水通道蛋白对动物机体健康影响研究进展

水通道蛋白(aquaporins, AQPs)是一种重要的跨膜通道蛋白,在动物机体不同组织器官(脑、肝脏、肾脏、肠道等)中先后被发现,并具有特殊生物学功能.研究表明, AQPs不仅承担着动物机体内水和部分小分子物质的运输,而且在动物腹泻、便秘、应激和免疫等方面也发挥着关键作用.目前,关于AQPs的研究主要集中于对AQPs结构功能的挖掘,用敲除小鼠构建AQPs缺失模型并探讨其对人类机体健康的作用机制,以及AQPs对畜禽健康作用效应的探讨.本文主要综述了近年来AQPs对动物机体健康影响的研究进展,特别是对畜禽健康的营养调控策略进行了前景展望.同时结合生物信息学的方法预测畜禽与鼠AQPs基因和蛋白的同源性,以期为AQPs在动物营养研究及科学应用上提供理论参考.     

肺水通道蛋白1,5与肺损伤的研究进展

正水通道蛋白(AQPs)是一种可快速完成水分子细胞内外跨膜转运的跨膜蛋白家族,对维持细胞内外水平衡有重要作用。肺损伤是临床上常见危重病症,死亡率高。有大量研究证实,水通道蛋白(AQPs)与肺水清除密切相关,其中AQP1,5在肺水转运中尤为重要,这对近年来国内外关于肺内液体跨膜转运及细胞内外环境平衡调节机制的研究及临床肺损伤的认识和治疗具有重要临床意义。作者就肺水通     

昆虫水通道蛋白的研究进展

昆虫水通道蛋白(Aquaporins,AQPs)是一种膜蛋白,它们是昆虫维持体内水分平衡的必要蛋白,有关它们的研究不断深入。因此,本文对昆虫水通道蛋白的最新研究成果进行了概述,旨在引起人们对该类蛋白的兴趣,以便系统了解和研究该类蛋白。目前研究表明:昆虫典型的AQPs是由250-300个氨基酸残基组成,其分子量在23-35 k Da,包含6个疏水性横跨膜区域、两个NPA结构单元(asparagine-proline-alanine)等。系统发育分析发现:已知昆虫AQPs可分为5大类,分别为DRIP、BIB、PRIP、RPIPs和LHIPs。昆虫AQPs除了运送水分子外,还可以运输其他的一些小分子溶质,如尿素、甘油、海藻糖等。它们还具有组织特异性表达特性,可能在昆虫的多个生理活动中起到重要的作用,因此它们的功能仍需进一步研究证实。此外,昆虫AQPs的深入研究还将会给害虫综合治理提供新的思路。     

植物水通道蛋白的干旱应答机制研究进展

干旱胁迫是严重影响全球作物生产的非生物胁迫之一,研究植物耐旱机制已成为一个重要领域。水通道蛋白是一类特异、高效转运水及其它小分子底物的膜通道蛋白,在植物中具有丰富的亚型,参与调节植物的水分吸收和运输。近10年来,水通道蛋白在植物不同生理过程中的作用,一直受到研究人员的关注,特别是在非生物胁迫方面,而研究表明水通道蛋白在干旱胁迫下对植物的耐旱性起着至关重要的作用,能维持细胞水分稳态和调控环境胁迫快速响应。水通道蛋白在植物耐旱过程中的调控机制及功能较复杂,而关于其应答机制和不同亚型功能性研究的报道甚少。该文综述了植物水通道蛋白的分类、结构、表达调控和活性调节,分别从植物水通道蛋白响应干旱表达调控机制、水通道蛋白基因表达的时空特异性、水通道蛋白基因的表达与蛋白丰度,水通道蛋白基因的耐旱转化四个方面阐明干旱胁迫下植物水通道蛋白的表达,重点阐述其参与植物干旱胁迫应答的作用机制,并提出水通道蛋白研究的主要方向。     

水通道蛋白研究动态

水通道蛋白是对水专一的通道蛋白,它普遍存在于动、植物及微生物中,不同水通道蛋白之间具有类似特征.哺乳动物中水通道蛋白主要分为六类,分布于水分代谢活跃的器官中;植物除了质膜上水通道蛋白外,液泡膜也存在着水通道蛋白,它们在植物生长,发育及胁迫适应中起着重要作用.目前有关水通道蛋白的详细的结构和功能信息主要来自对红细胞膜上水通道蛋白的研究,它由同源的四聚体组成,每个单体具有独立的水通道功能,四聚体在膜上分布具有不对称性,在膜内侧四聚体呈伸展状态,在膜外侧形成大的中心空腔.     

植物水通道蛋白及其活性调节

水通道蛋白是对水专一的通道蛋白,普遍存在于动、植物及微生物中。研究表明高等植物的质膜和液泡膜上存在着丰富的水通道蛋白,其种类繁多,分布广泛,并具有一定的组织特异性。植物水通道蛋白的活性受到严格的调控,其调节方式主要有两种,分别为基因水平的表达调控和翻译后的修饰作用。     

植物水通道蛋白及其活性调节

水通道蛋白是对水专一的通道蛋白,普遍存在于动、植物及微生物中。研究表明高等植物的质膜和液泡膜上存在着丰富的水通道蛋白,其种类繁多,分布广泛,并具有一定的组织特异性。植物水通道蛋白的活性受到严格的调控,其调节方式主要有两种,分别为基因水平的表达调控和翻译后的修饰作用。     

植物液泡膜水通道蛋白的结构、分布和功能研究进展

植物液泡膜水通道蛋白(tonoplast intrinsic proteins, TIPs)是植物体内水分子和一些小分子溶质跨液泡膜运输的通道。TIPs介导胞内或胞间的水分跨膜运输,在维持植物细胞的水分平衡过程中起着至关重要的作用。由于TIPs特异的定位在液泡膜上,长久以来一直被用作不同植物物种和组织中液泡识别的标记物。本综述介绍了液泡膜水通道蛋白的发现、结构、分类以及亚细胞和组织定位、基因表达和蛋白功能等方面的研究进展,初步探讨了植物液泡膜水通道蛋白研究中存在的问题及今后的研究热点,希望能为相关的科研人员在研究液泡膜定位的水通道蛋白中提供帮助。     

冬虫夏草金水相生治疗肺脏疾病的作用及其生理基础

虫草及其衍生品保护肺、肾,具有抗肺癌、抗肺肾纤维化、保护肾功能、抗炎等作用,对支气管哮喘和肺癌辅助治疗的作用较好地体现了其补益肺肾的功效,而其对肺肾的共同作用暗合传统医学"金水相生"的理论。肺主气司呼吸、主行水,而肾主纳气、主水,对于机体的水液代谢共同发挥重要的作用。现代研究表明,肺和肾脏中与水液代谢相关的共同生理和病理学基础可能主要是水通道蛋白(aquaporins,AQPs)。AQPs在肺和肾脏中广泛存在,并参与调控二脏中水液分泌、吸收及细胞内外水的平衡。作为我国传统名贵中药,冬虫夏草具有补益肺肾、益精填髓等功效,而虫草及其相关产品在临床应用过程中体现出来的对肺肾相关疾病的共同调控效果,目前尚未有系统研究。文中基于金水相生理论,以水通道蛋白家族为生理学基础,就冬虫夏草对肺脏相关疾病的作用及机制进行综述,初步探索在金水相生理论指导下虫草通过对AQPs的调控,治疗肺部疾病的临床应用和科学内涵。     

藻类水通道蛋白的研究进展

目前,大量水通道蛋白已在古菌、细菌、真菌、动物和植物中相继被发现,但对于低等植物——藻类水通道蛋白的研究相对较少。藻类与陆地高等植物在生长环境方面存在较大差异,因此其体内存在的水通道蛋白在功能作用机制方面与高等植物会有不同。所有藻类的生长发育过程都与水分传导息息相关,而藻类水通道蛋白不仅仅是水分运输的通道蛋白,同时还具有其他生理生化功能,是一类多功能蛋白。与植物水通道蛋白相比,藻类水通道蛋白的研究起步较晚。在2004年从莱茵衣藻中得到第一个水通道蛋白后,越来越多的研究者开始对藻类体内存在的水通道蛋白产生关注。近年来,在一些藻类全基因组测序完成的基础之上,研究者对藻类水通道蛋白的探索也有了新的进展。迄今为止,已有8个不同亚族的藻类水通道蛋白被确定出来,而且在近两年内,又有研究者从南极冰藻、条斑紫菜和羊栖菜中发现新的藻类水通道蛋白。综述了当前藻类水通道蛋白的分类和结构特征等方面的研究进展,并结合新发现的几种藻类水通道蛋白,阐述了藻类处于胁迫环境时水通道蛋白的特异性表达和所发挥的生理功能,为后续相关藻类水通道蛋白的研究奠定一定的理论基础。     

植物水孔蛋白研究进展

水孔蛋白是植物重要的膜功能蛋白,不仅介导植物各组织间水分的高效转运,还参与植物体内其他物质的跨膜转运,同时在植物光合作用、生长发育、免疫应答以及信号转导等生理过程中也发挥重要作用。本文主要综述了植物水孔蛋白结构特征和分类,多种生理功能,以及其转录水平和转录后水平活性调节等方面的最新研究进展,并就如何系统全面地开展水孔蛋白参与植物生长发育过程的分子调控机制研究提出展望。植物水孔蛋白的深入研究有助于阐明植物体内物质转运的分子机理及其生理作用机制,对指导农业生产中作物的生长发育调控有重要理论意义。     

植物水孔蛋白的亚细胞分布与生理功能研究浅析

水孔蛋白(aquaporin,AQP)因具有水转运活性而得名,然而随着研究的深入,水孔蛋白转运活性的多样性与生理功能的多样性不断被报道．本文综合分析了植物水孔蛋白亚细胞定位与功能多样性的研究进展,重点综述了植物水孔蛋白广泛的亚细胞分布特点,以及亚细胞上的再分布现象与植物水孔蛋白生理功能多样性间的关系,并对植物水孔蛋白研究中存在的 问题及研究方向进行了分析,认为水孔蛋白多样化的生理功能的作用机制需要结合其组织定位与亚细胞定位进行分析才能 揭示．     

Water transport by aquaporins in the extant plant Physcomitrella patens

Although aquaporins (AQPs) have been shown to increase membrane water permeability in many cell types, the physiological role of this increase was not always obvious. In this report, we provide evidence that in the leafy stage of development (gametophore) of the moss Physcomitrella patens, AQPs help to replenish more rapidly the cell water that is lost by transpiration, at least if some water is in the direct vicinity of the moss plant. Three AQP genes were cloned in P. patens: PIP2;1, PIP2;2, and PIP2;3. The water permeability of the membrane was measured in protoplasts from leaves and protonema. A significant decrease was measured in protoplasts from leaves and protonema of PIP2;1 or PIP2;2 knockouts but not the PIP2;3 knockout. No phenotype was observed when knockout plants were grown in closed petri dishes with ample water supply. Gametophores isolated from the wild type and the pip2;3 mutant were not sensitive to moderate water stress, but pip2;1 or pip2;2 gametophores expressed a water stress phenotype. The knockout mutant leaves were more bent and twisted, apparently suffering from an important loss of cellular water. We propose a model to explain how the AQPs PIP2;1 and PIP2;2 delay leaf dessication in a drying atmosphere. We suggest that in ancestral land plants, some 400 million years ago, APQs were already used to facilitate the absorption of water.     

Transgenic banana plants overexpressing a native plasma membrane aquaporin MusaPIP1;2 display high tolerance levels to different abiotic stresses

Water transport across cellular membranes is regulated by a family of water channel proteins known as aquaporins (AQPs). As most abiotic stresses like suboptimal temperatures, drought or salinity result in cellular dehydration, it is imperative to study the cause–effect relationship between AQPs and the cellular consequences of abiotic stress stimuli. Although plant cells have a high isoform diversity of AQPs, the individual and integrated roles of individual AQPs in optimal and suboptimal physiological conditions remain unclear. Herein, we have identified a plasma membrane intrinsic protein gene (MusaPIP1;2) from banana and characterized it by overexpression in transgenic banana plants. Cellular localization assay performed using MusaPIP1;2::GFP fusion protein indicated that MusaPIP1;2 translocated to plasma membrane in transformed banana cells. Transgenic banana plants overexpressing MusaPIP1;2 constitutively displayed better abiotic stress survival characteristics. The transgenic lines had lower malondialdehyde levels, elevated proline and relative water content and higher photosynthetic efficiency as compared to equivalent controls under different abiotic stress conditions. Greenhouse‐maintained hardened transgenic plants showed faster recovery towards normal growth and development after cessation of abiotic stress stimuli, thereby underlining the importance of these plants in actual environmental conditions wherein the stress stimuli is often transient but severe. Further, transgenic plants where the overexpression of MusaPIP1;2 was made conditional by tagging it with a stress‐inducible native dehydrin promoter also showed similar stress tolerance characteristics in in vitro and in vivo assays. Plants developed in this study could potentially enable banana cultivation in areas where adverse environmental conditions hitherto preclude commercial banana cultivation.     

Characterization of Leishmania donovani aquaporins shows presence of subcellular aquaporins similar to tonoplast intrinsic proteins of plants

Leishmania donovani, a protozoan parasite, resides in the macrophages of the mammalian host. The aquaporin family of proteins form important components of the parasite-host interface. The parasite-host interface could be a potential target for chemotherapy. Analysis of L. major and L. infantum genomes showed the presence of five aquaporins (AQPs) annotated as AQP9 (230aa), AQP putative (294aa), AQP-like protein (279aa), AQP1 (314aa) and AQP-like protein (596aa). We report here the structural modeling, localization and functional characterization of the AQPs from L. donovani. LdAQP1, LdAQP9, LdAQP2860 and LdAQP2870 have the canonical NPA-NPA motifs, whereas LdAQP putative has a non-canonical NPM-NPA motif. In the carboxyl terminal to the second NPA box of all AQPs except AQP1, a valine/alanine residue was found instead of the arginine. In that respect these four AQPs are similar to tonoplast intrinsic proteins in plants, which are localized to intracellular organelles. Confocal microscopy of L. donovani expressing GFP-tagged AQPs showed an intracellular localization of LdAQP9 and LdAQP2870. Real-time PCR assays showed expression of all aquaporins except LdAQP2860, whose level was undetectable. Three-dimensional homology modeling of the AQPs showed that LdAQP1 structure bears greater topological similarity to the aquaglyceroporin than to aquaporin of E. coli. The pore of LdAQP1 was very different from the rest in shape and size. The cavity of LdAQP2860 was highly irregular and undefined in geometry. For functional characterization, four AQP proteins were heterologously expressed in yeast. In the fps1Δ yeast cells, which lacked the key aquaglyceroporin, LdAQP1 alone displayed an osmosensitive phenotype indicating glycerol transport activity. However, expression of LdAQP1 and LdAQP putative in a yeast gpd1Δ strain, deleted for glycerol production, conferred osmosensitive phenotype indicating water transport activity or aquaporin function. Our analysis for the first time shows the presence of subcellular aquaporins and provides structural and functional characterization of aquaporins in Leishmania donovani.     

Functions of water channels in male and female reproductive systems

Twelve water channels (aquaporins) are expressed in mammalian reproductive systems, and play very important roles in maintaining water homeostasis in reproductive cells. Impairment of their functions can result in attenuated male and female fertility. Alteration of AQPs expression is also found in reproductive tissues of the patients with polycystic ovarian syndrome, endometriosis or endometrium carcinoma. A lot of data have increased understanding of the functions and mechanisms of regulation of aquaporins at both the molecular and the clinical level. Researches have also focused on aquaporins as therapeutic targets. This review discusses recent advances in uncovering the physiological and pathophysiological roles of aquaporins in the reproductive systems.     

Structural insights into the Aedes aegypti aquaporins and aquaglyceroporins – an in silico study

There has been a fair bit of understanding on the structure–function relationship of Aquaporins (AQPs) from plants and vertebrates obtained from available X-ray crystallography data. However, there is a lacuna in understanding the structure of AQPs from sanguinivorous insects like the mosquito where it plays a crucial role in survival. In this study, we have built homology models for the Aedes aegypti AQPs, identified key channel lining residues and compared the structure and sequence with orthodox AQPs. Although Ar/R filter residues of AaAQP1 were exactly similar to orthodox AQPs, AaAQP2 has a substitution at LE1position possibly making it less efficient in high capacity water transport. The huge difference in the selectivity filter region of AaAQP3 suggests a different transport property for this channel. The changes observed in the H5 position of the filter of AaAQP4 and AaAQP5 may explain the presence of a larger pore aperture to permit the passage of larger solute molecules. AaAQP6 possesses a completely hydrophobic filter like that in mammalian super aquaporins. The identified key residues are pivotal in understanding the mechanism of action and gating of these channels.     

What Are Aquaporins For?

The prime function of aquaporins (AQPs) is generally believed to be that of increasing water flow rates across membranes by raising their osmotic or hydraulic permeability. In addition, this applies to other small solutes of physiological importance. Notable applications of this simple permeability hypothesis (SPH) have been epithelial fluid transport in animals, water exchanges associated with transpiration, growth and stress in plants, and osmoregulation in microbes. We first analyze the need for such increased permeabilities and conclude that in a range of situations at the cellular, subcellular and tissue levels the SPH cannot satisfactorily account for the presence of AQPs. The analysis includes an examination of the effects of the genetic elimination or reduction of AQPs (knockouts, antisense transgenics and null mutants). These either have no effect, or a partial effect that is difficult to explain, and we argue that they do not support the hypothesis beyond showing that AQPs are involved in the process under examination. We assume that since AQPs are ubiquitous, they must have an important function and suggest that this is the detection of osmotic and turgor pressure gradients. A mechanistic model is proposed—in terms of monomer structure and changes in the tetrameric configuration of AQPs in the membrane—for how AQPs might function as sensors. Sensors then signal within the cell to control diverse processes, probably as part of feedback loops. Finally, we examine how AQPs as sensors may serve animal, plant and microbial cells and show that this sensor hypothesis can provide an explanation of many basic processes in which AQPs are already implicated. Aquaporins are molecules in search of a function; osmotic and turgor sensors are functions in search of a molecule.