CXCL12过表达促进骨髓基质干细胞整合素αv／β3介导的黏附和增殖

研究利用骨髓基质干细胞移植治疗急性心肌梗死时趋化因子CXCL12过表达对由整合素介导αv/β3的干细胞黏附和增殖过程的影响.采用重组DNA技术使得骨髓基质干细胞过表达趋化因子CXCL12,采用western blot法检测CXCL12过表达后骨髓基质干细胞整合素αv/β3表达量的变化.在体外通过黏附实验观察趋化因子CXCL12过表达对整合素介导的细胞与细胞外基质黏附过程的影响,并在心肌梗死大鼠模型中通过检测报告基因观测CXCL12对移植后整合素介导骨髓基质干细胞增殖的作用.基因重组后骨髓基质干细胞过表达了具有生物活性的趋化因子CXC12,趋化因子CXCL12过表达使骨髓基质干细胞整合素αv/β3表达明显增多,并促进了整合素介导的细胞与细胞外基质黏附.CXCL12还使细胞移植后位于梗死区的细胞数量增多.且这一作用也与整合素αv/β3有关.CXCL12过表达通过促进骨髓基质干细胞整合素αv/β3表达提高了移植干细胞黏附和增殖能力,有利于骨髓基质干细胞移植后在心肌梗死区域的生长和分化.     

G蛋白与整合素αⅡbβ3的双向信号转导

整合素是一类细胞表面受体家族分子,通过双向信号转导参与细胞与细胞外基质、细胞与细胞的粘附以及细胞的迁移.整合素αⅡbβ3(GPⅡb-Ⅲa)特异表达于巨核/血小板系,并且是其含量最多的膜糖蛋白,介导血小板的粘附、伸展、聚集等.G蛋白在整合素αⅡbβ3双向信号转导中发挥重要作用,其中较受关注的是:异源三聚体G蛋白和小G蛋白Rap1参与整合素αⅡbβ3的内向外信号转导;小G蛋白(Rho A、Rac等)和Gα13参与整合素αⅡbβ3的外向内信号转导.在蛋白质结构与功能关系的层面,本文总结了G蛋白的结构、分类、功能以及近年来G蛋白在整合素αⅡbβ3双向信号转导中作用的研究进展.     

骨桥蛋白与生殖

骨桥蛋白是细胞外基质的重要成分,它含有RGD序列,其主要受体为整合素αVβ3,二者相互作用共同参与介导细胞的聚集、黏附、增殖和迁移及免疫调节一系列重要过程.研究发现子宫内膜腺上皮细胞表达骨桥蛋白和其受体整合素αVβ3,且其在子宫内膜种植窗口期分泌至宫腔,推测与内膜容受性的建立及受精卵的种植有关.     

整合素αVβ3与病毒感染

整合素αvβ3是一类表达于细胞表面的跨膜糖蛋白粘附分子,由α和β两种Ⅰ型膜蛋白亚单位以非共价键形式连接形成异源二聚体分子。整合素αvβ3可表达于多种细胞,细胞外信号通过不同分子可与其发生相互作用,经整合素αvβ3将细胞外信号传递至细胞内,引起钙离子、Pyk2和磷脂酰肌醇-3(PI-3)激酶等细胞内信号发生变化。整合素αvβ3在血管生成、胚胎发育、肿瘤转移、免疫应答等多种生理和病理过和中发挥着重要的作用。近几年,整合素αvβ3与病毒感染的相关研究进展迅速,本文就整合素αvβ3与病毒感染作一综述。1整合素αvβ3概述1·1整合素αv…     

整合素及其信号传导通路

整合素是位于细胞表面的重要黏附分子,通过其双向信号传导通路,介导细胞与细胞外基质及细胞与细胞间的黏附.整合素由胞外域、跨膜域和胞内域3部分组成.胞内域与细胞内信号分子结合,启动胞内一胞外信号传导激活整合素,提高与相应配体亲合力.而胞外域与相应配体结合后,通过胞外-胞内信号传导,调节细胞生存、增殖、黏附、分化功能.近年研究显示,整合素结构功能及信号传导通路异常与多种疾病有关.     

整合素的构象变化与亲和力调控

整合素(integrin)是由α、β两个亚单位通过非共价键连接而组成的异源二聚体。每种α、β亚单位都是含有多种结构域的大分子量Ⅰ型穿膜糖蛋白。它在细胞与细胞间、细胞与基质间相互作用的过程中发挥着十分关键的作用。整合素多种结构域的空间排列决定了其构象特征,而整合素的不同构象状态与其亲和力呈高度相关。对αVβ133整合素晶体结构的解析使我们对整合素的结构与功能有了更进一步的理解。     

整合素去活化的调控机制

整合素(integrin)是一类重要的细胞表面黏附分子,是由α和β两个亚基通过非共价键组成的异源二聚体,对于免疫反应、免疫细胞的组织定位、凝血、组织愈伤、癌细胞转移以及组织和器官的发育等都至关重要。整合素的功能依赖于对其配体结合的亲和性及其所介导的信号转导的动态调控,整合素活化受阻或是过度活化都会引发多种疾病。目前,对整合素的活化机制的了解比较深入,研究发现,整合素活化的最终步骤是由talin和kindlin等胞内调控蛋白结合β亚基胞内段引起的;但是对于调控整合素去活化的机制了解较少。该文重点介绍了负调控整合素活化的蛋白分子及相关分子机制。     

整合素活化及其介导的黏着斑成熟与肿瘤转移

整合素是一类由α和β两个亚基组成的异源二聚体单次跨膜细胞黏附分子,通过与其对应配体相互作用,介导细胞与细胞、细胞与胞外基质之间的黏附,同时可以将细胞外信号传递至胞内,并招募一系列胞内蛋白与整合素胞内段结合,在细胞膜上形成超分子结构,激活下游信号。整合素的活化进程伴随着其胞外结构域由折叠构象转变为伸展构象以及胞内结构域的彼此分离。在细胞迁移过程中,整合素参与黏着斑的形成,连接胞外基质和细胞骨架,传递胞内-胞外的力学信号驱使细胞迁移。肿瘤微环境介导的整合素活化可促进多种类型细胞向肿瘤部位迁移,共同实现血管生成及肿瘤转移。本文对整合素的活化过程,其介导黏着斑动态变化引发的细胞迁移及对肿瘤转移的影响进行综述。     

整合素介导的细胞信号转导研究进展

整合素是细胞表面重要的受体,介导细胞-细胞和细胞-细胞外基质(extracellular matrix,ECM)的粘附。整合素通过与ECM配体结合可活化特定的信号转导途径,引起细胞发生反应,包括形态改变、伸展、迁移、增殖、分化、存活等,从而决定了与细胞粘附相关的多种生物学功能。因此,对整合素介导的信号转导过程的认识将有助于人们对细胞粘附机制和功能的理解。     

整合素β3亚单位胞内区在骨桥蛋白诱导血管平滑肌细胞黏附和迁移中的作用

为阐明整合素β3亚单位胞内区及其不同保守序列在骨桥蛋白（OPN）诱导血管平滑肌细胞（VSMC）黏附和迁移中所起的作用, 构建了整合素β3亚单位胞内区肽段真核表达载体（p-EGFP-C3-β3CD）, 并人工合成了含有β3亚单位胞内区不同保守序列（NXXY）的寡肽（肽-747和肽-759）, 通过导入VSMC, 观察它们对OPN诱导VSMC黏附和迁移的影响.结果显示, 整合素β3胞内区在VSMC中强制性表达可使细胞在OPN上的黏附和迁移明显下降（分别为对照组的34.3%和31.7%）,导入肽-747、肽-759和肽-747+肽-759均可显著抑制VSMC的黏附和迁移, 其中肽-747+肽-759的作用更强(分别为对照组的36.4%和31.1%). 免疫荧光结果显示, 在转染p-EGFP-C3-β3-CD或肽-747+肽-759的VSMC中, 黏着斑蛋白的磷酸化水平降低, 黏着斑形成明显减少.研究结果表明, 整合素β3亚单位胞内区及其NXXY保守序列在黏着斑相关蛋白募集、黏着斑形成及VSMC黏附和迁移方面发挥重要作用.     

Adhesion properties of human bladder cell lines with extracellular matrix components: the role of integrins and glycosylation

Integrin subunits present on human bladder cells displayed heterogeneous functional specificity in adhesion to extracellular matrix proteins (ECM). The non-malignant cell line (HCV29) showed significantly higher adhesion efficiency to collagen IV, laminin (LN) and fibronectin (FN) than cancer (T24, Hu456) and v-raf transfected (BC3726) cell lines. Specific antibodies to the alpha(2), alpha(5) and beta(1) integrin subunits inhibited adhesion of the non-malignant cells, indicating these integrin participation in the adhesion to ECM proteins. In contrast, adhesion of cancer cells was not inhibited by specific antibodies to the beta(1) integrin subunit. Antibodies to alpha(3) integrin increased adhesion of cancer cells to collagen, LN and FN, but also of the HCV29 line with collagen. It seems that alpha(3) subunit plays a major role in modulation of other integrin receptors especially in cancer cells. Differences in adhesion to ECM proteins between the non-malignant and cancer cell lines in response to Gal and Fuc were not evident, except for the v-raf transfected cell line which showed a distinct about 6-fold increased adhesion to LN on addition of both saccharides. N-Acetylneuraminic acid inhibited adhesion of all cell lines to LN and FN irrespective of their malignancy.     

Unraveling ICAP-1 function: Toward a new direction?

Cell adhesion to either the extracellular matrix (ECM) or to neighboring cells is of critical importance during both physiological and pathological situations. Integrins are a large family of cell adhesion receptors composed of two non-covalently linked alpha and beta subunits. They have a well-identified dual function of mediating both firm adhesion and signaling. The short cytoplasmic domain of integrin can interact with cytoplasmic proteins that are either shared by several different integrins or specific for one type of integrin. Integrin cytoplasmic domain-associated protein-1 (ICAP-1) is a small cytoplasmic protein that specifically interacts with the beta1 integrin subunit. In this review we will discuss recent findings on ICAP-1, not only at the structural and functional level, but also its possible interconnection in other signaling pathways such as those that control cell proliferation.     

Induction of migration of periodontal ligament cells by selective regulation of integrin subunits

The recruitment of tissue‐resident stem cells is important for wound regeneration. Periodontal ligament cells (PDL cells) are heterogeneous cell populations with stemness features that migrate into wound sites to regenerate periodontal fibres and neighbouring hard tissues. Cell migration is regulated by the local microenvironment, coordinated by growth factors and the extracellular matrix (ECM). Integrin‐mediated cell adhesion to the ECM provides essential signals for migration. We hypothesized that PDL cell migration could be enhanced by selective expression of integrins. The migration of primary cultured PDL cells was induced by platelet‐derived growth factor‐BB (PDGF‐BB). The effects of blocking specific integrins on migration and ECM adhesion were investigated based on the integrin expression profiles observed during migration. Up‐regulation of integrins α3, α5, and fibronectin was identified at distinct localizations in migrating PDL cells. Treatment with anti‐integrin α5 antibodies inhibited PDL cell migration. Treatment with anti‐integrin α3, α3‐blocking peptide, and α3 siRNA significantly enhanced cell migration, comparable to treatment with PDGF‐BB. Furthermore, integrin α3 inhibition preferentially enhanced adhesion to fibronectin via integrin α5. These findings indicate that PDL cell migration is reciprocally regulated by integrin α3‐mediated inhibition and α5‐mediated promotion. Thus, targeting integrin expression is a possible therapeutic strategy for periodontal regeneration.     

整联蛋白结构及其功能研究进展

整联蛋白是广泛存在于真核细胞表面的完整的膜受体家族,包括由至少18种不同的α亚基及8种β亚基形成的20多种αβ异二聚体。整联蛋白配体主要有胶原蛋白、纤维结合蛋白、层粘连蛋白、玻连蛋白、血小板凝血酶敏感蛋白、胞间黏附分子、细胞反受体、补体蛋白,以及多种细菌和病毒蛋白,在介导血管内皮细胞和肿瘤细胞的黏附、淋巴细胞运输、肿瘤生长及感染等都有重要的作用。     

Regulation of axonal outgrowth and pathfinding by integrin-ECM interactions

Developing neurons use a combination of guidance cues to assemble a functional neural network. A variety of proteins immobilized within the extracellular matrix (ECM) provide specific binding sites for integrin receptors on neurons. Integrin receptors on growth cones associate with a number of cytosolic adaptor and signaling proteins that regulate cytoskeletal dynamics and cell adhesion. Recent evidence suggests that soluble growth factors and classic axon guidance cues may direct axon pathfinding by controlling integrin-based adhesion. Moreover, because classic axon guidance cues themselves are immobilized within the ECM and integrins modulate cellular responses to many axon guidance cues, interactions between activated receptors modulate cell signals and adhesion. Ultimately, growth cones control axon outgrowth and pathfinding behaviors by integrating distinct biochemical signals to promote the proper assembly of the nervous system. In this review, we discuss our current understanding how ECM proteins and their associated integrin receptors control neural network formation.     

Transmembrane and cytoplasmic domains in integrin activation and protein-protein interactions (Review)

Integrins are heterodimeric membrane-spanning adhesion receptors that are essential for a wide range of biological functions. Control of integrin conformational states is required for bidirectional signalling across the membrane. Key components of this control mechanism are the transmembrane and cytoplasmic domains of the α and β subunits. These domains are believed to interact, holding the integrin in the inactive state, while inside-out integrin activation is accompanied by domain separation. Although there are strong indications for domain interactions, the majority of evidence is insufficient to precisely define the interaction interface. The current best model of the complex, derived from computational calculations with experimental restraints, suggests that integrin activation by the cytoplasmic protein talin is accomplished by steric disruption of the α/β interface. Better atomic-level resolution structures of the α/β transmembrane/cytoplasmic domain complex are still required for the resting state integrin to corroborate this. Integrin activation is also controlled by competitive interactions involving the cytoplasmic domains, particularly the β-tails. The concept of the β integrin tail as a focal adhesion interaction ‘hub’ for interactions and regulation is discussed. Current efforts to define the structure and affinity of the various complexes formed by integrin tails, and how these interactions are controlled, e.g. by phosphorylation and localization, are described.     

Integrin diversity brings specificity in mechanotransduction

Cells sense and respond to the biochemical and physical properties of the extracellular matrix (ECM) through adhesive structures that bridge the cell cytoskeleton and the surrounding environment. Integrin‐mediated adhesions interact with specific ECM proteins and sense the rigidity of the substrate to trigger signalling pathways that, in turn, regulate cellular processes such as adhesion, motility, proliferation and differentiation. This process, called mechanotransduction, influenced by the involvement of different integrin subtypes and their high ECM–ligand binding specificity, contributes to the cell‐type‐specific mechanical responses. In this review, we describe how the expression of particular integrin subtypes affects cellular adaptation to substrate rigidity. We then explain the role of integrins and associated proteins in mechanotransduction, focusing on their specificity in mechanosensing and force transmission.     

Identification of nucleolin as a lipid-raft-dependent β1-integrin-interacting protein in A375 cell migration

Lipid rafts are related to cell surface receptor function. Integrin is a major surface receptor protein in cell adhesion and migration on the extracellular matrix (ECM). Here, we showed that lipid rafts played a critical role in human melanoma A375 cell spreading and migration on fibronectin; an important component of the ECM that interacts with β1 integrin. We found that the disruption of lipid rafts did not markedly inhibit the expression and activation of β1 integrin. By coimmunoprecipitation and mass spectrometry, we investigated the influence of lipid rafts on the β1 integrin complex and identified nucleolin as a potential lipid-raft-dependent β1-integrin-interacting protein. Upon confirmation of the interaction between β1 integrin and nucleolin, further studies revealed that nucleolin colocalized with β1 integrin in lipid rafts and raft disruption interrupted their association. In addition, knockdown of nucleolin markedly attenuated A375 cell spreading and migration on fibronectin. Taken together, we demonstrated that nucleolin is a critical lipid-raft-dependent β1-integrin-interacting protein in A375 cell spreading and migration on fibronectin.     

Proteomic analysis of α4β1 integrin adhesion complexes reveals α-subunit-dependent protein recruitment

Integrin adhesion receptors mediate cell-cell and cell-extracellular matrix interactions, which control cell morphology and migration, differentiation, and tissue integrity. Integrins recruit multimolecular adhesion complexes to their cytoplasmic domains, which provide structural and mechanosensitive signaling connections between the extracellular and intracellular milieux. The different functions of specific integrin heterodimers, such as α4β1 and α5β1, have been attributed to distinct signal transduction mechanisms that are initiated by selective recruitment of adhesion complex components to integrin cytoplasmic tails. Here, we report the isolation of ligand-induced adhesion complexes associated with wild-type α4β1 integrin, an activated α4β1 variant in the absence of the α cytoplasmic domain (X4C0), and a chimeric α4β1 variant with α5 leg and cytoplasmic domains (α4Pα5L), and the cataloguing of their proteomes by MS. Using hierarchical clustering and interaction network analyses, we detail the differential recruitment of proteins and highlight enrichment patterns of proteins to distinct adhesion complexes. We identify previously unreported components of integrin adhesion complexes and observe receptor-specific enrichment of molecules with previously reported links to cell migration and cell signaling processes. Furthermore, we demonstrate colocalization of MYO18A with active integrin in migrating cells. These datasets provide a resource for future studies of integrin receptor-specific signaling events.