Essential role for oncogenic Ras in tumour maintenance.

Advanced malignancy in tumours represents the phenotypic endpoint of successive genetic lesions that affect the function and regulation of oncogenes and tumour-suppressor genes. The established tumour is maintained through complex and poorly understood host-tumour interactions that guide processes such as angiogenesis and immune sequestration. The many different genetic alterations that accompany tumour genesis raise questions as to whether experimental cancer-promoting mutations remain relevant during tumour maintenance. Here we show that melanoma genesis and maintenance are strictly dependent upon expression of H-RasV12G in a doxycycline-inducible H-Ras12G mouse melanoma model null for the tumour suppressor INK4a. Withdrawal of doxycycline and H-RasV12G down-regulation resulted in clinical and histological regression of primary and explanted tumours. The initial stages of regression involved marked apoptosis in the tumour cells and host-derived endothelial cells. Although the regulation of vascular endothelial growth factor (VEGF) was found to be Ras-dependent in vitro, the failure of persistent endogenous and enforced VEGF expression to sustain tumour viability indicates that the tumour-maintaining actions of activated Ras extend beyond the regulation of VEGF expression in vivo. Our results provide genetic evidence that H-RasV12G is important in both the genesis and maintenance of solid tumours.     

Structural and mechanistic insights into the interaction between Rho and mammalian Dia

Formins are involved in a variety of cellular processes that require the remodelling of the cytoskeleton. They contain formin homology domains FH1 and FH2, which initiate actin assembly. The Diaphanous-related formins form a subgroup that is characterized by an amino-terminal Rho GTPase-binding domain (GBD) and an FH3 domain, which bind somehow to the carboxy-terminal Diaphanous autoregulatory domain (DAD) to keep the protein in an inactive conformation. Upon binding of activated Rho proteins, the DAD is released and the ability of the formin to nucleate and elongate unbranched actin filaments is induced. Here we present the crystal structure of RhoC in complex with the regulatory N terminus of mammalian Diaphanous 1 (mDia1) containing the GBD/FH3 region, an all-helical structure with armadillo repeats. Rho uses its 'switch' regions for interacting with two subdomains of GBD/FH3. We show that the FH3 domain of mDia1 forms a stable dimer and we also identify the DAD-binding site. Although binding of Rho and DAD on the N-terminal fragment of mDia1 are mutually exclusive, their binding sites are only partially overlapping. On the basis of our results, we propose a structural model for the regulation of mDia1 by Rho and DAD.     

Molecular cloning of cDNAs encoding a guanine-nucleotide-releasing factor for Ras p21.

The stimulation of a variety of cell surface receptors promotes the accumulation of the active, GTP-bound form of Ras proteins in cells. This is a critical step in signal transduction because inhibition of Ras activation by anti-Ras antibodies or dominant inhibitory Ras mutants blocks many of the effects of these receptors on cellular function. To reach the active GTP-bound state, Ras proteins must first release bound GDP. This rate-limiting step in GTP binding is thought to be catalysed by a guanine-nucleotide-releasing factor (GRF). Here we report the cloning of complementary DNAs from a rat brain library that encode a approximately 140K GRF for Ras p21 (p140Ras-GRF). Its carboxy-terminal region is similar to that of CDC25, a GRF for Saccharomyces cerevisiae RAS. This portion of Ras-GRF accelerated the release of GDP from RasH and RasN p21 in vitro, but not from the related RalA, or CDC42Hs GTP-binding proteins. A region in the amino-terminal end of Ras-GRF is similar to both the human breakpoint cluster protein, Bcr, and the dbl oncogene product, a guanine-nucleotide-releasing factor for CDC42Hs. An understanding of Ras-GRF function will enhance our knowledge of the many signal transduction pathways mediated by Ras proteins.     

Spatio-temporal images of growth-factor-induced activation of Ras and Rap1.

G proteins of the Ras family function as molecular switches in many signalling cascades; however, little is known about where they become activated in living cells. Here we use FRET (fluorescent resonance energy transfer)-based sensors to report on the spatio-temporal images of growth-factor-induced activation of Ras and Rap1. Epidermal growth factor activated Ras at the peripheral plasma membrane and Rap1 at the intracellular perinuclear region of COS-1 cells. In PC12 cells, nerve growth factor-induced activation of Ras was initiated at the plasma membrane and transmitted to the whole cell body. After three hours, high Ras activity was observed at the extending neurites. By using the FRAP (fluorescence recovery after photobleaching) technique, we found that Ras at the neurites turned over rapidly; therefore, the sustained Ras activity at neurites was due to high GTP/GDP exchange rate and/or low GTPase activity, but not to the retention of the active Ras. These observations may resolve long-standing questions as to how Ras and Rap1 induce different cellular responses and how the signals for differentiation and survival are distinguished by neuronal cells.     

中性粒细胞与淋巴细胞比值与哮喘严重程度的关系

为研究外周血中性粒细胞与淋巴细胞比值(neutrophil/lymphocyte ratio,NLR)与哮喘严重程度的关系,收集2016年10月～2017年9月在徐州医科大学附属医院确诊的成人慢性持续期哮喘患者135例,将其分为轻、中和重度3组,其中轻度组41人,中度组46人,重度组48人。分别测定1 s用力呼气容积(forced expiratory volume in 1 second,FEV1)、FEV1占预计值百分比(FEV1 percentage of predicted,FEV1%pred)、用力肺活量(forced vital capacity,FVC)及FEV1/FVC,检测血常规、C反应蛋白(C-reactive protein,CRP),记录哮喘控制测试(asthma control test,ACT)评分。结果表明轻、中、重度组NLR水平呈依次升高,3组间存在统计学差异(P 0. 05)。NLR与哮喘患者FEV1%pred呈负相关(r=-0. 478,P 0. 05),NLR与ACT评分呈负相关(r=-0. 64,P 0. 05),NLR与CRP呈正相关(r=0. 361,P 0. 05)。NLR、中性粒细胞计数、嗜酸粒细胞计数、淋巴细胞计数、CRP对重症哮喘诊断的曲线下面积分别为0. 709、0. 666、0. 584、0. 667(均P 0. 05),NLR诊断重症哮喘的最佳临界值为6. 79,敏感性45. 59%,特异性96. 35%。可见血清NLR与成人哮喘临床严重程度相关,检测NLR水平对判断哮喘临床严重程度可能有一定的价值。     

文廷式与徐建寅的交谊

以百余年前的文字碎片连缀起文廷式与徐建寅的交谊始末;分析两人建立在志同道合基础上的深切情谊对于各自的人生历程的深远影响;由此也可见晚清士林君子志趣之一斑。     

病毒性心肌炎与人类主要组织相容性复合体 多态性的相关性研究

目的 探索主要组织相容性复合体(major histocompatibility complex,MHC)等位基因与病毒性心肌炎(viral myocarditis,VMC)的关联性,以阐明VMC的免疫遗传学特征,并进一步探寻VMC发病中的保护基因,为可能的基因治疗提供靶基因探索新途径。方法 创建急性病毒性心肌炎的小鼠模型,通过血清炎症因子IFN-γ水平、心肌组织病理改变及心肌组织MHC基因表达水平的不同反映出病毒性心肌炎与MHC多态性之间有无相关性。结果 在32只病毒组小鼠中,MudoEb 5检测阳性的共有24只(基因频率37.5%),MudoEb 7检测阳性的有9只(基因频率14.1%),对照组中检测出MudoEb5阳性的有 6只(基因频率9.4%),MudoEb7阳性共2只(基因频率3.1%),两种等位基因的表达与对照组相比差异均有统计学意义(MudoEb 5 λ2=20.33 P=0.00 OR=13,MudoEb 7,λ2=5.38 P=0.02 OR=5.7)。结论 MudoEb5、MudoEb7基因型表达水平与COXB3的感染小鼠的病理改变存在正相关,并根据统计学分析,两种等位基因型可能为VMC小鼠的易感基因,其中MudoEb5基因型与VMC的病理相关密切程度更高。     

Association of the Shc and Grb2/Sem5 SH2-containing proteins is implicated in activation of the Ras pathway by tyrosine kinases.

The mammalian shc gene encodes two overlapping, widely expressed proteins of 46 and 52K, with a carboxy-terminal SH2 domain that binds activated growth factor receptors, and a more amino-terminal glycine/proline-rich region. These shc gene products (Shc) are transforming when overexpressed in fibroblasts. Shc proteins become phosphorylated on tyrosine in cells stimulated with a variety of growth factors, and in cells transformed by v-src (ref. 2), suggesting that they are tyrosine kinase targets that control a mitogenic signalling pathway. Here we report that tyrosine-phosphorylated Shc proteins form a specific complex with a non-phosphorylated 23K polypeptide encoded by the grb2/sem-5 gene. The grb2/sem-5 gene product itself contains an SH2 domain, which mediates binding to Shc, and is implicated in activation of the Ras guanine nucleotide-binding protein by tyrosine kinases in both Caenorhabditis elegans and mammalian cells. Consistent with a role in signalling through Ras, shc overexpression induced Ras-dependent neurite outgrowth in PC12 cells. These results suggest that Shc tyrosine phosphorylation can couple tyrosine kinases to Grb2/Sem-5, through formation of a Shc-Grb2/Sem-5 complex, and thereby regulate the mammalian Ras signalling pathway.     

情感隐喻与颜色词的语义关联阐释

隐喻核心不在于语言本身,而在于从始发域到目标域的跨域映现。分析颜色词语义理据可以得知:情感隐喻发挥了巨大的作用,使思维的扩展成为可能,隐喻的使用者通过知识可以理解颜色词的隐喻义。同时,文化内涵也对颜色词隐喻义的理解产生了较大的影响。     

GTPase activity of dynamin and resulting conformation change are essential for endocytosis

Dynamin is a large GTPase with a relative molecular mass of 96,000 (Mr 96K) that is involved in clathrin-mediated endocytosis and other vesicular trafficking processes. Although its function is apparently essential for scission of newly formed vesicles from the plasma membrane, the nature of dynamin's role in the scission process is still unclear. It has been proposed that dynamin is a regulator (similar to classical G proteins) of downstream effectors. Here we report the analysis of several point mutants of dynamin's GTPase effector (GED) and GTPase domains. We show that oligomerization and GTP binding alone, by dynamin, are not sufficient for endocytosis in vivo. Rather, efficient GTP hydrolysis and an associated conformational change are also required. These data argue that dynamin has a mechanochemical function in vesicle scission.     

萃取过程的量热研究：Ⅲ.萃取剂之间的缔合作用

本文利用量热滴定的方法,研究了萃取有机相中酸性萃取剂P204、P507、P272和PMBP与中性磷酸酯之间的缔合作用,求出相应的缔合常数β以及热力学函数△H、△S、△G。