UMLS:C0033036 - FACTA Search

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Query: UMLS:C0033036 (APC)
10,214 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Using normal MDCK cells, and MDCK cells stably transfected with a temperature-sensitive viral src allele (pp60 ts-v-src), we have examined the composition and tyrosine phosphorylation of the E-cadherin complex. E-cadherin is a transmembrane calcium-dependent cell-cell adhesion molecule that is complexed with cytoplasmic proteins including alpha-catenin, beta-catenin, plakoglobin (gamma-catenin), and actin. We have identified two heterodimeric complexes which demonstrate that alpha-catenin interacts directly with beta-catenin, or with plakoglobin, in the absence of E-cadherin. beta-Catenin has previously been shown to bind directly to E-cadherin. We propose that E-cadherin associates with alpha-catenin, and thereby the actin cytoskeleton, via either beta-catenin or plakoglobin. We have further identified three new but related protein components of the E-cadherin complex, which are each cross-reactive by Western blot analysis to antibodies directed against p120, a phosphotyrosine substrate of src, and a phosphotyrosine, phosphoserine, and phosphothreonine substrate of growth factor-stimulated signaling pathways. Greater quantities of the p120-related proteins were found present in the E-cadherin immunoprecipitates of ts-src MDCK cells compared to normal MDCK cells, while two of the p120 cross-reactive species were significantly tyrosine phosphorylated in both normal and ts-src MDCK cells. The association of p120-related species with the E-cadherin complex adds them to our consideration of possible modulators of cadherin function. Likewise, the newly identified alpha-catenin-beta-catenin and alpha-catenin-plakoglobin dimers may have interesting biological properties, conceivably including the titration of catenins between cadherin and APC complexes.
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PMID:The E-cadherin complex contains the src substrate p120. 753 97

Recent reports suggest that the beta-catenin-T-cell factor (Tcf) (BCT) signaling pathway is important in the progression of prostate cancer. Evidence suggests that the androgen receptor (AR) can repress BCT-mediated transcription both in prostate cancer and colon cancer cells (Chesire and Isaacs, 2002). In this study, we validate such findings and show that repression of BCT signaling is facilitated by competition between the AR and Tcf. Measurements of the Tcf transcriptional reporter (TOPFLASH) indicated that AR+DHT-mediated repression can inhibit BCT transcription in the presence of WT and exogenous activating beta-catenin (Delta1-130 bp). Transient transfections in SW480 cells (APC(mut/mut)) showed that this mode of repression is functionally independent of APC-mediated beta-catenin ubiquitination. Using a recently developed red flourescent protein (HcRed), we demonstrate novel observations about the nuclear distribution of Tcf. Furthermore, with the use of red (HcRed-AR and HcRed-Tcf) and green fusion proteins (beta-catenin-EGFP), we provide morphological evidence of a reciprocal balance of nuclear beta-catenin-EGFP (BC-EGFP). By cotransfecting in LNCaP prostate tumor cells and using quantitative imaging software, we demonstrated a 62.0% colocalization of HcRed-AR and BC-EGFP in the presence of DHT and 63.3% colocalization of HcRed-Tcf/BC-EGFP in the absence of DHT. Costaining for activated RNA Pol II (phosphoserine 2) and HcRed-Tcf suggested that Tcf foci contain transcriptional 'hotspots' validating that these sites have the capacity for transcriptional activity. Given this apparent androgen-dependent competition for nuclear BC-EGFP, we chose to assess our hypothesis by in vivo and in vitro binding assays. SW480 cells transiently transfected with an AR expression construct, treated with DHT and immunoprecipitated for Tcf showed less associated beta-catenin when compared to Tcf precipitates from untreated cells. Furthermore, by treating cells with DHT+Casodex, we were able to abrogate the androgen-sensitive AR/beta-catenin interaction, in addition to relieving transcriptional repression of the TOPFLASH reporter. In vitro binding assays, with increasing amounts of AR(S35), resulted in decreased Tcf(S35) association with immunoprecipitated recombinant beta-catenin-HIS. These data suggest that in steady-state conditions, AR has the ability to compete out Tcf binding for beta-catenin. Finally, using SW480 cells, we show that AR-mediated repression of the BCT pathway has implications for cell cycle progression and in vitro growth. Using FACs analysis, we observed a 26.1% increase in accumulation of cells in the G1 phase of the cell cycle, while in vitro growth assays showed a 35% reduction in viable cells transfected with AR+DHT treatment. Together, our data strongly suggest that a reciprocal balance of nuclear beta-catenin facilitates AR-mediated repression of BCT-driven transcription and cell growth.
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PMID:Functional localization and competition between the androgen receptor and T-cell factor for nuclear beta-catenin: a means for inhibition of the Tcf signaling axis. 1294 8

Here, we will review the evidence showing that mitotic exit is initiated by regulated proteolysis and then driven by the PPP family of phosphoserine/threonine phosphatases. Rapid APC/C^CDC ²⁰ and ubiquitin-dependent proteolysis of cyclin B and securin initiates sister chromatid separation, the first step of mitotic exit. Because proteolysis of Aurora and Polo family kinases dependent on APC/C^CDH ¹ is relatively slow, this creates a new regulatory state, anaphase, different to G2 and M-phase. We will discuss how the CDK1-counteracting phosphatases PP1 and PP2A-B55, together with Aurora and Polo kinases, contribute to the temporal regulation and order of events in the different stages of mitotic exit from anaphase to cytokinesis. For PP2A-B55, these timing properties are created by the ENSA-dependent inhibitory pathway and differential recognition of phosphoserine and phosphothreonine. Finally, we will discuss how Aurora B and PP2A-B56 are needed for the spatial regulation of anaphase spindle formation and how APC/C-dependent destruction of PLK1 acts as a timer for abscission, the final event of cytokinesis.
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PMID:Getting out of mitosis: spatial and temporal control of mitotic exit and cytokinesis by PP1 and PP2A. 3149 26