scholarly journals Chibby cooperates with 14-3-3 to regulate β-catenin subcellular distribution and signaling activity

2008 ◽  
Vol 181 (7) ◽  
pp. 1141-1154 ◽  
Author(s):  
Feng-Qian Li ◽  
Adaobi Mofunanya ◽  
Kimberley Harris ◽  
Ken-Ichi Takemaru
Keyword(s):  
Transcriptional Activation ◽  
Nuclear Export ◽  
Molecular Mechanisms ◽  
Affinity Purification ◽  
Nuclear Accumulation ◽  
Binding Motif ◽  
Transcriptional Coactivator ◽  
Evolutionarily Conserved ◽  
Canonical Wnt ◽  
Affinity Purification Mass Spectrometry

β-Catenin functions in both cell–cell adhesion and as a transcriptional coactivator in the canonical Wnt pathway. Nuclear accumulation of β-catenin is the hallmark of active Wnt signaling and is frequently observed in human cancers. Although β-catenin shuttles in and out of the nucleus, the molecular mechanisms underlying its translocation remain poorly understood. Chibby (Cby) is an evolutionarily conserved molecule that inhibits β-catenin–mediated transcriptional activation. Here, we identified 14-3-3ε and 14-3-3ζ as Cby-binding partners using affinity purification/mass spectrometry. 14-3-3 proteins specifically recognize serine 20 within the 14-3-3–binding motif of Cby when phosphorylated by Akt kinase. Notably, 14-3-3 binding results in sequestration of Cby into the cytoplasm. Moreover, Cby and 14-3-3 form a stable tripartite complex with β-catenin, causing β-catenin to partition into the cytoplasm. Our results therefore suggest a novel paradigm through which Cby acts in concert with 14-3-3 proteins to facilitate nuclear export of β-catenin, thereby antagonizing β-catenin signaling.

scholarly journals Hippo Pathway: An Emerging Regulator of Craniofacial and Dental Development

2017 ◽  
Vol 96 (11) ◽  
pp. 1229-1237 ◽  
Author(s):  
J. Wang ◽  
J.F. Martin
Keyword(s):  
Signaling Pathways ◽  
Molecular Mechanisms ◽  
Tooth Development ◽  
Hippo Pathway ◽  
Binding Motif ◽  
Hippo Signaling ◽  
Transcriptional Coactivator ◽  
Hippo Signaling Pathway ◽  
Evolutionarily Conserved ◽  
The Hippo Pathway

The evolutionarily conserved Hippo signaling pathway is a vital regulator of organ size that fine-tunes cell proliferation, apoptosis, and differentiation. A number of important studies have revealed critical roles of Hippo signaling and its effectors Yap (Yes-associated protein) and Taz (transcriptional coactivator with PDZ binding motif) in tissue development, homeostasis, and regeneration, as well as in tumorigenesis. In addition, recent studies have shown evidence of crosstalk between the Hippo pathway and other key signaling pathways, such as Wnt signaling, that not only regulates developmental processes but also contributes to disease pathogenesis. In this review, we summarize the major discoveries in the field of Hippo signaling and what has been learned about its regulation and crosstalk with other signaling pathways, with a particular focus on recent findings involving the Hippo-Yap pathway in craniofacial and tooth development. New and exciting studies of the Hippo pathway are anticipated that will significantly improve our understanding of the molecular mechanisms of human craniofacial and tooth development and disease and will ultimately lead to the development of new therapies.

Targeting of canonical WNT signaling ameliorates experimental sclerodermatous chronic graft-versus-host disease

Blood ◽  
2021 ◽  
Author(s):  
Yun Zhang ◽  
Lichong Shen ◽  
Katja Dreissigacker ◽  
Honglin Zhu ◽  
Thuong Trinh-Minh ◽  
...  
Keyword(s):  
Wnt Signaling ◽  
Graft Versus Host Disease ◽  
Molecular Mechanisms ◽  
Nuclear Accumulation ◽  
Clinical Use ◽  
Canonical Wnt Signaling ◽  
Hematopoietic Stem ◽  
Host Disease ◽  
Graft Versus Host ◽  
Canonical Wnt

Chronic graft-versus-host disease (cGvHD) is a major life-threatening complication of allogeneic hematopoietic stem cell transplantation. The molecular mechanisms underlying cGvHD remain poorly understood and targeted therapies are not well established for clinical use. Here, we examined the role of the canonical WNT pathway in sclerodermatous cGvHD (sclGvHD). WNT signaling was activated in human sclGvHD with increased nuclear accumulation of the transcription factor β-catenin and WNT-biased gene expression signature in lesional skin. Treatment with highly selective tankryase inhibitor G007-LK, CK1α agonist pyrvinium or LRP6 inhibitor salinomycin, abrogated the activation of WNT signaling and protected against experimental cGvHD, without significant impact on graft-versus-leukemia effect (GvL). Treatment with G007-LK, pyrvinium or salinomycin almost completely prevented the development of clinical and histological features in the B10.D2 (H-2d)→BALB/c (H-2d) and in the LP/J (H-2b)→C57BL/6 (H-2b) model of sclGvHD. Inhibition of canonical WNT signaling reduced the release of extracellular matrix from fibroblasts and reduced leukocyte influx, suggesting that WNT signaling stimulates fibrotic tissue remodeling by direct effects on fibroblasts and by indirect, inflammation-dependent effects in sclGvHD. Our findings may have direct translational potential, as pyrvinium is in clinical use and tankyrase inhibitors are in clinical trials for other implications.

scholarly journals MondoA, a Novel Basic Helix-Loop-Helix–Leucine Zipper Transcriptional Activator That Constitutes a Positive Branch of a Max-Like Network

2000 ◽  
Vol 20 (23) ◽  
pp. 8845-8854 ◽  
Author(s):  
Andrew N. Billin ◽  
Alanna L. Eilers ◽  
Kathryn L. Coulter ◽  
Jennifer S. Logan ◽  
Donald E. Ayer
Keyword(s):  
Transcriptional Activation ◽  
Nuclear Export ◽  
Mammalian Cells ◽  
Leucine Zipper ◽  
Functional Characterization ◽  
Nuclear Accumulation ◽  
Cytoplasmic Localization ◽  
Basic Helix Loop Helix ◽  
Helix Loop Helix

ABSTRACT Max is a common dimerization partner for a family of transcription factors (Myc, Mad [or Mxi]), and Mnt [or Rox] proteins) that regulate cell growth, proliferation, and apoptosis. We recently characterized a novel Max-like protein, Mlx, which interacts with Mad1 and Mad4. Here we describe the cloning and functional characterization of a new family of basic helix-loop-helix–leucine zipper heterodimeric partners for Mlx termed the Mondo family. MondoA forms homodimers weakly and does not interact with Max or members of the Myc or Mad families. MondoA and Mlx associate in vivo, and surprisingly, they are localized primarily to the cytoplasm of cultured mammalian cells. Treatment of cells with the nuclear export inhibitor leptomycin B results in the nuclear accumulation of MondoA and Mlx, demonstrating that they shuttle between the cytoplasmic and nuclear compartments rather than having exclusively cytoplasmic localization. MondoA preferentially forms heterodimers with Mlx, and this heterocomplex can bind to, and activate transcription from, CACGTG E-boxes when targeted to the nucleus via a heterologous nuclear localization signal. The amino termini of the Mondo proteins are highly conserved among family members and contain separable and autonomous cytoplasmic localization and transcription activation domains. Therefore, Mlx can mediate transcriptional repression in conjunction with the Mad family and can mediate transcriptional activation via the Mondo family. We propose that Mlx, like Max, functions as the center of a transcription factor network.

scholarly journals Identification of intracellular glycosaminoglycan-interacting proteins by affinity purification mass spectrometry

2021 ◽  
Vol 0 (0) ◽  
Author(s):  
Henning Großkopf ◽  
Sarah Vogel ◽  
Claudia Damaris Müller ◽  
Sebastian Köhling ◽  
Jan-Niklas Dürig ◽  
...  
Keyword(s):  
Mass Spectrometry ◽  
Molecular Mechanisms ◽  
Protein Localization ◽  
Affinity Purification ◽  
Intracellular Localization ◽  
Enrichment Analysis ◽  
Transport Processes ◽  
Interacting Proteins ◽  
Affinity Purification Mass Spectrometry ◽  
Functional Components

Abstract Glycosaminoglycans (GAGs) are essential functional components of the extracellular matrix (ECM). Artificial GAGs like sulfated hyaluronan (sHA) exhibit pro-osteogenic properties and boost healing processes. Hence, they are of high interest for supporting bone regeneration and wound healing. Although sulfated GAGs (sGAGs) appear intracellularly, the knowledge about intracellular effects and putative interaction partners is scarce. Here we used an affinity-purification mass spectrometry-based (AP-MS) approach to identify novel and particularly intracellular sGAG-interacting proteins in human bone marrow stromal cells (hBMSC). Overall, 477 proteins were found interacting with at least one of four distinct sGAGs. Enrichment analysis for protein localization showed that mainly intracellular and cell-associated interacting proteins were identified. The interaction of sGAG with α2-macroglobulin receptor-associated protein (LRPAP1), exportin-1 (XPO1), and serine protease HTRA1 (HTRA1) was confirmed in reverse assays. Consecutive pathway and cluster analysis led to the identification of biological processes, namely processes involving binding and processing of nucleic acids, LRP1-dependent endocytosis, and exosome formation. Respecting the preferentially intracellular localization of sGAG in vesicle-like structures, also the interaction data indicate sGAG-specific modulation of vesicle-based transport processes. By identifying many sGAG-specific interacting proteins, our data provide a resource for upcoming studies aimed at molecular mechanisms and understanding of sGAG cellular effects.

scholarly journals Multi-parameter analysis of the kinetics of NF-κB signalling and transcription in single living cells

2002 ◽  
Vol 115 (6) ◽  
pp. 1137-1148 ◽  
Author(s):  
Glyn Nelson ◽  
Luminita Paraoan ◽  
David G. Spiller ◽  
Geraint J. C. Wilde ◽  
Mark A. Browne ◽  
...  
Keyword(s):  
Transcription Factor ◽  
Transcriptional Activation ◽  
Nuclear Export ◽  
Mammalian Cells ◽  
Nuclear Translocation ◽  
Fluorescent Proteins ◽  
Parameter Analysis ◽  
Nuclear Accumulation ◽  
Fusion Protein Expression ◽  
Kinetics Of

Proteins of the NF-κB transcription factor family normally reside in the cytoplasm of cells in a complex with IκB inhibitor proteins. Stimulation with TNFα leads to proteosomal degradation of the IκB proteins and nuclear translocation of the NF-κB proteins. Expression of p65 and IκBα fused to fluorescent proteins was used to measure the dynamics of these processes in transfected HeLa cells. Simultaneous visualisation of p65-dsRed translocation and IκBα-EGFP degradation indicated that in the presence of dual fluorescent fusion protein expression,the half-time of IκBα-EGFP degradation was reduced and that of p65 translocation was significantly increased when compared with cells expressing the single fluorescent fusion proteins. These results suggest that the ratio of IκBα and p65 determine the kinetics of transcription factor translocation into the nucleus and indicate that the complex of p65 and IκBα is the true substrate for TNFα stimulation in mammalian cells. When cells were treated with the CRM-1-dependent nuclear export inhibitor,leptomycin B (LMB), there was nuclear accumulation of IκBα-EGFP and p65-dsRed, with IκBα-EGFP accumulating more rapidly. No NF-κB-dependent transcriptional activation was seen in response to LMB treatment. Following 1 hour treatment with LMB, significant IκBα-EGFP nuclear accumulation, but low levels of p65-dsRed nuclear accumulation, was observed. When these cells were stimulated with TNFα, degradation of IκBα-EGFP was observed in both the cytoplasm and nucleus. A normal transient transcription response was observed in the same cells using luminescence imaging of NF-κB-dependent transcription. These observations suggest that both normal activation and post-induction repression of NF-κB-dependent transcription occur even when nuclear export of NF-κB is inhibited. The results provide functional evidence that other factors, such as modification of p65 by phosphorylation, or interaction with other proteins such as transcriptional co-activators/co-repressors, may critically modulate the kinetics of transcription through this signalling pathway.

PRAMEF2-mediated dynamic regulation of YAP signaling promotes tumorigenesis

2021 ◽  
Vol 118 (40) ◽  
pp. e2105523118
Author(s):  
Madhurima Ghosh ◽  
Sanjeev Das
Keyword(s):  
Molecular Mechanisms ◽  
Nuclear Accumulation ◽  
Dependent Manner ◽  
Transcriptional Coactivator ◽  
Dynamic Regulation ◽  
Cancer Testis Antigens ◽  
Ubiquitin Ligase Complex ◽  
Insight Into ◽  
Cancer Testis

PRAMEF2 is a member of the PRAME multigene family of cancer testis antigens, which serve as prognostic markers for several cancers. However, molecular mechanisms underlying its role in tumorigenesis remain poorly understood. Here, we report that PRAMEF2 is repressed under conditions of altered metabolic homeostasis in a FOXP3-dependent manner. We further demonstrate that PRAMEF2 is a BC-box containing substrate recognition subunit of Cullin 2–based E3 ubiquitin ligase complex. PRAMEF2 mediates polyubiquitylation of LATS1 kinase of the Hippo/YAP pathway, leading to its proteasomal degradation. The site for ubiquitylation was mapped to the conserved Lys860 residue in LATS1. Furthermore, LATS1 degradation promotes enhanced nuclear accumulation of the transcriptional coactivator YAP, resulting in increased expression of proliferative and metastatic genes. Thus, PRAMEF2 promotes malignant phenotype in a YAP-dependent manner. Additionally, elevated PRAMEF2 levels correlate with increased nuclear accumulation of YAP in advanced grades of breast carcinoma. These findings highlight the pivotal role of PRAMEF2 in tumorigenesis and provide mechanistic insight into YAP regulation.

scholarly journals Microtubule-Dependent Subcellular Redistribution of the Transcriptional Coactivator p/CIP

2002 ◽  
Vol 22 (18) ◽  
pp. 6611-6626 ◽  
Author(s):  
Majdi S. Qutob ◽  
Rabindra N. Bhattacharjee ◽  
Elisa Pollari ◽  
Siu Pok Yee ◽  
Joseph Torchia
Keyword(s):  
Nuclear Export ◽  
Hormone Receptors ◽  
Phorbol Esters ◽  
Fluorescent Protein ◽  
Nuclear Hormone Receptor ◽  
Nuclear Accumulation ◽  
Dependent Manner ◽  
Transcriptional Coactivator ◽  
Microtubule Network ◽  
Cytoplasmic Accumulation

ABSTRACT The transcriptional coactivator p/CIP is a member of a family of nuclear receptor coactivator/steroid receptor coactivator (NCoA/SRC) proteins that mediate the transcriptional activities of nuclear hormone receptors. We have found that p/CIP is predominantly cytoplasmic in a large proportion of cells in various tissues of the developing mouse and in a number of established cell lines. In mouse embryonic fibroblasts, serum deprivation results in the redistribution of p/CIP to the cytoplasmic compartment and stimulation with growth factors or tumor-promoting phorbol esters promotes p/CIP shuttling into the nucleus. Cytoplasmic accumulation of p/CIP is also cell cycle dependent, occurring predominantly during the S and late M phases. Leptomycin B (LMB) treatment results in a marked nuclear accumulation, suggesting that p/CIP undergoes dynamic nuclear export as well as import. We have identified a strong nuclear import signal in the N terminus of p/CIP and two leucine-rich motifs in the C terminus that resemble CRM-1-dependent nuclear export sequences. When fused to green fluorescent protein, the nuclear export sequence region is cytoplasmic and is retained in the nucleus in an LMB-dependent manner. Disruption of the leucine-rich motifs prevents cytoplasmic accumulation. Furthermore, we demonstrate that cytoplasmic p/CIP associates with tubulin and that an intact microtubule network is required for intracellular shuttling of p/CIP. Immunoaffinity purification of p/CIP from nuclear and cytosolic extracts revealed that only nuclear p/CIP complexes possess histone acetyltransferase activity. Collectively, these results suggest that cellular compartmentalization of NCoA/SRC proteins could potentially regulate nuclear hormone receptor-mediated events as well as integrating signals in response to different environmental cues.

scholarly journals The general mRNA exporters Mex67 and Mtr2 play distinct roles in nuclear export of tRNAs in Trypanosoma brucei

2019 ◽  
Vol 47 (16) ◽  
pp. 8620-8631
Author(s):  
Eva Hegedűsová ◽  
Sneha Kulkarni ◽  
Brandon Burgman ◽  
Juan D Alfonzo ◽  
Zdeněk Paris
Keyword(s):  
Protein Synthesis ◽  
Trypanosoma Brucei ◽  
Nuclear Export ◽  
Nuclear Accumulation ◽  
Down Regulation ◽  
Regulation Of Expression ◽  
Alternative Pathways ◽  
Transport Receptors ◽  
Evolutionarily Conserved ◽  
Family Based

Abstract Transfer RNAs (tRNAs) are central players in protein synthesis, which in Eukarya need to be delivered from the nucleus to the cytoplasm by specific transport receptors, most of which belong to the evolutionarily conserved beta-importin family. Based on the available literature, we identified two candidates, Xpo-t and Xpo-5 for tRNA export in Trypanosoma brucei. However, down-regulation of expression of these genes did not disrupt the export of tRNAs to the cytoplasm. In search of alternative pathways, we tested the mRNA export complex Mex67-Mtr2, for a role in tRNA nuclear export, as described previously in yeast. Down-regulation of either exporter affected the subcellular distribution of tRNAs. However, contrary to yeast, TbMex67 and TbMtr2 accumulated different subsets of tRNAs in the nucleus. While TbMtr2 perturbed the export of all the tRNAs tested, silencing of TbMex67, led to the nuclear accumulation of tRNAs that are typically modified with queuosine. In turn, inhibition of tRNA nuclear export also affected the levels of queuosine modification in tRNAs. Taken together, the results presented demonstrate the dynamic nature of tRNA trafficking in T. brucei and its potential impact not only on the availability of tRNAs for protein synthesis but also on their modification status.

scholarly journals BMAL1 Shuttling Controls Transactivation and Degradation of the CLOCK/BMAL1 Heterodimer

2006 ◽  
Vol 26 (19) ◽  
pp. 7318-7330 ◽  
Author(s):  
Ilmin Kwon ◽  
Jiwon Lee ◽  
Seok Hoon Chang ◽  
Neon Cheol Jung ◽  
Byung Ju Lee ◽  
...  
Keyword(s):  
Transcriptional Activation ◽  
Nuclear Export ◽  
Clock Gene ◽  
Clock Genes ◽  
Nuclear Accumulation ◽  
Cry Proteins ◽  
Embryonic Mouse ◽  
E Box ◽  
Localization Signal ◽  
Functional Nuclear Localization Signal

ABSTRACT CLOCK and BMAL1 are bHLH-PAS-containing transcription factors that bind to E-box elements and are indispensable for expression of core circadian clock components such as the Per and Cry genes. A key step in expression is the heterodimerization of CLOCK and BMAL1 and their accumulation in the nucleus with an approximately 24-h periodicity. We show here that nucleocytoplasmic shuttling of BMAL1 is essential for transactivation and for degradation of the CLOCK/BMAL1 heterodimer. Using serial deletions and point mutants, we identified a functional nuclear localization signal and Crm1-dependent nuclear export signals in BMAL1. Transient-transfection experiments revealed that heterodimerization of CLOCK and BMAL1 accelerates their turnover, as well as E-box-dependent clock gene transcription. Moreover, in embryonic mouse fibroblasts, robust transcription of Per2 is tightly associated with massive degradation of the CLOCK/BMAL1 heterodimer. CRY proteins suppressed this process during the transcription-negative phase and led to nuclear accumulation of the CLOCK/BMAL1 heterodimer. Thus, these findings suggest that the decrease of BMAL1 abundance during the circadian cycle reflects robust transcriptional activation of clock genes rather than inhibition of BMAL1 synthesis.

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