terminally differentiated non-dividing cells, but how they do this is unclear. The cytoplasmic NPC protein Nup358/RanBP2 was identified as an HIV-1 co-factor in previous studies. Here we report that HIV-1 capsid (CA) binds directly to the cyclophilin domain of Nup358/RanBP2. Fusion of the Nup358/RanBP2 cyclophilin (Cyp) domain to the tripartite motif of TRIM5 created a novel inhibitor of HIV-1 replication, consistent with an interaction in vivo. In contrast to CypA binding to HIV-1 CA, Nup358 binding is insensitive to inhibition with cyclosporine, allowing contributions from CypA and Nup358 to be distinguished. Inhibition of CypA reduced dependence on Nup358 and the nuclear basket protein Nup153, suggesting that CypA regulates the choice of the nuclear import machinery that is engaged by the virus. HIV-1 cyclophilin-binding mutants CA G89V and P90A favored integration in genomic regions with a higher density of transcription units and associated features than wild type virus. Integration preference of wild type virus in the presence of cyclosporine was similarly altered to regions of higher transcription density. In contrast, HIV-1 CA alterations in another patch on the capsid surface that render the virus less sensitive to Nup358 or TRN-SR2 depletion (CA N74D, N57A) resulted in integration in genomic regions sparse in transcription units. Both groups of CA mutants are impaired in replication in HeLa cells and human monocyte derived macrophages. Our findings link HIV-1 engagement of cyclophilins with both integration targeting and replication efficiency and provide insight into the conservation of viral cyclophilin recruitment.
5. 确定造血干细胞的起源
【动态】
造血干细胞（HSCs）和更早一波的限制性的网织红细胞/骨髓祖细胞（EMPs）在孕体生血内皮细胞时区脱离来。从胚胎干细胞或诱导多醒目细胞能够体外生产EMPs，但生产HSCs的起劲大多失败了。EMPS和HSCs的形成都需要转录因子Runx1及其非DNA-团结朋侪核团结因子β (CBFβ)。美国科学家最近的研究显示孕体中EMP和HSC形成中对CBFβ的需要在时间和空间上是差别的。在表达Tek的细胞中CBFβ的泛内皮表达对形成EMP已经足够，但对HSC形成却还不敷。另一方面，在表达Ly6a的细胞中，CBFβ的表达对形成HSC足够但对形成EMP还不敷。其数据批注EMPs和HSCs是从生血内皮细胞的差别群分解来的，而Ly6a特异性的标记爆发HSC的生血内皮。
【点评】
该研究较量准确地确定了造血干细胞的前体细胞并发明了其特异性标记Ly6a。
【参考论文】
Cell Stem Cell, 2011; 9 (6): 541 DOI: 10.1016/j.stem.2011.10.003
Erythroid/Myeloid Progenitors and Hematopoietic Stem Cells Originate from Distinct Populations of Endothelial Cells
Michael J. Chen, Yan Li, Maria Elena De Obaldia, et al.
Hematopoietic stem cells (HSCs) and an earlier wave of definitive erythroid/myeloid progenitors (EMPs) differentiate from hemogenic endothelial cells in the conceptus. EMPs can be generated in vitro from embryonic or induced pluripotent stem cells, but efforts to produce HSCs have largely failed. The formation of both EMPs and HSCs requires the transcription factor Runx1 and its non-DNA binding partner core binding factor β (CBFβ). Here we show that the requirements for CBFβ in EMP and HSC formation in the conceptus are temporally and spatially distinct. Panendothelial expression of CBFβ in Tek-expressing cells was sufficient for EMP formation, but was not adequate for HSC formation. Expression of CBFβ in Ly6a-expressing cells, on the other hand, was sufficient for HSC, but not EMP, formation. The data indicate that EMPs and HSCs differentiate from distinct populations of hemogenic endothelial cells, with Ly6a expression specifically marking the HSC-generating hemogenic endothelium.
6. 葡聚糖水凝胶对三度烧伤的治疗效果
【动态】
对深度烧伤的创伤愈合效果而言血管新生是个要害的决议因素。美国约翰霍普金斯医学院的科学家以为基于葡聚糖的水凝胶能够作为指导性平台增进3度烧伤的血管新生和皮肤再生。葡聚糖水凝胶软而韧，有时机提高烧伤治疗效果。他们首先制订了一套用葡聚糖水凝胶治疗老鼠烧伤的程序，其中遵照临床规范削除全厚层烧伤皮肤，然后用葡聚糖水凝胶和敷料层笼罩伤处。该程序能包管整个愈合时代水凝胶能够完好无损牢靠在伤处以简化烧伤治疗的处置惩罚。一项3周的比照研究批注葡聚糖水凝胶增进了带有完整附件的真皮再生。水凝胶平台增进了早期炎症细胞浸润导致其快速降解，增进了生血管细胞向愈合中伤处的浸润。内皮细胞进入水凝胶平台在第7日最先能够新生血管，使得血流比治疗和不治疗的比照组显著增添。到第21天，用水凝胶治疗的烧伤处发天生熟的上皮结构有毛囊和皮脂腺。治疗5周后，水凝胶增进了头发的新生，并且表皮形态和厚度与正常老鼠皮肤相似。总的看来，他们的证据显示定制的单独使用葡聚糖水凝胶，不加任何生长因子、细胞因子或细胞，能够增进显着的血管新生和皮肤再生，并可能引出新的皮肤创伤治疗要领。
【点评】
该研究发明在烧伤老鼠削痂后单独使用葡聚糖水凝胶能够增进血管新生和正常皮肤的再生。
【参考论文】
PNAS December 27, 2011 vol. 108 no. 52 20976-20981
Dextran hydrogel scaffolds enhance angiogenic responses and promote complete skin regeneration during burn wound healing
Guoming Suna, Xianjie Zhangb, Yu-I Shena, et al.
Neovascularization is a critical determinant of wound-healing outcomes for deep burn injuries. We hypothesize that dextran-based hydrogels can serve as instructive scaffolds to promote neovascularization and skin regeneration in third-degree burn wounds. Dextran hydrogels are soft and pliable, offering opportunities to improve the management of burn wound treatment. We first developed a procedure to treat burn wounds on mice with dextran hydrogels. In this procedure, we followed clinical practice of wound excision to remove full-thickness burned skin, and then covered the wound with the dextran hydrogel and a dressing layer. Our procedure allows the hydrogel to remain intact and securely in place during the entire healing period, thus offering opportunities to simplify the management of burn wound treatment. A 3-week comparative study indicated that dextran hydrogel promoted dermal regeneration with complete skin appendages. The hydrogel scaffold facilitated early inflammatory cell infiltration that led to its rapid degradation, promoting the infiltration of angiogenic cells into the healing wounds. Endothelial cells homed into the hydrogel scaffolds to enable neovascularization by day 7, resulting in an increased blood flow significantly greater than treated and untreated controls. By day 21, burn wounds treated with hydrogel developed a mature epithelial structure with hair follicles and sebaceous glands. After 5 weeks of treatment, the hydrogel scaffolds promoted new hair growth and epidermal morphology and thickness similar to normal mouse skin. Collectively, our evidence shows that customized dextran-based hydrogel alone, with no additional growth factors, cytokines, or cells, promoted remarkable neovascularization and skin regeneration and may lead to novel treatments for dermal wounds.