接头蛋白c-Crk的结构和功能

接头蛋白c-CrK是原癌基因c-CrK表达的产物,参与了受体酪氨酸激酶和整合蛋白等多种分子的信号转导。C-CrK是最初发现于禽类病毒中的v-CrK在组织细胞中的同源物,通过mRNA选择性剪接产生两种形式的蛋白质c-CrKI和c-CrKⅡ,在各种组织中广泛表达。C-CrK分子在N端包含有一个SH2结构域,在C端两个SH3结构域。CrKL是CrK家族的另一个成员,但由不同的基因编码,其结构与c-CrKII十分相似。C-CrK蛋白质本身不具备任何酶活性,它通过SH2和SH3结构域连接蛋白质,使得不能直接相互作用的信号分子发生相互作用。c-CrK II的SH2结构域可以与含有磷酸化酪氨酸YXXP模体的蛋白质结合,如桩蛋白(paxillin)、Cas、c-Cbl和自身磷酸化的酪氨酸蛋白激酶受体等。SH3结构域与蛋白质中富含脯氨酸的PXLPXK模体结合,如C3G和DOCKl80等信号分子。由于c-CrK能够同众多的蛋白质信号分子结合,使得c-CrK广泛参与细胞内不同信号途径的信号转导。     

抗原受体启动淋巴细胞活化信号传导中的接头蛋白

接头蛋白(adapter puoteins)是一类既无激酶活性,也无转录因子活性,但可介导信号蛋白分子之间或信号蛋白与脂类分子间相互作用的蛋白分子。在抗原受体启动的淋巴细胞活化信号传导途径中,接头蛋白分子发挥着重要的衔接和调节作用。本文介绍与T细胞活化相关的LAT、SLP-76和Gads,与B细胞活化相关的BLNK与MAPK途径相关的Grb2、Shc、Sos和Vav分子,及具有负性调节作用的Cb1接头蛋白分子近年来的研究进展。     

T细胞活化的跨膜接头蛋白

Ｔ细胞通过抗原受体 (ＴＣＲ)识别抗原后 ,经ＣＤ3分子激活多种蛋白酪氨酸激酶 (ＰＴＫ)和胞质接头蛋白 ,从而活化一系列胞质激酶 ,如磷脂酰肌醇 3激酶 (ＰＩ3Ｋ)、磷脂酶Ｃγ(ＰＬＣγ)、Ｒａｓ激酶等 ,再经一系列信号传递激活转录因子调节基因表达 ,使细胞表现功能。最近发现了一组ＴＣＲ相关的跨膜接头蛋白 ,包括Ｔ细胞活化的连接分子 (ｌｉｎｋｅｒｆｏｒａｃｔｉｖａ ｔｉｏｎｏｆＴｃｅｌｌｓ,ＬＡＴ)、ＳＨＰ2相互作用跨膜接头蛋白 (ＳＨＰ2 ｉｎｔｅｒａｃｔｉｎｇｔｒａｎｓｍｅｍｂｒａｎｅａｄａｐｔｏｒｐｒｏｔｅｉｎ ,ＳＩＴ…     

缝隙连接蛋白43羧基端结构域的研究进展

缝隙连接蛋白43(connexin43,Cx43)形成通道,使细胞间可直接进行分子(分子量<1 kDa)交换及信息交流。Cx43是最普遍表达的缝隙连接蛋白,除通道功能外,其他生物学功能主要体现在羧基末端(carboxyl terminal, CT)结构域。Cx43 CT结构域存在与其他蛋白、激酶、因子等相互作用的位点,这些位点可能是治疗预防疾病的潜在靶点。本综述就近年来所研究的CT结构域与相关信号分子作用位点作一总结,旨在为治疗涉及Cx43 CT的疾病提供新思路。     

卷曲蛋白受体与肿瘤的研究进展

Wnt基因超家族编码一系列分泌型糖蛋白,由Wnt蛋白介导的Wnt信号通路是一个进化上高度保守的信号通路,在胚胎发育、细胞生长、干细胞增殖中发挥重要的作用.此外研究发现Wnt通路在癌症发生发展中也起着重要作用.Wnt信号配体-Frizzled受体,由Frizzled基因编码,属于7次跨膜蛋白受体家族,与G蛋白偶联受体的结构相似,目前研究发现,从无脊椎动物到脊椎动物至少有10个家族成员,其在心血管系统和其他器官系统中广泛表达.基于这些研究基础,本文将重点阐述Frizzled受体蛋白与疾病的可能或潜在的关系.由于Frizzled受体蛋白在疾病当中发挥了重要作用,并且在癌症中起着分子靶点的作用,我们有理由相信,Frizzled受体将成为一个有效的肿瘤治疗的分子靶点.     

肿瘤相关成纤维细胞与肿瘤微环境

肿瘤的发展过程与肿瘤微环境密切相关,而肿瘤相关成纤维细胞(CAFs)是上述微环境中最主要的宿主细胞,CAFs是一类不同细胞源性的细胞群,可来源于多种细胞包括静止的成纤维细胞、上皮细胞、内皮细胞和间质干细胞的分化过程。体内和体外生物学实验均证实,成纤维细胞在肿瘤微环境中并不是被动的对肿瘤发展提供支持,而是发挥了至关重要的作用,所以靶向CAFs有望成为肿瘤治疗的新方向,对CAFs相关分子标记物和分子事件的进一步探索将为抗肿瘤的临床治疗提供新的思路。本文将对CAFs的来源以及CAFs对肿瘤发生发展、转移及VEGF耐受等方面的作用做一综述。     

肿瘤相关成纤维细胞与肿瘤微环境

肿瘤的发展过程与肿瘤微环境密切相关,而肿瘤相关成纤维细胞（CAFs）是上述微环境中最主要的宿主细胞,CAFs是一类不同细胞源性的细胞群,可来源于多种细胞包括静止的成纤维细胞、上皮细胞、内皮细胞和间质干细胞的分化过程。体内和体外生物学实验均证实,成纤维细胞在肿瘤微环境中并不是被动的对肿瘤发展提供支持,而是发挥了至关重要的作用,所以靶向CAFs有望成为肿瘤治疗的新方向,对CAFs相关分子标记物和分子事件的进一步探索将为抗肿瘤的临床治疗提供新的思路。本文将对CAFs的来源以及CAFs对肿瘤发生发展、转移及VEGF耐受等方面的作用做一综述。     

接头蛋白CIN85的结构与功能

CIN85与CD2AP构成了一个接头蛋白家族,在个体发育中担当重要角色并和多种疾病的病理机制相关。它们在功能结构域的序列上有很高的相似性,并具有细胞骨架蛋白的特点。近来研究表明CIN85在受体酪氨酸激酶(RTK)的内吞与降解、细胞凋亡、细胞局部黏附等许多生物学过程中发挥重要作用。     

细胞骨架相关蛋白SM22α与肿瘤

平滑肌22α（smooth muscle 22 alpha,SM22α）蛋白是一种细胞骨架相关蛋白,其在种属间的高度同源性和进化上的高度保守性提示了其重要的生物学意义。最新研究发现,SM22α在多种肿瘤组织中表达异常,该蛋白除可通过与肌动蛋白相互作用参与细胞骨架重构外,还可作为信号分子参与细胞生长,细胞外基质降解和血管生成。其作为一种新型抑癌基因,在肿瘤发生、发展中的作用日益成为人们关注的焦点。本文就SM22α的结构特征、表达特点及其与肿瘤的关系进行综述。     

细胞骨架相关蛋白SM22α与肿瘤

平滑肌22α(smooth muscle 22 alpha,SM22α)蛋白是一种细胞骨架相关蛋白,其在种属间的高度同源性和进化上的高度保守性提示了其重要的生物学意义.最新研究发现,SM22α在多种肿瘤组织中表达异常,该蛋白除可通过与肌动蛋白相互作用参与细胞骨架重构外,还可作为信号分子参与细胞生长,细胞外基质降解和血管生成.其作为一种新型抑癌基因,在肿瘤发生,发展中的作用日益成为人们关注的焦点.本文就SM22α的结构特征、表达特点及其与肿瘤的关系进行综述.     

多功能的胞内衔接蛋白syntenin

Syntenin蛋白是在原核生物及真核生物中广泛存在的一类胞内衔接蛋白（adaptor proteins）. Syntenin由N端结构域（N-terminal domain,NTD）、两个串联的PDZ结构域(postsynaptic density protein, disc large and zonula occludens, PDZ)和C端结构域（C-terminal domain,CTD）组成,在生物进化过程中相对保守. Syntenin蛋白的PDZ结构域可与不同膜受体C端的PDZ结合基序（PDZ-binding motif,PBM）特异性结合, PDZ结构域结合受体的多样性导致了syntenin功能的多样性. 本文综述了syntenin蛋白的发现与分布及其结构特征,对syntenin在肿瘤转移、细胞质膜蛋白组装、参与动物免疫等领域的研究成果进行了较为详细的综述,同时介绍了syntenin在参与动物胚胎发育调控、血管生成和轴突生长等方面的研究进展.     

蛋白酪氨酸磷酸酶SHP-2在乳腺癌细胞移动及粘附中的作用

探讨蛋白酪氨酸磷酸酶SHP 2在乳腺癌细胞MCF 7的移动及粘附中的作用 .利用基因重组技术分别将野生型SHP 2与突变型SHP 2与绿色荧光蛋白GFP的基因片段构成重组质粒 (SHP 2 GFP、SHP 2C >S GFP) .脂质体转染法分别转入MCF 7中 ,表达成功后筛选并建立SHP 2 GFP和SHP 2C >S GFP细胞株 .荧光显微镜观察细胞移动情况 ,免疫印迹法检测粘附分子E 钙粘蛋白和金属蛋白酶MMP 1及MMP 9的表达 .实验后建立SHP 2 GFP及SHP 2C >S GFP细胞株 ,同时观察到SHP 2C >S GFP细胞的形态发生明显改变 :从梭形状态变成圆形状态 .荧光显微镜发现 ,MCF 7细胞和SHP 2 GFP、SHP 2C >S GFP转染的细胞在 3h、6h、9h的移动情况分别是MCF 7为 10 %、2 3%、5 4% ,SHP 2 GFP为 15 %、4 9%、98% ,SHP 2C >S GFP为 4 %、11%、30 % .免疫印迹结果表明 ,SHP 2C >S GFP细胞的E 钙粘蛋白表达比SHP 2 GFP细胞明显升高 (P <0 0 5 ) .MMP 1及MMP 9的表达量在SHP 2 GFP细胞中有所增强 (P <0 0 5 ) .实验表明 ,SHP 2可能通过调节粘附分子和基质金属磷酸酶而在细胞移动、粘附中发挥重要作用     

Bivalent Motif-Ear Interactions Mediate the Association of the Accessory Protein Tepsin with the AP-4 Adaptor Complex

The heterotetrameric (ϵ-β4-μ4-σ4) complex adaptor protein 4 (AP-4) is a component of a non-clathrin coat involved in protein sorting at the trans-Golgi network (TGN). Considerable interest in this complex has arisen from the recent discovery that mutations in each of its four subunits are the cause of a congenital intellectual disability and movement disorder in humans. Despite its physiological importance, the structure and function of this coat remain poorly understood. To investigate the assembly of the AP-4 coat, we dissected the determinants of interaction of AP-4 with its only known accessory protein, the ENTH/VHS-domain-containing protein tepsin. Using a variety of protein interaction assays, we found that tepsin comprises two phylogenetically conserved peptide motifs, [GS]LFXG[ML]X[LV] and S[AV]F[SA]FLN, within its C-terminal unstructured region, which interact with the C-terminal ear (or appendage) domains of the β4 and ϵ subunits of AP-4, respectively. Structure-based mutational analyses mapped the binding site for the [GS]LFXG[ML]X[LV] motif to a conserved, hydrophobic surface on the β4-ear platform fold. Both peptide-ear interactions are required for efficient association of tepsin with AP-4, and for recruitment of tepsin to the TGN. The bivalency of the interactions increases the avidity of tepsin for AP-4 and may enable cross-linking of multiple AP-4 heterotetramers, thus contributing to the assembly of the AP-4 coat. In addition to revealing critical aspects of this coat, our findings extend the paradigm of peptide-ear interactions, previously established for clathrin-AP-1/AP-2 coats, to a non-clathrin coat.     

The Transmembrane Adaptor Protein LIME Is Essential for Chemokine-Mediated Migration of Effector T Cells to Inflammatiory Sites

Lck-interacting transmembrane adaptor 1 (LIME) has been previously identified as a raft-associated transmembrane protein expressed predominantly in T and B lymphocytes. Although LIME is shown to transduce the immunoreceptor signaling and immunological synapse formation via its tyrosine phosphorylation by Lck, a Src-family kinase, the in vivo function of LIME has remained elusive in the previous studies. Here we report that LIME is preferentially expressed in effector T cells and mediates chemokine-mediated T cell migration. Interestingly, in LIME^-/- mice, while T cell receptor stimulation-dependent proliferation, differentiation to effector T cells, cytotoxic T lymphocyte (CTL) function and regulatory T lymphocyte (Treg) function were normal, only T cell-mediated inflammatory response was significantly defective. The reduced inflammation was accompanied by the impaired infiltration of leukocytes and T cells to the inflammatory sites of LIME^-/- mice. More specifically, the absence of LIME in effector T cells resulted in the reduced migration and defective morphological polarization in response to inflammatory chemokines such as CCL5 and CXCL10. Consistently, LIME^-/- effector T cells were found to be defective in chemokine-mediated activation of Rac1 and Rap1, and dysregulated phosphorylation of Pyk2 and Cas. Taken together, the present findings show that LIME is a critical regulator of inflammatory chemokine-mediated signaling and the subsequent migration of effector T cells to inflammatory sites.     

In vivo functional analysis of the daughter of sevenless protein in receptor tyrosine kinase signaling

One mechanism used by receptor tyrosine kinases to relay a signal to different downstream effector molecules is to use adaptor proteins that provide docking sites for a variety of proteins. The daughter of sevenless (dos) gene was isolated in a genetic screen for components acting downstream of the Sevenless (Sev) receptor tyrosine kinase. Dos contains a N-terminally located PH domain and several tyrosine residues within consensus binding sites for a number of SH2 domain containing proteins. The structural features of Dos and experiments demonstrating tyrosine phosphorylation of Dos upon Sev activation suggested that Dos belongs to the family of multisite adaptor proteins that include the Insulin Receptor Substrate (IRS) proteins, Gab1, and Gab2. Here, we studied the structural requirements for Dos function in receptor tyrosine kinase mediated signaling processes by expressing mutated dos transgenes in the fly. We show that mutant Dos proteins lacking the putative binding sites for the SH2 domains of Shc, PhospholipaseC-γ (PLC-γ) and the regulatory subunit of Phosphoinositide 3-kinase (PI3-K) can substitute the loss of endogenous Dos function during development. In contrast, tyrosine 801, corresponding to a predicted Corkscrew (Csw) tyrosine phosphatase SH2 domain binding site, is essential for Dos function. Furthermore, we assayed whether the Pleckstrin homology (PH) domain is required for Dos function and localization. Evidence is provided that deletion or mutation of the PH domain interferes with the function but not with localization of the Dos protein. The Dos PH domain can be replaced by the Gab1 PH domain but not by a heterologous membrane anchor, suggesting a specific function of the PH domain in regulating signal transduction.     

Efficient T-cell receptor signaling requires a high-affinity interaction between the Gads C-SH3 domain and the SLP-76 RxxK motif

The relationship between the binding affinity and specificity of modular interaction domains is potentially important in determining biological signaling responses. In signaling from the T-cell receptor (TCR), the Gads C-terminal SH3 domain binds a core RxxK sequence motif in the SLP-76 scaffold. We show that residues surrounding this motif are largely optimized for binding the Gads C-SH3 domain resulting in a high-affinity interaction (K(D)=8-20 nM) that is essential for efficient TCR signaling in Jurkat T cells, since Gads-mediated signaling declines with decreasing affinity. Furthermore, the SLP-76 RxxK motif has evolved a very high specificity for the Gads C-SH3 domain. However, TCR signaling in Jurkat cells is tolerant of potential SLP-76 crossreactivity, provided that very high-affinity binding to the Gads C-SH3 domain is maintained. These data provide a quantitative argument that the affinity of the Gads C-SH3 domain for SLP-76 is physiologically important and suggest that the integrity of TCR signaling in vivo is sustained both by strong selection of SLP-76 for the Gads C-SH3 domain and by a capacity to buffer intrinsic crossreactivity.     

信号分子调控细菌生物被膜形成的分子机制

细菌生物被膜(Bacterial biofilm,BF)是黏附于机体黏膜或生物材料表面、由细菌及其分泌的多聚糖、蛋白质和核酸等组成的被膜状生物群体,是造成持续性感染的重要原因之一。细菌在生长繁殖时会产生一些次级代谢产物,部分会作为生物信号分子在细胞内或细胞间传递信息,使细菌在多细胞水平协调统一相互配合,以完成一些重要的生理学功能,如生物发光、BF的形成、运动与固定态生活方式的转换等。信号分子在BF形成过程中起着重要的调控作用。文中从密度感应系统(Quorum-sensing systems,QS)、环二鸟苷酸(Cyclic diguanylate,c-di-GMP)、双组分系统(Two-component systems,TCS)和sRNA等方面介绍影响BF形成的相关信号分子,重点对BF形成过程中的信号分子调控机制进行概述,这对于深入揭示信号分子调控BF形成的机制十分必要。     

B淋巴细胞信号转导相关接头蛋白Bam32与Hic-5的相互作用

32kDB淋巴细胞接头分子(Bam32)是调控B细胞抗原受体(Bcellantigenreceptor,BCR)信号转导通路的关键蛋白质分子之一.为了研究Bam32的功能及其作用机理,应用酵母双杂交技术筛选了能与Bam32相互作用的蛋白质分子.筛选发现1个呈强阳性反应的克隆,其基因编码Hic5,为paxillin蛋白家族成员之一.Paxillin是整合素(integrin)信号转导通路中的关键蛋白质分子,而整合素在细胞对细胞外基质分子的粘附、细胞运动等方面起了重要的作用,因此对Bam32与Hic5的相互作用进行了进一步研究.用293T细胞共转染和特异性免疫共沉淀法证实,Bam32可在哺乳动物细胞中与Hic5共沉淀,证明它们可以在细胞内相互作用.应用免疫共沉淀法和抗磷酸化酪氨酸抗体检测显示,激酶Lyn可导致Bam32和Hic5的磷酸化.这些研究结果提示,Bam32与Hic5的相互作用可能在激活下游分子的信号转导级联反应以及调节细胞的粘附和运动等功能中发挥了重要的作用.