Letteratura scientifica selezionata sul tema "Transcriptional coactivator with PDZ-binding motif proteins"

Yes-associated protein (YAP, also known as YAP1) and its paralogue TAZ (with a PDZ-binding motif) are transcriptional coactivators that switch between the cytoplasm and nucleus and regulate the organ size and tissue homeostasis. This review focuses on the research progress on YAP/TAZ signaling proteins in myocardial infarction, cardiac remodeling, hypertension and coronary heart disease, cardiomyopathy, and aortic disease. Based on preclinical studies on YAP/TAZ signaling proteins in cellular/animal models and clinical patients, the potential roles of YAP/TAZ proteins in some cardiovascular diseases (CVDs) are summarized.

TAZ (transcriptional coactivator with PDZ-binding motif), also called WWTR1 (WW domain containing transcription regulator 1), is a 14-3-3-binding molecule homologous to Yes-associated protein. TAZ acts as a coactivator for several transcription factors as well as a modulator of membrane-associated PDZ domain-containing proteins, but its (patho)physiological roles remain unknown. Here we show that gene inactivation of TAZ in mice resulted in pathological changes in the kidney and lung that resemble the common human diseases polycystic kidney disease and pulmonary emphysema. Taz-null/ lacZ knockin mutant homozygotes demonstrated renal cyst formation as early as embryonic day 15.5 with dilatation of Bowman's capsules and proximal tubules, followed by pelvic dilatation and hydronephrosis. After birth, only one-fifth of TAZ-deficient homozygotes grew to adulthood and demonstrated multicystic kidneys with severe urinary concentrating defects and polyuria. Furthermore, adult TAZ-deficient homozygotes exhibited diffuse emphysematous changes in the lung. Thus TAZ is essential for developmental mechanisms involved in kidney and lung organogenesis, whose disturbance may lead to the pathogenesis of common human diseases.

The functional consequences of the interaction of transcriptional coregulators with the human thyroid hormone receptor (TR) in mammalian cells are complex. We have used the yeast, Saccharomyces cerevisiae, which lack endogenous nuclear receptors (NRs) and NR coregulators, as a model to decipher mechanisms regulating transcriptional activation by TR. In effect, this system allows the reconstitution of TR mediated transcription complexes by the expression of specific combinations of mammalian proteins in yeast. In this yeast system, human adenovirus 5 early region 1A (E1A), a natural N-CoR splice variant (N-CoRI) or an artificial N-CoR truncation (N-CoRC) coactivate unliganded TRs and these effects are inhibited by thyroid hormone (TH). E1A contains a short peptide sequence that resembles known corepressor-NR interaction motifs (CoRNR box motif, CBM), and this motif is required for TR binding and coactivation. N-CoRI and N-CoRC contain three CBMs, but only the C-terminal CBM1 is critical for coactivation. These observations in a yeast model system suggest that E1A and N-CoRI are naturally occurring TR coactivators that bind in the typical corepressor mode. These findings also raise the possibility that alternative splicing events which form corepressor proteins containing only C-terminal CBM motifs could represent a novel mechanism in mammalian cells for regulating constitutive transcriptional activation by TRs.

How extracellular cues are transduced to the nucleus is a fundamental issue in biology. The paralogous WW-domain proteins YAP (Yes-associated protein) and TAZ (transcriptional coactivator with PDZ-binding motif; also known as WWTR1, for WW-domain containing transcription regulator 1) constitute a pair of transducers linking cytoplasmic signaling events to transcriptional regulation in the nucleus. A cascade composed of mammalian Ste20-like (MST) and large tumor suppressor (LATS) kinases directs multisite phosphorylation, promotes 14-3-3 binding, and hinders nuclear import of YAP and TAZ, thereby inhibiting their transcriptional coactivator and growth-promoting activities. A similar cascade regulates the trafficking and function of Yorkie, the fly orthologue of YAP. Mammalian YAP and TAZ are expressed in various tissues and serve as coregulators for transcriptional enhancer factors (TEFs; also referred to as TEADs, for TEA-domain proteins), runt-domain transcription factors (Runxs), peroxisome proliferator-activated receptor γ (PPARγ), T-box transcription factor 5 (Tbx5), and several others. YAP and TAZ play distinct roles during mouse development. Both, and their upstream regulators, are intimately linked to tumorigenesis and other pathogenic processes. Here, we review studies on this family of signal-responsive transcriptional coregulators and emphasize how relative sequence conservation predicates their function and regulation, to provide a conceptual framework for organizing available information and seeking new knowledge about these signal transducers.

ABSTRACT Members of the 160-kDa nuclear receptor coactivator family (p160 coactivators) bind to the conserved AF-2 activation function found in the hormone binding domains of nuclear receptors (NR) and are potent transcriptional coactivators for NRs. Here we report that the C-terminal region of p160 coactivators glucocorticoid receptor interacting protein 1 (GRIP1), steroid receptor coactivator 1 (SRC-1a), and SRC-1e binds the N-terminal AF-1 activation function of the androgen receptor (AR), and p160 coactivators can thereby enhance transcriptional activation by AR. While they all interact efficiently with AR AF-1, these same coactivators have vastly different binding strengths with and coactivator effects on AR AF-2. p160 activation domain AD1, which binds secondary coactivators CREB binding protein (CBP) and p300, was previously implicated as the principal domain for transmitting the activating signal to the transcription machinery. We identified a new highly conserved motif in the AD1 region which is important for CBP/p300 binding. Deletion of AD1 only partially reduced p160 coactivator function, due to signaling through AD2, another activation domain located at the C-terminal end of p160 coactivators. C-terminal coactivator fragments lacking AD1 but containing AD2 and the AR AF-1 binding site served as efficient coactivators for full-length AR and AR AF-1. The two signal input domains (one that binds NR AF-2 domains and one that binds AF-1 domains of some but not all NRs) and the two signal output domains (AD1 and AD2) of p160 coactivators played different relative roles for two different NRs: AR and thyroid hormone receptor.

The Hippo pathway is a conserved pathway that interconnects with several other pathways to regulate organ growth, tissue homoeostasis and regeneration, and stem cell self-renewal. This pathway is unique in its capacity to orchestrate multiple processes, from sensing to execution, necessary for organ expansion. Activation of the Hippo pathway core kinase cassette leads to cytoplasmic sequestration of the nuclear effectors YAP (Yes-associated protein) and TAZ (transcriptional coactivator with PDZ-binding motif), consequently disabling their transcriptional co-activation function. Components upstream of the core kinase cassette have not been well understood, especially in vertebrates, but are gradually being elucidated and include cell polarity and cell adhesion proteins.

ABSTRACT Transcriptional activation by the estrogen receptor is mediated through its interaction with coactivator proteins upon ligand binding. By systematic mutagenesis, we have identified a group of conserved hydrophobic residues in the ligand binding domain that are required for binding the p160 family of coactivators. Together with helix 12 and lysine 366 at the C-terminal end of helix 3, they form a hydrophobic groove that accommodates an LXXLL motif, which is essential for mediating coactivator binding to the receptor. Furthermore, we demonstrated that the high-affinity binding of motif 2, conserved in the p160 family, is due to the presence of three basic residues N terminal to the core LXXLL motif. The recruitment of p160 coactivators to the estrogen receptor is therefore likely to depend not only on the LXXLL motif making hydrophobic interactions with the docking surface on the receptor, but also on adjacent basic residues, which may be involved in the recognition of charged residues on the receptor to allow the initial docking of the motif.

ABSTRACT Transcriptional activation requires both access to DNA assembled as chromatin and functional contact with components of the basal transcription machinery. Using the hormone-bound vitamin D3receptor (VDR) ligand binding domain (LBD) as an affinity matrix, we previously identified a novel multisubunit coactivator complex, DRIP (VDR-interacting proteins), required for transcriptional activation by nuclear receptors and several other transcription factors. In this report, we characterize the nuclear receptor binding features of DRIP205, a key subunit of the DRIP complex, that interacts directly with VDR and thyroid hormone receptor in response to ligand and anchors the other DRIP subunits to the nuclear receptor LBD. In common with other nuclear receptor coactivators, DRIP205 interaction occurs through one of two LXXLL motifs and requires the receptor's AF-2 subdomain. Although the second motif of DRIP205 is required only for VDR binding in vitro, both motifs are used in the context of an retinoid X receptor-VDR heterodimer on DNA and in transactivation in vivo. We demonstrate that both endogenous p160 coactivators and DRIP complexes bind to the VDR LBD from nuclear extracts through similar sequence requirements, but they do so as distinct complexes. Moreover, in contrast to the p160 family of coactivators, the DRIP complex is devoid of any histone acetyltransferase activity. The results demonstrate that different coactivator complexes with distinct functions bind to the same transactivation region of nuclear receptors, suggesting that they are both required for transcription activation by nuclear receptors.

The paralogues Yes-associated protein (YAP) and transcriptional coactivator with PDZ-binding motif (TAZ) control cell proliferation and cell fate determination from embryogenesis to ageing. In the skin epidermis, these proteins are involved in both homeostatic cell renewal and injury-induced regeneration and also drive carcinogenesis and other pathologies. YAP and TAZ are usually considered downstream of the Hippo pathway. However, they are the central integrating link for the signalling microenvironment since they are involved in the interplay with signalling cascades induced by growth factors, cytokines, and physical parameters of the extracellular matrix. In this review, we summarise the evidence on how YAP and TAZ are activated in epidermal keratinocytes; how YAP/TAZ-mediated signalling cooperates with other signalling molecules at the plasma membrane, cytoplasmic, and nuclear levels; and how YAP/TAZ ultimately controls transcription programmes, defining epidermal cell fate.

The p160 coactivators, steroid receptor coactivator 1, glucocorticoid receptor interacting protein 1 (GRIP1) and the activator of thyroid and retinoic acid receptor, have two activation domains, AD1 and AD2, which transmit the activation signal from the DNA-bound nuclear receptor to the chromatin and/or transcription machinery. In screening for mammalian proteins that bind the AD2 of GRIP1, we identified a mouse actin-binding protein, alpha actinin 2 (mACTN2). mACTN2 was expressed in the heart, skeletal muscle, lung, brain and testis, but there was no expression in the spleen, liver or kidney. Interestingly, the expression level of mACTN2 in the developing embryo depended on the embryonic stage. We further demonstrated that mACTN2 could enhance two transactivation activities of GRIP1, which in turn could enhance the homodimerization of mACTN2. Importantly, mACTN2 not only served as a primary coactivator for androgen receptor, estrogen receptor and thyroid receptor activities, but also acted synergistically with GRIP1 to enhance these nuclear receptor (NR) functions. However, the NR binding motif, LXXLL, conserved in mACTN2 and other actinin family proteins, might be a dispensable domain for its coactivator roles in NRs. These findings suggested that mACTN2 might play an important role in GRIP1-induced NR coactivator functions.

Des études épidémiologiques et expérimentales suggèrent que la progression de la maladie rénale chronique (MRC) après une lésion initiale est génétiquement déterminée, mais les réseaux génétiques qui contribuent à cette prédisposition restent inconnus. Parmi les voies moléculaires potentielles impliquées dans la MRC, cette étude s'est concentrée sur la voie Hippo, une cascade de signalisation conservée au cours de l'évolution et cruciale pour la régulation de la taille des organes et de la prolifération cellulaire. Les protéines paralogues YAP et TAZ, deux coactivateurs transcriptionnels de la voie Hippo, ont récemment été identifiées comme étant également des mécanosenseurs, capables de détecter un large éventail de signaux mécaniques et de les traduire en programmes transcriptionnels spécifiques aux cellules. L'activation de YAP et TAZ a été impliquée dans la progression de plusieurs maladies rénales et dans la transition de la lésion rénale aiguë (LRA) à la MRC . Cependant, les mécanismes sous-jacents restent obscurs et leur rôle dans des conditions physiologiques n'est pas encore bien compris. L'objectif de ce projet est d'élucider le rôle de YAP et TAZ dans les tubules rénaux. Tout d'abord, en utilisant la combinaison de modèles de souris transgéniques et de néphrectomie comme modèle de MRC, nous avons étudié l'effet de l'inactivation sélective du gène Yap ou Taz dans les cellules tubulaires rénales dans ce contexte de maladie. Nos résultats ont révélé une redondance potentielle entre ces deux protéines dans les cellules épithéliales tubulaires. Il est intéressant de noter que nos souris déficientes à la fois en YAP et en TAZ ont développé spontanément un phénotype rénal sévère avec des lésions tubulaires, de la fibrose et de l'inflammation, qui a été décrit en détail dans ce travail. Grâce à l'analyse transcriptomique, nous avons identifié une nouvelle signature moléculaire qui pourrait permettre de mieux comprendre les mécanismes régulés par YAP et TAZ dans les cellules tubulaires. Paradoxalement, dans notre modèle de double knock-out, nous avons observé une aggravation de l'expression et de l'activation de YAP et TAZ, parallèlement à la progression des lésions. Ceci semble être le résultat d'une expansion des cellules « non recombinées », montrant les rôles complexes de YAP et TAZ dans la communication avec les cellules voisines. Ces données démontrent le rôle essentiel de YAP et TAZ dans le maintien de l'homéostasie tubulaire et l'équilibre complexe nécessaire à leur régulation. Cette complexité peut avoir des implications pour les stratégies thérapeutiques ciblant l'inhibition de YAP et TAZ dans les maladies rénales, surtout si l'on considère les effets secondaires potentiels qui pourraient rendre ces approches plus difficiles
Epidemiological and experimental studies suggest that the progression of Chronic Kidney Disease (CKD) after an initial injury is genetically determined, but the genetic networks that contribute to this predisposition remain unknown. Among the potential molecular pathways involved in CKD, this study focused on the Hippo pathway, an evolutionarily conserved signaling cascade crucial for regulating organ size and cell proliferation. The paralogs proteins YAP and TAZ, two transcriptional coactivators of the Hippo pathway, have recently been identified also as mechanosensors, capable of detecting a wide range of mechanical cues and translating them into cell-specific transcriptional programs. Activation of YAP and TAZ has been implicated to the progression of several kidney diseases and in the transition from acute kidney injury (AKI) to CKD. However, the underlying mechanisms remain unclear and their role under physiological conditions is still not well understood. The aim of this project is to elucidate the role of YAP and TAZ in the renal tubules. First, using the combination of inducing transgenic mouse models and nephrectomy as a model of CKD, we investigated the effect of the selective inactivation of Yap or Taz gene in renal tubular cells in this disease context. Our findings revealed a potential redundancy between these two proteins in tubular epithelial cells. Interestingly, our mice deficient in both YAP and TAZ developed a spontaneous severe renal phenotype with tubular injury, fibrosis and inflammation, which was described in detail in this work. Through transcriptomic analysis, we identified a new novel molecular signature that may provide further insight into the mechanisms regulated by YAP and TAZ in tubular cells. Paradoxically, in our double knock-out model, we observed a worsening of YAP and TAZ expression and activation, in parallel with the lesion progression. This appeared to be the result of an expansion of the "non-recombined" cells, showing the complex roles of YAP and TAZ in the cross-talk with the neighbouring cells. These data demonstrated the essential role of YAP and TAZ in maintaining tubular homeostasis and the intricate balance required for their regulation. This complexity may have implications for therapeutic strategies targeting the inhibition of YAP and TAZ in kidney disease, especially considering the potential side effects that could make such approaches more challenging