1,720,957 research outputs found
ROLE OF PROTEIN KINASE PAK4 IN DIFFERENTIATION AND SURVIVAL OF HUMAN KERATINOCYTES AND REGULATION OF TRANSCRIPTION FACTOR P63
No full textThe serine/threonine kinase PAK4 is a Rho GTPases effector protein implicated in many critical biological processes, from cytoskeletal rearrangement, adhesion and motility, to cell survival and apoptosis. It has been also implicated in embryonic development and oncogenic transformation. Indeed, PAK4 is found overexpressed in many cancer cell lines and tissues, such as pancreatic, colon and squamous cell carcinomas. Its activation promotes cell migration and anchorage-independent growth, and its overexpression in fibroblasts causes tumor formation in athymic mice. Further, PAK4 can promote survival and protect cells from apoptosis induced by different stimuli. Despite its role is central in many processes, little is still known about signals that lead to its activation, or about its interactors. We reported that PAK4, through its N-terminal regulatory region, can interact with the translational machinery and that this interaction can lead to regulation of cap-independent IRES mediated translation, suggesting that PAK4 could elicit its functional role also by this mechanism. Moreover, we found that endogenous PAK4 is localized both in the nucleus and in the cytoplasm, and identification of a NES sequence supports the idea that PAK4 is subject to nucleo-cytoplasmic shuttling in vivo. Recently it has been reported that PAK4 can interact with the Keratinocyte Growth Factor (KGF) Receptor, and that PAK4 is activated following treatment with KGF or after UV irradiation in HaCaT human keratinocytes. For this reason, we decided to better investigate PAK4 role in differentiation and survival of HaCaT cells. To evaluate PAK4 role in signalling mechanisms that control survival and differentiation in human keratinocytes, we down-regulated PAK4 expression in HaCaT cells by RNA interference. As already reported, in control HaCaT cells PAK4 expression increases following confluence-induced differentiation. Our data show that PAK4 expression results to be necessary for proper differentiation, since PAK4 knock down HaCaT cells fail to differentiate, as indicated by mis-regulation of Keratin1, Keratin14 and also p63, a master regulator for epithelial tissue differentiation. The PAK4 pro-survival role is also confirmed in HaCaT cells by the higher sensitivity of silenced cells to UV induced apoptosis. In order to understand if PAK4 may act through p63 modulation, we evaluated activated PAK4 effects on p63 stability and transcriptional activity. Our data show that active PAK4 expression can both modulate p63 protein levels and inhibit its transcriptional activity, and that post-translational modifications on p63 protein could be involved.
Our work shows that PAK4 is implicated in regulation of keratinocyte differentiation and response to UV irradiation in HaCaT cells. Moreover, PAK4 can regulate the transcriptional factor p63 on both activity and stability. This suggests that PAK4 could elicit its functions in the epidermis at different levels, in particular, in transition from the proliferative to the differentiation layers of keratinocytes. All together our data reveal a new mechanism for PAK4 regulation of cellular processes implicated in homeostasis of tissues like epidermis. Considering that such mechanisms could be relevant in multi-layered epithelia in general, and that many tumors are epithelial in origin, it will be of great interest to better investigate the physiological and pathological role of PAK4 in these contexts
Protein kinase PAK4 is involved in keratinocyte differentiation and modulates transcription factor p63
No full textThe epidermis is a multilayered, stratified epithelium continuously regenerated by keratinocytes through a terminal differentiation process called cornification. Recently, it has been shown that in epithelial cells PAK4 interacts with Keratinocyte Growth Factor (KGF) Receptor, and is activated following KGF or UV exposure. PAK4 is a member of the PAK family of serine/threonine kinases, originally identified as an effector protein of the RhoGTPase CDC42. While PAK4 is expressed at low levels in most adult tissues, it is found overexpressed in tumor cell lines and primary tumors, and its locus amplification is recurrent in many cancers, including squamous cell carcinoma. Considering that PAK4 is involved in many cellular processes necessary for proper development and homeostasis of epidermis, like cell adhesion, motility and control of cell death, and that its expression is increased during keratinocyte differentiation, in this work we evaluated PAK4 role in signalling mechanisms that control differentiation and survival in human keratinocytes. Using the RNA interference technique, we first showed that PAK4 down-regulation sensitizes HaCaT cells to UV induced apoptosis, confirming its pro-survival role also in keratinocytes. Secondly, we could demonstrate that PAK4 is necessary for the differentiation process induced by confluence growth: PAK4 knock-down cells show a loss of Keratin1 induction and impaired down-regulation of transcription factor p63, a master regulator of epithelial tissue differentiation. We then evaluated activated PAK4 effects on p63 stability and function. Our data show that active PAK4 can both modulate protein levels of the α and β isoforms of DNp63, and inhibit its trancriptional activity. Our results show that PAK4 plays a relevant role in differentiation of human keratinocytes, and suggest a novel p63 regulatory network that could be implicated in epithelial tissues pathologies
N-terminal interaction domain implicates PAK4 in translational regulation and reveals novel cellular localization signals
No full textThe serine/threonine kinase PAK4 is a Rho GTPases effector protein implicated in many critical biological processes, including regulation of cell morphology and motility, embryonic development, cell survival, response to infection, and oncogenic transformation. Consistently with its pro-oncogenic features, PAK4 was found to be overexpressed in many cancer cell lines and tissues, and to be necessary to promote activation of survival pathways. PAK4, like other Paks, is now considered a promising target for specific therapy. Little is known on its modes of regulation, molecular partners, and substrates. Because the N-terminal regulatory moiety plays important roles in PAK4 activity and functions, even independently of GTPase interactions, in this study we employed an affinity chromatography approach to identify N-terminal domain binding partners. Within this protein region we identified a novel interaction domain involved in association with ribonucleoprotein (RNP) complexes, suggesting PAK4 implications in translational regulation. Indeed, we found that active PAK4 can affect (cap-independent) translation from specific IRES sequences in vivo, and that the N-terminal domain is critical for this regulation. Further, we could establish that within the RNP interacting sequence PAK4 regulatory domain contains targeting elements that drive cytoplasmic localization and act as nuclear export signal. Functional implication of endogenous PAK4 protein, which was found in both cytoplasmic and nuclear fractions, in IRES-mediated translation further underlines the significance of the reported findings. Our data reveal novel means for PAK4 regulation of gene expression, and provide new elements to understand the molecular mechanisms that determine PAK4 cellular localization and functions
Going Beyond Counting First Authors in Author Co-citation Analysis
Get PDFThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Get PDF“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Appropriate Similarity Measures for Author Cocitation Analysis
Get PDFWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
Dispelling the Myths Behind First-author Citation Counts
Get PDFWe conducted a full-scale evaluative citation analysis study of scholars in the XML research field to explore just how different from each other author rankings resulting from different citation counting methods actually are, and to demonstrate the capability of emerging data and tools on the Web in supporting more realistic citation counting methods. Our results contest some common arguments for the continued
use of first-author citation counts in the evaluation of scholars, such as high correlations between author rankings by first-author citation counts and other citation
counting methods, and high costs of using more realistic citation counting methods that are not well-supported by the ISI databases. It is argued that increasingly available digital full text research papers make it possible for citation analysis studies to go beyond what the ISI databases have directly supported and to employ more
sophisticated methods
koamabayili/VECTRON-author-checklist: VECTRON author checklist
No full textWe have done our best to complete the author checklist relating to the use of animals in the hut study. Note that the objective for the hut study was to evaluate the IRS treatment applications for residual efficacy against Anopheles mosquitoes, including the local An. coluzzii mosquito population. Cows were only used to attract mosquitoes into the huts and no tests were carried out directly on the cows. The author checklist is intended for use with studies where experiments are carried out on animals, which is why we have had such difficulty in completing this for the hut study, as many of the questions do not relate to how the cows were used
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