The mechanical behaviors of filamentous actin (F-actin) bundles play an essential role in filopodial protrusions at the leading edge of crawling cells. These bundles consist of parallel actin filaments that are hexago...The mechanical behaviors of filamentous actin (F-actin) bundles play an essential role in filopodial protrusions at the leading edge of crawling cells. These bundles consist of parallel actin filaments that are hexagonally packed and interconnected via cross-linking proteins including α-actinin, filamin, and fascin. As pushing against the plasma membrane and/or external barriers, the actin bundles in filopodial protrusion inevitably encounter a compressive load. The bending stiffness and buckling stability of actin bundles are therefore important in determining the filopodia architecture and subsequent cell morphology. In this work, we employ a coarse-grained molecular dynamics model to investigate the buckling behaviors of cross-linked actin bundles under compression, which explicitly accounts for the properties of constituent filaments and the mechanical descriptions of cross-linkers. The bending stiffness of actin bundles exhibits a generic size effect depending on the number of filaments in the bundles, explicitly depending on the degree of inter-filament coupling. The distinct buckling modes are analyzed for bundles with different coupling states and strengths of cross-linkers. This study could clarify the stability and buckling mechanisms of parallelly packed actin bundles and the structure-function relations of mechanical components in filopodial protrusion.展开更多
This paper proposes a novel four-dimensional approach to the structural study of protein complexes. In the approach, the surface of a protein molecule is to be described using the intersection of a pair of four-dimens...This paper proposes a novel four-dimensional approach to the structural study of protein complexes. In the approach, the surface of a protein molecule is to be described using the intersection of a pair of four-dimensional triangular cones (with multiple top vertexes). As a mathematical toy model of protein complexes, we consider complexes of closed trajectories of n-simplices (n=2,3,4...), where the design problem of protein complexes corresponds to an extended version of the Hamiltonian cycle problem. The problem is to find “a set of” closed trajectories of n-simplices which fills the n-dimensional region defined by a given pair of n+1 -dimensional triangular cones. Here we give a solution to the extended Hamiltonian cycle problem in the case of n=2 using the discrete differential geometry of triangles (i.e., 2-simplices).展开更多
Plastins are a family of actin binding proteins （ABPs） known to cross-link actin microfilaments in mammalian cells, creating actin microfilament bundles necessary to confer cell polarity and cell shape. Plastins als...Plastins are a family of actin binding proteins （ABPs） known to cross-link actin microfilaments in mammalian cells, creating actin microfilament bundles necessary to confer cell polarity and cell shape. Plastins also support cell movement in response to changes in environment, involved in cell/tissue growth and development. They also confer plasticity to cells and tissues in response to infection or other pathological conditions （e.g., inflammation）. In the testis, the cell-cell anchoring junction unique to the testis that is found at the Sertoli cell-cell interface at the blood-testis barrier （BTB） and at the Sertoli-spermatid （e.g., 8-19 spermatids in the rat testis） is the basal and the apical ectoplasmic specialization （ES）, respectively. The ES is an F-actin-rich anchoring junction constituted most notably by actin microfilament bundles. A recent report using RNAi that specifically knocks down plastin 3 has yielded some insightful information regarding the mechanism by which plastin 3 regulates the status of actin microfilament bundles at the ES via its intrinsic actin filament bundling activity. Herein, we provide a brief review on the role of plastins in the testis in light of this report, which together with recent findings in the field, we propose a likely model by which plastins regulate ES function during the epithelial cycle of sDermatogenesis via their intrinsic activity on actin microfilament organization in the rat testis.展开更多
Long myosin light chain kinase (L-MLCK) contains five DFRXXL motifs with ability to bind F-actin. Binding stoichiometry data indicated that each DFRXXL motif might bind each G-actin, but its biological significance re...Long myosin light chain kinase (L-MLCK) contains five DFRXXL motifs with ability to bind F-actin. Binding stoichiometry data indicated that each DFRXXL motif might bind each G-actin, but its biological significance remained unknown. We hypothesized that L-MLCK might act as an F-actin bundle peptides by its multiple binding sites of 5DFRXXL motifs to actin. In order to characterize F-actin-bundle formation properties of 5DFRXXL region of long myosin light chain kinase, we expressed and purified 5DFRXXL peptides tagged with HA in vitro. The properties of 5DFRXXL peptides binding to myofilaments or F-actin were analyzed by binding stoichiometries assays. The results indicated that 5DFRXXL peptides bound to myofilaments or F-actin with high affinity. KD values of 5DFRXXL binding to myofilaments and F-actin were 0.45 and 0.41 μmol/L, re- spectively. Cross-linking assay demonstrated that 5DFRXXL peptides could bundle F-actin efficiently. Typical F-actin bundles were observed morphologically through determina- tion of confocal and electron microscopy after adding 5DFRXXL peptides. After transfection of pEGFP-5DFRXXL plasmid into eukaryocyte, spike structure was observed around cell membrane edge. We guess that such structure formation may be attributable to F-actin over-bundle forma- tion caused by 5DFRXXL peptides. Therefore, we suppose that L-MLCK may be a new bundling protein and somehow play a certain role in organization of cell skeleton besides mediating cell contraction by it kinase activity.展开更多
目的分析肌动蛋白结合蛋白1(fascin actin-bundling protein 1,FSCN1)在头颈部鳞状细胞癌(head and neck squamous cell carcinoma,HNSCC)中的表达及与预后的关系。方法TCGA数据库中下载HNSCC的RNASeq数据和临床特征数据,分析FSCN1在HN...目的分析肌动蛋白结合蛋白1(fascin actin-bundling protein 1,FSCN1)在头颈部鳞状细胞癌(head and neck squamous cell carcinoma,HNSCC)中的表达及与预后的关系。方法TCGA数据库中下载HNSCC的RNASeq数据和临床特征数据,分析FSCN1在HNSCC中的表达及与预后的关系。LinkedOmics数据库分析HNSCC中与FSCN1的共表达基因并进行富集分析。结果正常组织及HNSCC组织中FSCN1表达量分别为6.97(5.79,7.52)和9.10(8.54,9.56),FSCN1在HNSCC组织中高表达(P<0.01);HNSCC组织及癌旁组织中FSCN1表达量分别为9.395(8.966,9.764)和7.084(5.907,7.543),HNSCC组织中FSCN1表达量升高(P<0.01)。N分期、淋巴及血管侵犯及FSCN1表达与患者的生存相关(P<0.05)。FSCN1的共表达基因主要富集的生物学过程包括细胞黏附、血管生成等,分子功能包括细胞黏附分子结合、钙黏着蛋白绑定等,细胞组分包括黏着斑、质膜等,KEGG通路包括黏着斑、肌动蛋白骨架的调控等信号通路。免疫组化证实,与癌旁组织相比,HNSCC患者癌组织中FSCN1表达水平升高(χ^(2)=19.285,P<0.001),FSCN1主要表达于细胞胞浆中。结论FSCN1与HNSCC临床预后显著相关且可作为靶向治疗的一个新靶点。展开更多
基金the National Natural Science Foundation of China (Grants 11672268, 11621062, and 91748209)the Zhejiang Provincial Natural Science Foundation of China (Grant LR16A020001)the Fundamental Research Funds for Central Universities of China (Grant 2017FZA4029).
文摘The mechanical behaviors of filamentous actin (F-actin) bundles play an essential role in filopodial protrusions at the leading edge of crawling cells. These bundles consist of parallel actin filaments that are hexagonally packed and interconnected via cross-linking proteins including α-actinin, filamin, and fascin. As pushing against the plasma membrane and/or external barriers, the actin bundles in filopodial protrusion inevitably encounter a compressive load. The bending stiffness and buckling stability of actin bundles are therefore important in determining the filopodia architecture and subsequent cell morphology. In this work, we employ a coarse-grained molecular dynamics model to investigate the buckling behaviors of cross-linked actin bundles under compression, which explicitly accounts for the properties of constituent filaments and the mechanical descriptions of cross-linkers. The bending stiffness of actin bundles exhibits a generic size effect depending on the number of filaments in the bundles, explicitly depending on the degree of inter-filament coupling. The distinct buckling modes are analyzed for bundles with different coupling states and strengths of cross-linkers. This study could clarify the stability and buckling mechanisms of parallelly packed actin bundles and the structure-function relations of mechanical components in filopodial protrusion.
文摘This paper proposes a novel four-dimensional approach to the structural study of protein complexes. In the approach, the surface of a protein molecule is to be described using the intersection of a pair of four-dimensional triangular cones (with multiple top vertexes). As a mathematical toy model of protein complexes, we consider complexes of closed trajectories of n-simplices (n=2,3,4...), where the design problem of protein complexes corresponds to an extended version of the Hamiltonian cycle problem. The problem is to find “a set of” closed trajectories of n-simplices which fills the n-dimensional region defined by a given pair of n+1 -dimensional triangular cones. Here we give a solution to the extended Hamiltonian cycle problem in the case of n=2 using the discrete differential geometry of triangles (i.e., 2-simplices).
文摘Plastins are a family of actin binding proteins （ABPs） known to cross-link actin microfilaments in mammalian cells, creating actin microfilament bundles necessary to confer cell polarity and cell shape. Plastins also support cell movement in response to changes in environment, involved in cell/tissue growth and development. They also confer plasticity to cells and tissues in response to infection or other pathological conditions （e.g., inflammation）. In the testis, the cell-cell anchoring junction unique to the testis that is found at the Sertoli cell-cell interface at the blood-testis barrier （BTB） and at the Sertoli-spermatid （e.g., 8-19 spermatids in the rat testis） is the basal and the apical ectoplasmic specialization （ES）, respectively. The ES is an F-actin-rich anchoring junction constituted most notably by actin microfilament bundles. A recent report using RNAi that specifically knocks down plastin 3 has yielded some insightful information regarding the mechanism by which plastin 3 regulates the status of actin microfilament bundles at the ES via its intrinsic actin filament bundling activity. Herein, we provide a brief review on the role of plastins in the testis in light of this report, which together with recent findings in the field, we propose a likely model by which plastins regulate ES function during the epithelial cycle of sDermatogenesis via their intrinsic activity on actin microfilament organization in the rat testis.
基金supported by the National Natural Science Foundation of China(Grant No.30470852)the National Gongguan Project of China(Grant No.21001BA710B).
文摘Long myosin light chain kinase (L-MLCK) contains five DFRXXL motifs with ability to bind F-actin. Binding stoichiometry data indicated that each DFRXXL motif might bind each G-actin, but its biological significance remained unknown. We hypothesized that L-MLCK might act as an F-actin bundle peptides by its multiple binding sites of 5DFRXXL motifs to actin. In order to characterize F-actin-bundle formation properties of 5DFRXXL region of long myosin light chain kinase, we expressed and purified 5DFRXXL peptides tagged with HA in vitro. The properties of 5DFRXXL peptides binding to myofilaments or F-actin were analyzed by binding stoichiometries assays. The results indicated that 5DFRXXL peptides bound to myofilaments or F-actin with high affinity. KD values of 5DFRXXL binding to myofilaments and F-actin were 0.45 and 0.41 μmol/L, re- spectively. Cross-linking assay demonstrated that 5DFRXXL peptides could bundle F-actin efficiently. Typical F-actin bundles were observed morphologically through determina- tion of confocal and electron microscopy after adding 5DFRXXL peptides. After transfection of pEGFP-5DFRXXL plasmid into eukaryocyte, spike structure was observed around cell membrane edge. We guess that such structure formation may be attributable to F-actin over-bundle forma- tion caused by 5DFRXXL peptides. Therefore, we suppose that L-MLCK may be a new bundling protein and somehow play a certain role in organization of cell skeleton besides mediating cell contraction by it kinase activity.
文摘目的分析肌动蛋白结合蛋白1(fascin actin-bundling protein 1,FSCN1)在头颈部鳞状细胞癌(head and neck squamous cell carcinoma,HNSCC)中的表达及与预后的关系。方法TCGA数据库中下载HNSCC的RNASeq数据和临床特征数据,分析FSCN1在HNSCC中的表达及与预后的关系。LinkedOmics数据库分析HNSCC中与FSCN1的共表达基因并进行富集分析。结果正常组织及HNSCC组织中FSCN1表达量分别为6.97(5.79,7.52)和9.10(8.54,9.56),FSCN1在HNSCC组织中高表达(P<0.01);HNSCC组织及癌旁组织中FSCN1表达量分别为9.395(8.966,9.764)和7.084(5.907,7.543),HNSCC组织中FSCN1表达量升高(P<0.01)。N分期、淋巴及血管侵犯及FSCN1表达与患者的生存相关(P<0.05)。FSCN1的共表达基因主要富集的生物学过程包括细胞黏附、血管生成等,分子功能包括细胞黏附分子结合、钙黏着蛋白绑定等,细胞组分包括黏着斑、质膜等,KEGG通路包括黏着斑、肌动蛋白骨架的调控等信号通路。免疫组化证实,与癌旁组织相比,HNSCC患者癌组织中FSCN1表达水平升高(χ^(2)=19.285,P<0.001),FSCN1主要表达于细胞胞浆中。结论FSCN1与HNSCC临床预后显著相关且可作为靶向治疗的一个新靶点。
