植物小G 蛋白功能的研究进展

近年来,小G蛋白的调控途径已经成为人们研究细胞信号转导过程的热点问题。小G蛋白家族包括Ras、Rab、Rho、Arf和Ran亚家族,它们起着许多不同的重要细胞生理作用,例如基因表达、细胞骨架重组装、微管的形成以及囊泡和核孔运输机制。这些小G蛋白作为重要的分子开关,具有一个非常保守的功能区域,即I-IV结构区,它起着关键性作用。从拟南芥(Arabidopsis thaliana)基因组预测分析得出,拟南芥含有93个小G蛋白同源序列,包含Rab、Rho、Arf和Ran亚家族,但没有Ras亚家族。本文主要阐述了迄今在植物中研究小G蛋白各个亚家族功能的最新进展,并对植物、酵母和动物相关的同源蛋白的生理功能进行比较和推测。     

植物小G蛋白功能的研究进展

近年来,小G蛋白的调控途径已经成为人们研究细胞信号转导过程的热点问题.小G蛋白家族包括Ras、Rab、Rho、Arf和Ran亚家族,它们起着许多不同的重要细胞生理作用,例如基因表达、细胞骨架重组装、微管的形成以及囊泡和核孔运输机制.这些小G蛋白作为重要的分子开关,具有一个非常保守的功能区域,即I-Ⅳ结构区,它起着关键性作用.从拟南芥(Arabidopsisthaliana)基因组预测分析得出,拟南芥含有93个小G蛋白同源序列,包含Rab、Rho、Arf和Ran亚家族,但没有Ras亚家族.本文主要阐述了迄今在植物中研究小G蛋白各个亚家族功能的最新进展,并对植物、酵母和动物相关的同 源蛋白的生理功能进行比较和推测.     

植物细胞G蛋白研究进展

ＧＴＰ结合调节蛋白（ＧＴＰ－ｂｉｎｄｉｎｇｒｅｇｕｌａｔｏｒｙｐｒｏｔｅｉｎｓ）,简称Ｇ蛋白,是活细胞内一类具有重要生理调节功能的蛋白质。此类蛋白由于其生理调节功能有赖于与三磷酸鸟苷（ＧＴＰ）的结合与水解ＧＴＰ的活性而得名。自从７０年代初在动物细胞中首先发现Ｇ蛋白的存在以来,有关Ｇ蛋白的研究发展迅速。现在已不仅知道在几乎所有真核细胞中存在Ｇ蛋白,而且已经证明Ｇ蛋白在细胞信号转导过程中有着非常重要的调节作用［１～６］。Ｇ蛋白的发现和研究,不仅使人们对细胞信号转导以及神经系统的信息传递有了新的进一步…     

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.     

植物异三聚体G蛋白研究进展

异三聚体鸟嘌呤核苷结合蛋白（简称G蛋白）是真核细胞中保守的信号转导分子,通常与G蛋白偶联受体一起将细胞外信号传递到胞质中。许多研究表明植物G蛋白介导的信号转导途径在光、激素、糖等响应过程中发挥着精细的调控作用。本文重点介绍近年来植物G蛋白在复合体组成、生化特性及其工作模式等方面的研究进展。     

小G蛋白在植物抗病性中的作用

小G蛋白一类是低分子量GTP结合蛋白,其分子量大约20～30 kDa.小G蛋白作为重要的分子开关参与了细胞许多重要生理信号途径的调控.近几年在植物中的研究、尤其是对模式植物水稻杭病分子机制的研究发现,Rho家族的小G蛋白在植物抗病信号传导途径的调控中起了关健的作用.本文对植物特有的Rho家族小G蛋白在植物免疫反应中的最...     

G—蛋白及其在植物信号转导中的作用

ＧＴＰ结合蛋白（ＧＴＰ－ｂｉｎｄｉｎｇｐｒｏｔｅｉｎ）在生物体内有数种类型,包括转录因子、微管蛋白和信号转导蛋白,最后一种已成为当今研究的热点。结合ＧＴＰ的调节蛋白（ＧＴＰ－ｂｉｎｄｉｎｇｒｅｇｕｌａｔｏｒｙｐｒｏｔｅｉｎｓ,简称Ｇ－蛋白）于７０年代...     

植物G蛋白偶联受体及其在信号转导中的作用

G蛋白偶联受体(G protein-coupled receptors,GPCRs)是具有7个跨膜螺旋的蛋白质受体,是人体内最大的蛋白质超家族.GPCRs能调控细胞周期,参与多种植物信号通路以及影响一系列的代谢和分化活动.简要介绍了GPCR和G蛋白介导的信号转导机制,GPCRs的结构和植物GPCR及其在植物跨膜信号转导中的作用,并对GPCR的信号转导机制及植物抗病反应分子机制的研究提出展望.     

G蛋白偶联受体二聚化研究进展

G蛋白偶联受体是细胞膜受体最大的家族,参与调节多种生理过程,在信号识别及转导中具有重要作用,传统观点认为G蛋白偶联受体作为单体起作用,近年来,越来越多的证据表明,G蛋白偶联受体不仅能以二聚体形式存在,而且在细胞信号转导中起重要作用,尤其是对阿片受体异源二聚体的研究,推动了这一领域的研究。本文综述了G蛋白偶联受体二聚化研究进展,以及同源和异源二聚体的结构与功能。     

Activation of the Small GTPase Ral in Platelets

Ral is a ubiquitously expressed Ras-like small GTPase which is abundantly present in human platelets. The biological function of Ral and the signaling pathway in which Ral is involved are largely unknown. Here we describe a novel method to measure Ral activation utilizing the Ral binding domain of the putative Ral effector RLIP76 as an activation-specific probe. With this assay we investigated the signaling pathway that leads to Ral activation in human platelets. We found that Ral is rapidly activated after stimulation with various platelet agonists, including α-thrombin. In contrast, the platelet antagonist prostaglandin I₂ inhibited α-thrombin-induced Ral activation. Activation of Ral by α-thrombin could be inhibited by depletion of intracellular Ca²⁺, whereas the induction of intracellular Ca²⁺ resulted in the activation of Ral. Our results show that Ral can be activated by extracellular stimuli. Furthermore, we show that increased levels of intracellular Ca²⁺ are sufficient for Ral activation in platelets. This activation mechanism correlates with the activation mechanism of the small GTPase Rap1, a putative upstream regulator of Ral guanine nucleotide exchange factors.     

Active ROP2 GTPase inhibits ABA- and CO2-induced stomatal closure

ROP GTPases function as molecular switches in diverse cellular processes. Previously, we showed that ROP2 GTPase is activated upon light irradiation, and thereby negatively regulates light-induced stomatal opening. Here we studied the role of ROP2 during stomatal closure. The expression of a constitutively active form of ROP2 (CA-rop2) in Arabidopsis thaliana and Vicia faba resulted in slower and reduced stomatal closure in response to abscisic acid (ABA) and CO(2) . In contrast, the expression of a dominant-negative form of ROP2 (DN-rop2) and the knockout mutation of ROP2 (rop2 KO) promoted ABA-induced stomatal closure in Arabidopsis. As early as 10 min after ABA treatment, ROP2 was inactivated and translocated to the cytoplasm of the stomatal guard cells. To elucidate the mechanism by which active ROP2 suppresses stomatal closure, we monitored endocytotic membrane trafficking, which is regulated by Rho GTPases in animal cells. We found that the endocytosis of plasma membrane (PM), as tracked by FM4-64, was lower in CA-rop2-expressing guard cells than in those of wild-type plants, which suggests that active ROP2 suppresses the endocytotic internalization of PM, a process required for stomatal closure. Together, our results suggest that ROP2 is inactivated by ABA, and that this inactivation is required for the timely stomatal closure.     

小分子GTP酶的结构与功能

小分子GTP酶是真核生物中普遍存在的一类分子量较小的蛋白质,它们具有保守的GTP结合结构域．在GTP酶类中自成一个超家族。根据序列结构的不同它们又分为多个家族,不同的家族分别在诸如细胞信号转导、胞质骨架的建成和物质转运等过程中起着非常重要的调控功能。     

植物成花素的研究进展

许多植物由营养生长向生殖生长的转换都是由日照长度控制的,而植物叶片可感知日长信号并诱导成花素的合成。成花素从韧皮部运输到茎顶端,使顶端分生组织基因表达发生变化进而成花。其中,FT作为成花素的主要组分,在该转换过程中处于核心地位。本文综合近年的研究,介绍成花素及其作用机理。     

The Emerging Role of the RAB25 Small GTPase in Cancer

RAB25, a member of the rat sarcoma (RAS) family of small GTPase, has been implicated in the pathophysiology of ovarian, breast and other cancers. Its role in endosomal transport and recycling of cell-surface receptors and signaling proteins presents a novel paradigm for the disruption of cellular pathways and promotion of tumor development and aggressiveness. Variations in structure and post-translational modifications control the localization of RAS superfamily proteins to specific subcellular compartments and recruitment of downstream effectors, allowing these small GTPases to function as sophisticated modulators of a complex and diverse range of cellular processes. Here, we review the link between RAB25 and tumor development and current knowledge regarding its possible roles in cancer.     

Small GTPase Rho regulates thrombin-induced platelet aggregation

Platelets play essential roles in hemostasis and thrombosis by aggregating with each other. However, the molecular mechanism governing platelet aggregation is not yet fully understood. Here, we established an assay system using platelets permeabilized with streptolysin-O to analyze mechanism of the thrombin-induced aggregation, focusing upon a controversial issue in the field whether small GTPase Rho regulates the aggregation. Incubation of the permeabilized platelets with Rho GDP-dissociation inhibitor, an inhibitory regulator for Rho family GTPases, extracted Rho family proteins extensively from the plasma and intracellular membranes, and inhibited the thrombin-induced aggregation. Incubation of the permeabilized platelets with botulinum exoenzyme C3, which specifically inhibits Rho function by ADP-ribosylating it, abolished the thrombin-induced aggregation. Thus, Rho is involved in thrombin-induced aggregation of platelets.