Novel Insights into the Allosteric Activation of the Epidermal Growth Factor Receptor

EGF receptor activation requires both ligand-binding and receptor-mediated dimerization through receptor domain II. The relationship between these processes, however, remains unclear. We have decoupled these processes to examine the ligand-binding affinity and the structure of constitutively-monomeric and -dimeric forms of the EGF receptor, as well as EGF receptor that dimerizes upon ligand-binding. Surprisingly, monomeric receptor binds to the ligands EGF and TGFα with an affinity equivalent to that of dimerizing receptor but with a unique binding enthalpy. This shows that monomeric, ligated EGF receptor adopts a state that is distinct from that of EGF receptor within a homodimer, and this state may be relevant to heterodimeric ErbB signaling complexes. Constitutively-dimerized receptor binds ligand with elevated affinity; however, it still requires ligand to form the receptor domain II dimeric interface. In the absence of ligand, no ordered, receptor domain II-mediated dimer interface is formed. Thus, the affinity effect does not arise from any pre-organization or stabilization of the ligand-binding sites on the receptor, but rather through an entropic effect of enforcing dimerization. Thus, pre-formed human receptor dimers require allosteric activation by ligand in order to signal, and this allosteric mechanism is distinct from that we recently observed for the D. melanogaster EGF receptor. Our observations on the allosteric mechanism of EGF receptor activation prompted us to ask whether other EGF receptor ligands may exert unique allosteric effects. To this end, we investigated the allosteric effects of the ligands Amphiregulin, Epiregulin, and Epigen on EGF receptor. We report that Epiregulin and Epigen, in particular, exert unique allosteric regulation on the receptor, as evidenced by divergent effects of EGFR variants on ligand-binding. Finally, we have studied ligand-binding and dimerization of receptors bearing activating extracellular mutations that cause glioblastoma. We report that these mutations elevate ligand-binding affinity, but they do not drive receptor dimerization. Our findings inform a revised model of ligand-induced receptor activation, in which the dimerization interface is highly sensitive to the presence and the identity of the bound ligand, and the domain I/domain II interface plays a crucial auto-inhibitory role

Reading Places: Literacy, Democracy and the Public Library in Cold War America

Review of: "Reading Places: Literacy, Democracy and the Public Library in Cold War America," by Christine Pawley, part of the book series "Studies in Print Culture and the History of the Book.

Discerning users of information: A qualitative analysis of student inquiry

A shift is needed in information and digital literacy instruction and assessment led by elementary and secondary school librarians with an emphasis on the evaluation of information sources. The need is in response to widespread societal sharing of mis- and disinformation related to political news including the politicizing of scientific understandings of a disease and the ensuing distrust of the messages of public health officials during the COVID-19 global pandemic. In this article, I create an instructional framework for information evaluation that is grounded in data derived from a qualitative content analysis of published research, standards, and theoretical perspectives and that is confirmed using data derived from examples of middle school students\u27 inquiry research. Three overarching themes resulted from the analysis: blend media and research skills throughout the curriculum, ground information evaluation skills within a guided inquiry information process approach, and embed information evaluation skills in every grade and subject so they are taught beyond the context of news

Impact of a Less Restrictive Circulation Policy in an Elementary Library

School communities and educational standards clearly recognize that reading is a foundational skill for all learners. In light of this, the American Association of School Librarians (AASL, 2010) notes the critical position of teacher librarians to partner with other educators to promote literacy and provide opportunities for library use. Specifi cally, school libraries are charged with providing “open, non-restricted access to a varied high quality collection of reading materials in multiple formats that refl ect academic needs and personal interests” (para. 6). AASL (2011) supports open access through fl exible scheduling in the library to give students access to materials throughout the school day. The theory behind this position statement posits that the more students read (in both variety and quantity of text), the better readers they become (Krashen, 2004). Research in support of self-selected reading shows that student access to a school library of at least 500 books is associated with higher reading scores (Krashen, 2011, p. 29). Krashen ( 2011) makes a compelling argument for providing greater attention and support to libraries: “The obvious practical implication is that if we are serious about encouraging literacy development, we need to be serious about providing access to reading material” and provide more than “lip service to improving libraries” (p. 28). One aspect of providing greater access to reading material is increasing borrowing privileges. The current study examines how a change in library policy to reduce restrictions on borrowing privileges impacts students’ actual borrowing habits and the loss of books. Teacher librarians who use restrictive circulation policies of one book at a time inhibit students’ access to books, potentially undermining their reading growth. Sadly, the majority of teacher librarians, 71% of respondents in one Iowa survey, allowed kindergarteners to check out only one library book at a time (Johnson & Donham, 2012). Fortunately, 36% of those respondents said they decided to raise their borrowing limits after the survey. However, national K–12 level data reveal policies that limit students’ access to books. An informal online poll administered by Library Media Connection showed that 33% of the teacher librarians who responded said they limited their students to one or two books at a time; an additional 36% limited students to three or four books (“One Question Survey,” 2009). These limitations counter best practices established through research that emphasizes the need for expanded exposure to books in order to support reading growth (AASL, 2010; ALA, 1996; Allington, 2014; Krashen, 2004; Krashen, Lee, & McQuillan, 2012)

Reading Promotion Events Recommended for Elementary Students

One of the major professional goals of teacher librarians is to teach students a love of reading, so that they will independently choose to read throughout their lives

Real-time analysis of the binding of fluorescent VEGF₁₆₅a to VEGFR2 in living cells: Effect of receptor tyrosine kinase inhibitors and fate of internalized agonist-receptor complexes

Vascular endothelial growth factor (VEGF) is an important mediator of angiogenesis. Here we have used a novel stoichiometric protein-labeling method to generate a fluorescent variant of VEGF (VEGF₁₆₅a-TMR) labeled on a single cysteine within each protomer of the antiparallel VEGF homodimer. VEGF₁₆₅a-TMR has then been used in conjunction with full length VEGFR2, tagged with the bioluminescent protein NanoLuc, to undertake a real time quantitative evaluation of VEGFR2 binding characteristics in living cells using bioluminescence resonance energy transfer (BRET). This provided quantitative information on VEGF-VEGFR2 interactions. At longer incubation times, VEGFR2 is internalized by VEGF₁₆₅a-TMR into intracellular endosomes. This internalization can be prevented by the receptor tyrosine kinase inhibitors (RTKIs) cediranib, sorafenib, pazopanib or vandetanib. In the absence of RTKIs, the BRET signal is decreased over time as a consequence of the dissociation of agonist from the receptor in intracellular endosomes and recycling of VEGFR2 back to the plasma membrane