世界生命科學(xué)前沿動(dòng)態(tài)周報(bào)（七十）

（12.12-12.18/2011）
美寶國(guó)際集團(tuán):陶國(guó)新 

主要內(nèi)容：特別的GATA因子是內(nèi)胚層上皮-間質(zhì)轉(zhuǎn)化的保守誘導(dǎo)物；影響疤痕形成的物理因素；蛋白亞磺?；诩?xì)胞信號(hào)通路中的重要調(diào)節(jié)作用；HIV病毒進(jìn)入細(xì)胞核的“鑰匙”；確定造血干細(xì)胞的起源；葡聚糖水凝膠對(duì)三度燒傷的治療效果。

焦點(diǎn)動(dòng)態(tài)：影響疤痕形成的物理因素。

1. 特別的GATA因子是內(nèi)胚層上皮-間質(zhì)轉(zhuǎn)化的保守誘導(dǎo)物
【動(dòng)態(tài)】
上皮-間質(zhì)轉(zhuǎn)化（EMT）使靜止的上皮細(xì)胞轉(zhuǎn)變?yōu)橛幸苿?dòng)能力的間充質(zhì)細(xì)胞狀態(tài)，西班牙科學(xué)家最近證明果蠅內(nèi)胚層的EMT依賴GATA因子Srp。當(dāng)Srp異位激活后作用類似于高效的EMT觸發(fā)劑。Srp通過(guò)下調(diào)但不阻斷聯(lián)接蛋白dE鈣粘素（dE-Cad）而影響內(nèi)胚層的EMT。而且，Srp通過(guò)直接抑制crumbs(crb)基因重定位dE-Cad。他們的研究還顯示Srp的直接同源物人GATA-6在哺乳動(dòng)物細(xì)胞中誘導(dǎo)類似的轉(zhuǎn)變。類似于Srp，人GATA-6通過(guò)下調(diào)但不阻斷E-Cad起作用，并誘導(dǎo)抑制Crumbs 的直接同源物crb2。總的看來(lái)，他們的研究發(fā)現(xiàn)一套在發(fā)育學(xué)和病理學(xué)中GATA因子是選擇性的保守的觸發(fā)物抑制上皮細(xì)胞的上皮特性而賦予其遷移能力。

【點(diǎn)評(píng)】
該研究發(fā)現(xiàn)上皮-間質(zhì)轉(zhuǎn)化依賴GATA因子，對(duì)于深入了解生物發(fā)育以及腫瘤發(fā)展有推動(dòng)作用。

【參考論文】
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. 影響疤痕形成的物理因素
【動(dòng)態(tài)】
纖維增生旺盛是受傷后常見(jiàn)的并發(fā)癥，原因尚不明了。一個(gè)常被忽視的創(chuàng)傷修復(fù)的關(guān)鍵因素是機(jī)械力，機(jī)械力通過(guò)細(xì)胞內(nèi)包括焦點(diǎn)粘連激酶（FAK）在內(nèi)的焦點(diǎn)粘連成分調(diào)節(jié)細(xì)胞-基質(zhì)相互作用。美國(guó)斯坦福大學(xué)的科學(xué)家最近報(bào)道了皮膚損傷后FAK被激活，這一過(guò)程被機(jī)械力負(fù)載所加強(qiáng)。在疤痕增生動(dòng)物模型中，敲除成纖維細(xì)胞特異性的FAK的老鼠明顯比對(duì)照老鼠炎癥和纖維化都少。他們發(fā)現(xiàn)FAK通過(guò)細(xì)胞外相關(guān)激酶（ERK）物理性的觸發(fā)單核細(xì)胞化學(xué)引誘物-1（MCP-1，也叫CCL2）的分泌，這是一種與人體纖維病變有關(guān)的高效趨化因子。類似地，敲除MCP-1的老鼠形成的疤痕最小，意味著炎癥趨化因子途徑是FAK通過(guò)力傳導(dǎo)誘導(dǎo)纖維化的主要機(jī)理。用小分子抑制FAK能夠在人體細(xì)胞中阻斷這些作用，并且通過(guò)調(diào)節(jié)MCP-1信號(hào)和炎癥細(xì)胞的招募而減少實(shí)驗(yàn)動(dòng)物的疤痕形成。這些發(fā)現(xiàn)合在一起表明機(jī)械力通過(guò)炎癥FAK–ERK–MCP-1途徑調(diào)節(jié)纖維化以及針對(duì)FAK的分子策略能夠有效的解除機(jī)械力與病理疤痕形成的關(guān)聯(lián)。

【點(diǎn)評(píng)】
該研究闡明了機(jī)械力可以通過(guò)增強(qiáng)炎癥反應(yīng)誘導(dǎo)組織纖維化增生。解除機(jī)械力的影響能夠改善纖維化狀況。

【參考論文】
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. 蛋白亞磺?；诩?xì)胞信號(hào)通路中的重要調(diào)節(jié)作用
【動(dòng)態(tài)】
蛋白亞磺?；且环N翻譯后修飾，在高等真核生物中逐漸顯示出其重要性。但是，研究其多樣性的作用還是很有挑戰(zhàn)性的，尤其是在天然的細(xì)胞環(huán)境內(nèi)。美國(guó)科學(xué)家最近開(kāi)發(fā)利用DYn-2，一種新的化學(xué)選擇性探針檢測(cè)人體細(xì)胞內(nèi)的亞磺?；牡鞍?。他們的研究表明表皮生長(zhǎng)因子受體介導(dǎo)的信號(hào)導(dǎo)致過(guò)氧化氫的產(chǎn)生和下游蛋白的氧化。另外，他們還證明DYn-2能夠細(xì)胞內(nèi)亞磺?；实牟町?，這種差異與靶蛋白的定位差異有關(guān)。他們還發(fā)現(xiàn)過(guò)氧化氫在表皮生長(zhǎng)因子受體的關(guān)鍵活性位點(diǎn)半胱氨酸（Cys797）進(jìn)行直接修飾能夠增強(qiáng)其酪氨酸激酶活性?？偲饋?lái)看，他們的發(fā)現(xiàn)顯示亞磺?；穷愃朴诹姿峄娜中孕盘?hào)機(jī)制，牽涉到其他受體酪氨酸激酶和針對(duì)蛋白中氧化敏感的半胱氨酸的不可逆抑制劑。
【點(diǎn)評(píng)】
蛋白亞磺?；诩?xì)胞信號(hào)調(diào)節(jié)中作用的提高，會(huì)促進(jìn)以調(diào)節(jié)蛋白亞磺?；癁槟繕?biāo)的藥物研究和開(kāi)發(fā)。但是更重要的意義在于，這表明蛋白翻譯后修飾有多種方式都很重要，生命自身的調(diào)節(jié)遠(yuǎn)比我們已知的更為復(fù)雜巧妙。

【參考論文】
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病毒進(jìn)入細(xì)胞核的“鑰匙”
【動(dòng)態(tài)】
慢病毒像HIV-1橫穿核膜孔復(fù)合物（NPC）并感染終末分化的不分裂細(xì)胞，它們?nèi)绾巫龅降倪€不清楚。以前的研究已發(fā)現(xiàn)胞漿NPC蛋白Nup358/RaBP2是HIV-1輔因子。最近英國(guó)和美國(guó)的科學(xué)家報(bào)道HIV-1病毒殼（CA）直接結(jié)合到Nup358/RaBP2的親環(huán)素（cyclophilin, Cyp）結(jié)構(gòu)域。該Cyp與三重TRIM5的融合產(chǎn)生了一種新的HIV-1復(fù)制抑制劑，與體內(nèi)的一種相互作用一致。與CypA結(jié)合到HIV-1 CA相反，Nup358的結(jié)合對(duì)環(huán)孢霉素的抑制不敏感，借此可以區(qū)分CypA和Nup358的影響。抑制CypA減少了對(duì)Nup358和核籃蛋白Nup153的依賴，表明CypA調(diào)節(jié)病毒參與的核內(nèi)轉(zhuǎn)運(yùn)機(jī)制的選擇。相比野生型病毒，HIV-1 病毒殼的Cyp結(jié)合突變G89V和P90A在高密度轉(zhuǎn)錄單位的基因區(qū)域有更多整合和相關(guān)特征。野生型病毒在環(huán)孢霉素存在時(shí)的整合傾向性與高密度轉(zhuǎn)錄區(qū)域有類似的改變。相反，HIV-1 CA在使得病毒對(duì)Nup358 或 TRN-SR2 刪除（CA N74D, N57A）更不敏感的殼表面另一區(qū)域的改變導(dǎo)致整合到少有轉(zhuǎn)錄單位的基因區(qū)域。兩組CA突變?cè)贖eLa細(xì)胞和人單核細(xì)胞源巨噬細(xì)胞的復(fù)制中受到損害。他們的發(fā)現(xiàn)將HIV-1銜接親環(huán)素與整合目標(biāo)和復(fù)制效率聯(lián)系起來(lái)，并對(duì)病毒親環(huán)素招募的保守性提供了新見(jiàn)解。

【點(diǎn)評(píng)】
該研究闡明了艾滋病毒HIV-1與親環(huán)素的相互作用決定了往核內(nèi)轉(zhuǎn)運(yùn)的途徑、整合的目標(biāo)以及復(fù)制的效率。對(duì)于開(kāi)發(fā)新的抗艾滋病藥物會(huì)有推動(dòng)作用。

【參考論文】
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. 確定造血干細(xì)胞的起源
【動(dòng)態(tài)】
造血干細(xì)胞（HSCs）和更早一波的限定性的網(wǎng)織紅細(xì)胞/骨髓祖細(xì)胞（EMPs）在孕體生血內(nèi)皮細(xì)胞時(shí)區(qū)分開(kāi)來(lái)。從胚胎干細(xì)胞或誘導(dǎo)多能干細(xì)胞能夠體外生產(chǎn)EMPs，但生產(chǎn)HSCs的努力大多失敗了。EMPS和HSCs的形成都需要轉(zhuǎn)錄因子Runx1及其非DNA-結(jié)合伴侶核結(jié)合因子β (CBFβ)。美國(guó)科學(xué)家最近的研究顯示孕體中EMP和HSC形成中對(duì)CBFβ的需要在時(shí)間和空間上是不同的。在表達(dá)Tek的細(xì)胞中CBFβ的泛內(nèi)皮表達(dá)對(duì)形成EMP已經(jīng)足夠，但對(duì)HSC形成卻還不夠。另一方面，在表達(dá)Ly6a的細(xì)胞中，CBFβ的表達(dá)對(duì)形成HSC足夠但對(duì)形成EMP還不夠。其數(shù)據(jù)表明EMPs和HSCs是從生血內(nèi)皮細(xì)胞的不同群分化來(lái)的，而Ly6a特異性的標(biāo)記產(chǎn)生HSC的生血內(nèi)皮。
【點(diǎn)評(píng)】
該研究比較精確地確定了造血干細(xì)胞的前體細(xì)胞并發(fā)現(xiàn)了其特異性標(biāo)志Ly6a。

【參考論文】
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. 葡聚糖水凝膠對(duì)三度燒傷的治療效果
【動(dòng)態(tài)】
對(duì)深度燒傷的創(chuàng)傷愈合效果而言血管新生是個(gè)關(guān)鍵的決定因素。美國(guó)約翰霍普金斯醫(yī)學(xué)院的科學(xué)家認(rèn)為基于葡聚糖的水凝膠能夠作為引導(dǎo)性平臺(tái)促進(jìn)3度燒傷的血管新生和皮膚再生。葡聚糖水凝膠軟而韌，有機(jī)會(huì)提高燒傷治療效果。他們首先制定了一套用葡聚糖水凝膠治療老鼠燒傷的程序，其中遵循臨床規(guī)范削除全厚層燒傷皮膚，然后用葡聚糖水凝膠和敷料層覆蓋傷處。該程序能保證整個(gè)愈合期間水凝膠能夠完好無(wú)損固定在傷處以簡(jiǎn)化燒傷治療的處理。一項(xiàng)3周的對(duì)照研究表明葡聚糖水凝膠促進(jìn)了帶有完整附件的真皮再生。水凝膠平臺(tái)促進(jìn)了早期炎癥細(xì)胞浸潤(rùn)導(dǎo)致其快速降解，促進(jìn)了生血管細(xì)胞向愈合中傷處的浸潤(rùn)。內(nèi)皮細(xì)胞進(jìn)入水凝膠平臺(tái)在第7日開(kāi)始能夠新生血管，使得血流比治療和不治療的對(duì)照組顯著增加。到第21天，用水凝膠治療的燒傷處產(chǎn)生成熟的上皮結(jié)構(gòu)有毛囊和皮脂腺。治療5周后，水凝膠促進(jìn)了頭發(fā)的新生，并且表皮形態(tài)和厚度與正常老鼠皮膚相似?？偟目磥?lái)，他們的證據(jù)顯示定制的單獨(dú)使用葡聚糖水凝膠，不加任何生長(zhǎng)因子、細(xì)胞因子或細(xì)胞，能夠促進(jìn)明顯的血管新生和皮膚再生，并可能引出新的皮膚創(chuàng)傷治療方法。

【點(diǎn)評(píng)】
該研究發(fā)現(xiàn)在燒傷老鼠削痂后單獨(dú)使用葡聚糖水凝膠能夠促進(jìn)血管新生和正常皮膚的再生。

【參考論文】
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.