磷酸化与泛素化修饰对雷帕霉素靶蛋白复合物1(TORC1)信号通路的调控

TORC1是一个在真核生物中高度保守的激酶复合物,能通过感应营养物质、生长因子、能量水平等信号调节细胞代谢水平和生长。TORC1信号通路的失调与代谢紊乱、神经病变、癌症和衰老密切相关。本文比较了酵母细胞及哺乳动物细胞中TORC1的结构与功能,并着重综述了磷酸化和泛素化修饰在TORC1信号通路中的作用。由于磷酸化和泛素化在传导外界信号至TORC1以及调节TORC1下游通路中均发挥重要作用,因此深入研究磷酸化和泛素化对TORC1信号通路的影响,将为药物靶点的发现提供新思路。

左归降糖解郁方通过调控SIRT1/TORC1通路增加糖尿病并发抑郁症大鼠海马神经元树突棘密度

目的:探明左归降糖解郁方调控糖尿病并发抑郁症大鼠海马SIRT1/TORC1信号通路并增加神经元树突棘的机制。方法:建立糖尿病并发抑郁症大鼠模型,并分别给予高、中、低剂量(20.52、10.26和5.13 g/kg)左归降糖解郁方。采用ELISA法测评各组大鼠血糖和胰岛素抵抗水平,采用强迫游泳实验和悬尾实验评价大鼠的抑郁样行为,采用Golgi-Cox染色观察海马神经元树突棘形态,采用Western blot法检测海马组织中SIRT1和TORC1蛋白表达。随后,给予模型大鼠海马脑区注射SIRT1的激动剂SRT2104和抑制剂sirtinol,研究SIRT1/TORC1信号通路影响树突棘形态的分子途径。最后,在给予高剂量左归降糖解郁方的基础上注射sirtinol,进一步明确左归降糖解郁方调控海马SIRT1/TORC1信号和树突棘密度的分子机制。结果:左归降糖解郁方可有效降低模型大鼠血糖含量和胰岛素抵抗指数,减少抑郁样行为,并显著改善大鼠海马神经元树突棘形态,增加海马SIRT1和TORC1蛋白表达。机制研究发现,SIRT1激动剂可显著增加海马TORC1、p-CREB和BDNF的表达及树突棘密度,而SIRT1抑制剂则显著抑制了左归降糖解郁方对模型大鼠海马TORC1、p-CREB和BDNF表达及树突棘密度的作用。结论:左归降糖解郁方可通过激活海马SIRT1/TORC1信号通路改善海马神经营养作用,从而进一步调节海马神经元树突棘形态。

PI3K/AKT/TORC1信号通路对丝素蛋白合成转录因子SGF1表达的影响

SGF1(silk gland factor 1)是一种转录调控因子,属于Fox家族的Fox A亚家族成员,能够启动丝素基因的表达,合成丝素蛋白。已知果蝇和其他高等动物中的PI3K/AKT/TORC1信号通路可以调控Fox转录蛋白的表达。为了探究家蚕幼虫后部丝腺(PSG)中PI3K/AKT/TORC1信号通路对SGF1表达水平的影响,对4龄第4天和5龄第7天家蚕幼虫分别注射信号通路抑制剂Wort、Rapa和LY294,24 h后解剖取出后部丝腺,一组用于免疫组织化学染色实验,另一组用于提取蛋白质进行Western blot检测。免疫组织化学染色实验表明,与对照组相比,注射3种信号通路抑制剂的家蚕幼虫后部丝腺组织的绿色荧光亮度明显减弱;Western blot检测表明,与对照组相比,实验组家蚕幼虫后部丝腺的蛋白质浓度有所下降。综合以上结果初步得出PI3K/AKT/TORC1信号通路抑制剂处理均可降低家蚕幼虫后部丝腺中SGF1表达的结论,即提示可以通过上游信号通路PI3K/AKT/TORC1影响SGF1的表达水平,进而调控丝素蛋白的合成。

Effects of dietary protein restriction on muscle fiber characteristics and m TORC1 pathway in the skeletal muscle of growing-finishing pigs

Background： To investigate the effects of dietary crude protein（CP） restriction on muscle fiber characteristics and key regulators related to protein deposition in skeletal muscle, a total of 18 growing-finishing pigs（62.30 ± 0.88 kg）were allotted to 3 groups and fed with the recommended adequate protein（AP, 16 % CP） diet, moderately restricted protein（MP, 13 % CP） diet and low protein（LP, 10 % CP） diet, respectively. The skeletal muscle of different locations in pigs, including longissimus dorsi muscle（LDM）, psoas major muscle（PMM） and biceps femoris muscle（BFM） were collected and analyzed.Results： Results showed that growing-finishing pigs fed the MP or AP diet improved（P 〈 0.01） the average daily gain and feed： gain ratio compared with those fed the LP diet, and the MP diet tended to increase（P = 0.09） the weight of LDM. Moreover, the ATP content and energy charge value were varied among muscle samples from different locations of pigs fed the reduced protein diets. We also observed that pigs fed the MP diet up-regulated（P 〈 0.05） muscular m RNA expression of all the selected key genes, except that myosin heavy chain（My HC） IIb,My HC IIx, while m RNA expression of ubiquitin ligases genes was not affected by dietary CP level. Additionally, the activation of mammalian target of rapamycin complex 1（m TORC1） pathway was stimulated（P 〈 0.05） in skeletal muscle of the pigs fed the MP or AP diet compared with those fed the LP diet.Conclusion： The results suggest that the pigs fed the MP diet could catch up to the growth performance and the LDM weight of the pigs fed the AP diet, and the underlying mechanism may be partly due to the alteration in energy status, modulation of muscle fiber characteristics and m TORC1 activation as well as its downstream effectors in skeletal muscle of different locations in growing-finishing pigs.

Elongator复合物在低浓度氨基酸条件下对TORC1活性的影响

目的:研究Elongator复合物在低浓度氨基酸条件下对TORC1活性的影响。方法:通过生长实验来观察Elongator突变体在低浓度氨基酸和低浓度亮氨酸条件下的生长程度;通过免疫印迹法检测核糖体蛋白S6的磷酸化水平来检测TORC1的活性;将GFP-ATG8质粒转入到Elongator突变体及野生型酵母菌株WT里,并通过免疫印迹法检测游离的GFP蛋白的水平来检测体内自噬。结果:生长实验显示Elongator突变体在低浓度氨基酸条件下显示过度生长的特性,并且这种过度生长可被TORC1抑制剂雷帕霉素所抑制;免疫印迹检测TORC1活性的实验以及检测体内自噬实验显示Elongator突变体在低浓度氨基酸条件下TORC1活性上升,而自噬进程被抑制;进一步实验证明Elongator突变体可特异性忽略低浓度亮氨酸而激活TORC1,抑制自噬,从而持续生长。结论:Elongator复合物在氨基酸信号下可抑制TORC1的活性,同时促进体内自噬进程。推测Elongator复合物可通过抑制TORC1信号通路确保细胞内蛋白翻译的准确性。

蜕皮激素和IIS-TORC1信号的分子互作

蜕皮激素信号主导调控昆虫的蜕皮和变态,决定昆虫的发育时间;IIS-TORC1信号整合生长因子、激素、营养和能量信号,决定昆虫的生长速率。蜕皮激素和IIS-TORC1信号之间发生3种分子互作:(1)IIS-TORC1信号促进前胸腺和卵巢合成蜕皮激素前体。(2)在蜕皮和变态期间,蜕皮激素抑制脂肪体细胞内IIS-TORC1信号、Myc的转录、细胞生长及其内分泌功能,导致脑神经分泌细胞分泌胰岛素样肽的功能减弱,从而降低昆虫全身性的IIS-TORC1信号。(3)在幼虫摄食期间,胰岛素信号抑制FOXO的转录活性,降低了蜕皮激素受体EcR的转录共激活因子DOR编码基因的转录水平,从而阻碍了蜕皮激素信号传导。蜕皮激素信号和IIS-TORC1信号协同调控发育时间和生长速率共同决定昆虫的个体大小。

亮氨酰-tRNA合成酶通过细胞内的亮氨酸调节雷帕霉素受体复合物(TORC1)活性的新功能

TORC1(target of rapamycin complex 1)可整合营养、能量、生长因子及氨基酸等多种细胞外信号,调控基因转录、蛋白质翻译、核糖体合成等生物过程,在细胞生长和凋亡中发挥极为重要的作用。亮氨酰-tRNA合成酶(LeuRS)的经典功能是催化合成亮氨酰-tRNA直接参与遗传信息的解码合成蛋白质。最新研究结果表明人细胞质LeuRS除了经典功能外,还参与调控TORC1途径。综述了LeuRS的非经典功能,它是如何通过感受细胞内的亮氨酸浓度来调节TORC1活性的。这些结果表明了古老的氨基酰-tRNA合成酶家族在进化的过程中被赋予了新的功能。

酿酒酵母TORC1通路上游调控元件以及在核糖体合成中的作用

酿酒酵母的TORC1(target of rapamycin complex 1)复合体是由Kog1、Lst8、Tco89以及Tor1或者Tor2组成,其中,Tor1和Tor2最初是作为雷帕霉素作用靶点而在1991年被发现的。近年来的一些研究表明,TORC1以及另一个相似的复合体TORC2参与营养代谢、核糖体合成、细胞周期、自噬衰老等细胞进程。近几年来对TORC1上游调控元件EGO(escape from rapamycin-induced growth arrest)复合体的深入研究,很大程度上解释了TORC1对氨基酸的感知途径。核糖体的生物合成是高度耗能的过程,而TORC1在r RNA转录及核糖体蛋白合成的过程中起到重要的控制作用。该文以酿酒酵母TORC1为例,回顾它的发现过程,并综述近几年在TORC1上游调控元件以及核糖体合成中作用的研究进展。

mTORC1在慢性肾功能不全胰岛素抵抗中的作用

代谢综合征(MetS)在慢性肾功能不全(CKD)患者中普遍存在,与CKD预后密切相关。胰岛素抵抗(IR)作为MetS的基础,是非糖尿病CKD患者疾病进展的独立危险因素。而mTORC1信号通路可感受多种环境变化调节机体的生长代谢稳态,参与肿瘤、肥胖、2型糖尿病等多种疾病发生发展过程。mTORC1过度激活被认为是2型糖尿病IR的机制之一,但在CKD疾病状态下,mTORC1与IR的关系尚不十分清楚。本文就CKD疾病状下,mTORC1对胰岛素信号通路的影响,做一简要概述,为CKD患者IR的治疗提供参考。

ESCRT与TORC1共同调控微自噬

微自噬是真核生物体利用溶酶体直接降解蛋白质和受损细胞器的过程,在维持细胞稳态和生长发育中发挥重要作用。作为影响自噬流进程的关键复合物,内体分选转运复合体(endosomal sorting complex required for transport,ESCRT)和雷帕霉素靶蛋白复合体1(target of rapamycin complex 1,TORC1)在微自噬的调控通路中存在协同作用。本文通过系统性归纳并总结ESCRT与TORC1共同调控微自噬的分子机制,同时比较在不同类型的自噬中调控机制的差异,分析该领域仍存在的一些未解之谜,为发现调控自噬的新型分子机制提供可行性思路,为人类自噬相关疾病药物的研究提供潜在新靶点。

Sestrin2在运动防治骨骼肌萎缩中的作用研究进展

骨骼肌约占人体重量的40%,是人体内重要的运动和代谢器官,对于维持机体正常生命活动至关重要。长期卧床、骨骼肌去神经支配、营养不良、增龄等因素均会导致骨骼肌萎缩的发生。运动干预作为一种经济、有效的肌萎缩防治手段,目前已广泛应用于临床骨骼肌萎缩的治疗,但其机制尚未完全明了。研究发现,应激诱导蛋白Sestrins介导了运动调节机体代谢以延缓衰老的进程,且有氧运动显著增加骨骼肌Sestrin2的表达。本文总结近些年来国内外有关Sestrin2在运动防治骨骼肌萎缩中的作用研究进展,分析Sestrin2介导运动改善骨骼肌萎缩的可能机制,以期为运动干预防治肌萎缩提供新的理论依据。

RAB1A在肿瘤发生发展中的作用研究进展

RAB1A是一种小三磷酸鸟苷(guanosine triphosphate, GTP)酶,是内质网和高尔基体之间囊泡转运的重要调节成分,可以在非活性GDP结合形式和活性GTP结合形式之间转化。RAB1A除了在囊泡转运中的作用外,还参与营养感应、信号转导、细胞迁移和自噬调节。RAB1A更多是作为癌基因发挥作用,主要通过激活哺乳动物雷帕霉素靶蛋白复合体1(mammalian target of rapamycin complex 1,mTORC1)信号通路,调节肿瘤细胞增殖、迁移、侵袭和转移。研究表明,RAB1A的异常激活与结直肠癌、HCC、乳腺癌、胃癌、前列腺癌等多种恶性肿瘤的发生发展密切相关。本文主要就RAB1A的结构与功能、在肿瘤发生发展中的作用及相关信号通路进行综述。

Current status of PI3K-mTOR inhibition in hormone-receptor positive, HER2-negative breast cancer

Breast cancer (BC) is the most common cancer in women and second only to lung cancer in terms of mortality. Among the three different BC subtypes, the oestrogen receptor positive represents nearly 70% of all cases and it is usually treated with anti-oestrogen drugs. However, the majority of hormone receptor positive metastatic BC patients develop resistance to anti-oestrogen treatments.The need for more down-stream therapies brought to the development of therapeutic strategies inhibiting the phosphatidylinositol 3-kinase-mammalian target of rapamycin (mTOR) pathway. Inhibitors of the mTOR have been tested in different clinical trials; everolimus has been Food and Drug Administration approved for the treatment of oestrogen receptor positive/human epidermal growth factor receptor 2 negative BC patients in combination with exemestane in patients who have progressed to anastrozole or letrozole after the encouraging results coming from BOLERO-2 trial. Similar results were obtained by the TAMRAD investigatory study testing tamoxifen in combination with everolimus in advanced BC. This editorial focuses on the results from BOLERO-2, BOLERO 4 and BOLERO-6, which tested the clinical importance of mTOR inhibition. We comment also on the role of phosphatidylinositol 3-kinase-mTOR inhibition as reported in the BELLE-2 and BELLE-3 trials and the future directions for the inhibition of this tumour metabolic axis.

Construction and identification of recombinant lentivirus-mediated gene transfer system for rat transducer of regulated CREB activity 1

Objective： To construct a recombinant lentivirus vector which carries SD rat transducer of regulated CREB activity-1（TORC1） gene and examine its ability to express the TORC 1 gene in vitro. Methods： The coding sequence of SD rat TORC 1 gene was amplified using PCR and cloned into pGC-FU vector. 293T cells were transfected using Lipofectamine 2000 and packaged for the recombinant lentivirus particles. When the cloned sequence was identified to be right, the recombinant lentivirus particles were amplified in a large quantity. The titer of virus was determined by real-time PCR and the level of TORC1 expression was examined by Western blot. Results： The recombinant lentivirus vector carrying TORC1 was constructed successfully and could express TORC1 at a high level in 293T cells in vitro, and the titer determined by real-time PCR was 2 × 10^8 TU/ml. Conclusion： The recombinant lentivirus vector could express TORCl gene at a high level, and was very helpful in the study of exploring the effect of TORC1 on spinal cord injury.

BmSLC7A5 is essential for silk protein synthesis and larval development in Bombyx mori

Insects produce silk to form cocoons,nests,and webs,which are important for their survival and reproduction.However,little is known about the molecular mecha-nism of silk protein synthesis at the translation level.The solute carrier family 7(SLC7)genes are involved in activating the target of rapamycin complex 1(TORC1)signaling pathway and protein translation process,but the physiological roles of SLC7 genes in silk-producing insects have not been reported.Here,we found that amino acid signaling regulates silk protein synthesis and larval development via the L-type amino acid trans-porter 1(LAT1;also known as SLC7A5)in Bombyx mori.A total of 12 SLC7 homologs were identified in the silkworm genome,among which BmSLC7A5 was found to be a silk gland-enriched gene and may be involved in leucine transport.Bioinformatics analy-sis indicated that SLC7A5 displays high homology and a close phylogenetic relationship in silk-producing insects.Subsequently,we found that leucine treatment significantly in-creased silk protein synthesis by improving the transcription and protein levels of silk genes.Furthermore,systemic and silk gland-specific knockout of BmSLC7A5 led to de-creased silk protein synthesis by inhibiting TORC1 signaling,and somatic mutation also resulted in arrested development from the 5th instar to the early pupal stage.Altogether,our study reveals that BmSLC7A5 is involved in regulating silk protein synthesis and larval development by affecting the TORC1 signaling pathway,which provides a new strategy and target for improving silk yield.

An enhanced network of energy metabolism,lysine acetylation,and growth-promoting protein accumulation is associated with heterosis in elite hybrid rice

Heterosis refers to the superior performance of a hybrid compared with its parental lines.Although several genetic and molecular models have been proposed to explain heterosis,it remains unclear how hybrid cells integrate complementary gene expression or activity to drive heterotic growth.In this work,we show that accumulation of growth-promoting and energy metabolism proteins,enhanced energy metabolism activities,and increased protein lysine acetylation were associated with superior growth of the panicle meristem in the elite hybrid rice Shanyou 63 relative to its parental varieties.Metabolism of nuclear/cytosolic acetylcoenzyme A was also enhanced in the hybrid,which paralleled increases in histone H3 acetylation to selectively target the expression of growth-promoting and metabolic genes.Lysine acetylation of cellular proteins,including TARGET OF RAPAMYCIN complex 1,ribosomal proteins,and energy metabolism enzymes,was also augmented and/or remodeled to modulate their activities.The data indicate that an enhanced network of energy-producing metabolic activity and growth-promoting histone acetylation/gene expression in the hybrid could contribute to its superior growth rate and may constitute a model to explain heterosis.

Ribosome biogenesis protein Urb1 acts downstream of mTOR complex 1 to modulate digestive organ development in zebrafish

Ribosome biogenesis is essential for the cell growth and division. Disruptions in ribosome biogenesis result in developmental defects and a group of diseases, known as ribosomopathies. Here, we report a mutation in zebrafish urb1, which encodes an essential ribosome biogenesis protein. The urb1 cq31 mutant exhibits hypoplastic digestive organs, which is caused by impaired cell proliferation with the differentiation of digestive organ progenitors unaffected. Knockdown of mtor or raptor leads to similar hypoplastic phenotypes and reduced expression of urb1 in the digestive organs. Overexpression of Urb1 results in overgrowth of digestive organs, and can efficiently rescue the hypoplastic liver and pancreas in the mtor and raptor morphants. Reduced syntheses of free ribosomal subunits and impaired assembly of polysomes are observed in the urb1 mutant as well as in the mtor and raptor morphants, which can be rescued by the Urb1 overexpression. These data demonstrate that Urb1 plays an important role in governing ribosome biogenesis and protein synthesis downstream of mammalian/mechanistic target of rapamycin complex 1（mTORC1）, thus regulating the development of digestive organs. Our study indicates the requirement of hyperactive protein synthesis for the digestive organ development.

Twists and turns—How we stepped into and had fun in the “boring” lipid field

Compared to proteins and RNAs, functional specificities associated with structural variations in fatty acids and lipids have been greatly underexplored. This review describes how our lab naively started to work on lipids 14 years ago, and how we have gradually overcome obstacles to address some interesting biological questions by combining genetics with biochemical methods on the nematode Caenorhabditis elegans. Our studies have revealed lipid variants and their metabolic pathways, in specific tissues, impact development and behaviors by regulating specific signaling events. The review also discusses the general research approach, style of lab management, and funding mechanisms that have facilitated the frequent research direction changes in the lab, including the journey into the lipid field.

Recent advances in amino acid sensing and new challenges for protein nutrition in aquaculture

From the conventional knowledge of protein nutrition to the molecular nutrition of amino acids, our understanding of protein/amino acid nutrition is rapidly increasing. Amino acids control cell growth and metabolism through two amino acid-sensingpathways, i.e. target of rapamycin complex 1 (TORC1) and the general control nonderepressible 2 (GCN2) signaling pathway.In the amino acid-abundant status, TORC1 dominates intracellular signaling and increases protein synthesis and cell growth.In contrast, amino acid deprivation actives GCN2 resulting in repression of general protein synthesis but facilitates the aminoacid transport and synthesis process. By integrating and coordinating nutrition and hormone signaling, TORC1 and GCN2control the switch of the catabolism and anabolism phase in most eukaryotes. Now, we appreciate that the availability ofindividual amino acids is sensed by intracellular sensors. These cutting-edge findings expand our knowledge of amino acidnutrition. Although the TORC1 and GCN2 were discovered decades ago, the study of molecular amino acid nutrition inaquaculture animals is still at its infancy. The aquaculture industry is highly dependent on the supply of fishmeal, which isthe major protein source in aquacultural animal diets. Some concerted efforts were conducted to substitute for fishmeal dueto limited supply of it. However, the concomitant issues including the unbalanced amino acid profile of alternative proteinsources limited the utilization of those proteins. Continued study of the molecular nutrition of amino acid in aquacultureanimals may be expected in the immediate future to expand our knowledge on the utilization of alternative protein sources.