Disruption of the Cdc42/Par6/aPKC or Dlg/Scrib/Lgl polarity complex promotes epithelial proliferation via overlapping mechanisms

The establishment and maintenance of apical-basal polarity is a defining characteristic and essential feature of functioning epithelia. Apical-basal polarity (ABP) proteins are also tumor suppressors that are targeted for disruption by oncogenic viruses and are commonly mutated in human carcinomas. Disruption of these ABP proteins is an early event in cancer development that results in increased proliferation and epithelial disorganization through means not fully characterized. Using the proliferating Drosophila melanogaster wing disc epithelium, we demonstrate that disruption of the junctional vs. basal polarity complexes results in increased epithelial proliferation via distinct downstream signaling pathways. Disruption of the basal polarity complex results in JNK-dependent proliferation, while disruption of the junctional complex primarily results in p38-dependent proliferation. Surprisingly, the Rho-Rok-Myosin contractility apparatus appears to play opposite roles in the regulation of the proliferative phenotype based on which polarity complex is disrupted. In contrast, non-autonomous Tumor Necrosis Factor (TNF) signaling appears to suppress the proliferation that results from apical-basal polarity disruption, regardless of which complex is disrupted. Finally we demonstrate that disruption of the junctional polarity complex activates JNK via the Rho-Rok-Myosin contractility apparatus independent of the cortical actin regulator, Moesin

β-Catenin Phosphorylated at Serine 45 Is Spatially Uncoupled from β-Catenin Phosphorylated in the GSK3 Domain: Implications for Signaling

C. elegans and Drosophila generate distinct signaling and adhesive forms of β-catenin at the level of gene expression. Whether vertebrates, which rely on a single β-catenin gene, generate unique adhesive and signaling forms at the level of protein modification remains unresolved. We show that β-catenin unphosphorylated at serine 37 (S37) and threonine 41 (T41), commonly referred to as transcriptionally Active β-Catenin (ABC), is a minor nuclear-enriched monomeric form of β-catenin in SW480 cells, which express low levels of E-cadherin. Despite earlier indications, the superior signaling activity of ABC is not due to reduced cadherin binding, as ABC is readily incorporated into cadherin contacts in E-cadherin-restored cells. β-catenin phosphorylated at serine 45 (S45) or threonine 41 (T41) (T41/S45) or along the GSK3 regulatory cassette S33, S37 or T41 (S33/37/T41), however, is largely unable to associate with cadherins. β-catenin phosphorylated at T41/S45 and unphosphorylated at S37 and T41 is predominantly nuclear, while β-catenin phosphorylated at S33/37/T41 is mostly cytoplasmic, suggesting that β-catenin hypophosphorylated at S37 and T41 may be more active in transcription due to its enhanced nuclear accumulation. Evidence that phosphorylation at T41/S45 can be spatially separated from phosphorylations at S33/37/T41 suggests that these phosphorylations may not always be coupled, raising the possibility that phosphorylation at S45 serves a distinct nuclear function

Activity of the β-catenin phosphodestruction complex at cell–cell contacts is enhanced by cadherin-based adhesion

It is well established that cadherin protein levels impact canonical Wnt signaling through binding and sequestering β-catenin (β-cat) from T-cell factor family transcription factors. Whether changes in intercellular adhesion can affect β-cat signaling and the mechanism through which this occurs has remained unresolved. We show that axin, APC2, GSK-3β and N-terminally phosphorylated forms of β-cat can localize to cell–cell contacts in a complex that is molecularly distinct from the cadherin–catenin adhesive complex. Nonetheless, cadherins can promote the N-terminal phosphorylation of β-cat, and cell–cell adhesion increases the turnover of cytosolic β-cat. Together, these data suggest that cadherin-based cell–cell adhesion limits Wnt signals by promoting the activity of a junction-localized β-cat phosphodestruction complex, which may be relevant to tissue morphogenesis and cell fate decisions during development

Large expert-curated database for benchmarking document similarity detection in biomedical literature search

Document recommendation systems for locating relevant literature have mostly relied on methods developed a decade ago. This is largely due to the lack of a large offline gold-standard benchmark of relevant documents that cover a variety of research fields such that newly developed literature search techniques can be compared, improved and translated into practice. To overcome this bottleneck, we have established the RElevant LIterature SearcH consortium consisting of more than 1500 scientists from 84 countries, who have collectively annotated the relevance of over 180 000 PubMed-listed articles with regard to their respective seed (input) article/s. The majority of annotations were contributed by highly experienced, original authors of the seed articles. The collected data cover 76% of all unique PubMed Medical Subject Headings descriptors. No systematic biases were observed across different experience levels, research fields or time spent on annotations. More importantly, annotations of the same document pairs contributed by different scientists were highly concordant. We further show that the three representative baseline methods used to generate recommended articles for evaluation (Okapi Best Matching 25, Term Frequency-Inverse Document Frequency and PubMed Related Articles) had similar overall performances. Additionally, we found that these methods each tend to produce distinct collections of recommended articles, suggesting that a hybrid method may be required to completely capture all relevant articles. The established database server located at https://relishdb.ict.griffith.edu.au is freely available for the downloading of annotation data and the blind testing of new methods. We expect that this benchmark will be useful for stimulating the development of new powerful techniques for title and title/abstract-based search engines for relevant articles in biomedical research.Peer reviewe

P38 MAPK is required for proliferation following junctional complex disruption, but not for proliferation following basolateral complex disruption.

<p>(A-D, F-H) Confocal immunofluorescent localization of DE-cadherin and GFP (Aa-Da), and MMP1 (Ab-Db) in wing discs expressing GFP with P35 only (Aa and Ab), Cdc42-RNAi and P35 (Ba and Bb), Cdc42-RNAi, p38a-RNAi, and P35 (Ca and Cb), Cdc42-RNAi, p38b-RNAi, and P35 (Da and Db), via <i>ptc-GAL4</i>. (E) Quantification of GFP area/total wing disc area in conditions shown in A-D, n>13. Statistical comparisons to “A” are shown in black, while statistical comparisons to “B” are shown in red. Confocal immunofluorescent localization of DE-cadherin and GFP (Fa-Ha), and MMP1 (Fb-Hb) in wing discs expressing GFP with Dlg-RNAi#1 and P35 (Fa and Fb), Dlg-RNAi#1, P35, and p38a-RNAi (Ga and Gb), Dlg-RNAi#1, P35, and p38b-RNAi (Ha and Hb), via <i>ptc-GAL4</i>. (I) Quantification of GFP area/total wing disc area in conditions shown in A and F-H, n>8. Scale bars represent 100μm. AU—Arbitrary Units.</p

The ERM protein Moesin regulates Rho-JNK independent of the junctional polarity complex.

<p>Confocal immunofluorescent localization of DE-cadherin, GFP, and MMP1 in wing discs expressing GFP with P35 alone (Aa and Ab), Cdc42-RNAi and P35 (Ba and Bb), Moe-RNAi and P35 (Ca and Cb), Cdc42-RNAi, Moe-RNAi, and P35 (Da and Db), Cdc42-RNAi, Moe, and P35 (Ea and Eb), via <i>ptc-GAL4</i>. (F) Quantification of GFP area/total wing disc area in conditions shown in A-D, n>12. Scale bars represent 100μm. AU—Arbitrary Units.</p

Depletion of Rho/Rok/Myosin suppresses proliferation following junctional complex disruption + P35, and promotes proliferation following basolateral complex disruption + P35.

<p>Confocal immunofluorescent localization of DE-cadherin, GFP, and MMP1 in wing discs expressing GFP with P35 alone (Aa and Ab), Cdc42-RNAi and P35 (Ba and Bb), Cdc42-RNAi and P35 in a <i>rho1</i>^<i>72F</i> heterozygous background (Ca and Cb), and Cdc42-RNAi and P35 in a <i>zip</i>^<i>1</i> heterozygous background (Da and Db), via <i>ptc-GAL4</i>. (E) Quantification of GFP area/total wing disc area in conditions shown in A-D, n>9. Confocal immunofluorescent localization of DE-cadherin, GFP and MMP1 in wing discs expressing GFP with Dlg-RNAi#1 and P35 (Fa and Fb), Dlg-RNAi#1, Rho1-RNAi, and P35 (Ga and Gb), Dlg-RNAi#1, Rok-RNAi, and P35 (Ha and Hb), via <i>ptc-GAL4</i>. (I) Quantification of GFP area/total wing disc area in conditions shown in A, F-H, n>17. Confocal immunofluorescent localization of DE-cadherin, GFP and MMP1 in wing discs expressing GFP with Scrib-RNAi and P35 (Ja and Jb), Scrib-RNAi and P35 in a <i>rho1</i>^<i>72F</i> heterozygous background (Ka and Kb), Scrib-RNAi, Rok-RNAi, and P35 (La and Lb), and Scrib-RNAi and P35 in a <i>zip</i>^<i>1</i> heterozygous background (Ma and Mb), via <i>ptc-GAL4</i>. (N) Quantification of GFP area/total wing disc area in conditions shown in A, J-M, n>18. Scale bars represent 100μm. AU—Arbitrary Units.</p

Hyperproliferation following junctional complex disruption specifically requires the upstream JNK-KK, Mekk1; hyperproliferation following basolateral complex disruption is dependent on multiple upstream kinases.

<p>(A) Schematic of JNK MAPK signaling in <i>Drosophila melanogaster</i>. (B-H, J-O) Confocal immunofluorescent localization of DE-cadherin, GFP, and MMP1 in wing discs expressing P35 and GFP alone (Aa and Ab), Cdc42-RNAi, P35 (Ca and Cb), Cdc42-RNAi, Slpr-RNAi, and P35 (Da and Db), Cdc42-RNAi, Tak1-RNAi, and P35 (Ea and Eb), Cdc42-RNAi, Mekk1-RNAi, and P35 (Fa and Fb), Cdc42-RNAi, Wnd-RNAi, and P35 (Ga and Gb), Cdc42-RNAi, Ask1-RNAi, and P35 (Ha and Hb), via <i>ptc-GAL4</i>. (I) Quantification of GFP area/total wing disc area in conditions shown in B-H, n>13. (J-O) Confocal immunofluorescent localization of DE-cadherin and MMP1 in wing discs expressing Dlg-RNAi and P35 (Ja and Jb), Dlg-RNAi, Bsk-RNAi, and P35 (Ka and Kb), Dlg-RNAi, Mkk4-RNAi, and P35 (La and Lb), Dlg-RNAi, Tak1-RNAi, and P35 (Ma and Mb), Dlg-RNAi, Hep-RNAi, and P35 (Na and Nb), and Dlg-RNAi, Mekk1-RNAi, and P35 (Oa and Ob), via <i>ptc-GAL4</i>. (P) Quantification of GFP area/total wing disc area in conditions shown in B and J-O, n>13. Statistical comparisons to “B” are shown in black, while statistical comparisons to “J” are shown in red. Scale bars represent 100μm. AU—Arbitrary Units.</p