非编码RNA在细胞自噬中的研究进展 *

细胞自噬是细胞在应激条件下降解胞内受损成分的过程,涉及多信号分子参与。在疾病发生、发展过程中,细胞自噬既可抑制或延缓疾病发展,还可使病情恶化,故寻找在不同阶段调控细胞自噬作用的因子探究其有效作用靶点具有重要意义。非编码RNA(noncoding RNA,ncRNA)是从基因组中转录出来的不行使编码蛋白质作用的一类RNA的总称。进几年来,越来越多不同ncRNA被发现,并在动物机体生理和病理过程中发挥着重要的调控作用。已有研究表明,ncRNA在细胞自噬发生过程起到重要的调控作用。从微小RNA(MicroRNA,miRNA)、长链非编码RNA(Long noncoding RNAs,lncRNA)、环状RNA(CircularRNA,circRNA)几方面综述了ncRNA在细胞自噬通路中的调节作用,为癌症等疾病治疗以及分子标记提供理论指导和新思路。     

氨基酸缺乏诱导细胞自噬及miRNA调控机制

氨基酸是生物体内不可缺少的营养成分和生命活动最基本的物质之一,并对动物体的新陈代谢起到至关重要的作用。自噬是细胞内通过降解和回收细胞内生物大分子和受损细胞器,以完成本身代谢和某些细胞器更新的过程。研究证实氨基酸缺乏能诱导细胞自噬,而这种反应大部分是依赖于m TORC1信号通路的方式实现的,但总氨基酸或单体氨基酸调节细胞自噬的分子作用机制和自噬水平有很大差别,且相关方面的分子调节机制尚未完全清楚,需要进一步阐明。mi RNA是一类长度为18-24 nt的非编码核苷酸,参与细胞增殖、分化、自噬与凋亡等多种生命活动。研究表明mi RNA在氨基酸缺乏诱导细胞自噬过程中的也发挥重要调控机制。就不同氨基酸缺乏调控自噬相关机制加以综述,并探讨mi RNA在其中起到的关键作用。旨在为治疗自噬相关代谢提供思路。     

细胞自噬在冠状病毒感染中的作用

细胞自噬是一种保守的广泛存在于真核细胞内的溶酶体依赖性分解代谢途径,其通过形成双层膜结构的自噬体降解蛋白质和细胞器,参与物质循环和稳态维持。同时,自噬也能作为机体免疫防御的一部分发挥抗病毒的作用,或是被病毒利用以促进其自身增殖。冠状病毒是一种有囊膜的单股正链RNA病毒,能够诱导双层膜囊泡形成转录复合物,进一步指导病毒基因组的合成。研究表明多个冠状病毒成员能够诱导自噬发生,自噬参与了病毒增殖的多个环节。本文拟对细胞自噬的概况及作用、自噬在病毒感染特别是冠状病毒感染中的作用进行综述,以期为揭示冠状病毒的致病机理提供参考,并为开发冠状病毒的治疗方案提供新思路。     

自噬在小RNA病毒感染中的作用

自噬是真核细胞所特有的一种高度保守的经溶酶体途径降解细胞内错误折叠或多余蛋白质、受损细胞器、胞内病原体的细胞代谢过程。小RNA病毒脱壳感染细胞时,快速激活自噬途径,诱导形成大量双层膜结构的自噬体。自噬能激活细胞表面的模式识别受体以及干扰素途径,增强组织相容性复合物对病毒抗原的提呈作用,发挥抑制小RNA病毒感染的天然免疫功能;此外,自噬体为小RNA病毒提供复制相关蛋白质和非细胞裂解性释放途径,促进感染细胞的胞内、胞外出现更多成熟的小RNA病毒粒子。该文对细胞自噬与小RNA病毒感染的研究概况与进展作一综述,为进一步开展解析不同小RNA病毒感染与自噬发生的时间、空间等的关系及阐明自噬作用于小RNA病毒感染的分子机制等研究提供参考。     

长链非编码RNA调控自噬的研究进展

长链非编码RNA (lncRNA)是转录本长度超过200个核苷酸的RNA分子,不具备蛋白质编码功能。细胞自噬是真核生物的一种高度保守、用来降解和循环再利用细胞内生物大分子或受损细胞器的过程,有助于维持机体内环境稳态。自噬研究是当下生命科学研究的热点,前期研究发现,lncRNA在细胞自噬调控中发挥着重要作用,深入探索lncRNA调控自噬的分子机制及其与疾病发生的关系对预防和治疗多种人类重大疾病具有重要意义。该文就目前为止报道过的部分lncRNA参与自噬调控的最新进展进行归纳总结,以期为lncRNA调控自噬的相关研究及其在肿瘤等疾病治疗中的作用提供参考。     

MiRNA对自噬的调控及在癌症中的作用CSCD

自噬(autophagy)通过溶酶体途径降解并循环利用胞质组分,在维持细胞内平衡、细胞生长、器官形成等方面扮演着重要作用。自噬异常通常与人类疾病相关。mi RNA是调控基因表达的重要分子,影响着众多信号通路。mi RNA通过调节自噬相关信号通路,对肿瘤细胞的生长起着重要的调节作用。本文讨论一些对自噬有重要调控作用的mi RNA,并阐述了在癌症形成的过程中,mi RNA通过对自噬各环节的调控,对癌症的促进或抑制发挥的重要作用。     

病毒感染中细胞自噬研究进展

细胞自噬是一种依赖于溶酶体的细胞内降解途径,用于细胞维持内环境的稳态.自噬广泛存在于真核细胞的生理、病理过程中.研究发现自噬与病毒之间的相互作用是一个复杂且多向化的过程,一方面自噬能够参与机体免疫应答、发挥抗病毒效应;另一方面,细胞的自噬机制也可被病毒操纵,以利于其自身复制.本文对近年来细胞自噬与病毒感染的相互作用进展,尤其是病毒如何调控自噬以促进其复制和致病的机制加以综述.     

MiRNA对自噬的调控及在癌症中的作用

自噬(autophagy)通过溶酶体途径降解并循环利用胞质组分,在维持细胞内平衡、细胞生长、器官形成等方面扮演着重要作用。自噬异常通常与人类疾病相关。mi RNA是调控基因表达的重要分子,影响着众多信号通路。mi RNA通过调节自噬相关信号通路,对肿瘤细胞的生长起着重要的调节作用。本文讨论一些对自噬有重要调控作用的mi RNA,并阐述了在癌症形成的过程中,mi RNA通过对自噬各环节的调控,对癌症的促进或抑制发挥的重要作用。     

抑癌基因p53与细胞自噬

细胞自噬(autophagy)是一种在进化上高度保守的代谢通路,它发生的分子机制和信号调控途径相当复杂,其中mTOR信号通路和Beclin1复合物发挥了最重要的调控作用,p53也是细胞自噬重要的调节因子。研究发现,p53可通过多种途径调节细胞自噬水平,这主要决定于它的亚细胞定位。在细胞核中,p53可通过多种方式上调细胞自噬;而在细胞质中,p53对细胞自噬具有负性调节作用,可抑制细胞自噬的发生。探究清楚p53与细胞自噬之间的调控关系将有助于人类正确认识由于细胞自噬功能异常所诱导的肿瘤的发生发展过程,从而最终攻克各种肿瘤性疾病。     

LncRNA:一种新型调控细胞自噬的分子

细胞自噬(autophagy)与肿瘤、病原体感染、神经退行性疾病等密切相关。长链非编码RNA(long noncoding RNA,lnc RNA)是一组长度超过200 nt、无蛋白质编码功能的转录本。lnc RNA可作为一种新型调控细胞自噬的分子,深入了解lnc RNA在细胞自噬过程中的调控作用,对细胞自噬相关疾病的治疗与预防都具有重要的意义。现介绍近期lnc RNA对细胞自噬调控研究的新进展。     

Autophagy is involved in influenza A virus replication

Autophagy is involved in the replication of viruses, especially those that perform RNA assembly on the surface of cytoplasmic membrane in host cells. However, little is known about the regulatory role of autophagy in influenza A virus replication. Using fluorescence and electron microscopy, we observed that autophagosomes can be induced and identified upon influenza A virus infection. The virus increased the amount of the autophagosome marker protein microtubule-associated protein light chain 3-II (LC3-II) and enhanced autophagic flux. When autophagy was pharmacologically inhibited by either 3-methylademine or wortmannin, the titers of influenza A virus were remarkably decreased. Viral reduction via autophagy inhibition was further confirmed by RNA interference, through which two different proteins required for autophagy were depleted. Noticeably, the compounds utilized had no marked effect on virus entry or cell viability, either of which might limit viral replication. Furthermore, alteration of cellular autophagy via pharmacological reagents or RNA interference impaired viral protein accumulation. Taken together, these findings indicate that autophagy is actively involved in influenza A virus replication.     

Role of autophagy in innate viral recognition

Plasmacytoid dendritic cells (pDCs) detect viruses in the acidified endosomes via Toll-like receptors (TLRs) upon endocytosis of virions. Yet, pDC responses to certain single-stranded RNA viruses occur only following live viral infection. In our recent study, we presented evidence that the recognition of such viruses by TLR7 requires autophagy. We speculate that the requirement for autophagy in viral recognition reflects the necessity for transportation of cytosolic viral replication intermediates into the lysosome where TLR7 is activated. In addition, autophagy was found to be required for pDCs to produce type I interferon (IFN) in response to both ssRNA and dsDNA viruses. These results indicated that autophagy plays a key role in mediating virus detection and IFNalpha secretion in pDCs, and suggest that cytosolic replication intermediates of ssRNA viruses serve as pathogen signatures recognized by TLR7.     

IRGM is a common target of RNA viruses that subvert the autophagy network

Autophagy is a conserved degradative pathway used as a host defense mechanism against intracellular pathogens. However, several viruses can evade or subvert autophagy to insure their own replication. Nevertheless, the molecular details of viral interaction with autophagy remain largely unknown. We have determined the ability of 83 proteins of several families of RNA viruses (Paramyxoviridae, Flaviviridae, Orthomyxoviridae, Retroviridae and Togaviridae), to interact with 44 human autophagy-associated proteins using yeast two-hybrid and bioinformatic analysis. We found that the autophagy network is highly targeted by RNA viruses. Although central to autophagy, targeted proteins have also a high number of connections with proteins of other cellular functions. Interestingly, immunity-associated GTPase family M (IRGM), the most targeted protein, was found to interact with the autophagy-associated proteins ATG5, ATG10, MAP1CL3C and SH3GLB1. Strikingly, reduction of IRGM expression using small interfering RNA impairs both Measles virus (MeV), Hepatitis C virus (HCV) and human immunodeficiency virus-1 (HIV-1)-induced autophagy and viral particle production. Moreover we found that the expression of IRGM-interacting MeV-C, HCV-NS3 or HIV-NEF proteins per se is sufficient to induce autophagy, through an IRGM dependent pathway. Our work reveals an unexpected role of IRGM in virus-induced autophagy and suggests that several different families of RNA viruses may use common strategies to manipulate autophagy to improve viral infectivity.     

Akt plays a critical role in replication of nonsegmented negative-stranded RNA viruses

The order Mononegavirales (comprised of nonsegmented negative-stranded RNA viruses or NNSVs) contains many important pathogens. Parainfluenza virus 5 (PIV5), formerly known as simian virus 5, is a prototypical paramyxovirus and encodes a V protein, which has a cysteine-rich C terminus that is conserved among all paramyxoviruses. The V protein of PIV5, like that of many other paramyxoviruses, plays an important role in regulating viral RNA synthesis. In this work, we show that V interacts with Akt, a serine/threonine kinase, also known as protein kinase B. Both pharmacological inhibitors and small interfering RNA against Akt1 reduced PIV5 replication, indicating that Akt plays a critical role in PIV5 replication. Furthermore, treatment with Akt inhibitors also reduced the replication of several other paramyxoviruses, as well as vesicular stomatitis virus, the prototypical rhabdovirus, indicating that Akt may play a more universal role in NNSV replication. The phosphoproteins (P proteins) of NNSVs are essential cofactors for the viral RNA polymerase complex and require heavy phosphorylation for their activity. Inhibition of Akt activity reduced the level of P phosphorylation, suggesting that Akt is involved in regulating viral RNA synthesis. In addition, Akt1 phosphorylated a recombinant P protein of PIV5 purified from bacteria. The finding that Akt plays a critical role in replication of NNSV will lead to a better understanding of how these viruses replicate, as well as novel strategies to treat infectious diseases caused by NNSVs.     

Mechanisms of Non-segmented Negative Sense RNA Viral Antagonism of Host RIG-I-Like Receptors

The pattern recognition receptors RIG-I-like receptors (RLRs) are critical molecules for cytosolic viral recognition and for subsequent activation of type I interferon production. The interferon signaling pathway plays a key role in viral detection and generating antiviral responses. Among the many pathogens, the non-segmented negative sense RNA viruses target the RLR pathway using a variety of mechanisms. Here, I review the current state of knowledge on the molecular mechanisms that allow non-segmented negative sense RNA virus recognition and antagonism of RLRs.     

Role of Autophagy in Innate Viral Recognition

Plasmacytoid dendritic cells (pDCs) detect viruses in the acidified endosomes via Toll-like receptors (TLRs) upon endocytosis of virions. Yet, pDC responses to certain single-stranded RNA viruses occur only following live viral infection. In our recent study, we presented evidence that the recognition of such viruses by TLR7 requires autophagy. We speculate that the requirement for autophagy in viral recognition reflects the necessity for transportation of cytosolic viral replication intermediates into the lysosome where TLR7 is activated. In addition, autophagy was found to be required for pDCs to produce type I interferon (IFN) in response to both ssRNA and dsDNA viruses. These results indicated that autophagy plays a key role in mediating virus detection and IFNα secretion in pDCs, and suggest that cytosolic replication intermediates of ssRNA viruses serve as pathogen signatures recognized by TLR7.

Addendum to:

Autophagy-Dependent Viral Recognition by Plasmacytoid Dendritic Cells

H.K. Lee, J.M. Lund, B. Ramanathan, N. Mizushima and A. Iwasaki

Science 2007; In press     

Autophagy–virus interplay in plants: from antiviral recognition to proviral manipulation

Autophagy is a conserved self-cleaning and renewal system required for cellular homeostasis and stress tolerance. Autophagic processes are also implicated in the response to ‘non-self’ such as viral pathogens, yet the functions and mechanisms of autophagy during plant virus infection have only recently started to be revealed. Compelling evidence now indicates that autophagy is an integral part of antiviral immunity in plants. It can promote the hypersensitive cell death response upon incompatible viral infections or mediate the selective elimination of entire particles and individual proteins from compatible viruses in a pathway similar to xenophagy in animals. Several viruses, however, have evolved measures to antagonize xenophagic degradation or utilize autophagy to suppress disease-associated cell death and other defence pathways like RNA silencing. Here, we highlight the current advances and gaps in our understanding of the complex autophagy–virus interplay and its consequences for host immunity and viral pathogenesis in plants.     

Autophagy and RNA virus interactomes reveal IRGM as a common target

Several intracellular pathogens have the ability to avoid or exploit the otherwise destructive process of autophagy. RNA viruses are constantly confronted with cellular autophagy, and several of them hijack autophagy during the infectious cycle to improve their own replication. Nevertheless, our knowledge of viral molecular strategies used to manipulate autophagy remains limited. Our study allowed the identification of molecular interactions between 44 autophagy-associated proteins and 83 viral proteins belonging to five different RNA virus families. This interactome revealed that the autophagy network machinery is highly targeted by RNA viruses. Interestingly, whereas some autophagy-associated proteins are targeted by only one RNA virus family, others are recurrent targets of several families. Among them, we found IRGM as the most targeted autophagy-associated protein. Downregulation of IRGM expression prevents autophagy induction by measles virus, HCV and HIV-1, and compromises viral replication. Our work combined interactomic and analytical approaches to identify potential pathogen virulence factors targeting autophagy.     

Autophagy and RNA virus interactomes reveal IRGM as a common target

Several intracellular pathogens have the ability to avoid or exploit the otherwise destructive process of autophagy. RNA viruses are constantly confronted with cellular autophagy, and several of them hijack autophagy during the infectious cycle to improve their own replication. Nevertheless, our knowledge of viral molecular strategies used to manipulate autophagy remains limited. Our study allowed the identification of molecular interactions between 44 autophagy-associated proteins and 83 viral proteins belonging to five different RNA virus families. This interactome revealed that the autophagy network machinery is highly targeted by RNA viruses. Interestingly, whereas some autophagy-associated proteins are targeted by only one RNA virus family, others are recurrent targets of several families. Among them, we found IRGM as the most targeted autophagy-associated protein. Downregulation of IRGM expression prevents autophagy induction by measles virus, HCV and HIV-1, and compromises viral replication. Our work combined interactomic and analytical approaches to identify potential pathogen virulence factors targeting autophagy.