Rho GTPases与肿瘤

Rho GTPases参与调控细胞的多种关键生物学行为,特别是细胞的生长、细胞骨架的形成、转录调节等生物学过程. 在肿瘤的发生发展中Rho GTPases也扮演了重要的角色．本文将回顾Rho GTPases的调控（包括经典及非经典调控方式）及其关键成员（RhoA、Cdc42及Rac1）与临床肿瘤的研究进展,特别是它们参与调控肿瘤的增殖、迁移、侵袭、凋亡等恶性生物学行为,从而为研发靶向Rho GTPases的小分子/基因药物了奠定基础．     

Rho GTPases及其在口腔领域的新应用

Rho GTPases是重要的信号转导分子,参与多种重要的细胞生命活动,如肌动蛋白细胞骨架的重构、细胞黏附、细胞运动、囊泡运输、基因表达和细胞周期的调控等.调节这些生物信号的转导通路非常复杂,因此,Rho GTPases早已成为研究的热点.最新的研究进展集中在描述Rho GTPases具体在细胞的哪个部位发生反应与参与通路的具体的分子及新功能等,同时细胞分子实验已经证实Rho GTPases在肌动蛋白细胞骨架的组装、细胞粘附、细胞运动、和基因表达等方面的作用与临床上多种口腔疾病,如正畸,牙周疾病的发生有密切关系.因此,对Rho GTPases的研究可能为口腔领域正畸,牙周病的治疗提供新的思路.     

Rho GTPase对细胞骨架及信号通路的多重影响

Rho GTPase最基本的功能是结合和水解鸟嘌呤核苷酸，目前已从晡乳动物中分离出16种不同的Rho GTPases，其中以Rho、Rac和Cdc42最为人们关注。研究发现Rho GTPases参与基因转录、细胞周期进程的调控及多条信号通路的调节，与细胞凋亡、肿瘤侵润及细胞骨架构成关系密切。现普遍认为Rho GTPases是调节细胞功能的一类重要蛋白分子，越来越多的Rho家族成员及其调控的蛋白数量逐渐被发现和认识。     

Rho GTPases和细胞凋亡

细胞凋亡涉及细胞骨架的形态学改变,Rho GTPases在细胞骨架改变中起着至关重要的作用。近年来的研究揭示了Rho蛋白家族在肌动蛋白(actin)聚合、解聚及actin-myosin的分子调节机制。同时越来越多的研究表明,Rho GTPases在巨噬细胞吞噬凋亡小体中也发挥了关键作用。本综述就Rho GTPases信号途径在细胞凋亡中细胞骨架的结构改变及凋亡小体被吞噬过程中的作用进行具体讨论。     

乳腺癌细胞迁移的调节与转移

细胞迁移是乳腺癌侵袭和转移中的关键步骤之一.癌细胞在迁移过程中主要受到Rho GTPases的调节,发生肌动蛋白骨架重组,获得定向迁移的能力;高迁移能力的癌细胞通过与胞外基质成分相互作用,为迁移创造合适的微环境;最后迁移的癌细胞在靶器官的趋化作用下在特定部位驻足生长,这些环节共同作用导致乳腺癌转移.研究细胞迁移复杂的分子机制将为控制乳腺癌转移提供新的策略.     

小G蛋白ROP的研究进展

小G蛋白(small GTPases)是近年来研究细胞信号转导过程的热点问题,包括Ras、Rab、Rho、Arf和Ran5个亚家族,其中ROP蛋白是Rho家族成员,为植物特有,在调控细胞生长、发育及调节植物对环境响应等各方面起重要作用.对ROP蛋白的活性调节和功能进行了重点介绍.     

胞质M-CSF诱导HeLa细胞侵袭和迁移

为探讨巨噬细胞集落刺激因子(M-CSF)对人宫颈癌细胞(He La细胞)侵袭和迁移的影响及机制,采用胞质定位空载体p CMV/cyto/myc与重组载体p CMV/cyto/myc-M-CSF稳定转染He La细胞株,建立稳定高表达胞质M-CSF的细胞系(He La-M细胞).经Transwell实验观察胞质M-CSF对He La细胞侵袭和迁移能力的影响,逆转录-聚合酶链式反应及蛋白质印迹检测细胞Rho三磷酸鸟苷酶(Rho GTPases)及基质金属酶的表达,明胶酶谱法检测基质金属蛋白酶2的活性.结果显示,与转染空载体的He La细胞(He La-C细胞)和对照组He La细胞比较,胞质M-CSF的高表达可明显增强He La细胞在体外的侵袭和迁移能力,其机制与Rho GTPases的活化,以及MMP2表达上调及其活性增高密切相关.     

VEGF通过调节黏着斑促进间充质干细胞的黏附及铺展

间充质干细胞（mesenchymalstemcells,MSCs）具有多向分化潜能并能在体外趋化剂或细胞因子的作用下进行定向迁移,体内移植后可趋向迁移至脑瘤病灶区。细胞黏附是细胞迁移的首要条件,了解细胞黏附及其调控有助于细胞迁移机制的研究。细胞黏附及铺展涉及到黏着斑（f0－caladhesions,FAs）的动态变化以及细胞骨架的重排。细胞铺展面积在黏附过程中逐渐增大,黏附初期形成的小的黏着复合物逐渐成熟,聚集在一起形成较大的FAs。肌动蛋白（F—actin）聚集形成的螺线圈样微丝结构逐渐被应力纤维代替,细胞也由圆形变为具有极性的梭形或多角形。黏着斑激酶（focal adhesion kinase,FAK）和桩蛋白（paxillin）具有调节FAs聚合及骨架重排的作用,其中,Y397－FAK和Y31／Y118－paxillin的磷酸化活性在细胞铺展过程中不断变化。FAs组装时,Y397－FAK的磷酸化活性升高;FAs成熟后,Y397．FAK的磷酸化活性下降。活化的FAK能够磷酸4LY31／Y118-paxillin,激活paxillin参与调节细胞骨架的形成和排列。血管内皮生长因子（vascular endothelial growthfactor,VEGF）诱导~SMSCs黏附过程中,细胞面积变大,完全铺展的时间缩短,黏着斑及细胞骨架的形成均提前。另外,VEGF诱导的细胞铺展过程中形成的FAs形态细长,数量较多。该研究表明,VEGF通过调节黏着斑和细胞骨架促L~MSCs的黏附与铺展,提示vEGF可以通过调节黏着斑进而调控MSCs的定向迁移,为细胞迁移行为的研究提供理论基础。     

Rho小G蛋白相关激酶的结构与功能

Rho小G蛋白家族是Ras超家族成员之一,人类Rho小G蛋白包括20个成员,研究最清楚的有RhoA、Rac1和Cdc42。Rho小G蛋白参与了诸如细胞骨架调节、细胞移动、细胞增殖、细胞周期调控等重要的生物学过程。在这些生物学过程的调节中,Rho小G蛋白的下游效应蛋白质如蛋白激酶（p21-activated kinase,PAK）、ROCK（Rho-kinase）、PKN（protein kinase novel）和MRCK（myotonin-related Cdc42-binding kinase）发挥了不可或缺的作用。迄今研究发现,PAK可调节细胞骨架动力学和细胞运动,另外,PAK通过MAPK（mitogen-activated protein kinases）参与转录、细胞凋亡和幸存通路及细胞周期进程;ROCK与肌动蛋白应力纤维介导黏附复合物的形成及与细胞周期进程的调节有关;哺乳动物的PKN与RhoA/B/C相互作用介导细胞骨架调节;MRCK与细胞骨架重排、细胞核转动、微管组织中心再定位、细胞移动和癌细胞侵袭等有关。该文简要介绍Rho小G蛋白下游激酶PAK、ROCK、PKN和MRCK的结构及其在细胞骨架调节中的功能,重点总结它们在真核细胞周期调控中的作用,尤其是在癌细胞周期进程中所发挥的作用,为寻找癌症治疗的新靶点提供理论依据。     

Rho激酶与脂肪细胞分化的研究进展

白色脂肪组织的过度沉积与肥胖症、II型糖尿病和脂肪肝等疾病的发生密切相关,已有的研究发现,体外培养的间充质干细胞在被诱导向脂肪细胞分化的过程中,细胞形态会由最初的长梭形逐渐变圆,最终形成胞内充满一个巨大脂滴的圆形细胞。Rho激酶是参与细胞运动的主要激酶之一,在调控细胞生长、胞质分裂、细胞迁移、转化和侵袭等方面发挥着重要的作用,近年来已逐渐成为新药研发的重要靶点之一。最近的研究显示Rho激酶间接影响不同转录因子表达,从而影响细胞的分化命运,且Rho激酶与胚胎干细胞的成脂分化有紧密联系。本文就Rho激酶与脂肪细胞分化的相关研究进展做一综述。     

How important are Rho GTPases in neurosecretion?

Rho GTPases are small GTP binding proteins belonging to the Ras superfamily which act as molecular switches that regulate many cellular function including cell morphology, cell to cell interaction, cell migration and adhesion. In neuronal cells, Rho GTPases have been proposed to regulate neuronal development and synaptic plasticity. However, the role of Rho GTPases in neurosecretion is poorly documented. In this review, we discuss data that highlight the importance of Rho GTPases and their regulators into the control of neurotransmitter and hormone release in neurons and neuroendocrine cells, respectively.     

Roles of Rho-family GTPases in cell polarisation and directional migration

Polarised cell migration is a tightly regulated process that occurs in tissue development, chemotaxis and wound healing. Rho-family GTPases, including Cdc42, Rac1 and RhoA, play a central role in establishing cell polarisation, which requires asymmetric and ordered distribution of the signalling molecules and the cytoskeleton. Recent advances reveal that Rho GTPases, together with phosphatidylinositol 3-kinase, contribute to asymmetric phosphatidylinositol 3,4,5-trisphosphate distribution via a positive-feedback loop. Phosphatidylinositol 3,4,5-trisphosphate thereby activates the signalling cascades to the cytoskeleton as a second messenger. Rho GTPases also capture and stabilise microtubules through their effectors (e.g. IQGAP1, mDia and Par6) near the cell cortex, leading to polarised cell morphology and directional cell migration. Thus, elucidation of the signal transduction cascades from receptors to Rho GTPases and, subsequently, from Rho GTPases to microtubules has begun.     

Notch信号在盐酸法舒地尔诱导大鼠骨髓间充质干细胞向神经元分化过程中的作用

目的:探讨Notch信号通路在盐酸法舒地尔诱导大鼠骨髓间充质干细胞(MSCs)向神经元分化中的作用。方法:实验分为未转染组、转染组(转染Rn-Notch1-siRNA)、阳性对照组(转染Rn-MAPK-1 Control siRNA)及阴性对照组(转染Negative Control siRNA)等4组。采用盐酸法舒地尔诱导大鼠MSCs分化为神经元。倒置荧光显微镜下观察MSCs转染后荧光表达情况;RT-PCR检测Notch1、Hes1和MAPK1 mRNA的表达变化;免疫细胞化学法检测Notch1、神经元烯醇化酶(NSE)、神经微丝蛋白亚单位(NF-M)和胶质纤维酸性蛋白(GFAP)的表达变化;MTT方法检测细胞存活率。结果:①siRNA转染72h,MSCs荧光表达最强,转染率可达91.3%±4.2%;同时,转染组MSCs的Notch1和Hes1 mRNA转录下降(P0.05);MTT提示转染组细胞存活率也显著减少(P0.05)。②盐酸法舒地尔可以诱导MSCs向神经元分化,其中以转染组诱导效果最佳,NSE、NF-M的表达率显著的高于其它各组(P0.05)。结论:盐酸法舒地尔在诱导大鼠MSCs向神经元分化过程中,可能存在Notch信号通路与RhoA/Rho激酶通路信号的协同作用,共同促进MSCs向神经元分化。     

VEGF isoforms

The Rho-family of p21 small GTPases are directly linked to the regulation of actin-based motile machinery and play a key role in the control of cell migration. Aside from the original and most well-characterized canonical Rho GTPases RhoA, Rac1, and Cdc42, numerous isoforms of these key proteins have been identified and shown to have specific roles in regulating various cellular motility processes. The major difficulty in addressing these isoform-specific effects is that isoforms typically contain highly similar primary amino acid sequences and thus are able to interact with the same upstream regulators and the downstream effector targets. Here, we will introduce the major members of each GTPase subfamily and discuss recent advances in the design and application of fluorescent resonance energy transfer-based probes, which are at the forefront of the technologies available to directly probe the differential, spatiotemporal activation dynamics of these proteins in live single cells. Currently, it is possible to specifically detect the activation status of RhoA vs. RhoC isoforms, as well as Cdc42 vs. TC-10 isoforms in living cells. Clearly, additional efforts are still required to produce biosensor systems capable of detecting other isoforms of Rho GTPases including RhoB, Rac2/3, RhoG, etc. Through such efforts, we will uncover the isoform-specific roles of these near-identical proteins in living cells, clearly an important area of the Rho GTPase biology that is not yet fully appreciated.     

The role of GTPase-activating protein ARHGAP26 in human cancers

Rho GTPases are molecular switches that play an important role in regulating the behavior of a variety of tumor cells. RhoA GTPase-activating protein 26 (ARHGAP26) is a GTPase-activating protein and inhibits the activity of Rho GTPases by promoting the hydrolytic ability of Rho GTPases. It also affects tumorigenesis and progression of various tumors through several methods, including formation of abnormal fusion genes and circular RNA. This review summarizes the biological functions and molecular mechanisms of ARHGAP26 in different tumors, proposes the potential clinical value of ARHGAP26 in cancer treatment, and discusses current issues that need to be addressed.

     

Rho GAPs and GEFs

Within blood vessels, endothelial cell–cell and cell–matrix adhesions are crucial to preserve barrier function, and these adhesions are tightly controlled during vascular development, angiogenesis, and transendothelial migration of inflammatory cells. Endothelial cellular signaling that occurs via the family of Rho GTPases coordinates these cell adhesion structures through cytoskeletal remodelling. In turn, Rho GTPases are regulated by GTPase-activating proteins (GAPs) and guanine nucleotide exchange factors (GEFs). To understand how endothelial cells initiate changes in the activity of Rho GTPases, and thereby regulate cell adhesion, we will discuss the role of Rho GAPs and GEFs in vascular biology. Many potentially important Rho regulators have not been studied in detail in endothelial cells. We therefore will first overview which GAPs and GEFs are highly expressed in endothelium, based on comparative gene expression analysis of human endothelial cells compared with other tissue cell types. Subsequently, we discuss the relevance of Rho GAPs and GEFs for endothelial cell adhesion in vascular homeostasis and disease.     

Regulation of microtubules in cell migration

Directional cell migration is a fundamental process in all organisms that is stringently regulated during tissue development, chemotaxis and wound healing. Migrating cells have a polarized morphology with an asymmetrical distribution of signaling molecules and the cytoskeleton. Microtubules are indispensable for the directional migration of certain cells. Recent studies have shown that Rho family GTPases, which are key regulators of cell migration, affect microtubules, in addition to the actin cytoskeleton and adhesion. Rho family GTPases capture and stabilize microtubules through their effectors at the cell cortex, leading to a polarized microtubule array; in turn, microtubules modulate the activities of Rho family GTPases. In this article, we discuss how a polarized microtubule array is established and how microtubules facilitate cell migration.     

Rho GTPase isoforms in cell motility: Don't fret,we have FRET

The Rho-family of p21 small GTPases are directly linked to the regulation of actin-based motile machinery and play a key role in the control of cell migration. Aside from the original and most well-characterized canonical Rho GTPases RhoA, Rac1, and Cdc42, numerous isoforms of these key proteins have been identified and shown to have specific roles in regulating various cellular motility processes. The major difficulty in addressing these isoform-specific effects is that isoforms typically contain highly similar primary amino acid sequences and thus are able to interact with the same upstream regulators and the downstream effector targets. Here, we will introduce the major members of each GTPase subfamily and discuss recent advances in the design and application of fluorescent resonance energy transfer-based probes, which are at the forefront of the technologies available to directly probe the differential, spatiotemporal activation dynamics of these proteins in live single cells. Currently, it is possible to specifically detect the activation status of RhoA vs. RhoC isoforms, as well as Cdc42 vs. TC-10 isoforms in living cells. Clearly, additional efforts are still required to produce biosensor systems capable of detecting other isoforms of Rho GTPases including RhoB, Rac2/3, RhoG, etc. Through such efforts, we will uncover the isoform-specific roles of these near-identical proteins in living cells, clearly an important area of the Rho GTPase biology that is not yet fully appreciated.