Cell Adhesion: Separation of p120's Powers?

The catenin p120 is involved in many processes, including cell-cell adhesion and cancer. Recent work explores whether p120 independently regulates two key binding partners, RhoGTPase and cadherin.     

p120-catenin and β-catenin differentially regulate cadherin adhesive function

Vascular endothelial (VE)-cadherin, the major adherens junction adhesion molecule in endothelial cells, interacts with p120-catenin and β-catenin through its cytoplasmic tail. However, the specific functional contributions of the catenins to the establishment of strong adhesion are not fully understood. Here we use bioengineering approaches to identify the roles of cadherin–catenin interactions in promoting strong cellular adhesion and the ability of the cells to spread on an adhesive surface. Our results demonstrate that the domain of VE-cadherin that binds to β-catenin is required for the establishment of strong steady-state adhesion strength. Surprisingly, p120 binding to the cadherin tail had no effect on the strength of adhesion when the available adhesive area was limited. Instead, the binding of VE-cadherin to p120 regulates adhesive contact area in a Rac1-dependent manner. These findings reveal that p120 and β-catenin have distinct but complementary roles in strengthening cadherin-mediated adhesion.     

RPTPμ tyrosine phosphatase promotes adipogenic differentiation via modulation of p120 catenin phosphorylation

Adipocyte differentiation can be regulated by the combined activity of protein tyrosine kinases (PTKs) and protein tyrosine phosphatases (PTPs). In particular, PTPs act as key regulators in differentiation-associated signaling pathways. We recently found that receptor-type PTPμ (RPTPμ) expression is markedly increased during the adipogenic differentiation of 3T3-L1 preadipocytes and mesenchymal stem cells. Here, we investigate the functional roles of RPTPμ and the mechanism of its involvement in the regulation of signal transduction during adipogenesis of 3T3-L1 cells. Depletion of endogenous RPTPμ by RNA interference significantly inhibited adipogenic differentiation, whereas RPTPμ overexpression led to an increase in adipogenic differentiation. Ectopic expression of p120 catenin suppressed adipocyte differentiation, and the decrease in adipogenesis by p120 catenin was recovered by introducing RPTPμ. Moreover, RPTPμ induced a decrease in the cytoplasmic p120 catenin expression by reducing its tyrosine phosphorylation level, consequently leading to enhanced translocation of Glut-4 to the plasma membrane. On the basis of these results, we propose that RPTPμ acts as a positive regulator of adipogenesis by modulating the cytoplasmic p120 catenin level. Our data conclusively demonstrate that differentiation into adipocytes is controlled by RPTPμ, supporting the utility of RPTPμ and p120 catenin as novel target proteins for the treatment of obesity.     

稳定表达p120ctn的人肺腺癌A549细胞株的构建

目的:构建稳定表达p120ctn的A549细胞株,以研究p120ctn蛋白在肺癌发生和转移过程中的作用。方法:通过分子克隆,将pc DNA3.1多克隆位点插入Flag标签的编码序列,得到pc DNA.Flag表达载体。然后PCR扩增p120ctn的编码序列,插入Flag标签下游,构建pc DNA.Flag-p120ctn质粒,筛选阳性克隆并进行酶切及测序鉴定。利用脂质体Lipofectamine 2000将pc DNA.Flag-p120ctn质粒转染到肺癌细胞A549中,通过G418筛选得到稳定转染细胞株,免疫印迹法检测p120ctn的表达。结果:本文构建了融合有Flag标签的p120ctn真核表达载体并转染到A549中,免疫印迹结果表明p120ctn蛋白在A549细胞中高效的表达。结论:本文成功构建了稳定高表达p120ctn的A549细胞模型,为深入研究p120ctn在肺癌的发生和转移过程中的作用奠定了基础。     

δ-catenin affects the localization and stability of p120-catenin by competitively interacting with E-cadherin

E-cadherin is a member of the cadherin family of Ca²⁺-dependent cell-cell adhesion molecules. p120-Catenin and δ-catenin are known to bind to similar juxtamembrane regions of E-cadherin, and p120-catenin is known to stabilize E-cadherin. However, the function of competition between p120-catenin and δ-catenin for E-cadherin has not been fully explained. In this report, we show that cells overexpressing δ-catenin contain less p120-catenin than control cells at the cell-cell interface and that this causes the relocalization of p120-catenin from the plasma membrane to the cytosol. We show that successful binding by one to E-cadherin adversely affects the stability of the other.     

p120ctn、Kaiso及matrilysin在非小细胞肺癌中的表达及其意义

目的探讨p120catenin(p120ctn)、Kaiso和matrilysin在非小细胞肺癌(non-small cell lung cancer,NSCLC)发生发展中的作用。方法采用免疫组织化学法检测98例NSCLC(52例肺鳞状细胞癌和46例肺腺癌)以及16例支气管扩张症组织中p120ctn、Kaiso和matrilysin的表达情况,分析NSCLC中p120ctn、Kaiso和matrilysin与临床病理特征的关系及三者表达的相关性。结果在NSCLC组织和支气管扩张症组织中,p120ctn蛋白异常表达率分别为74.5%、6.3%,两组之间表达率比较有统计学差异(P<0.001);在肺癌细胞、杯状细胞、纤毛细胞、基底细胞中Kaiso蛋白异位表达率分别为63.3%、6.3%、6.3%、37.5%,肺癌细胞与杯状细胞、纤毛细胞表达率比较有统计学差异(P<0.001)。p120ctn蛋白异常表达、matrilysin蛋白细胞质表达均与NSCLC组织学类型密切相关(P<0.05),Kaiso蛋白异位表达与NSCLC分化程度密切相关(P<0.05)。在NSCLC组织中,Kaiso细胞核表达与matrilysin细胞质表达存在显著负相关(r=-0.23,P=0.02)。结论 p120ctn可能通过与Kaiso在胞质内异位表达,解除了Kaiso对靶基因的抑制作用,促进matrilysin的细胞质表达,而参与肺癌的发生发展。     

Gα(12) binds to the N-terminal regulatory domain of p120(ctn), and downregulates p120(ctn) tyrosine phosphorylation induced by Src family kinases via a RhoA independent mechanism

p120 Catenin (p120(ctn)) regulates cadherin stability, and thus facilitates strong cell-cell adhesion. Previously, we demonstrated that Gα(12) interacts with p120(ctn). In the present study, we have delineated a region of p120(ctn) that binds to Gα(12). We report that the N-terminal region of p120(ctn) (amino acids 1-346) is necessary and sufficient for the interaction. While the coiled-coiled domain and a charged region, comprising a.a 102-120, were found to be dispensable, amino acids 121-323 were required for p120(ctn) binding to Gα(12). This region harbors the phosphorylation domain of p120(ctn) and has been postulated as important for RhoA regulation. Downregulation of Src family kinase-induced tyrosine phosphorylation of p120(ctn) was observed in the presence of activated Gα(12). This down-regulation was triggered by three different Gα(12) mutants uncoupled from RhoA signalling. Furthermore, a dominant active form of RhoA did not reduce Src-induced phosphoryaltion of p120(ctn). In summary, our results suggest that Gα(12) binds to p120(ctn) and modulates its phosphorylation status through a Rho-independent mechanism. Gα(12) emerges as an important regulator of p120(ctn) function, and possibly of cadherin-mediated adhesion and/or cell motility.     

Acidic extracellular pH induces p120-catenin-mediated disruption of adherens junctions via the Src kinase-PKCδ pathway

An acidic microenvironment induces disruption of adherens junctions (AJs) of hepatoma cells. This study investigated the impact of an acidic extracellular pH (pHe) on p120-catenin (p120-ctn) serine phosphorylation. pH 6.6 treatment increased intracellular calcium levels, activated protein kinase C (PKC)α and PKCδ, and decreased serine phosphorylation of p120-ctn. Further knockdown of PKCα and δ by small interference RNA (siRNA) prevented the pH 6.6-induced downregulation of p120-ctn at AJ and the serine dephosphorylation of p120-ctn. Moreover, PP2 pretreatment and siRNA of c-Src abrogated the pH 6.6-induced PKCδ activation. Together, the c-Src-PKCδ cascade and PKCα regulate the acidic pHe-induced AJ disruption.     

Concomitant Loss of p120-Catenin and β-Catenin Membrane Expression and Oral Carcinoma Progression with E-Cadherin Reduction

The binding of p120-catenin and β-catenin to the cytoplasmic domain of E-cadherin establishes epithelial cell-cell adhesion. Reduction and loss of catenin expression degrades E-cadherin-mediated carcinoma cell-cell adhesion and causes carcinomas to progress into aggressive states. Since both catenins are differentially regulated and play distinct roles when they dissociate from E-cadherin, evaluation of their expression, subcellular localization and the correlation with E-cadherin expression are important subjects. However, the same analyses are not readily performed on squamous cell carcinomas in which E-cadherin expression determines the disease progression. In the present study, we examined expression and subcellular localization of p120-catenin and β-catenin in oral carcinomas (n = 67) and its implications in the carcinoma progression and E-cadherin expression using immunohitochemistry. At the invasive front, catenin-membrane-positive carcinoma cells were decreased in the dedifferentiated (p120-catenin, P < 0.05; β-catenin, P < 0.05) and invasive carcinomas (p120-catenin, P < 0.01; β-catenin, P < 0.05) and with the E-cadherin staining (p120-catenin, P < 0.01; β-catenin, P < 0.01). Carcinoma cells with β-catenin cytoplasmic and/or nuclear staining were increased at the invasive front compared to the center of tumors (P < 0.01). Although the p120-catenin isoform shift from three to one associates with carcinoma progression, it was not observed after TGF-β, EGF or TNF-α treatments. The total amount of p120-catenin expression was decreased upon co-treatment of TGF-β with EGF or TNF-α. The above data indicate that catenin membrane staining is a primary determinant for E-cadherin-mediated cell-cell adhesion and progression of oral carcinomas. Furthermore, it suggests that loss of p120-catenin expression and cytoplasmic localization of β-catenin fine-tune the carcinoma progression.     

β-Catenin和p120的S亚硝基化:内皮高通透性的一种新的调控机制

<正>内皮粘着连接蛋白是调控微血管通透性的关键分子。血小板激活因子(platelet-activating factor,PAF)通过转运eNOS至胞浆并激活eNOS依赖的一氧化氮信号通路增加内皮对大分子物质的通透性。但是一氧化氮信号在粘着连接处调控内皮通透性的具体机制目前还不清楚。本文作者假设PAF是通过对粘着连接蛋白的S亚硝基化从而导致内皮高通透性。他们的研究结果发表在2012年8月17日在线出版的《循环研究》(Circulation Research)杂志上。文中,作者在ECV-eNOSGFP、EAhy926、毛细血管后微静脉内皮细胞三种细胞系以及在体小鼠睾提肌检测了PAF刺激的     

p53家族新成员：p51

p53是一种广谱的肿瘤抑制基因,其新家族成员p51具有同p53相似的DNA结合特笥和相似的功能,同样可以转录激活p53基因的内源性靶分子,如细胞周期抑制基因p21、导致细胞凋亡和生长受抑。本文阐述了它的研究进展。     

p63和p63参与p53依赖的细胞凋亡过程

人们通常用经典的操作式学习方法来训练动物的行为 ,使动物学会根据外部信号 (如声音 )产生特定的行为反应 ,以获取奖赏 (如食物 )。而本文的作者用脑内植入微电极进行脑区刺激的方法教会动物如何学习 ,可以去除用来产生信号和奖赏的外部环境对实验的限制。这一动物模型使操作者能远距离地指挥动物的行为 ,很像控制智能机器人的方法。电刺激能否产生等同于信号或奖赏的效应 ,取决于它所刺激的脑区。作者在自由活动大鼠的躯体感觉皮层 (ＳＩ)左右两侧胡须代表区和内侧前脑束 (ＭＦＢ)内植入电极加以刺激 ,以产生信号和奖赏效应 ,据此准确地指…     

Solution structure of the human BTK SH3 domain complexed with a proline-rich peptide from p120cbl

X-linked agammaglobulinemia (XLA), an inherited disease, is caused by mutations in the Bruton's tyrosine kinase (BTK). The absence of functional BTK leads to failure of B cell differentiation which incapacitates antibody production in XLA patients leading to, sometimes lethal, bacterial infections. Point mutation in the BTK gene that leads to deletion of C-terminal 14 aa residues of BTK SH3 domain was found in one patient family. To understand the role of BTK in B cell development, we have determined the solution structure of BTK SH3 domain complexed with a proline-rich peptide from the protein product of c-cbl protooncogene (p120^cbl). Like other SH3 domains, BTK SH3 domain consists of five -strands packed in two -sheets forming a -barrel-like structure. The rmsd calculated from the averaged coordinates for the BTK SH3 domain residues 218–271 and the p120^cbl peptide residues 6–12 of the complex was 0.87 Å (±0.16 Å) for the backbone heavy atoms (N, C, and C) and 1.64 Å (±0.16 Å) for all heavy atoms. Based on chemical shift changes and inter-molecular NOEs, we have found that the residues located in the RT loop, n-Src loop and helix-like loop between 4 and 5 of BTK SH3 domain are involved in ligand binding. We have also determined that the proline-rich peptide from p120^cbl binds to BTK SH3 domain in a class I orientation. These results correlate well with our earlier observation that the truncated BTK SH3 domain (deletion of 4, 5 and the helix-like loop) exhibits weaker affinity for the p120^cbl peptide. It is likely that the truncated SH3 domain fails to present to the ligand the crucial residues in the correct context and hence the weaker binding. These results delineate the importance of the C-terminus in the binding of SH3 domains and also indicate that improper folding and the altered binding behavior of mutant BTK SH3 domain likely lead to XLA.     

GPR120的研究进展

游离脂肪酸作为组织能量来源以及介导各种细胞进程的信号分子,其生理功能长期以来受到广泛关注。外周游离脂肪酸水平的升高与肥胖、脂代谢紊乱以及糖尿病紧密相关。GPR120作为一新的长链脂肪酸受体,参与调节体内一系列的代谢过程,如激素分泌、细胞增殖及脂质生成等。作为肥胖、糖尿病的潜在治疗靶标,值得更深入的研究。     

低剂量顺铂通过p38MAPK介导的DNMT1下调降低p21与p16启动子甲基化上调p21与p16表达

低剂量顺铂可通过诱导p21与p16表达而诱导肿瘤细胞早衰,但其机制不明。本研究探讨了低剂量顺铂诱导的HeLa细胞衰老过程中p21与p16的上调机制。低剂量顺铂（4 μmol/L）处理HeLa细胞后,DNA甲基转移酶DNMT1蛋白水平降低;p21与p16启动子甲基化水平降低,二者mRNA及蛋白质水平升高;顺铂对DNMT1蛋白水平的降低作用与其激活p38MAPK有关,用SB203580抑制p38MAPK可部分逆转顺铂对DNMT1蛋白水平以及p21与p16启动子甲基化的降低作用,从而部分逆转顺铂对p21与p16表达的诱导;抑制p38MAPK 也可部分逆转低剂量顺铂诱导的HeLa细胞早衰。上述结果表明,低剂量顺铂可通过p38MAPK信号通路下调p21与p16启动子甲基化水平,进而上调二者的表达。这些结果为解析低剂量顺铂诱导肿瘤细胞早衰的信号转导机制提供了实验依据。     

Are p27 and p21 Cytoplasmic Oncoproteins?

By causing cytoplasmic mislocation of p27 and p21, the Akt oncogenic kinase functionally inactivates these nuclear tumor suppressor proteins. Is cytoplasmic localization of p27 and p21 simply equivalent to loss of their function or are new functions acquired in the cytoplasm? Indeed, several lines of evidence suggest that cytoplasmic p27 and p21 may be oncoproteins with antiapoptotic activities.     

p73基因

ｐ７３基因黄君富房殿春鲁容（第三军医大学西南医院分子生物学实验室,重庆４０００３８）关键词ｐ７３ｐ５３抑癌基因人们对抑癌基因ｐ５３在肿瘤发生中的作用已进行了较为深入的研究,ｐ５３基因的缺失及失活与５０％的人类肿瘤发生有关。人们早就认为,在复杂的生物学...     

Direct duplication 2p14→2p23

Summary A malformed male newborn was first diagnosed as having Smith-Lemli-Opitz syndrome. Extensive cytogenetic studies, including Q, G, C, R and T banding and BudR treatment, were applied, finally leading the authors to conclude that the patient had a partial 2p trisomy caused by direct duplication 2p142p23. This was a de novo chromosome abnormality, as both parents had normal karyotypes.     

Are p27 and p21 cytoplasmic oncoproteins?

By causing cytoplasmic mislocation of p27 and p21, the Akt oncogenic kinase functionally inactivates these nuclear tumor suppressor proteins. Is cytoplasmic localization of p27 and p21 simply equivalent to loss of their function or are new functions acquired in the cytoplasm? Indeed, several lines of evidence suggest that cytoplasmic p27 and p21 may be oncoproteins with antiapoptotic activities.