世界生命科學前沿動態(tài)周報（七十一）

（12.19-12.25/2011）
美寶國際集團:陶國新 

　　主要內(nèi)容：產(chǎn)前喂食甘露糖避免新生老鼠的先天糖基化代謝疾??；失去Pten的基質(zhì)纖維母細胞促進腫瘤發(fā)展；基于納米線的單細胞內(nèi)視鏡；隱花色素輔受體介導節(jié)律性抑制糖皮質(zhì)激素受體；HIF-1α缺失加速表皮老化影響再上皮化生；癌細胞能無限分裂的機理。

　　焦點動態(tài)：基于納米線的單細胞內(nèi)視鏡。

1. 產(chǎn)前喂食甘露糖避免新生老鼠的先天糖基化代謝疾病
【動態(tài)】
　　糖基化Ia先天疾病是由編碼磷酸甘露糖酶2（PMM2）的基因突變引起的糖代謝紊亂，造成多系統(tǒng)的疾病伴有嚴重的精神運動和智力障礙。德國科學家用一種次形態(tài)突變的老鼠模型，在交配前和懷孕期通過飲水飼喂母鼠甘露糖，其后代即使攜帶上述先天疾病的基因突變，也能正常發(fā)育，克服了該病對胚胎的傷害。該結(jié)果突顯了胚胎發(fā)育中糖基化的必要作用，可能會引出治療該種疾病的新方法。

【點評】
　　該研究有助于更好的理解這一代謝疾病的分子機理和胚胎發(fā)育的關(guān)鍵步驟，有可能第一次為該疾病找到治療方法。

【參考論文】
Nature Medicine, 2011; DOI:10.1038/nm.2548
Successful prenatal mannose treatment for congenital disorder of glycosylation-Ia in mice
Anette Schneider, Christian Thiel, Jan Rindermann, et al.  
Congenital disorder of glycosylation-Ia (CDG-Ia, also known as PMM2-CDG) is caused by mutations in the gene that encodes phosphomannomutase 2 (PMM2, EC 5.4.2.8) leading to a multisystemic disease with severe psychomotor and mental retardation. In a hypomorphic Pmm2 mouse model, we were able to overcome embryonic lethality by feeding mannose to pregnant dams. The results underline the essential role of glycosylation in embryonic development and may open new treatment options for this disease.

2. 失去Pten的基質(zhì)纖維母細胞促進腫瘤發(fā)展
【動態(tài)】
　　基質(zhì)纖維母細胞的PTEN（磷酸酶）表達抑制了乳腺上皮癌的生長，但機理未明。利用蛋白質(zhì)組學和表達圖譜測定，美國科學家顯示乳腺基質(zhì)纖維母細胞缺失Pten基因會激活致癌的分泌蛋白組協(xié)調(diào)微環(huán)境中其他類型細胞的轉(zhuǎn)錄重編程。下調(diào)miR-320和上調(diào)其一個直接靶點ETS2是Pten缺失的基質(zhì)纖維母細胞誘導致癌的分泌蛋白組的關(guān)鍵事件，致癌的分泌蛋白組轉(zhuǎn)而促進腫瘤發(fā)生和腫瘤細胞侵襲。他們發(fā)現(xiàn)腫瘤微環(huán)境的纖維母細胞因缺失Pten而導致miR-320數(shù)量劇降，進而使ETS2蛋白數(shù)量大漲，最終大量的ETS2蛋白激活許多基因，使纖維母細胞分泌50多種因子刺激臨近癌細胞的增殖和侵襲，也引起腫瘤中和整個乳腺里的其他纖維母細胞重編程。Pten–miR-320–Ets2調(diào)節(jié)的分泌蛋白組的表達區(qū)分開了人體正常的乳腺基質(zhì)組織與腫瘤基質(zhì)，并與乳腺癌的復發(fā)強烈相關(guān)。該研究表明miR-320是在基質(zhì)纖維母細胞中重組腫瘤微環(huán)境并阻礙腫瘤發(fā)展的Pten腫瘤抑制軸的一個關(guān)鍵部分。

【點評】
　　該研究促進了對于腫瘤微環(huán)境在腫瘤發(fā)展中的作用的理解，并為防治癌癥提供了新的研究途徑。

【參考論文】
Nature Cell Biology, 2011; DOI: 10.1038/ncb2396
Reprogramming of the tumour microenvironment by stromal PTEN-regulated miR-320
Bronisz, J. Godlewski, J. A. Wallace, et al. 
PTEN (Phosphatase and tensin homolog deleted on chromosome 10) expression in stromal fibroblasts suppresses epithelial mammary tumours, but the underlying molecular mechanisms remain unknown. Using proteomic and expression profiling, we show that Pten loss from mammary stromal fibroblasts activates an oncogenic secretome that orchestrates the transcriptional reprogramming of other cell types in the microenvironment. Downregulation of miR-320 and upregulation of one of its direct targets, ETS2 (v-ets erythroblastosis virus E26 oncogene homolog 2) are critical events inPten-deleted stromal fibroblasts responsible for inducing this oncogenic secretome, which in turn promotes tumour angiogenesis and tumour-cell invasion. Expression of the Pten–miR-320–Ets2-regulated secretome distinguished human normal breast stroma from tumour stroma and robustly correlated with recurrence in breast cancer patients. This work reveals miR-320 as a critical component of the Pten tumour-suppressor axis that acts in stromal fibroblasts to reprogramme the tumour microenvironment and curtail tumour progression.

3. 基于納米線的單細胞內(nèi)視鏡
【動態(tài)】
　　基于納米線和納米管的能夠安全穿透細胞膜進入細胞的靈敏一維探針在高分辨率高通量的基因及藥物遞送，生物感測和單細胞電生理學中有潛在用途。但是，這些探針在次波長水平跨膜的光通訊中的使用還受到限制。美國科學家的最新研究顯示在光纖錐形尖上貼附一個納米線波導管能夠?qū)⒖梢姽庖牖畹牟溉閯游锛毎麅?nèi)的區(qū)域，也能夠檢測來自亞細胞區(qū)域的光信號并有高空間分辨率。而且，將內(nèi)視鏡插入細胞內(nèi)及引導激光的光照沒有在細胞內(nèi)引起明顯毒性。

【點評】
　　該技術(shù)的出現(xiàn)使得直接肉眼觀察單個活細胞內(nèi)亞細胞水平的結(jié)構(gòu)和生命活動成為可能。

【參考論文】
Nature Nanotechnology, 2011; DOI: 10.1038/nnano.2011.226
Nanowire-based single-cell endoscopy

Ruoxue Yan, Ji-Ho Park, Yeonho Choi, et al.
One-dimensional smart probes based on nanowires and nanotubes that can safely penetrate the plasma membrane and enter biological cells are potentially useful in high-resolution,  and high-throughput,  gene and drug delivery, biosensing, and single-cell electrophysiology. However, using such probes for optical communication across the cellular membrane at the subwavelength level remains limited. Here, we show that a nanowire waveguide attached to the tapered tip of an optical fibre can guide visible light into intracellular compartments of a living mammalian cell, and can also detect optical signals from subcellular regions with high spatial resolution. Furthermore, we show that through light-activated mechanisms the endoscope can deliver payloads into cells with spatial and temporal specificity. Moreover, insertion of the endoscope into cells and illumination of the guided laser did not induce any significant toxicity in the cells.
 
4. 隱花色素輔受體介導節(jié)律性抑制糖皮質(zhì)激素受體
【動態(tài)】                      
　　哺乳動物的代謝有高度的節(jié)律性，涉及核激素受體的主要激素回路表現(xiàn)出互通的晝夜循環(huán)。然而，合乎邏輯的解釋核激素受體與生物鐘之協(xié)調(diào)的機理還不清楚。美國德國和荷蘭的科學家的最新研究顯示兩個生理節(jié)奏的輔受體隱花色素1和2能夠以配體依賴的方式與糖皮質(zhì)激素受體相互作用，并在老鼠胚胎纖維母細胞中整體改變對糖皮質(zhì)激素的轉(zhuǎn)錄反應(yīng)：隱花色素缺失極大地減少了基因抑制，大約使地塞米松誘導的基因數(shù)量翻倍，提示隱花色素廣泛的拮抗糖皮質(zhì)激素受體激活并促進其抑制。在老鼠中，基因缺失隱花色素1和/或2會導致葡萄糖耐受和血循環(huán)中結(jié)構(gòu)性的高水平的皮質(zhì)酮，提示相耦聯(lián)的腎上腺軸抑制的減少和糖皮質(zhì)激素在肝臟中轉(zhuǎn)活化的增加。從基因上說，隱花色素1和2 以激素依賴的方式與磷酸烯醇丙酮酸羧激酶1促進子中糖皮質(zhì)激素反應(yīng)成分相關(guān)聯(lián)，并且地塞米松誘導的磷酸烯醇丙酮酸羧激酶1基因的轉(zhuǎn)錄在缺失隱花色素的肝臟中顯著增加。這些結(jié)果表明存在一種特別機制，借此隱花色素將生物鐘活動和受體靶基因與支撐正常代謝平衡的復雜基因回路相藕聯(lián)。

【點評】
　　該研究發(fā)現(xiàn)了身體生物鐘和糖代謝體系之間缺失的環(huán)節(jié)，可能有助于解釋睡眠和營養(yǎng)代謝之間的關(guān)聯(lián)。

【參考論文】
Nature. 2011, 480(7378):552-6. doi:10.1038/nature10700.
Cryptochromes mediate rhythmic repression of the glucocorticoid receptor
Katja A. Lamia, Stephanie J. Papp, Ruth T. Yu, et al. 
Mammalian metabolism is highly circadian and major hormonal circuits involving nuclear hormone receptors display interlinked diurnal cycling. However, mechanisms that logically explain the coordination of nuclear hormone receptors and the clock are poorly understood. Here we show that two circadian co-regulators, cryptochromes 1 and 2, interact with the glucocorticoid receptor in a ligand-dependent fashion and globally alter the transcriptional response to glucocorticoids in mouse embryonic fibroblasts: cryptochrome deficiency vastly decreases gene repression and approximately doubles the number of dexamethasone-induced genes, suggesting that cryptochromes broadly oppose glucocorticoid receptor activation and promote repression. In mice, genetic loss of cryptochrome 1 and/or 2 results in glucose intolerance and constitutively high levels of circulating corticosterone, suggesting reduced suppression of the hypothalamic-pituitary-adrenal axis coupled with increased glucocorticoid transactivation in the liver. Genomically, cryptochromes 1 and 2 associate with a glucocorticoid response element in the phosphoenolpyruvate carboxykinase 1 promoter in a hormone-dependent manner, and dexamethasone-induced transcription of the phosphoenolpyruvate carboxykinase 1 gene was strikingly increased in cryptochrome-deficient livers. These results reveal a specific mechanism through whichcryptochromes couple the activity of clock and receptor target genes to complex genomic circuits underpinning normal metabolic homeostasis.

5. HIF-1α缺失加速表皮老化影響再上皮化生
【動態(tài)】
　　在老鼠和人體的皮膚中，缺氧誘導因子HIF-1α是在表皮，主要是基底層中表達。HIF-1α已被證明有重要的系統(tǒng)性功能：在去除表皮中HIF-1α的老鼠中調(diào)節(jié)腎臟紅細胞生成素的生產(chǎn)，以及表皮中HIF-1α高表達帶來的血管型。但是，HIF-1α 在角化細胞生理中的局部作用還沒有闡明。法國科學家用敲除靶向角化細胞的HIF-1α基因的老鼠模型來研究HIF-1α在表皮中的作用。這些老鼠皮膚延遲出現(xiàn)皮膚表型，并表現(xiàn)為皮膚萎縮和瘙癢發(fā)炎，部分原因是牽涉層粘連蛋白332（Ln-332）和整合素的基底膜失調(diào)。研究者門也用重建的表皮研究了老鼠實驗結(jié)果與人體皮膚的相關(guān)性，結(jié)果顯示在人體角化細胞中抑制HIF-1α基因妨礙了形成能存活的重建人體表皮。隨著HIF-1α靜默而降低的角化細胞生長潛力與Ln-322 、 α6 和β1整合素表達 的降低有關(guān)?？偟恼f來，這些結(jié)果表明HIF-1α在皮膚穩(wěn)態(tài)特別是表皮老化期間扮演一定的角色。

【點評】
　　該研究揭示了HIF-1α在表皮形成中的作用，有助于進一步了解皮膚的發(fā)育和生理。

【參考論文】
J Cell Sci, 2011, doi:10.1242/jcs.082370
Loss of epidermal hypoxia-inducible factor-1α accelerates epidermal aging and affects re-epithelialization in human and mouse
Hamid Reza Rezvani, Nsrein Ali, Martin Serrano-Sanchez, et al.
In mouse and human skin, HIF-1α is constitutively expressed in the epidermis, mainly in the basal layer. HIF-1α has been shown to have crucial systemic functions: regulation of kidney erythropoietin production in mice with constitutive HIF-1α epidermal deletion, and hypervascularity following epidermal HIF-1α overexpression. However, its local role in keratinocyte physiology has not been clearly defined. To address the function of HIF-1α in the epidermis, we used the mouse model of HIF-1α knockout targeted to keratinocytes (K14-Cre/Hif1aflox/flox). These mice had a delayed skin phenotype characterized by skin atrophy and pruritic inflammation, partly mediated by basement membrane disturbances involving laminin-332 (Ln-332) and integrins. We also investigated the relevance of results of studies in mice to human skin using reconstructed epidermis and showed that HIF-1α knockdown in human keratinocytes impairs the formation of a viable reconstructed epidermis. A diminution of keratinocyte growth potential, following HIF-1α silencing, was associated with a decreased expression of Ln-322 and α6 integrin and β1 integrin. Overall, these results indicate a role of HIF-1α in skin homeostasis especially during epidermal aging.

6. 癌細胞能無限分裂的機理
【動態(tài)】
　　德國、瑞典和瑞士的科學家最近發(fā)現(xiàn)了癌細胞能無限分裂的機理，這將有助于靶向癌癥治療。就細胞分裂而言，惡性腫瘤細胞打破了幾乎所有規(guī)律。這種細胞在沒有外部信號時，仍能分裂，這些細胞通過旁路而獲得關(guān)于生長的外部信號，所以仍能增殖。關(guān)于癌細胞能無限分裂的機制，至今科學家們還不是很清楚。該研究的研究人員發(fā)現(xiàn)了兩個關(guān)鍵因子的作用，就是c-Myc和SIRT1，在癌細胞中，前者能擺脫細胞內(nèi)的控制機制，促使癌細胞分裂。他們發(fā)現(xiàn)高度聚集的c-Myc蛋白可激活一種抑制細胞衰老和死亡的酶SIRT1，而這種酶又可反作用于c-Myc蛋白，如此形成一個回路，令c-Myc蛋白和SIRT1酶越來越多，最終促使癌細胞無限分裂。之前的研究表明SIRT1蛋白在長壽，糖代謝，以及胰島素分泌過程中扮演了重要角色。

【點評】
　　該研究揭示延伸細胞壽命與癌細胞生長之間的關(guān)聯(lián)，也提出了一種治療癌癥的新靶標系統(tǒng)，未來有助于開發(fā)新型治療方法。

【參考論文】
PNAS  2011, doi:10.1073/pnas.1105304109
The c-MYC oncoprotein, the NAMPT enzyme, the SIRT1-inhibitor DBC1, and the SIRT1 deacetylase form a positive feedback loop
Antje Menssen, Per Hydbring, Karsten Kapelle, et al.

Silent information regulator 1 (SIRT1) represents an NAD+-dependent deacetylase that inhibits proapoptotic factors including p53. Here we determined whether SIRT1 is downstream of the prototypic c-MYC oncogene, which is activated in the majority of tumors. Elevated expression of c-MYC in human colorectal cancer correlated with increased SIRT1 protein levels. Activation of a conditional c-MYC allele induced increased levels of SIRT1 protein, NAD+, and nicotinamide-phosphoribosyltransferase (NAMPT) mRNA in several cell types. This increase in SIRT1 required the induction of the NAMPT gene by c-MYC. NAMPT is the rate-limiting enzyme of the NAD+ salvage pathway and enhances SIRT1 activity by increasing the amount of NAD+. c-MYC also contributed to SIRT1 activation by sequestering the SIRT1 inhibitor deleted in breast cancer 1 (DBC1) from the SIRT1 protein. In primary human fibroblasts previously immortalized by introduction of c-MYC, down-regulation of SIRT1 induced senescence and apoptosis. In various cell lines inactivation of SIRT1 by RNA interference, chemical inhibitors, or ectopic DBC1 enhanced c-MYC-induced apoptosis. Furthermore, SIRT1 directly bound to and deacetylated c-MYC. Enforced SIRT1 expression increased and depletion/inhibition of SIRT1 reduced c-MYC stability. Depletion/inhibition of SIRT1 correlated with reduced lysine 63-linked polyubiquitination of c-Myc, which presumably destabilizes c-MYC by supporting degradative lysine 48-linked polyubiquitination. Moreover, SIRT1 enhanced the transcriptional activity of c-MYC. Taken together, these results show that c-MYC activates SIRT1, which in turn promotes c-MYC function. Furthermore, SIRT1 suppressed cellular senescence in cells with deregulated c-MYC expression and also inhibited c-MYC–induced apoptosis. Constitutive activation of this positive feedback loop may contribute to the development and maintenance of tumors in the context of deregulated c-MYC.