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Molecular interactions of the Src homology 2 domain protein Shb with phosphotyrosine residues, tyrosine kinase receptors and Src homology 3 domain proteins
No full textThe molecular interactions of the Src homology 2 (SH2) domain and the N-terminal proline-rich sequence motifs (pro-1 to pro-5) of the SH2 protein Shb with other components were presently characterised. Using a degenerate phosphopeptide library the preferred binding site for the Shb SH2 domain was determined to pTyr-Thr/Val/Ile-X-Leu at positions +1 to +3 relative the phosphotyrosine residue. Experiments with competing peptides and platelet-derived growth factor (PDGF) beta-receptor mutants with Y to F substitutions in autophosphorylation sites revealed multiple binding sites for the Shb SH2 domain in the receptor. The Shb SH2 domain also binds to in vitro phosphorylated fibroblast growth factor receptor-1 (FGFR-1) mainly through position Y776. The receptor experiments suggest that other residues besides the +1 to +3 positions may also be of significance for Shb binding. The pro-4/pro-5 motif of Shb binds in vitro particularly well to the Src, p85 alpha PI3-kinase and Eps8 SH3 domains expressed as GST fusion proteins. However, the GST-SH3 domain fusion proteins tested bind in vitro to peptides corresponding to the pro-1 to pro-5 motifs of Shb with low affinity and selectivity, suggesting that sequences outside the core proline motif may also be important for Shb-SH3 domain interactions. In vivo association between Shb-SH3 domain proteins v-Src and Eps8 was detected by coimmunoprecipitation. PDGF treatment did not affect the association between Eps8 and Shb. The data suggest that Shb is an adaptor protein linking SH3 domain proteins to tyrosine kinases or other tyrosine phosphorylated proteins
The endothelial adaptor molecule TSAd is required for VEGF-induced angiogenic sprouting through junctional c-Src activation
No full textActivation of vascular endothelial growth factor (VEGF) receptor 2 (VEGFR2) by VEGF binding is critical for vascular morphogenesis. In addition, VEGF disrupts the endothelial barrier by triggering the phosphorylation and turnover of the junctional molecule VE-cadherin, a process mediated by the VEGFR2 downstream effectors T cell-specific adaptor (TSAd) and the tyrosine kinase c-Src. We investigated whether the VEGFR2-TSAd-c-Src pathway was required for angiogenic sprouting. Indeed, Tsad-deficient embryoid bodies failed to sprout in response to VEGF. Tsad-deficient mice displayed impaired angiogenesis specifically during tracheal vessel development, but not during retinal vasculogenesis, and in VEGF-loaded Matrigel plugs, but not in those loaded with FGF. The SH2 and proline-rich domains of TSAd bridged VEGFR2 and c-Src, and this bridging was critical for the localization of activated c-Src to endothelial junctions and elongation of the growing sprout, but not for selection of the tip cell. These results revealed that vascular sprouting and permeability are both controlled through the VEGFR2-TSAd-c-Src signaling pathway in a subset of tissues, which may be useful in developing strategies to control tissue-specific pathological angiogenesis
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
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