整合素信号对离子通道的影响

整合素受体具有一次跨膜结构 ,膜外部分可识别配体(如纤维黏连蛋白、层黏连蛋白等 )或细胞外基质上 (ＥＣＭ )的精氨酸 -氨基乙酸 -门冬氨酸 (ＲＧＤ)结构并与之结合 ,而胞内端除可与细胞骨架等结构蛋白结合外 ,还可与多种信号蛋白如局部黏附蛋白 (ＦＡＫ)、整合素连接激酶 (ＩＬＫ)、蛋白激酶Ｃ(ＰＫＣ)等结合[1 2 ] ,因此其不仅仅具有将细胞与细胞外基质、细胞与细胞物理连接的作用 ,还被认为是理想的信号转导分子 ,在细胞内外信号转导中发挥重要作用[3 4] 。当与配体结合后 ,整合素受体可兴奋而发生聚集 ,引起多种信号分子在其周围分布 …     

67 ku层黏连蛋白受体与肿瘤侵袭和转移

层黏连蛋白是细胞外基质重要的成分之一。67 ku层黏连蛋白受体(67 ku laminin receptor,67 LR)是层黏连蛋白的一个非整合素受体。它是一种多功能蛋白,既参与核糖体的组装、成熟过程,又参与细胞的信号转导,还可作为多种病毒的细胞膜受体。可以和层黏连蛋白相互作用,调节肿瘤的增殖、黏附、微血管形成,加速细胞外基质的降解,促进肿瘤的侵袭转移,其作用机制可能与MAPK信号通路有关。67 LR在多种肿瘤中高表达,还可以作为肿瘤免疫治疗的靶标。     

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-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。     

整合素在烧伤创面愈合中的作用研究进展

整合素家族为跨膜糖蛋白受体家族,其作用是介导细胞与细胞外基质之间的相互作用,参与细胞相互之间的黏附功能。整合素通过双向信号转导,影响细胞的分化、增生与凋亡;整合素信号系统还可以通过调控细胞周期,产生细胞凋亡,影响瘢痕的形成。本文就整合素家族参与烧伤创面成纤维细胞分化、促进创面收缩,增强细胞外基质的收缩能力以及整合素连接激酶与创面愈合之间的关系作一综述。     

整合素与肾纤维化

整合素是一类跨细胞膜的糖蛋白细胞表面受体家族分子.在正常肾脏的实质及间质细胞中均有整合素的表达,在病变肾脏中,整合素有种类和数量的改变.在肾纤维化发生过程中肾间质炎症细胞浸润、成纤维细胞激活、细胞外基质过分沉积等均与整合素异常表达有关.对整合素与肾纤维关系的深入研究,有可能为肾纤维化的诊断与防治带来新的希望.     

整合素αvβ6对结肠癌细胞中整合素αvβ5内吞胞吐循环的影响

 目的：探讨整合素αvβ6对结肠癌细胞中整合素αvβ5内吞胞吐循环及细胞黏附、迁移能力的影响。方法：采用Western blotting检测不同细胞中整合素αvβ6和αvβ5的表达情况,通过整合素内吞实验、胞吐实验和capture-ELISA实验检测不同细胞中整合素αvβ6和αvβ5的内吞胞吐循环时相,利用细胞黏附实验和细胞迁移实验检测各种细胞在不同基质表面黏附和迁移能力的差异。结果：SW480、SW480 wild-type β6和SW480 mock细胞中整合素αv亚基和β5亚基的表达无显著差异（P>0.05）,SW480 wild-type β6细胞中整合素β6亚基的表达显著高于另外2种细胞（P<0.05）;SW480细胞中整合素αvβ5存在内吞胞吐循环,但当向SW480细胞中转染β6亚基后,整合素αvβ6进行内吞胞吐循环的同时,会对整合素αvβ5的内吞和胞吐过程产生抑制作用,差异有统计学意义（P<0.05）;3种细胞中整合素αvβ6和αvβ5的内吞胞吐循环的差异,会影响细胞在纤连蛋白（整合素αvβ6配体）和玻连蛋白（整合素αvβ5配体）表面的黏附和迁移能力。结论：整合素αvβ6和αvβ5拥有共同的α亚基,它们在细胞内的内吞胞吐循环存在某种竞争性关系,当二者同时存在时,整合素αvβ6会抑制αvβ5的内吞胞吐循环过程,并由此对细胞在相应基质表面黏附和迁移能力产生影响。     

TGFβ1基因对血管内皮细胞细胞外基质表达及与基质黏附的影响

了解TGFβ1基因对血管内皮细胞表达细胞外基质蛋白及与基质黏附力的影响。用DOTAP脂质体转染p MAMneo TGFβ1于原代培养的脐静脉内皮细胞,经G4 18筛选,TGFβ1表达经免疫荧光鉴定。Western blot确定 型胶原、纤黏连蛋白的表达,微管吸吮系统确定内皮细胞与基质的黏附力。结果表明生理情况下的内皮细胞能表达少量的TGFβ1及胶原、纤黏连蛋白。经G4 18筛选,外源性TGFβ1在血管内皮细胞中稳定表达,能显著提高胶原、纤黏连蛋白纤维的表达及细胞与基质的黏附。说明TGFβ1在血管组织工程中促进内皮细胞的黏附具有一定的应用价值。     

信息动态

整合素β4(integrin β4)是一种介导细胞和其外环境之间连接的跨膜受体,与层黏连蛋白结合可介导上皮细胞与基底膜黏附,是维持气道屏障完整性的重要分子.但是,衰老对其的影响尚不清楚.本研究检测了不同年龄段的大鼠气道上皮整合素β4表达,研究衰老对整合素β4表达的影响.     

表面微纳米沟槽结构对成纤维细胞黏附和骨架重排的促进作用

基底材料的拓扑形貌是影响细胞行为的重要因素之一,材料表面微纳米图案化不但可以提供规则的结构模版,用以研究细胞对生长环境的响应特性,而且可以为组织再生用支架和植入性器件的设计提供基础数据.以表面具有微纳米沟槽结构的聚氨酯薄膜为基底材料,选择在促进组织修复和再生中起重要作用的成纤维细胞为模型细胞,通过细胞活性检测和免疫荧光分析,探讨材料表面的微纳米图案结构对成纤维细胞黏附、增殖、形态以及细胞骨架发育的作用.实验结果表明,微纳米沟槽结构能够明显促进成纤维细胞在材料表面的黏附和增殖,并诱导细胞响应所生长的微纳米沟槽结构进行骨架重排.     

透明质酸及其受体对细胞运动的作用

透明质酸 (HA)是细胞外基质的主要成分之一。细胞外基质中的HA通过对基质装配产生影响 ,形成多孔性疏松的基质 ,从而促进细胞运动。细胞表面的HA不仅能够介导细胞与基质的初黏附 ,而且在细胞运动时可促进细胞与基质的部分去黏附。细胞内的HA通过与细胞内HA结合蛋白以及信号转导相关的酶相结合 ,作用于细胞骨架 ,调节细胞运动。HA与其受体CD4 4 ,RHAMM或Layilin结合 ,转导信号入细胞内 ,使细胞骨架的构型发生改变 ,并调节与细胞运动有关的蛋白水解酶的合成和释放 ,由此促进细胞的黏附和运动。     

Cross-talk between Fc receptors and integrins

Fc receptors (FcRs) and integrins are both key players of immune responses. These receptors are capable of independent signaling that leads to various cell functions. Recently, it is becoming clear that these receptors are also capable of modulating each other’s responses. This modulation is achieved by direct physical interactions of the receptors on the cell surface, or by one receptor modifying the signaling pathway of the other receptor. Receptor co-localization and resonance energy transfer studies have shown that Fc receptors and integrins interact on the cell surface. Biochemical and functional studies have shown that signaling from Fc receptors modulates integrin adhesiveness through a process called “inside-out signaling”. Other studies also show that the signaling from integrins modulates Fc receptor responses such as adhesion to immune complexes and cell mediated antibody-dependent cytotoxicity. This bi-directional cross-talk between Fc receptors and integrins is very important for the final cell function. Here, we review the latest information about interactions between Fc receptors and integrins.     

The vitronectin receptor (αVβ3) as an example for the role of integrins in T lymphocyte stimulation

Integrins are a family of cell surface receptors which mediate the adhesion of cells to each other or to extracellular matrix (ECM) proteins. The interaction of integrins with their ligands or counter-receptors was initially considered to be a one-way process in that cells actively regulate the interaction of integrins with their ligands (‘inside-out signal’). In contrast, it was not obvious that cells would receive a signal from the outside via the integrin heterodimers following ligand binding (‘outside-in signal’). Recent evidence increasingly supports the active role of integrins in cell activation and proliferation. Many reports describe the effects of integrin-mediated signaling in lymphoid cells. Our studies of γ/δ T cells, expressing the β3 integrin vitronectin receptor (VNR), reflect some of the consequences this active interaction between lymphocytes and the ECM could have for T cell activation and differentiation. The VNR has been described as a T cell costimulatory molecule. We recently reported that the VNR has the potential to stimulate cytokine secretion in T cell hybridomas without involvement of T cell receptor-mediated signals. Further studies demonstrated tyrosine phosphorylation of proteins following VNR cross-linking and the interaction of the VNR with protein kinases. Intensive research focuses on the signal transduction mechanisms of integrins and their interaction with other costimulatory or activation molecules. This knowledge is important to better understand the role of adhesion molecules, the ECM, and the cellular microenvironment for lymphocyte activation and differentation.     

Small GTPases, adhesion, cell cycle control and proliferation

In many cells, proliferation is under the coordinated control of growth factors and the extracellular matrix (ECM). Autocriny and anchorage-independent growth are observed in many transformed cells where this balance is often altered. The outside-in and inside-out exchanges are mediated by integrins, acting as molecular bridges between the ECM and the cytoskeleton. Integrins, as the major receptors for components of the ECM, are important not only for the physical aspects of cell adhesion, but also for two key aspects of cell fate: cell cycle progression, and apoptosis. The latter aspect will not be covered in the present analysis, which will rather focus on the data accumulated on Ras and Ras-related small GTPases such as Rho, Rac and Cdc42.     

Integrin expression in stem cells from bone marrow and adipose tissue during chondrogenic differentiation

The use of adult mesenchymal stem cells (MSC) in cartilage tissue engineering offers new perspectives in the generation of transplants for reconstructive surgery. The extracelular matrix (ECM) plays a key role in modulating the function and phenotype of the embedded cells and contains the integrins as adhesion receptors mediating cell-cell and cell-matrix interactions. In our study, characteristic changes in integrin expression during the course of chondrogenic differentiation of MSC from bone marrow and adipose tissue were compared. MSC were isolated from bone marrow biopsies and adipose tissue. During cell culture, chondrogenic differentiation was performed. The expression of integrins and their signaling components were analysed with microarray and immunohistochemistry in freshly isolated MSC and after chondrogenic differentiation. The fibronectin receptor (integrin alpha5beta1) was expressed by undifferentiated MSC, and expression rose during chondrogenic differentiation in both types of MSC. The components of the vitronectin/osteopontin receptors (alphavbeta5) were not expressed by freshly isolated MSC, and expression rose with ongoing differentiation. Receptors for the collagens (alpha1beta1, alpha2beta1, alpha3beta1) were weakly expressed by undifferentiated MSC and were activated during differentiation. Intracellular signaling components integrin-linked kinase (ILK) and CD47 showed increased expression with ongoing differentiation. For all integrins, no significant differences were be found in the 2 types of MSC. Integrin-mediated signaling appeared to play an important role in the generation and maintenance of the chondrocytic phenotype during chondrogenic differentiation. Particularly, the receptors for fibronectin, vitronectin, osteopontin and the collagens may be involved in the generation of the ECM. Intracellularly, their signals might be transduced by ILK and CD47. To fully harness the potential of these cells, future studies should be directed to ascertain their cellular and molecular characteristics for optimal identification, isolation, and expansion.     

Cultured cell-derived extracellular matrix scaffolds for tissue engineering

Cell-derived extracellular matrix (ECM) scaffolds have received considerable interest for tissue engineering applications. In this study, ECM scaffolds derived from mesenchymal stem cell (MSC), chondrocyte, and fibroblast were prepared by culturing cells in a selectively removable poly(lactic-co-glycolic acid) (PLGA) template. These three types of ECM scaffolds were used for in vitro cultures of MSC and fibroblasts to examine their potential as scaffolds for cartilage and skin tissue engineering. The MSC were cultured in MSC- and chondrocyte-derived ECM scaffolds. The ECM scaffolds supported cell adhesion, promoted both cell proliferation and the production of ECM and demonstrated a stronger stimulatory effect on the chondrogenesis of MSC compared with a conventional pellet culture method. Histological and immunohistochemical staining indicated that cartilage-like tissues were regenerated after the MSC were cultured in ECM scaffolds. Fibroblasts were cultured in the fibroblast-derived ECM scaffolds. Fibroblasts proliferated and produced ECM to fill the pores and spaces in the scaffold. After 2 weeks of culture, a uniform multilayered tissue was generated with homogenously distributed fibroblasts. Cell-derived ECM scaffolds have been demonstrated to facilitate tissue regeneration and will be a useful tool for tissue engineering.     

Expression of FAK-related non-kinase (FRNK) coincides with morphological change in the early stage of cell adhesion

Focal adhesion kinase (FAK), a protein tyrosine kinase, has recently been suggested to play a role in signal transduction through integrins. In fact, FAK is involved in cell proliferation and cell motility by performing signal transduction through integrins. FAK-related non-kinase (FRNK) has been found to be an inhibitor of FAK. As the expression level of FRNK in the cell is very low, the study of FRNK has been preferentially performed by gene overexpression, up to the present, and the role of constitutive FRNK in cells remains unclear. We hypothesized that FRNK is involved in the adhesion of cells to the extracellular matrix (ECM) and investigated the expression of FRNK by time kinetic analysis shortly after cell seeding. We found that FRNK expression was significantly increased in the cells during the early stage of cell adhesion to the ECM. These data indicated that FRNK plays an important role in cell adhesion during the very early stages of cell culture.     

Fibronectin facilitates adhesion of K562 leukemic cells normally growing in suspension to cationic surfaces.

The role of protein adsorption in the forced adhesive growth of K562 leukemic cells onto a cationic surface composed of polylysine was investigated. Numerous studies have demonstrated that adhesion in anchorage-dependent cells is mediated in vitro by adsorption of serum proteins [particularly proteins of the extracellular matrix (ECM) such as fibronectin and vitronectin] present in the growth medium. Specifically, adhesion has been shown to occur when ECM proteins attach to the substratum and act as ligands for specific receptors located on the surface of cells. K562 cells are human erythroleukemic cells that normally grow in suspension. These cells are not involved in the same cell adhesion processes as anchorage-dependent cells and do not need to be attached to ECM proteins in order to survive and grow. Thus, with these systems, it is possible to better determine the role of protein adsorption in the adhesion of cells, growing in suspension such as blood cells, onto charged surfaces. The results presented show that adhesion of K562 cells onto the positively charged polylysine surface in the presence of serum is mediated through specific interactions between fibronectin receptors present on K562 cells and fibronectin adsorbed onto that cationic surface. Specifically, determination of cell adhesion under different experimental conditions indicates that nonspecific charge interactions do not take place directly between the cells and polylysine, but rather take place between polylysine and fibronectin, which adsorbs onto the cationic polymer. In addition, flow cytometric analyses reveal that only fibronectin receptors are present on these cells and, consequently, only fibronectin can be responsible for the actual adhesion of these cells onto the cationic surface. In view of the data presented, the possibility should be considered that ECM components adsorbed onto surfaces with specific charges and/or belonging to certain functional groups are involved in structural and functional modifications in cells. These cells grow in suspension and are normally not involved in adhesion phenomena, though these components should be considered. These considerations should be made especially when designing biomaterials that can modulate the response of cells growing in suspension, such as blood cells, and also in tissue engineering of blood substitutes.     

Three-dimensional honeycomb-patterned chitosan/poly(L-lactic acid) scaffolds with improved mechanical and cell compatibility

Micro-size patterned surfaces trigger specific biological responses such as the promotion of cell growth, cell migration, cell differentiation, and ECM production. The aim of this work was to elaborate three-dimensional scaffolds with honeycomb patterned surfaces and large open pores, and to study the influence of surface patterning on cell behavior. In this study, we used water droplets as porogen material to prepare a novel type of chitosan sponge with large open pores on its surface. The sponges obtained were then immersed into 6 wt % Poly(L-lactic acid) chloroform solution to obtain honeycomb patterned composite porous scaffolds. The morphology and mechanical properties were characterized with SEM and compression testing. The fibroblast behaviors in scaffolds were analyzed with SEM, VG, PAS, live-dead staining, and flow cytometer. Results showed that these composite scaffolds possessed better mechanical properties and hierarchical porous structure than pure chitosan sponges. Cell culture revealed that the honeycomb patterned surface had positive influences on fibroblast behaviors, wherein the cell adhesion, proliferation, ECM secretion and viability were improved dramatically. Such a hierarchical composite scaffold would be a suitable candidate for tissue engineering purposes.     

Integrins in regulation of tissue development and function

Cell adhesion is indispensable for embryonic development and for proper tissue function. In metazoans, integrins are the major adhesion receptors that connect cells to components of the extracellular matrix. Integrins are implicated in assembly of extracellular matrices, cell adhesion and migration on extracellular matrices, and in vertebrates (in which the integrin family has expanded) they can also mediate cell-cell adhesion. Furthermore, integrin-mediated adhesion can modulate many different signal transduction cascades and support cell survival, proliferation, and influence the expression of differentiation-related genes. In this review we briefly explain how integrins can affect so many different aspects of cell behavior and discuss evidence for roles of integrins in tissue development, function, and disease.