Alreration of nuclear matrix-intermediate filament system and differential expression of nuclear matrix proteins during human hepatocarcinoma cell differentiation

AIM： To investigate the association between the configurational and compositional changes of nuclear matrix and the differentiation of carcinoma cells. METHODS： Cells cultured with or without 5 × 10^-3 mmol/L of hexamethylene bisacetamide （HMBA） on Nickel grids were treated by selective extraction and prepared for whole mount observation under electron microscopy. The samples were examined under transmission electron microscope. Nuclear matrix proteins were selectively extracted and subjected to subcellular proteomics study. The protein expression patterns were analyzed by PDQuest software. Spots of differentially expressed nuclear matrix proteins were excised and subjected to in situ digestion with trypsin. The peptides were analyzed by matrix-assisted laser- desorption/ionization time of flight mass spectrometry （MALDI-TOF-MS）. Data were submitted for database searching using Mascot tool （www.matrixscience.com）. RESULTS： The nuclear matrix （NM） and intermediate filament （IF） in SMMC-7721 hepatocarcinoma cells were found relatively sparse and arranged irregularly. The nuclear lamina was non-uniform, and two kinds of filaments were not tightly connected. After induction for differentiation by HMBA, the NM-IF filaments were concentrated and distributed uniformly. The heterogeneous population of filaments, including highly branched utrathin filaments could also be seen in the regular meshwork. The connection between the two kinds of filaments and the relatively thin, condensed and sharply demarcated lamina composed of intermediate- sized filaments was relatively fastened. Meanwhile, 21 NM proteins changed remarkably during SMMC-7721 cell differentiation. Four proteins, i.e. mutant Pystl, hypothetical protein, nucleophosminl, and LBP were downregulated, whereas four other proteins, eIF6, p44 subunit, 13-tubulin, and SIN3B were upregulated with the last one, SR2/ASF found only in the differentiated SMMC-7721 cells. CONCLUSION： The induced differentiation of SMMC-7721 cells by HMBA is accompanied by the configurational changes of nuclear matrix-intermediate filament （NM-IF） system and the compositional changes of nuclear matrix protein expression. These changes may be important morphological or functional indications of the cancer cell reversion.

Mechanical properties of crosslinks controls failure mechanism of hierarchical intermediate filament networks

Intermediate filaments are one of the key components of the cytoskeleton in eukaryotic cells, and their mechanical properties are found to be equally important for physiological function and disease. While the mechanical properties of single full length filaments have been studied, how the mechanical properties of crosslinks affect the mechanical property of the intermediate filament network is not well understood. This paper applies a mesoscopic model of the intermediate network with varied crosslink strengths to investigate its failure mechanism under the extreme mechanical loading. It finds that relatively weaker crosslinks lead to a more flaw tolerant intermediate filament network that is also 23% stronger than the one with strong crosslinks. These findings suggest that the mechanical properties of interfacial components are critical for bioinspired designs which provide intriguing mechanical properties.

High Performance Hydrophobic Interaction Chromatography-A New Approach to Separate Intermediates of Protein Folding──Ⅰ.Separation of Intermediates of Urea-unfolded α-Amylase

Based on the different hydrophobicities of the intermediates of proteins the various conformational intermediates of the refolding of a-amylase originally denatured with 8.0 mol/L urea solution were separated with high performance hydrophobic interaction chromatography(HPHIC). Compared to the separation of the same intermediates with weak anion exchange chromatography and size-exclusion chromatography the result obtained with HPHIC is the best It would be expected that HPHIC may be a strongly potential tool to separate intermediates of some proteins which cannot be, or cannot completely be refolded by HPHIC.

Computational and theoretical modeling of intermediate filament networks:Structure,mechanics and disease

Intermediate filaments, in addition to microtubules and actin microfilaments, are one of the three major components of the cytoskeleton in eukaryotic cells. It was discovered during the recent decades that in most cells, intermediate filament proteins play key roles to reinforce cells subjected to large-deformation, and that they participate in signal transduction, and it was proposed that their nanome- chanical properties are critical to perform those functions. However, it is still poorly understood how the nanoscopic structure, as well as the combination of chemical composition, molecular structure and interfacial properties of these protein molecules contribute to the biomechanical properties of filaments and filament networks. Here we review recent progress in computational and theoretical studies of the intermediate filaments network at various levels in the protein＇s structure. A multiple scale method is discussed, used to couple molecular modeling with atomistic detail to larger-scale material properties of the networked material. It is shown that a finer-trains-coarser method- ology as discussed here provides a useful tool in understanding the biomechanical property and disease mechanism of intermediate filaments, coupling experiment and simulation. It further allows us to improve the understanding of associated disease mechanisms and lays the foundation for engineering the mechanical properties of biomaterials.

The keratin intermediate filament-like system in maize protoplasts

The application of Penman's method of cell fractionation to plant protoplasts leads to our finding of keratin intermediate filament(IF)-like system in maize protoplasts,which was identified by using immunogold labelling with monoclonal antibody of cytokeratin from animal cells.Many gold particles were found to be bound on filaments,linked by 3 nm filaments.After further digestion and extraction with DNase I and ammonium sulphate.IF-like framework-lamina-nuclear matrix system was shown under electron microscope.That IF system exists in plant protoplasts just like in animal cells,and their main component is keratin-like protein.

Sequence analysis of keratin-like proteins and cloning of intermediate filament-like cDNA from higher plant cells

Two keratin-like proteins of 64 and 55 ku were purified from suspension cells of Caucus carota L, and their partial amino acid sequences were determined. The homological analysis showed that the sequence from the 64 ku protein was highly homological to p-glucosidase, and that from the 55 ku protein had no significant homologue in GenBank. Using conservative sequence of animal IF proteins as primer, we cloned a cDNA fragment from Daucus carota L. Southern blot and Northern blot results indicated that this cDNA fragment was a single copy gene and expressed both in suspension cells and leaves. Homological analysis revealed that it had moderate homology to a variety of a-helical proteins. Our results might shed more light on molecular characterization of IF existence in higher plant.

Time course of expression of intermediate filament protein vimentin,nestin and desmin in rat renal glomerular injury

Podocytes in renal glomemlus express unusual intermediate filament proteins （IFs） for visceral epithelial cells. IFs cytoskeleton is mainly composed of vimentin, nestin and desmin. Tissue injury is often accompanied by changes in gene expression of IFs. Enhanced desmin staining in variety of rat experimental including 2 4 puromycin nephrosis. It has not podocytes are observed in a models of podocyte injury aminonucleoside （PAN） been elucidated whether expression of vimentin and nestin is up-regulated in podocyte injury. To further gain insight into expression of IFs in podocytes, we investigated the time course of vimentin, nestin and desmin in PAN nephrosis.

Bone morphogenetic protein-7 induced bone marrow stromal cells differentiate into neuron-like cells

Bone morphogenetic protein-7 is widely accepted as an inducer for bone marrow stem cells differentiating into osteoblasts and chondrocytes. Whether bone marrow stromal cells differentiate into neuron-like cells remains unclear. The current study examined the presence of positive cells for intermediate filament protein and microtubule associated protein-2 in the cytoplasm of bone marrow stromal cells induced by bone morphogenetic protein-7 under an inverted microscope, while no expression of glial fibrillary acidic protein was found. Reverse transcription PCR electrophoresis also revealed a positive target band for intermediate filament protein and microtubule-associated protein 2 mRNA. These results confirmed that bone morphogenetic protein-7 induces rat bone marrow stromal cells differentiating into neuron-like cells.

Structure Characterization of the Folding Intermediates of Proteins

Although the native state and the fully unfolded state of proteins have been extensively studied, the folding pathway and intermediates in the protein folding process have not been thoroughly investigated. To understand the mechanisms of protein folding, the early intermediates in the protein folding process must be clearly characterized. The present paper is a mini review containing 20 references involving studies on folding intermediates of several proteins.

Breast cancer resistance protein （Bcrp） and the testis--an unexpected turn of events

Breast cancer resistance protein （Bcrp） is an ATP-dependent efflux drug transporter. It has a diverse spectrum of hydrophilic and hydrophobic substrates ranging from anticancer, antiviral and antihypertensive drugs, to organic anions, antibiotics, phytoestrogens （e.g., genistein, daidzein, coumestrol）, xenoestrogens and steroids （e.g., dehydroepiandrosterone sulfate）. Bcrp is an integral membrane protein in cancer and normal cells within multiple organs （e.g., brain, placenta, intestine and testis） that maintains cellular homeostasis by extruding drugs and harmful substances from the inside of cells. In the brain, Bcrp is a major component of the blood- brain barrier located on endothelial cells near tight junctions （TJs）. However, Bcrp is absent at the Sertoli cell blood-testis barrier （BTB）; instead, it is localized almost exclusively to the endothelial TJ in microvessels in the interstitium and the peritubular myoid cells in the tunica propria. Recent studies have shown that Bcrp is also expressed stage specifically and spatiotemporally by Sertoli and germ cells in the seminiferous epithelium of rat testes, limited only to a testis-specific cell adhesion ultrastructure known as the apical ectoplasmic specialisation （ES） in stage VI-early VIII tubules. These findings suggest that Bcrp is equipped by late spermatids and Sertoli cells to protect late-stage spermatids completing spermiogenesis. Furthermore, Bcrp was found to be associated with F （filamentous）-actin and several actin regulatory proteins at the apical ES and might be involved in the organisation of actin filaments at the apical ES in stage VII-VIII tubules. These findings will be carefully evaluated in this brief review.

血清长链非编码RNA肌动蛋白纤维相关蛋白1-反义RNA1水平与钙化性主动脉瓣狭窄病人左心室功能的相关性研究

目的 分析血清长链非编码RNA(lncRNA)肌动蛋白纤维相关蛋白1-反义RNA1(AFAP1-AS1)表达水平与钙化性主动脉瓣狭窄(CAS)病人左心室收缩及舒张功能的相关性。方法 于2020年1月至2021年12月,选取中国中医科学院广安门医院就诊的CAS病人129例作为CAS组[左心室射血分数(LVEF)≥50%],同期该院健康志愿者130例作为对照组。收集病人人口学资料、超声及实验室生化指标,检测血清lncRNA AFAP1-AS1表达。受试者操作特征曲线(ROC曲线)分析血清lncRNA AFAP1-AS1诊断CAS效能。结果 对照组血清lncRNA AFAP1-AS1表达水平(1.15±0.18)低于CAS组(1.58±0.30)(P<0.001)。轻度狭窄者血清lncRNA AFAP1-AS1表达水平(1.37±0.26)低于中、重度狭窄者,而中度狭窄者lncRNA AFAP1-AS1表达水平(1.59±0.30)低于重度狭窄者(1.79±0.34)(P<0.001)。ROC结果显示,血清lncRNA AFAP1-AS1诊断CAS、重度狭窄的曲线下面积分别为0.86[95%CI:(0.82,0.91)]、0.88[95%CI:(0.82,0.94)]。CAS组AVA水平低于对照组(P<0.001),左室舒张末期内径(LVEDD)、左室舒张末期容积(LVEDV)、室间隔厚度(IVST)、左室后壁厚度(LVPWT)、左房前后径(LAD)、主动脉瓣平均压差(PGmean)、主动脉瓣峰值流速(Vmax)水平高于对照组(均P<0.001)。相关性分析显示,血清lncRNA AFAP1-AS1与LVEDD、Vmax、二尖瓣口舒张早期血流速度峰值(E峰)、二尖瓣口舒张晚期血流速度峰值(A峰)、LVEDV、PGmean、LVESD呈正相关(r=0.60、0.66、0.72、0.68、0.56、0.57、0.50,均P<0.001),与LVEF、AVA呈负相关(r=-0.78、-0.62,均P<0.001)。结论 CAS病人血清lncRNA AFAP1-AS1表达水平升高,与CAS病情严重程度以及左心室舒张、收缩功能有关,并可作为无创血清标志物辅助临床诊断CAS。

棉和羽毛蛋白丝交织物的性能测试

对棉和羽毛蛋白丝交织物进行吸湿速干、透湿、抗静电和防紫外线性能测试,并与棉织物和棉涤纶丝织物进行对比分析,得出结论:棉羽毛蛋白丝织物的吸水率、滴水扩散时间、芯吸高度达到GB/T 21655.1—2023中吸湿速干织物Ⅱ级的要求,但干燥速率未达到吸湿速干织物要求:棉羽毛蛋白丝织物透湿性能较好,抗静电性能优异,符合防紫外线产品要求;棉羽毛蛋白丝织物适宜用作夏季服装面料。

‘曼赛龙柚’种子不同发育期高温耐性研究

全球变暖导致极端高温频发,植物种子不可避免地置身于高温胁迫环境之中。为探究种子高温耐性的生理基础,该文以中间型种子‘曼赛龙柚’(Citrus maxima‘Mansailong’)为实验材料,对不同发育阶段的种子进行高温处理,并同步检测各个发育时期种子的形态变化、可溶性蛋白和热稳定蛋白含量以及细胞超显微结构的变化。结果表明:(1)在花后23周到49周的整个发育过程中,种子含水量明显降低,鲜重显著增加,干重与鲜重的百分比也有明显的提高,这些指标均是在花后31周前后快速变化,到花后41周趋于稳定。(2)种子在花后29周获得完全的成苗能力和初步的高温耐性,此后高温耐性逐渐增加,并在花后37~49周之间快速提高。与种子高温耐性的变化相似,种子中可溶性蛋白和热稳定蛋白含量在花后23~49周均呈连续升高趋势,相关性分析表明在整个发育过程中这两者的积累与种子的高温耐性呈显著正相关。(3)超显微结构观察发现,随着种子的发育,线粒体逐渐减少,胚轴细胞体积逐渐变小,细胞中脂质体逐渐增多并且排列趋于规则,同时液泡由小变大且后期的液泡中充斥着黑色絮状物。综上所述,‘曼赛龙柚’种子在花后41周达到生理成熟,没有明显的成熟脱水过程;其高温耐性是在发育过程中获得并逐渐提高,直到种子发育的后期;种子中可溶性蛋白和热稳定蛋白含量的增加及细胞超显微结构的变化对种子高温耐性的发育具有重要贡献。

糖络宁调控细胞骨架干预糖尿病周围神经病变脱髓鞘的作用机制

目的 基于PDZ和LIM结构域蛋白7(PDZ and LIM domain protein 7,Pdlim7)和突触极蛋白(synaptopodin-2,Synpo2)调控的丝状肌动蛋白(filamentous actin, F-actin)探讨糖络宁改善糖尿病周围神经病变(diabetic peripheral neuropathy, DPN)脱髓鞘的干预作用及机制。方法 采用腹腔注射链脲佐菌素建立高血糖大鼠模型。将SD大鼠随机分为空白组、模型组、阳性药组(α-硫辛酸,20 mg/kg)和糖络宁组(10.9 g/kg),每组12只。干预12周后,观察透射电镜观察大鼠坐骨神经超微结构并统计髓鞘相对面积和G-ratio;检测鼠尾热痛阈值与坐骨神经神经传导速度,观察各组大鼠神经功能;4D-label free蛋白质组学联合生物信息学分析筛选DPN大鼠坐骨神经的差异性蛋白。采用蛋白免疫印迹法与免疫荧光法检测坐骨神经细胞骨架相关胶质纤维酸性蛋白、微管蛋白、F-actin和Pdlim7、Synpo2的表达。结果 与空白组比较,模型组坐骨神经髓鞘相对面积和G-ratio数值降低(P<0.05),热痛阈值增加(P<0.01),运动和感觉神经传导速度均降低(P<0.01);与模型组比较,糖络宁组髓鞘相对面积和G-ratio数值显著升高(P<0.01),热痛阈值降低(P<0.01),运动和感觉神经传导速度均增加(P<0.01)。蛋白质组学显示,糖络宁干预12周后,DPN大鼠坐骨神经差异蛋白多与细胞骨架、肌动蛋白结合及PDZ结构域和LIM结构域蛋白相关。与空白组比较,模型组坐骨神经中F-actin、Pdlim7和Synpo2表达降低(P<0.05,P<0.01,P<0.01);与模型组比较,糖络宁组F-actin、Pdlim7和Synpo2表达明显升高(P<0.01)。共定位结果表明,与空白组比较,模型组髓鞘上F-actin表达显著降低(P<0.01),与F-actin共定位的Pdlim7表达明显降低(P<0.01);与模型组比较,糖络宁组髓鞘上F-actin表达显著升高(P<0.01),与F-actin共定位的Pdlim7表达明显升高(P<0.01)。结论 糖络宁改善DPN坐骨神经脱髓鞘与调控细胞骨架相关,机制与增加Pdlim7和Synpo2的表达,进而增加细胞骨架蛋白F-actin生成而促进髓鞘生成有关。

Disassembly intermediates of RbsD protein remain oligomeric despite the loss of an intact secondary structure

Many proteins exist as homo-oligomers in living organisms wherein the change of oligomeric status apparently serves as an effective means for modulating their biological activities. We have previously reported that the homo-decameric RbsD from Escherichia coli undergoes stepwise disassembly and non-stepwise reassembly. Here the structural status of the urea-induced RbsD disassembly intermediates was examined, mainly using urea-containing polyacrylamide gel electrophoresis and chemical cross-linking. Such intermediates were found to remain oligomeric while losing their intact secondary structures. Such disassembly intermediates were able to effectively refold when the concentration of the urea denaturant was reduced to a lower level, or to refold/reassemble into the native decamers when urea was completely removed, as detected by non-denaturing polyacrylamide gel electrophoresis. These novel observations strongly suggest that the assembly of oligomeric proteins may occur before the completion of subunit folding.

Intermediate Filaments in Higher Plant Cells and Their Reconstitution in vitro

Delicate networks of 10-nm filaments were found to exist widely in suspension cells of cultured carrot and root tip cells of pea by selective extraction combined with whole mount and diethylene glycol distearate plastic embedment-free section for electron microscopy. These filament components are polypeptides of 52, 58, 62—64 and 50kD using Western blot analysis. A relatively uniform 10-nm filaments, as well as bundle of such filaments could be reconstituted in vitro. The reconstituted filaments were indistinguishable from native plant intermediate filaments in morphology and protein components. Thus the intermediate filaments are actually present in cytoplasm of higher plants. We also found no obvious specificity in tissues and species by comparison of the proteins among various types of plant cells.

Assembly characteristics of plant keratin intermediate filaments in vitro

After selective extraction and purification, plant keratin intermediate filaments were reassembled in vitro. Scanning tunneling microscope (STM) and transmission electron microscope (TEM) micrographs showed that acidic keratins and basic keratins can assemble into dimers and further into 10 nm filaments in vitro. In higher magnification images , it can be seen that fully assembled plant keratin intermediate filaments consist of several thinner filaments of 3 nm in diameter, which indicates the formation of protofilaments in the assembly processes. One of the explicit features of plant keratin intermediate filaments is a 24-25 nm periodic structural repeat alone the axis of both the 10 nm filaments and protofilaments. The periodic repeat is one of the fundamental characteristic of all intermediate filaments, and demonstrates the half staggered arrangement of keratin molecules within the filaments.

Joining actions: crosstalk between intermediate filaments and actin orchestrates cellular physical dynamics and signaling

Many key cellular functions are regulated by the interplay of three distinct cytoskeletal networks, made of actin filaments,microtubules, and intermediate filaments(IFs), which is a hitherto poorly investigated area of research. However, there are growing evidence in the last few years showing that the IFs cooperate with actin filaments to exhibit strongly coupled functions.This review recapitulates our current knowledge on how the crosstalk between IFs and actin filaments modulates the migration properties, mechano-responsiveness and signaling transduction of cells, from both biophysical and biochemical point of view.

THE KERATIN INTERMEDIATE FILAMENTLIKE SYSTEM IN THE PLANT MESOPHYLL CELLS

A delicate intermediate filament-like network of mesophyll cells was observed both in maize and tobacco, using selective extraction together with whole-mount cell preparation for electron microscopy. The filament of the network is about 10 nm in diameter. Further test using immuno-gold labeling with anti-keratin antibodies indicated that the component of the intermediate filament-like system was keratin-like protein. Such a keratin-like intermediate filament system existing in plant cells was demonstrated for the first time. Meanwhile, 3-nm size filaments and their connection with 10-nm filaments were also shown in maize and tobacco protoplasts.

THE KERATIN-LIKE INTERMEDIATE FILAMENT IN PLANT ROOT TIP CELLS

Ⅰ. INTRODUCTION Intermediate filaments with a diameter of 10 nm, known as a cytoskeleton system, are extensively present in animal cells. Whether the intermediate filaments are present in plant cells remains to be a question. Some investigators attempt to seek answers from various aspects, but it is still unsolved. Powell observed 7-nm filament in carrot suspension cells after treatment with high salt and Triton X-100. Dawson and Miller showed