Transformation-specific tyrosine phosphorylation of a novel cellular protein in chicken cells expressing oncogenic variants of the avian cellular src gene

EIF4A3-negatively driven circular RNA β-catenin (circβ-catenin) promotes colorectal cancer progression via miR-197-3p/CTNND1 regulatory axis

BACKGROUND

Circβ-catenin, our first reported circRNA, has been reported to mediate tumorigenesis in various cancers. However, its biological functions and underlying mechanisms in colorectal cancer (CRC) remain unknown.

METHODS

The qRT-PCR examination was used to detect the expression of circβ-catenin, miR-197-3p, and CTNND1 in cells and human tissues. Western blot was conducted to detect the protein expression levels. The biological function of circβ-catenin was verified by MTT, colony formation, wound healing, and transwell assays. The in vivo effects of circβ-catenin were verified by nude mice xenograft and metastasis models. The regulatory network of circβ-catenin/miR-197-3p/CTNND1 was confirmed via dual-luciferase reporter and RIP assays.

RESULTS

In the present study, circβ-catenin was found to promote CRC cell proliferation and metastasis in vitro and in vivo. Mechanistically, circβ-catenin served as miRNA decoy to directly bind to miR-197-3p, then antagonized the repression of the target gene CTNND1, and eventually promoted the malignant phenotype of CRC. More interestingly, the inverted repeated Alu pairs termed AluJb1/2 and AluY facilitated the biogenesis of circβ-catenin, which could be partially reversed by EIF4A3 binding to Alu element AluJb2.

CONCLUSIONS

Our findings illustrated a novel mechanism of circβ-catenin in modulating CRC tumorigenesis and metastasis, which provides a potential therapeutic target for CRC patients.

HTRA1 rs11528744, BCRA1 rs9928736, and B3GLCT rs4381465 are associated with age-related macular degeneration in a Chinese population

Purpose: Age-related macular degeneration (AMD) is a leading cause of vision loss. A Previous study based on the co-localization analysis of the genome-wide association study (GWAS) and eQTL genetic signals have reported that single nucleotide polymorphisms (SNPs), including rs760975, rs11528744, rs3761159, rs7212510, rs6965458, rs7559693, rs56108400, rs28495773, rs9928736, rs11777697, rs4381465 are associated with AMD in Americans. The aim of this study was to investigate the association of these SNPs in a Han Chinese population.

Methods: There were 576 patients with wet AMD and 572 healthy controls collected in this study. All SNPs were genotyped by flight mass spectrum. Hardy–Weinberg equilibrium was applied to evaluate allele distributions for both AMD and control groups. The genotype and allele frequencies were evaluated using the χ2 tests. Odds ratio (OR) and 95% confidence intervals (95% CI) were calculated for the risk of genotype and allele.

Results: Three of the 11 SNPs (rs11528744 in HTRA1, rs9928736 in BCRA1 and rs4381465 in B3GLCT) were found to be significantly associated with AMD in the allelic model (corrected p = 0.001, OR = 1.391, 95%CI = 1.179–1.640 for rs11528744; corrected p = 0.004, OR = 0.695, 95%CI = 0.544–0.888 for rs9928736; corrected p = 0.002, OR = 0.614, 95%CI = 0.448–0.841 for rs4381465). There were no differences for the remaining eight SNPs between AMD cases and healthy controls.

Conclusion: Our results showed that HTRA1 rs11528744, BCRA1 rs9928736, and B3GLCT rs4381465 were associated with wet AMD, suggesting that HTRA1, BCRA1, and B3GLCT genes may be involved in the development of AMD.

Long non-coding RNA KCNQ1OT1 up-regulates CTNND1 by sponging miR-329-3p to induce the proliferation, migration, invasion, and inhibit apoptosis of colorectal cancer cells

Background

Long non-coding RNAs (lncRNAs) have been certified to be involved in the occurrence and growth of diverse cancers, including CRC. The purpose of the research was to explore the effects of lncRNA KCNQ1 overlapping transcript 1 (KCNQ1OT1) on proliferation, migration, invasion, and apoptosis in CRC cells and its mechanism.

Methods

The levels of KCNQ1OT1 and miR-329-3p were examined by quantitative real-time polymerase chain reaction (qRT-PCR) in CRC tissues and cells. The mRNA and protein levels of catenin delta-1 (CTNND1) were measured by qRT-PCR and western blot analysis, respectively. The targets of KCNQ1OT1 and miR-329-3p were predicted by online software and confirmed by luciferase reporter assay. The cell proliferation, migration, invasion, and apoptosis were examined using 3-(4, 5-dimethylthiazol-2-yl)-2, 5-diphenyltetrazolium bromide (MTT), transwell, and apoptosis assay. The expression levels of CyclinD1, Bcl-2, MMP9, Cleaved-casp-3, and E-cadherin in SW480 and LS1034 cells were gauged by western blot analysis. Xenograft tumor model was structured to prove the biological role of KCNQ1OT1 of CRC in vivo.

Results

The levels of KCNQ1OT1 and CTNND1 were significantly increased in CRC tissues and cells. Knockdown of KCNQ1OT1 suppressed proliferation, migration, invasion, and induced apoptosis in CRC cells. Conversely, CTNND1 overexpression reversed the impact of KCNQ1OT1 knockdown on CRC cells. Moreover, CTNND1 was verified as a direct target of miR-329-3p, and miR-329-3p could specially bind to KCNQ1OT1. Also, the down-regulation of KCNQ1OT1 triggered the CRC progress by up-regulating CTNND1 expression in CRC cells. Besides, KCNQ1OT1 knockdown inhibited CRC tumor growth through the miR-329-3p/CTNND1 axis in vivo.

Conclusion

Our results indicated that KCNQ1OT1 could positively regulate CTNND1 expression by sponging miR-329-3p, thereby boosting the progression of CRC. Our findings provided the underlying therapy targets for CRC.

Rho GTPases in Gynecologic Cancers: In-Depth Analysis toward the Paradigm Change from Reactive to Predictive, Preventive, and Personalized Medical Approach Benefiting the Patient and Healthcare

Rho guanosine triphospatases (GTPases) resemble a conserved family of GTP-binding proteins regulating actin cytoskeleton dynamics and several signaling pathways central for the cell. Rho GTPases create a so-called Ras-superfamily of GTPases subdivided into subgroups comprising at least 20 members. Rho GTPases play a key regulatory role in gene expression, cell cycle control and proliferation, epithelial cell polarity, cell migration, survival, and apoptosis, among others. They also have tissue-related functions including angiogenesis being involved in inflammatory and wound healing processes. Contextually, any abnormality in the Rho GTPase function may result in severe consequences at molecular, cellular, and tissue levels. Rho GTPases also play a key role in tumorigenesis and metastatic disease. Corresponding mechanisms include a number of targets such as kinases and scaffold/adaptor-like proteins initiating GTPases-related signaling cascades. The accumulated evidence demonstrates the oncogenic relevance of Rho GTPases for several solid malignancies including breast, liver, bladder, melanoma, testicular, lung, central nervous system (CNS), head and neck, cervical, and ovarian cancers. Furthermore, Rho GTPases play a crucial role in the development of radio- and chemoresistance e.g. under cisplatin-based cancer treatment. This article provides an in-depth overview on the role of Rho GTPases in gynecological cancers, highlights relevant signaling pathways and pathomechanisms, and sheds light on their involvement in tumor progression, metastatic spread, and radio/chemo resistance. In addition, insights into a spectrum of novel biomarkers and innovative approaches based on the paradigm shift from reactive to predictive, preventive, and personalized medicine are provided.

Monoubiquitination of p120-catenin is essential for TGFβ-induced epithelial-mesenchymal transition and tumor metastasis

Disassembly of intercellular junctions is a hallmark of epithelial-mesenchymal transition (EMT). However, how the junctions disassemble remains largely unknown. Here, we report that E3 ubiquitin ligase Smurf1 targets p120-catenin, a core component of adherens junction (AJ) complex, for monoubiquitination during transforming growth factor β (TGFβ)-induced EMT, thereby leading to AJ dissociation. Upon TGFβ treatment, activated extracellular signal-regulated kinase 1/2 (ERK1/2) phosphorylates T900 of p120-catenin to promote its interaction with Smurf1 and subsequent monoubiquitination. Inhibition of T900 phosphorylation or ubiquitination of p120-catenin abrogates TGFβ-induced AJ dissociation and consequent tight junction (TJ) dissociation and cytoskeleton rearrangement, hence markedly blocking lung metastasis of murine breast cancer. Moreover, the T900 phosphorylation level of p120-catenin is positively correlated with malignancy of human breast cancer. Hence, our study reveals the underlying mechanism by which TGFβ induces dissociation of AJs during EMT and provides a potential strategy to block tumor metastasis.

Cadmium and Lead Decrease Cell-Cell Aggregation and Increase Migration and Invasion in Renca Mouse Renal Cell Carcinoma Cells

Metastatic renal cell carcinoma (RCC) remains an important clinical issue; the 5-year survival rate of patients with metastasis is approximately 12%, while it is 93% in those with localized disease. There is evidence that blood cadmium and lead levels are elevated in RCC. The current studies were designed to assess the impact of cadmium and lead on the progression of RCC. The disruption of homotypic cell-cell adhesion is an essential step in epithelial-to-mesenchymal transition and tumor metastasis. Therefore, we examined the impact of cadmium and lead on the cadherin/catenin complex in Renca cells-a mouse RCC cell line. Lead, but not cadmium, induced a concentration-dependent loss of E-cadherin, while cadmium, but not lead, increased p120-catenin expression, specifically isoform 1 expression. Lead also induced a substantial increase in matrix metalloproteinase-9 levels. Both cadmium and lead significantly decreased the number of Renca cell aggregates, consistent with the disruption of the cadherin/catenin complex. Both metals enhanced wound healing in a scratch assay, and increased cell migration and invasion. These data suggest that cadmium and lead promote RCC progression.

Hsa_circ_0002577 promotes endometrial carcinoma progression via regulating miR-197/CTNND1 axis and activating Wnt/β-catenin pathway

Circular RNA (circRNA) is involved in a wide range of life processes including tumorigenesis. However, the molecular mechanisms of circRNA in endometrial carcinoma (EC) carcinogenesis remain unclear. In the present study, we aimed to investigate the potential modulation of hsa_circ_0002577 on EC progression. Here, we showed that hsa_circ_0002577 expression was significantly upregulated in EC tissues, and high hsa_circ_0002577 expression was associated with advanced FIGO stage, lymph node metastasis, and poor overall survival rate of EC patients. In function assays, we demonstrated that hsa_circ_0002577 knockdown significantly reduced EC cells proliferation, migration, invasion ability in vitro and decreased tumor growth in vivo. In mechanism study, we revealed that hsa_circ_0002577 might act as a sponge for miR-197, and CTNND1 was revealed to be a target gene of miR-197. In addition, we revealed that the oncogenic effects of hsa_circ_0002577 were attributed to the regulation of miR-197/CTNND1/Wnt/β-catenin axis. Taken together, we indicated that hsa_circ_0002577 could play critical functions by hsa_circ_0002577/miR-197/CTNND1/Wnt/β-catenin signaling pathway, which served as a novel therapeutic application for EC treatment.

MUC16 impacts tumor proliferation and migration through cytoplasmic translocation of P120-catenin in epithelial ovarian cancer cells: an original research

Background

Epithelial ovarian cancer (EOC) remains one of the most lethal gynecologic cancers, and its pathogenetic mechanism remains unclear. Here we show that MUC16 promotes the translocation of p120-catenin (p120ctn) to the cytoplasm and consequently activates ras homolog (Rho) GTPases RhoA/Cdc42 activation to modulate the proliferation and migration abilities of EOC cells.

Methods

We collect 94 ovarian cancer (OC) patients’ tissue samples to constitute tissue microarray (TMA) and analyze the MUC16 and p120ctn expression levels. Lentivirus transfection is used to overexpress cytoplasmic tail domain (CTD) of MUC16 and CRISPR/Cas9 genome-editing system is firstly used to knock out MUC16 in EOC cells. The proliferation or migration ability of cells is analyzed by MTS or migration assay.

Results

We find that MUC16 and p120ctn are aberrantly overexpressed in 94 clinical OC samples compared with benign ovarian tumors (BOT). MUC16 is a critical inducer of the proliferation and migration of EOC cells and the CTD of MUC16 plays an important role during this process. In addition, we reveal the relationship between MUC16 and p120ctn, which has not previously been studied. We show that MUC16 promotes the translocation of p120ctn to the cytoplasm and consequently activates Rho GTPases to modulate the proliferation and migration abilities of EOC cells. The cell proliferation and migration abilities induced by MUC16 are mediated by p120ctn through RhoA/Cdc42 activation.

Conclusions

The highly expressed MUC16 promotes the translocation of p120ctn to the cytoplasm, where it activates RhoA/Cdc42 to modulate the proliferation and migration abilities of EOC cells. These findings may provide new targets for the treatment of EOC.

Electronic supplementary material

The online version of this article (10.1186/s12885-019-5371-4) contains supplementary material, which is available to authorized users.

Knockdown of P120 catenin aggravates endothelial injury under an impinging flow by inducing breakdown of adherens junctions

At present, the mechanisms underlying intracranial aneurysm (IA) development remain unclear; however, hemodynamics is considered a crucial factor in the induction of IA. To elucidate the association between hemodynamics and endothelial cell (EC) functions, a modified T chamber system was designed to simulate the adjustable hemodynamic conditions of an artery bifurcation. Normal human umbilical vein ECs (HUVECs) and HUVECs with P120 catenin (P120ctn) knockdown were cultured on coverslips and placed in the chamber. A flow rate of 250 or 500 ml/min impinged on the cell layer. Subsequently, the expression levels of P120ctn and other proteins, and EC morphological alterations, were examined. In normal HUVECs, after 3 h under a flow rate of 500 ml/min, the expression levels of P120ctn, vascular endothelial (VE)‑Cadherin, Kaiso and α‑catenin were decreased, whereas matrix metalloproteinase‑2 (MMP‑2) was increased. In HUVECs with P120ctn knockdown, the period during which ECs adhered to the coverslip was reduced to 1 h under a flow rate of 500 ml/min. In addition, the expression levels of VE‑Cadherin, Kaiso and α‑catenin in ECs were decreased, whereas those of MMP‑2 were increased after 1 h; more prominent alterations were detected under a 500 ml/min flow rate compared with a 250 ml/min flow rate. Adherens junctions (AJs) are critical to the maintenance of normal morphology and EC functioning in the vascular wall, and P120ctn is an important regulator of AJs. Loss of P120ctn may be induced by hemodynamic alterations. In response to changes in hemodynamic conditions, a loss of P120ctn may aggravate AJs between ECs, thus inducing inflammation in the vascular wall. Clinically, hemodynamic alterations may result in a loss of P120ctn and endothelial injury; therefore, P120ctn may have a critical role in inducing intracranial aneurysms.

Loss of E-Cadherin-Dependent Cell-Cell Adhesion and the Development and Progression of Cancer

Classical cadherins are the key molecules that control cell-cell adhesion. Notwithstanding this function, it is also clear that classical cadherins are more than just the "glue" that keeps the cells together. Cadherins are essential regulators of tissue homeostasis that govern multiple facets of cellular function and development, by transducing adhesive signals to a complex network of signaling effectors and transcriptional programs. In cancer, cadherins are often inactivated or functionally inhibited, resulting in disease development and/or progression. This review focuses on E-cadherin and its causal role in the development and progression of breast and gastric cancer. We provide a summary of the biochemical consequences and consider the conceptual impact of early (mutational) E-cadherin loss in cancer. We advocate that carcinomas driven by E-cadherin loss should be considered "actin-diseases," caused by the specific disruption of the E-cadherin-actin connection and a subsequent dependence on sustained actomyosin contraction for tumor progression. Based on the available data from mouse and human studies we discuss opportunities for targeted clinical intervention.

Cadherin complexes recruit mRNAs and RISC to regulate epithelial cell signaling

Cumulative evidence demonstrates that most RNAs exhibit specific subcellular distribution. However, the mechanisms regulating this phenomenon and its functional consequences are still under investigation. Here, we reveal that cadherin complexes at the apical zonula adherens (ZA) of epithelial adherens junctions recruit the core components of the RNA-induced silencing complex (RISC) Ago2, GW182, and PABPC1, as well as a set of 522 messenger RNAs (mRNAs) and 28 mature microRNAs (miRNAs or miRs), via PLEKHA7. Top canonical pathways represented by these mRNAs include Wnt/β-catenin, TGF-β, and stem cell signaling. We specifically demonstrate the presence and silencing of MYC, JUN, and SOX2 mRNAs by miR-24 and miR-200c at the ZA. PLEKHA7 knockdown dissociates RISC from the ZA, decreases loading of the ZA-associated mRNAs and miRNAs to Ago2, and results in a corresponding increase of MYC, JUN, and SOX2 protein expression. The present work reveals a mechanism that directly links junction integrity to the silencing of a set of mRNAs that critically affect epithelial homeostasis.

miR-223 promotes colon cancer by directly targeting p120 catenin

microRNA (miRNA) dysregulation is frequently observed in colon cancer. Previous studies found that miR-223 is upregulated in colon cancer and functions as an oncogene. Conversely, p120 is often downregulated or even absent in colon cancer, and is a likely tumor suppressor. The present study showed that increased miR-223 and decreased p120 levels are associated with colon cancer malignancy, and p120 expression is negatively correlated with miR-223 expression. A dual luciferase reporter assay showed that miR-223 directly targets p120. miR-223 upregulation in a colon cancer cell line upregulated c-Myc, cyclinD1, MMP7, and vimentin expression, downregulated E-cadherin, increased nuclear expression of β-catenin, and enhanced RhoA activation. We suggest miR-223 may promote colon cancer cell invasion and metastasis by downregulating p120, thereby reducing intercellular adhesion, promoting RhoA activity, and activating β-catenin signaling. Thus miR-223 functions as an oncogene in colon cancer and may be a potential diagnostic and therapeutic target for anti-colon cancer treatment.

Chromatin remodeling protein MORC2 promotes breast cancer invasion and metastasis through a PRD domain-mediated interaction with CTNND1

MORC family CW-type zinc finger 2 (MORC2) is a newly identified chromatin remodeling protein with emerging roles in the regulation of DNA damage response and gene transcription, but its mechanistic role in breast cancer development and progression remains unexplored. Here, we show that MORC2 promoted breast cancer invasion and metastasis and these effects depended on a proline-rich domain (PRD) within its carboxy-terminal region spanning residues 601–734. Induced expression of wild-type MORC2 did not significantly affect cell proliferation and cell-cycle progression, but promoted breast cancer cell migration and invasion in vitro and metastatic lung colonization in vivo. The PRD domain was dispensable for the protein stability and subcellular localization of MORC2, but depletion of the PRD domain substantially suppressed MORC2-mediated migration, invasion, and metastasis. Proteomic and biochemical analyses further demonstrated that wild-type MORC2, but not PRD deletion mutant, interacted with catenin delta 1 (CTNND1), a cadherin-associated protein that participates in tumor invasion and metastasis. Moreover, knockdown of endogenous CTNND1 by short hairpin RNAs suppressed the migratory and invasive potential of MORC2-expressing cells. Taken together, these results suggest that MORC2 promotes breast cancer invasion and metastasis through its PRD domain-mediated interaction with CTNND1.

CTNND1 755 T>G Promoter Polymorphism and Risk of Pancreatic Carcinoma in Chinese

OBJECTIVE

To investigate the relationship between 755 T>G polymorphisms in the CTNND1 gene, which is associated with the risk of pancreatic carcinoma in Chinese.

METHODS

CTNND1 755 T>G genotypes were determined by PCR-RFLP in 122 pancreatic carcinoma patients and 180 healthy controls matched for age and sex, who did not receive radiotherapy or chemotherapy for newly diagnosed and histopathologically confirmed pancreatic carcinoma.

RESULTS

In control subjects, the frequency of T/T and G/T genotypes, and T and G alleles was 79.4%, 17.2%, 88.1%, and 11.9%, respectively. The distribution of genotypes and allelotypes in the pancreatic carcinoma patients was significantly different from that in the controls (P = 0.007, P = 0.012). Combined GG and GT genotypes were found to have a higher OR in male pancreatic carcinoma patients and the group under the age of 70 years (males: OR, 1.409; 95%CI, 0.912~1.921; under 70 years: OR 1.626; 95% CI, 0.878~2.312). This study also showed a distinct difference in the distribution of P120ctn and single nucleotide polymorphisms (SNPs) between Chinese and Canadian (11.9% vs. 3.9%, P = 0.008).

CONCLUSION

CTNND1 755 T>G polymorphism may be a stratification marker to predict the susceptibility to pancreatic carcinoma, at least in Chinese. CTNND1 promoter SNPs is diverse in ethnic populations.

Cadherin tales: Regulation of cadherin function by endocytic membrane trafficking

Cadherins are the primary adhesion molecules in adherens junctions and desmosomes and play essential roles in embryonic development. Although significant progress has been made in understanding cadherin structure and function, we lack a clear vision of how cells confer plasticity upon adhesive junctions to allow for cellular rearrangements during development, wound healing and metastasis. Endocytic membrane trafficking has emerged as a fundamental mechanism by which cells confer a dynamic state to adhesive junctions. Recent studies indicate that the juxtamembrane domain of classical cadherins contains multiple endocytic motifs, or "switches," that can be used by cellular membrane trafficking machinery to regulate adhesion. The cadherin-binding protein p120-catenin (p120) appears to be the master regulator of access to these switches, thereby controlling cadherin endocytosis and turnover. This review focuses on p120 and other cadherin-binding proteins, ubiquitin ligases, and growth factors as key modulators of cadherin membrane trafficking.

The molecular effect of metastasis suppressors on Src signaling and tumorigenesis: new therapeutic targets

A major problem for cancer patients is the metastasis of cancer cells from the primary tumor. This involves: (1) migration through the basement membrane; (2) dissemination via the circulatory system; and (3) invasion into a secondary site. Metastasis suppressors, by definition, inhibit metastasis at any step of the metastatic cascade. Notably, Src is a non-receptor, cytoplasmic, tyrosine kinase, which becomes aberrantly activated in many cancer-types following stimulation of plasma membrane receptors (e.g., receptor tyrosine kinases and integrins). There is evidence of a prominent role of Src in tumor progression-related events such as the epithelial–mesenchymal transition (EMT) and the development of metastasis. However, the precise molecular interactions of Src with metastasis suppressors remain unclear. Herein, we review known metastasis suppressors and summarize recent advances in understanding the mechanisms of how these proteins inhibit metastasis through modulation of Src. Particular emphasis is bestowed on the potent metastasis suppressor, N-myc downstream regulated gene 1 (NDRG1) and its interactions with the Src signaling cascade. Recent studies demonstrated a novel mechanism through which NDRG1 plays a significant role in regulating cancer cell migration by inhibiting Src activity. Moreover, we discuss the rationale for targeting metastasis suppressor genes as a sound therapeutic modality, and we review several examples from the literature where such strategies show promise. Collectively, this review summarizes the essential interactions of metastasis suppressors with Src and their effects on progression of cancer metastasis. Moreover, interesting unresolved issues regarding these proteins as well as their potential as therapeutic targets are also discussed.

Genetic alterations of δ-catenin/NPRAP/Neurojungin (CTNND2): functional implications in complex human diseases

Some genes involved in complex human diseases are particularly vulnerable to genetic variations such as single nucleotide polymorphism, copy number variations, and mutations. For example, Ras mutations account for over 30 % of all human cancers. Additionally, there are some genes that can display different variations with functional impact in different diseases that are unrelated. One such gene stands out: δ-catenin/NPRAP/Neurojungin with gene designation as CTNND2 on chromosome 5p15.2. Recent advances in genome wide association as well as molecular biology approaches have uncovered striking involvement of δ-catenin gene variations linked to complex human disorders. These disorders include cancer, bipolar disorder, schizophrenia, autism, Cri-du-chat syndrome, myopia, cortical cataract-linked Alzheimer's disease, and infectious diseases. This list has rapidly grown longer in recent years, underscoring the pivotal roles of δ-catenin in critical human diseases. δ-Catenin is an adhesive junction-associated protein in the delta subfamily of the β-catenin superfamily. δ-Catenin functions in Wnt signaling to regulate gene expression and modulate Rho GTPases of the Ras superfamily in cytoskeletal reorganization. δ-Catenin likely lies where Wnt signaling meets Rho GTPases and is a unique and vulnerable common target for mutagenesis in different human diseases.

P120-Catenin Protects Endplate Chondrocytes From Intermittent Cyclic Mechanical Tension Induced Degeneration by Inhibiting the Expression of RhoA/ROCK-1 Signaling Pathway

STUDY DESIGN

The changes of endplate chondrocytes induced by intermittent cyclic mechanical tension (ICMT) were observed by realtime reverse transcription-polymerase chain reaction, immunofluorescence, and Western blot analysis.

OBJECTIVE

To investigate the role of RhoA/ROCK-1 signaling pathway and E-cadherin/P120-catenin complex in endplate chondrocytes degeneration induced by ICMT.

SUMMARY OF BACKGROUND DATA

ICMT can induce the endplate chondrocyte degeneration. However, the relationship between P120-catenin or RhoA/ROCK-1 signaling pathway and endplate chondrocytes degeneration induced by ICMT is not clear.

METHODS

ICMT (strain at 0.5 Hz sinusoidal curve at 8% elongation) was applied to rat endplate chondrocytes for 6 days, 16 hours a day. The cell viability and apoptosis were examined by the LIVE/DEAD assay and flow cytometry. Histological staining was used to examine the lumbar disc tissue morphology and extracellular matrix. To regulate RhoA/ROCK-1 signaling pathway and the expression of E-cadherin and P120-catenin, RhoA/ROCK-1 pathway-specific inhibitors, E-cadherin, and p120-catenin plasmid were applied. Coimmunoprecipitation was employed to examine the interaction between E-cadherin and P120-catenin, P120-catenin, and RhoA. The related gene expression and protein location was examined by realtime reverse transcription-polymerase chain reaction, Western blot, and immunofluorescence.

RESULTS

There was no change of viability verified by LIVE/DEAD assay and flow cytometry after ICMT loading. ICMT loading led to RhoA/ROCK-1 signaling activation and the loss of the chondrogenic phenotype of endplate chondrocytes. Inhibition of RhoA/ROCK-1 signaling pathway significantly ameliorated the degeneration induced by ICMT. The expression of P120-catenin and E-cadherin were inhibited by ICMT. ICMT reduced the interaction between P120-catenin and E-cadherin. Furthermore, over-expression of P120-catenin and E-cadherin can suppress the expression of chondrogenic gene, over-expression of P120-catenin can suppress the RhoA/ROCK-1 signaling pathway, but over-expression of E-cadherin cannot do it.

CONCLUSION

P120-catenin protects endplate chondrocytes from ICMT Induced degeneration by inhibiting the expression of RhoA/ROCK-1 signaling pathway.

LEVEL OF EVIDENCE

N/A.

p120-Catenin modulating nuclear factor-κB activation is partially RhoA/ROCKdependent in scratch injury

p120-catenin (p120) is known as a cadherin-associated protein that participates in tumor metastasis and invasion, as well as an anti-inflammatory mediator. Recently, its anti-inflammatory role is drawing increasing attention, but the regulatory mechanisms are still unknown. Here, we report that p120 modulated inflammatory responses partially depends on RhoA/ROCK pathway in scratch-induced injury in human bronchial epithelial cells (BECs). For the first time, we found that p120 was significantly reduced in BECs after scratching, which could induce interleukin-8 (IL-8) production through nuclear factor-κB (NF-κB) activation accompanied with IκBα phosphorylation. Over-expression of p120 3A could inhibit NF-κB activation and IL-8 mRNA expression and protein synthesis after scratching, while p120 knockdown by small interfering RNA could promote NF-κB activation and IL-8 mRNA expression and protein synthesis after scratching. Furthermore, we found that RhoA was the binding partner of p120 in BECs. Although total RhoA and p120-binded RhoA remained unchanged, the RhoA activity was increased after scratching. Chemical blockade of RhoA/ROCK signaling (Y27632) inhibited scratch-induced nuclear translocation of NF-κB p65. Over-expression of p120 3A attenuated scratch-induced RhoA activation, whereas silence of p120 significantly elevated scratch-induced RhoA activation in BCEs. Conclusively, these results indicate an anti-inflammatory effect of p120 in bronchial epithelial cells through its modulation of NF-κB signaling depending on RhoA/ROCK pathway.

Interaction of EGFR to δ-catenin leads to δ-catenin phosphorylation and enhances EGFR signaling

Expression of δ-catenin reportedly increases during late stage prostate cancer. Furthermore, it has been demonstrated that expression of EGFR is enhanced in hormone refractory prostate cancer. In this study, we investigated the possible correlation between EGFR and δ-catenin in prostate cancer cells. We found that EGFR interacted with δ-catenin and the interaction decreased in the presence of EGF. We also demonstrated that, on one hand, EGFR phosphorylated δ-catenin in a Src independent manner in the presence of EGF and on the other hand, δ-catenin enhanced protein stability of EGFR and strengthened the EGFR/Erk1/2 signaling pathway. Our findings added a new perspective to the interaction of EGFR to the E-cadherin complex. They also provided novel insights to the roles of δ-catenin in prostate cancer cells.

P120 catenin attenuates the angiotensin II-induced apoptosis of human umbilical vein endothelial cells by suppressing the mitochondrial pathway

Hypertension Hypertension impairs the morphological and functional integrity of circulation. Previous research has shown that the loss of endothelial cells (ECs) is a common event in many cardiovascular diseases. p120 catenin (p120ctn) plays an important role in the regulation of inflammatory responses in ECs. However, the functional significance of p120ctn in angiotensin II (AngII)-induced apoptosis of human umbilical vein endothelial cells (HUVECs) had not previously received much scholarly attention. In the present study, using western blot analysis and RT-PCR, we found that AngII-induced cell apoptosis was correlated with a significant decrease in p120ctn expression. The effect of AngII on cell viability was measured by CCK-8 assay. Knockdown of p120ctn with small hairpin RNA (shRNA) increased AngII-induced apoptosis of HUVECs, as demonstrated by Annexin V/PI staining and flow cytometric analysis. Knockdown of p120ctn with shRNA also increased cytochrome c release into the cytoplasm, and cleaved caspase-3 and -9 protein expression. These were accompanied by a decrease in the Bcl-2/Bax ratio (Bcl-2 and Bax protein expression were measured by western blot analysis), and in mitochondrial membrane potential, as measured using JC-1. Overexpression of p120ctn with adenovirus produced opposite effects. In the present study, we demonstrated that p120ctn attenuated AngII-induced apoptosis of HUVECs through the mitochondria-dependent pathway, suggesting that p120ctn plays a critical role in protecting ECs against apoptosis during hypertension.

The role of adherens junctions in the developing neocortex

The disproportional enlargement of the neocortex through evolution has been instrumental in the success of vertebrates, in particular mammals. The neocortex is a multilayered sheet of neurons generated from a simple proliferative neuroepithelium through a myriad of mechanisms with substantial evolutionary conservation. This developing neuroepithelium is populated by progenitors that can generate additional progenitors as well as post-mitotic neurons. Subtle alterations in the production of progenitors vs. differentiated cells during development can result in dramatic differences in neocortical size. This review article will examine how cadherin adhesion proteins, in particular α-catenin and N-cadherin, function in regulating the neural progenitor microenvironment, cell proliferation, and differentiation in cortical development.

The Src non-receptor tyrosine kinase paradigm: New insights into mammalian Sertoli cell biology

Src kinases are non-receptor tyrosine kinases that phosphorylate diverse substrates, which control processes such as cell proliferation, differentiation and survival; cell adhesion; and cell motility. c-Src, the prototypical member of this protein family, is widely expressed by several organs that include the testis. In the seminiferous epithelium of the adult rat testis, c-Src is highest at the tubule lumen during the release of mature spermatids. Other studies show that testosterone regulates spermatid adhesion to Sertoli cells via c-Src, indicating Src phosphorylates key substrates that prompt the disassembly of Sertoli cell-spermatid junctions. A more recent in vitro study reveals that c-Src participates in the internalization of proteins that constitute the blood-testis barrier, which is present between Sertoli cells, suggesting a similar mechanism of junction disassembly is at play during spermiation. In this review, we discuss recent findings on c-Src, with an emphasis on its role in spermatogenesis in the mammalian testis.

Phosphorylation and isoform use in p120-catenin during development and tumorigenesis

P120-catenin is essential to vertebrate development, modulating cadherin and small-GTPase functions, and growing evidence points also to roles in the nucleus. A complexity in addressing p120-catenin's functions is its many isoforms, including optional splicing events, alternative points of translational initiation, and secondary modifications. In this review, we focus upon how choices in the initiation of protein translation, or the earlier splicing of the RNA transcript, relates to primary sequences that harbor established or putative regulatory phosphorylation sites. While certain p120 phosphorylation events arise via known kinases/phosphatases and have defined outcomes, in most cases the functional consequences are still to be established. In this review, we provide examples of p120-isoforms as they relate to phosphorylation events, and thereby to isoform dependent protein-protein associations and downstream functions. We also provide a view of upstream pathways that determine p120's phosphorylation state, and that have an impact upon development and disease. Because other members of the p120 subfamily undergo similar processing and phosphorylation, as well as related catenins of the plakophilin subfamily, what is learned regarding p120 will by extension have wide relevance in vertebrates.

Regulation of Endothelial Adherens Junctions by Tyrosine Phosphorylation

Endothelial cells form a semipermeable, regulated barrier that limits the passage of fluid, small molecules, and leukocytes between the bloodstream and the surrounding tissues. The adherens junction, a major mechanism of intercellular adhesion, is comprised of transmembrane cadherins forming homotypic interactions between adjacent cells and associated cytoplasmic catenins linking the cadherins to the cytoskeleton. Inflammatory conditions promote the disassembly of the adherens junction and a loss of intercellular adhesion, creating openings or gaps in the endothelium through which small molecules diffuse and leukocytes transmigrate. Tyrosine kinase signaling has emerged as a central regulator of the inflammatory response, partly through direct phosphorylation and dephosphorylation of the adherens junction components. This review discusses the findings that support and those that argue against a direct effect of cadherin and catenin phosphorylation in the disassembly of the adherens junction. Recent findings indicate a complex interaction between kinases, phosphatases, and the adherens junction components that allow a fine regulation of the endothelial permeability to small molecules, leukocyte migration, and barrier resealing.

Inhibition of focal adhesion kinase induces apoptosis in bladder cancer cells via Src and the phosphatidylinositol 3-kinase/Akt pathway

Focal adhesion kinase (FAK) is a 125-kDa, cytosolic, non-receptor, protein tyrosine kinase localized at focal adhesions that can be activated by multiple inputs and in different manners. FAK is implicated in signaling pathways regulating cell movement, invasion, survival, gene expression and cancer stem cell self-renewal. The aim of the present study was to investigate whether FAK plays a role in the apoptosis of bladder cancer cells. The study employed in situ deoxynucleotidyl transferase-mediated dUTP-biotin nick end labeling and Annexin V labeling flow cytometry. It was found that both the knockdown of FAK and the suppression of FAK phosphorylation were able to induce apoptosis in bladder cancer cells. Caspase-3 was activated during the apoptosis induced by the suppression of FAK phosphorylation. Src was involved in FAK-regulated apoptosis in bladder cancer cells, while the suppression of Src phosphorylation was able to inhibit FAK tyrosine phosphorylation and induce apoptosis. Furthermore, phosphatidylinositol 3-kinase (PI3K)/Akt signaling was inhibited via the suppression of FAK tyrosine phosphorylation. Conversely, the expression of neither the general nor the tyrosine-phosphorylated FAK was regulated by inhibiting PI3K/Akt, which suggested that PI3K/Akt acted downstream of FAK to regulate apoptosis in bladder cancer cells. These findings indicate the presence of a mechanism of apoptosis involving FAK-mediated oncogenic signaling. FAK may function as an important regulator of extracellular signaling-mediated apoptosis in bladder cancer and be used as a novel therapeutic target in the treatment of the condition.

Distinct E-cadherin-based complexes regulate cell behaviour through miRNA processing or Src and p120 catenin activity

E-cadherin and p120 catenin (p120) are essential for epithelial homeostasis, but can also exert pro-tumorigenic activities. Here, we resolve this apparent paradox by identifying two spatially and functionally distinct junctional complexes in non-transformed polarized epithelial cells: one growth suppressing at the apical zonula adherens (ZA), defined by the p120 partner PLEKHA7 and a non-nuclear subset of the core microprocessor components DROSHA and DGCR8, and one growth promoting at basolateral areas of cell-cell contact containing tyrosine-phosphorylated p120 and active Src. Recruitment of DROSHA and DGCR8 to the ZA is PLEKHA7 dependent. The PLEKHA7-microprocessor complex co-precipitates with primary microRNAs (pri-miRNAs) and possesses pri-miRNA processing activity. PLEKHA7 regulates the levels of select miRNAs, in particular processing of miR-30b, to suppress expression of cell transforming markers promoted by the basolateral complex, including SNAI1, MYC and CCND1. Our work identifies a mechanism through which adhesion complexes regulate cellular behaviour and reveals their surprising association with the microprocessor.

p120-catenin participates in the progress of gastric cancer through regulating the Rac1 and Pak1 signaling pathway

p120-catenin (p120), an E-cadherin regulator, has been implicated as central to a series of genetic and epigenetic changes that ultimately lead to tumor progression and metastasis. Ras-related C3 botulinum toxin substrate 1 (Rac1)and p21-activated kinases (PAKs) are effectors of p120. In the present study, we examined the expression of p120, Rac1 and Pak1 using immunohistochemistry in human gastric cancer tissues. Then, we used the gastric cancer SGC7901 and AGS cell lines to explore the possible mechanism of p120, Rac1 and Pak1 in the progress of gastric cancer. Western blotting was used to detect the expression of p120, Rac1 and Pak1 in the two cell lines. Next, p120 was silenced using p120 siRNA or overexpression of p120 by transfection of the plasmid p120 1A into the two cell types, western blotting was used to investigate the expression changes of Rac1 and Pak1. Furthermore, the effects of p120 siRNA-mediated knockdown or overexpression on the proliferation and invasive ability of gastric cancer cells were investigated using wound healing test and Matrigel invasion assays. The results showed that p120 was downregulated in both poorly differentiated group and well differentiated human gastric cancer. However, Rac1 and Pak1 were upregulated in poorly differentiated tissues and remain low in well differentiated gastric cancer tissues. In the two gastric cancer cell lines, although the expression of Rac1 and Pak1 remained unchanged after the p120 knockdown, the expressions of Rac1 and Pak1 protein were decreased after p120 overexpression in both SGC7901 and AGS cells. Furthermore, knockdown of p120 promoted gastric cancer cell proliferation and invasion; overexpression of p120 reduced the proliferation and invasion of gastric cancer cells. In conclusion, based on our results, we speculate that p120 participates in the progress of gastric cancer through regulating Rac1 and Pak1, which provides a potential prevention and a promising therapeutical approach for the patients with gastric cancer.

Reduced expression of E-cadherin and p120-catenin and elevated expression of PLC-γ1 and PIKE are associated with aggressiveness of oral squamous cell carcinoma

Oral squamous cell carcinoma (OSCC) is one of the most lethal malignant tumors. The cadherin/catenin cell-cell adhesion complex plays a major role in cancer development and progression. p120-catenin (p120) is a cytoplasmic molecule closely associated with E-cadherin which activates phospholipase C-γ1 (PLC-γ1). Our previous studies indicate that activation of PLC-γ1 plays a critical role in epidermal growth factor (EGF)-induced migration and proliferation of squamous cell carcinoma (SCC) cells and phosphatidylinositol 3-kinase enhancer (PIKE) is highly expressed in SCC cells and mediates EGFR-dependent SCC cell proliferation. Our current study was to determine whether the expression of E-cadherin, p120, PLC-γ1, and PIKE, is associated with OSCC. To address this issue, we assessed levels and localization of E-cadherin, p120, PLC-γ1, and PIKE in specimen of 92 patients with OSCC by immunohistochemistry. The results showed that the expression of E-cadherin, and p120 negatively correlated with the tumor differentiation and the expression of PLC-γ1 and PIKE positively correlated with the tumor differentiation. The expression of PLC-γ1 and PIKE in OSCC stage T3 + T4 or in OSCC with lymph node metastasis was significantly higher than that in OSCC stage T1 + T2 or in OSCC without lymph node metastasis. The expression of p120 positively correlated with levels of E-cadherin but negatively correlated with levels of PLC-γ1 and PIKE in OSCC. These data indicate that increased expression of PLC-γ1 and PIKE and decreased expression of E-cadherin and p120 are associated with the aggressiveness of OSCC.

Expressions of E-cadherin, p120ctn, β-catenin and NF-κB in ulcerative colitis

This study was aimed to investigate the expressions of E-cadherin, p120ctn, β-catenin and NF-κB in ulcerative colitis (UC) tissues and the implications of their expressions in the pathogenesis of UC. The expressions of E-cadherin, p120ctn, β-catenin and NF-κB were detected by immunohistochemistry, and those of p120ctn and NF-κB by Western blotting in 23 cases of UC and 17 cases of normal colonic tissues. The relationship between the expression of E-cadherin or NF-κB and that of p120ctn was analyzed by Spearman rank correlation analysis. The results showed that in UC and normal colonic groups, the abnormal expression rate of E-cadherin, p120ctn, β-catenin, and NF-κB was 52.2% vs. 0 (P<0.05), 73.9% vs. 23.5% (P<0.05), 65.2% vs. 17.6% (P<0.05) and 78.4% vs. 23.5% (P<0.05), respectively. p120ctn expression was positively correlated with E-cadherin expression (r=0.404, P<0.05), but negatively with nuclear NF-κB expression (r= - 0.347, P<0.05). Western blotting showed that as compared with the normal controls, the p120ctn protein level was significantly decreased (P<0.05), whereas the NF-κB protein level was increased (P<0.05) in UC tissues. It was concluded that in the colonic tissues of UC patients, the expressions of E-cadherin, p120ctn and β-catenin are decreased, suggesting the mucosal barrier is impaired in UC. Moreover, NF-κB is increased and activated in the UC tissues, resulting in the inflammation in UC. p120ctn may influence the UC development through modulating intercellular adhesion and inflammatory response.

Pro-Tumorigenic Phosphorylation of p120 Catenin in Renal and Breast Cancer

Altered protein expression and phosphorylation are common events during malignant transformation. These perturbations have been widely explored in the context of E-cadherin cell-cell adhesion complexes, which are central in the maintenance of the normal epithelial phenotype. A major component of these complexes is p120 catenin (p120), which binds and stabilizes E-cadherin to promote its adhesive and tumor suppressing function. However, p120 is also an essential mediator of pro-tumorigenic signals driven by oncogenes, such as Src, and can be phosphorylated at multiple sites. Although alterations in p120 expression have been extensively studied by immunohistochemistry (IHC) in the context of tumor progression, little is known about the status and role of p120 phosphorylation in cancer. Here we show that tyrosine and threonine phosphorylation of p120 in two sites, Y228 and T916, is elevated in renal and breast tumor tissue samples. We also show that tyrosine phosphorylation of p120 at its N-terminus, including at the Y228 site is required for its pro-tumorigenic potential. In contrast, phosphorylation of p120 at T916 does not affect this p120 function. However, phosphorylation of p120 at T916 interferes with epitope recognition of the most commonly used p120 antibody, namely pp120. As a result, this antibody selectively underrepresents p120 levels in tumor tissues, where p120 is phosphorylated. Overall, our data support a role of p120 phosphorylation as a marker and mediator of tumor transformation. Importantly, they also argue that the level and localization of p120 in human cancer tissues immunostained with pp120 needs to be re-evaluated.

CD148 tyrosine phosphatase promotes cadherin cell adhesion

CD148 is a transmembrane tyrosine phosphatase that is expressed at cell junctions. Recent studies have shown that CD148 associates with the cadherin/catenin complex and p120 catenin (p120) may serve as a substrate. However, the role of CD148 in cadherin cell-cell adhesion remains unknown. Therefore, here we addressed this issue using a series of stable cells and cell-based assays. Wild-type (WT) and catalytically inactive (CS) CD148 were introduced to A431D (lacking classical cadherins), A431D/E-cadherin WT (expressing wild-type E-cadherin), and A431D/E-cadherin 764AAA (expressing p120-uncoupled E-cadherin mutant) cells. The effects of CD148 in cadherin adhesion were assessed by Ca²⁺ switch and cell aggregation assays. Phosphorylation of E-cadherin/catenin complex and Rho family GTPase activities were also examined. Although CD148 introduction did not alter the expression levels and complex formation of E-cadherin, p120, and β-catenin, CD148 WT, but not CS, promoted cadherin contacts and strengthened cell-cell adhesion in A431D/E-cadherin WT cells. This effect was accompanied by an increase in Rac1, but not RhoA and Cdc42, activity and largely diminished by Rac1 inhibition. Further, we demonstrate that CD148 reduces the tyrosine phosphorylation of p120 and β-catenin; causes the dephosphorylation of Y529 suppressive tyrosine residue in Src, a well-known CD148 site, increasing Src activity and enhancing the phosphorylation of Y228 (a Src kinase site) in p120, in E-cadherin contacts. Consistent with these findings, CD148 dephosphorylated both p120 and β-catenin in vitro. The shRNA-mediated CD148 knockdown in A431 cells showed opposite effects. CD148 showed no effects in A431D and A431D/E-cadherin 764AAA cells. In aggregate, these findings provide the first evidence that CD148 promotes E-cadherin adhesion by regulating Rac1 activity concomitant with modulation of p120, β-catenin, and Src tyrosine phosphorylation. This effect requires E-cadherin and p120 association.

p120 modulates LPS-induced NF-κB activation partially through RhoA in bronchial epithelial cells

p120-Catenin (p120) is an adherens junction protein recognized to regulate cell-cell adhesion. Emerging evidence indicates that p120 may also play an important role in inflammatory responses, and the regulatory mechanisms are still unknown. In the present study, we showed that p120 was associated with airway inflammation. p120 downregulation induced nuclear factor-κB (NF-κB) activation, accompanied with IκBα degradation, p65 nuclear translocation, and increased expression of interleukin-8 (IL-8) in lipopolysaccharide (LPS)- treated C57BL mice and human bronchial epithelial cells (BECs). Moreover, we first found that p120 directly coprecipitated with RhoA in BECs. After LPS stimulation, although total RhoA and p120-bound RhoA were unchanged, RhoA activity was increased. Y27632, a ROCK inhibitor, could partially inhibit nuclear translocation of p65. Overexpression of p120 inactivated RhoA and NF-κB in BECs, whereas p120 loss significantly increased RhoA activity, p65 nuclear translocation, and IL-8 expression. Taken together, our study supports the regulatory role of p120 in airway inflammation and reveals that p120 may modulate NF-κB signaling partially through RhoA.

Drosophila actin-Capping Protein limits JNK activation by the Src proto-oncogene

The Src family kinases c-Src, and its downstream effectors, the Rho family of small GTPases RhoA and Jun N-terminal kinase (JNK) have a significant role in tumorigenesis. In this report, using the Drosophila wing disc epithelium as a model system, we demonstrate that the actin-Capping Protein (CP) αβ heterodimer, which regulates actin filament (F-actin) polymerization, limits Src-induced apoptosis or tissue overgrowth by restricting JNK activation. We show that overexpressing Src64B drives JNK-independent loss of epithelial integrity and JNK-dependent apoptosis via Btk29A, p120ctn and Rho1. However, when cells are kept alive with the Caspase inhibitor P35, JNK acts as a potent inducer of proliferation via activation of the Yorkie oncogene. Reducing CP levels direct apoptosis of overgrowing Src64B-overexpressing tissues. Conversely, overexpressing capping protein inhibits Src64B and Rho1, but not Rac1-induced JNK signaling. CP requires the actin-binding domain of the α-subunit to limit Src64B-induced apoptosis, arguing that the control of F-actin mediates this effect. In turn, JNK directs F-actin accumulation. Moreover, overexpressing capping protein also prevents apoptosis induced by ectopic JNK expression. Our data are consistent with a model in which the control of F-actin by CP limits Src-induced apoptosis or tissue overgrowth by acting downstream of Btk29A, p120ctn and Rho1, but upstream of JNK. In turn, JNK may counteract the effect of CP on F-actin, providing a positive feedback, which amplifies JNK activation. We propose that cytoskeletal changes triggered by misregulation of F-actin modulators may have a significant role in Src-mediated malignant phenotypes during the early stages of cellular transformation.

p120 catenin is required for the stress response in Drosophila

p120ctn is a ubiquitously expressed core component of cadherin junctions and essential for vertebrate development. Surprisingly, Drosophila p120ctn (dp120ctn) is dispensable for adherens junctions and development, which has discouraged Drosophila researchers from further pursuing the biological role of dp120ctn. Here we demonstrate that dp120ctn loss results in increased heat shock sensitivity and reduced animal lifespan, which are completely rescued by ectopic expression of a dp120ctn-GFP transgene. Transcriptomic analysis revealed multiple relish/NF-κB target genes differentially expressed upon loss of dp120ctn. Importantly, this aberrant gene expression was rescued by overexpression of dp120ctn-GFP or heterozygosity for relish. Our results uncover a novel role for dp120ctn in the regulation of animal stress response and immune signalling. This may represent an ancient role of p120ctn and can influence further studies in Drosophila and mammals.

p120 catenin: an essential regulator of cadherin stability, adhesion-induced signaling, and cancer progression

p120 catenin is the best studied member of a subfamily of proteins that associate with the cadherin juxtamembrane domain to suppress cadherin endocytosis. p120 also recruits the minus ends of microtubules to the cadherin complex, leading to junction maturation. In addition, p120 regulates the activity of Rho family GTPases through multiple interactions with Rho GEFs, GAPs, Rho GTPases, and their effectors. Nuclear signaling is affected by the interaction of p120 with Kaiso, a transcription factor regulating Wnt-responsive genes as well as transcriptionally repressing methylated promoters. Multiple alternatively spliced p120 isoforms and complex phosphorylation events affect these p120 functions. In cancer, reduced p120 expression correlates with reduced E-cadherin function and with tumor progression. In contrast, in tumor cells that have lost E-cadherin expression, p120 promotes cell invasion and anchorage-independent growth. Furthermore, p120 is required for Src-induced oncogenic transformation and provides a potential target for future therapeutic interventions.

SRChing for the substrates of Src

By the mid 1980's, it was clear that the transforming activity of oncogenic Src was linked to the activity of its tyrosine kinase domain and attention turned to identifying substrates, the putative next level of control in the pathway to transformation. Among the first to recognize the potential of phosphotyrosine-specific antibodies, Parsons and colleagues launched a risky shotgun-based approach that led ultimately to the cDNA cloning and functional characterization of many of today's best-known Src substrates (for example, p85-Cortactin, p110-AFAP1, p130Cas, p125FAK and p120-catenin). Two decades and over 6000 citations later, the original goals of the project may be seen as secondary to the enormous impact of these protein substrates in many areas of biology. At the request of the editors, this review is not restricted to the current status of the substrates, but reflects also on the anatomy of the project itself and some of the challenges and decisions encountered along the way.

p120catenin alteration in cancer and its role in tumour invasion

Since its discovery in 1989 as a substrate of the Src oncogene, p120catenin has been revealed as an important player in cancer initiation and tumour dissemination. p120catenin regulates a wide range of cellular processes such as cell-cell adhesion, cell polarity and cell proliferation and plays a pivotal role in morphogenesis, inflammation and innate immunity. The pleiotropic effects of p120catenin rely on its interactions with numerous partners such as classical cadherins at the plasma membrane, Rho-GTPases and microtubules in the cytosol and transcriptional modulators in the nucleus. Alterations of p120catenin in cancer not only concern its expression level but also its intracellular localization and can lead to both pro-invasive and anti-invasive effects. This review focuses on the p120catenin-mediated pathways involved in cell migration and invasion and discusses the potential consequences of major cancer-related p120catenin alterations with respect to tumour spread.

Regulation of pre-fusion events: recruitment of M-cadherin to microrafts organized at fusion-competent sites of myogenic cells

Background

Previous research indicates that the membrane ruffles and leading edge of lamellipodia of myogenic cells contain presumptive fusion sites. A micrometer-sized lipid raft (microraft) is organized at the presumptive fusion site of mouse myogenic cells in a cell-contact independent way and serves as a platform tethering adhesion proteins that are relevant to cell fusion. However, the mechanisms underlying recruitment of adhesion proteins to lipid rafts and microraft organization remain unknown.

Results

Here we show that small G-protein Rac1 was required for microraft organization and subsequent cell fusion. However, Rac1 activity was unnecessary for recruitment of M-cadherin to lipid rafts. We found that p120 catenin (p120) binds to M-cadherin exclusively in lipid rafts of differentiating myogenic cells. The Src kinase inhibitor SU6656 prevented p120 binding to M-cadherin and their recruitment to lipid rafts, then suppressed microraft organization, membrane ruffling, and myogenic cell fusion. Suppression of membrane ruffling in SU6656-treated cells was partially restored by pretreatment with the protein tyrosine phosphatase inhibitor vanadate. The present analyses using an antibody to tyrosine phosphorylated p120 suggest that Src family kinases play a role in binding of p120 to M-cadherin and the recruitment of M-cadherin to lipid rafts through phosphorylation of putative substrates other than p120.

Conclusions

The present study showed that the procedure establishing fusion-competent sites consists of two sequential events: recruitment of adhesion complexes to lipid rafts and organization of microrafts. The recruitment of M-cadherin to lipid rafts depended on interaction with p120 catenin, whereas the organization of microrafts was controlled by a small G protein, Rac1.

Increased BCAR1 predicts poor outcomes of non-small cell lung cancer in multiple-center patients

OBJECTIVE

This study was designed to determine the prognostic value of BCAR1 expression and its associations with clinical-demographical characteristics in multiple centers of non-small cell lung cancer (NSCLC) patients.

METHODS

Gene expression microarray (mRNA) of 77 adenocarcinomas from Mayo Clinic, RNA-sequencing of 508 NSCLC from The Cancer Genome Atlas (TCGA), and immunohistochemistry stain of BCAR1-protein expression in 150 cases from Daping Hospital were included in the study. The association of mRNA or protein expression with patient clinical characteristics and overall survival was assessed in each dataset. We also predicted microRNAs (miRNA) that target BCAR1 using bioinformatics prediction tools and evaluated miRNA expression patterns with BCAR1 expression in miRNA-sequencing data of 74 lung cancer cases from TCGA dataset.

RESULTS

In the Mayo Clinic dataset, a higher BCAR1-mRNA level correlated significantly with more advanced tumor-stage and lymphatic metastasis. Similar changes were observed in the TCGA RNA-seq dataset. Additionally, higher BCAR1-mRNA levels predicted poorer survival in adenocarcinoma and squamous carcinoma from the TCGA dataset. The protein levels in the adenocarcinoma cases with lymphatic metastasis were significantly higher than of those without metastasis. Tumor tissues demonstrated remarkably higher levels of protein compared with matched normal tissues although there was no significant difference in BCAR1-mRNA expression between tumor and matched normal tissues was detected. In miRNAs that were downregulated in the tumors, Let-7f-2 and miR-22 differed the most (P < 0.001 and P = 0.007, respectively).

CONCLUSIONS

We confirmed that increased BCAR1 expression predicts poorer prognosis in NSCLC. We postulate that mRNA-protein decoupling of BCAR1 may be a result of reduced inhibition of specific miRNAs in tumor tissues, which warrants further study.

Expression of breast cancer anti-estrogen resistance 1 in relation to vascular endothelial growth factor, p53, and prognosis in esophageal squamous cell cancer

The purpose of this study was to clarify the role of breast cancer anti-estrogen resistance 1 (BCAR1) expression in relation to vascular endothelial growth factor (VEGF), p53, and proliferation in esophageal squamous cell cancer (ESCC). Expression of BCAR1, VEGF, p53, and the ki-67 proliferative index were examined by tissue microarray and immunohistochemistry in 106 specimens with ESCC and matched adjacent normal tissues. Among them, 40 cases were simultaneously examined by Western blot. Both Western blot and immunohistochemistry showed that BCAR1 expression was substantially higher in ESCC than in adjacent normal tissues (P < 0.001). BCAR1 expression was significantly connected with degree of tumor differentiation, with poorly differentiated tumors showing higher BCAR1 expression (P < 0.001). BCAR1 expression was significantly and positively correlated with VEGF and p53 expression levels (r= 0.541, P < 0.001; r= 0.374; P < 0.001) but not proliferative index (r= 0.44; P= 0.066). Additionally, a significant relationship was also observed between VEGF and p53 (r= 0.321; P= 0.001). Kaplan-Meier survival analysis revealed that patients with high BCAR1 expression had significantly shorter survival times than those with low BCAR1 expression levels (median survival 40 months vs. 27 months, P= 0.09). Multivariate analysis also revealed that levels of BCAR1 expression (hazard ratio 2.250, P= 0.015) was a significant and independent prognostic indicator. High expression of BCAR1 is associated with elevated VEGF and p53 expression levels, as well as poor prognosis in ESCC. Therefore, BCAR1 may be a potential candidate for predicting prognosis and a new therapy target for ESCC.

PKCα activation of p120-catenin serine 879 phospho-switch disassembles VE-cadherin junctions and disrupts vascular integrity

RATIONALE

Adherens junctions (AJs) are the primary intercellular junctions in microvessels responsible for endothelial barrier function. Homophilic adhesion of vascular endothelial (VE) cadherin forms AJs, which are stabilized by binding of p120-catenin (p120). p120 dissociation from VE-cadherin results in loss of VE-cadherin homotypic interaction and AJ disassembly; however, the signaling mechanisms regulating p120 dissociation from VE-cadherin are not understood.

OBJECTIVE

To address the mechanism of protein kinase C (PKC)-α function in increasing endothelial permeability, we determined the role of PKCα phosphorylation of p120 in mediating disruption of AJ integrity.

METHODS AND RESULTS

We showed that PKCα phosphorylation of p120 at serine (S)879 in response to thrombin or lipopolysaccharide challenge reduced p120 binding affinity for VE-cadherin and mediated AJ disassembly secondary to VE-cadherin internalization. In studies in mouse lung vessels, expression of the phosphodeficient S879A-p120 mutant prevented the increase in vascular permeability induced by activation of the thrombin receptor PAR-1.

CONCLUSIONS

PKCα phosphorylation of p120 at S879 is a critical phospho-switch mediating disassociation of p120 from VE-cadherin that results in AJ disassembly. Therefore, blocking PKCα-mediated p120 phosphorylation represents a novel targeted anti-inflammatory strategy to prevent disruption of vascular endothelial barrier function.

Competitive regulation of E-cadherin juxtamembrane domain degradation by p120-catenin binding and Hakai-mediated ubiquitination

p120-Catenin binding to, and Hakai-mediated ubiquitination of the E-cadherin juxtamembrane domain (JMD) are thought to be involved in regulating E-cadherin internalization and degradation. However, the relationship between these two pathways is not understood. We targeted the E-cadherin JMD to mitochondria (WT-JMD) to isolate this domain from the plasma membrane and internalization, and to examine protein modifications and degradation. WT-JMD localized to mitochondria, but did not accumulate there except when proteasome activity was inhibited. We found WT-JMD was ubiquitinated, and arginine substitution of lysines at position 5 (K5R) and 83 (K83R) resulted in the stable accumulation of mutant JMD at mitochondria. p120-Catenin did not localize, or bind to WT-JMD even upon proteasome inhibition, whereas the K5,83R-JMD mutant bound and localized p120-catenin to mitochondria. Mutation of the p120-catenin binding site in combination with these lysine mutations inhibited p120-catenin binding, but did not decrease JMD stability or its accumulation at mitochondria. Thus, increased stability of JMD lysine mutants was due to inhibition of ubiquitination and not to p120-catenin binding. Finally, mutation of these critical lysines in full length E-cadherin had similar effects on protein stability as WT-JMD. Our results indicate that ubiquitination of the JMD inhibits p120-catenin binding, and targets E-cadherin for degradation.

The function of p120 catenin in filopodial growth and synaptic vesicle clustering in neurons

The signaling by p120 catenin via its downstream effector RhoA is essential for filopodial growth and synaptic vesicle clustering along spinal axons and contributes to the formation of the neuromuscular junction.

At the developing neuromuscular junction (NMJ), physical contact between motor axons and muscle cells initiates presynaptic and postsynaptic differentiation. Using Xenopus nerve–muscle cocultures, we previously showed that innervating axons induced muscle filopodia (myopodia), which facilitated interactions between the synaptic partners and promoted NMJ formation. The myopodia were generated by nerve-released signals through muscle p120 catenin (p120ctn), a protein of the cadherin complex that modulates the activity of Rho GTPases. Because axons also extend filopodia that mediate early nerve–muscle interactions, here we test p120ctn's function in the assembly of these presynaptic processes. Overexpression of wild-type p120ctn in Xenopus spinal neurons leads to an increase in filopodial growth and synaptic vesicle (SV) clustering along axons, whereas the development of these specializations is inhibited following the expression of a p120ctn mutant lacking sequences important for regulating Rho GTPases. The p120ctn mutant also inhibits the induction of axonal filopodia and SV clusters by basic fibroblast growth factor, a muscle-derived molecule that triggers presynaptic differentiation. Of importance, introduction of the p120ctn mutant into neurons hinders NMJ formation, which is observed as a reduction in the accumulation of acetylcholine receptors at innervation sites in muscle. Our results suggest that p120ctn signaling in motor neurons promotes nerve–muscle interaction and NMJ assembly.

BCAR1 protein plays important roles in carcinogenesis and predicts poor prognosis in non-small-cell lung cancer

Objective

Our previous study suggested the potential clinical implications of BCAR1 in non-small-cell lung cancer (NSCLC) (Mol Diagn Ther. 2011. 15(1): 31–40). Herein, we aim to evaluate the predictive power of BCAR1 as a marker for poor prognosis in NSCLC cases, verify the carcinogenic roles of BCAR1 in the A549 lung adenocarcinoma cell line, and testify to the BCAR1/phospho-p38 axis.

Methods

Between January 2006 and June 2010, there were a total of 182 patients with NSCLC (151 cases with available follow up data, and 31 cases lost to follow-up due to the invalid contact information). We inspected BCAR1, phospho-BCAR1(Tyr410), phospho-p38(Thr180/Tyr182) and p38 expression in NSCLC tissues and matched adjacent normal tissues by immunoblotting and IHC. After BCAR1 -RNA interference in A549 cells, we inspected the protein expression (BCAR1, phospho-BCAR1, phospho-p38 and p38) and performed cell biology experiments (cell growth, migration and cycle).

Results

BCAR1 was overexpressed in NSCLC tissues (177/182) and cell lines (A549 and Calu-3). However, it was not detected in the normal adjacent tissue in 161 of the 182 cases. Higher BCAR1 levels were strongly associated with more poorly differentiated NSCLC and predicted poorer prognosis. BCAR1 knockdown caused cell growth arrest, cell migration inhibition and cell cycle arrest of A549 cells. Overexpression of BCAR1 was associated with activation of p38 in NSCLC cases, and BCAR1 knockdown caused reduction of phospho-p38 levels in A549 cells.

Conclusion

Overexpression of BCAR1 is a predictor of poor prognosis in NSCLC and plays important carcinogenic roles in carcinogenesis, probably via activation of p38 MAPK. However, further investigations are required immediately.