1,720,958 research outputs found
Protein kinase-zeta interacts with munc18c: role in GLUT4 trafficking
No full textAIMS/HYPOTHESIS: Insulin-stimulated glucose transport requires a signalling cascade through kinases protein kinase (PK) Czeta/lambda and PKB that leads to movement of GLUT4 vesicles to the plasma membrane. The aim of this study was to identify missing links between the upstream insulin-regulated kinases and the GLUT4 vesicle trafficking system. MATERIALS AND METHODS: A yeast two-hybrid screen was conducted, using as bait full-length mouse munc18c, a protein known to be part of the GLUT4 vesicle trafficking machinery. RESULTS: The yeast two-hybrid screen identified PKCzeta as a novel interactor with munc18c. Glutathione S transferase (GST) pull-downs with GST-tagged munc18c constructs confirmed the interaction, mapped a key region of munc18c that binds PKCzeta to residues 295-338 and showed that the N-terminal region of PKCzeta was required for the interaction. Endogenous munc18c was shown to associate with endogenous PKCzeta in vivo in various cell types. Importantly, insulin stimulation increased the association by approximately three-fold. Moreover, disruption of PKCzeta binding to munc18c by deletion of residues 295-338 of munc18c or deletion of the N-terminal region of PKCzeta markedly inhibited the ability of insulin to stimulate glucose uptake or GLUT4 translocation. CONCLUSIONS/INTERPRETATION: We have identified a physiological interaction between munc18c and PKCzeta that is insulin-regulated. This establishes a link between a kinase (PKCzeta) involved in the insulin signalling cascade and a known component of the GLUT4 vesicle trafficking pathway (munc18c). The results indicate that PKCzeta regulates munc18c and suggest a model whereby insulin triggers the docking of PKCzeta to munc18c, resulting in enhanced GLUT4 translocation to the plasma membrane.<br/
Characterization of PDK2 activity against protein kinase B gamma
No full textProtein kinase B (PKB), also known as Akt, is a serine/threonine protein kinase controlled by
insulin, various growth factors, and phosphatidylinositol 3-kinase. Full activation of the PKB enzyme
requires phosphorylation of a threonine in the activation loop and a serine in the C-terminal tail. PDK1
has clearly been shown to phosphorylate the threonine, but the mechanism leading to phosphorylation of
the serine, the PDK2 site, is unclear. A yeast two-hybrid screen using full-length human PKBç identified
protein kinase C (PKC) ú, an atypical PKC, as an interactor with PKBç, an association requiring the
pleckstrin homology domain of PKBç. Endogenous PKBç was shown to associate with endogenous PKCú
both in cos-1 cells and in 3T3-L1 adipocytes, demonstrating a physiological interaction. Immunoprecipitates
of PKCú, whether endogenous PKCú from insulin-stimulated 3T3-L1 adipocytes or overexpressed PKCú
from cos-1 cells, phosphorylated S472 (the C-terminal serine phosphorylation site) of PKBç, in vitro. In
vivo, overexpression of PKCú stimulated the phosphorylation of approximately 50% of the PKBç
molecules, suggesting a physiologically meaningful effect. However, pure PKCú protein was incapable
of phosphorylating S472 of PKBç. Antisense knockout studies and use of a PDK1 inhibitor showed that
neither PKB autophosphorylation nor phosphorylation by PDK1 accounted for the S472 phosphorylation
in PKCú immunoprecipitates. Staurosporine inhibited the PKCú activity but not the PDK2 activity in
PKCú immunoprecipitates. Together these results indicate that an independent PDK2 activity exists that
physically associates with PKCú and that PKCú, by binding PKBç, functions to deliver the PDK2 to a
required location. PKCú thus functions as an adaptor, associating with a staurosporine-insensitive PDK2
enzyme that catalyzes the phosphorylation of S472 of PKBç. Because both PKCú and PKB have been
proposed to be required for mediating a number of crucial insulin responses, formation of an active signaling
complex containing PKCú, PKB, and PDK2 is an attractive mechanism for ensuring that all the critical
sites on targets such as glycogen synthase kinase-3 are phosphorylated
Role of protein kinase B in breast cancer
No full textBreast cancer is the most common cancer in women and is increasing in both the developed and developing countries. There is an urgent need to understand the precise mechanisms of tumour development in breast cancer, to develop new treatment strategies and to identify predictive markers for tumour aggressiveness and therapy resistance.A protein called protein kinase B (PKB, also called Akt) is frequently elevated in breast cancers and has been implicated as a key player in breast cancer development and progression. The activation level of PKB is also thought to correlate with patient outcome. However, the function of the three isoforms of PKB in mediating the crucial responses is unknown. We have developed a set of antisense phosphorothioate oligonucleotide probes that target antisense-active regions in PKB and that enable >90% knockdown of all three known PKB isoforms (alpha, beta and gamma), either individually or in various combinations, including removal of all three isoforms together. We have demonstrated that these agents specifically and potently prevent the growth of breast cancer cells. Application of these antisense agents offers a unique opportunity to understand how PKB works and contributes to breast cancer, and to provide insight into the role of signalling by individual PKB isoforms in breast cancer cells. Such work may also identify clinically relevant markers of disease, thereby enabling better predictors of patient outcome, and provide the necessary intellectual framework for the development of PKB-isoform selective inhibitors (for example, antisense oligonucleotides, small chemical inhibitors) as novel therapeutic agents.<br/
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe 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
Full text link“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
Full text linkWe 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
Full text linkWe 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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