p120 catenin is required for the stress response in Drosophila

p120ctn is a ubiquitously expressed core component of cadherin junctions and essential for vertebrate development. Surprisingly, Drosophila p120ctn (dp120ctn) is dispensable for adherens junctions and development, which has discouraged Drosophila researchers from further pursuing the biological role of dp120ctn. Here we demonstrate that dp120ctn loss results in increased heat shock sensitivity and reduced animal lifespan, which are completely rescued by ectopic expression of a dp120ctn-GFP transgene. Transcriptomic analysis revealed multiple relish/NF-κB target genes differentially expressed upon loss of dp120ctn. Importantly, this aberrant gene expression was rescued by overexpression of dp120ctn-GFP or heterozygosity for relish. Our results uncover a novel role for dp120ctn in the regulation of animal stress response and immune signalling. This may represent an ancient role of p120ctn and can influence further studies in Drosophila and mammals

Transformed epithelia trigger non-tissue-autonomous tumor suppressor response by adipocytes via activation of toll and Eiger/TNF signaling

High tumor burden is associated with increased levels of circulating inflammatory cytokines that influence the pathophysiology of the tumor and its environment. The cellular and molecular events mediating the organismal response to a growing tumor are poorly understood. Here, we report a bidirectional crosstalk between epithelial tumors and the fat body—a peripheral immune tissue—in Drosophila. Tumors trigger a systemic immune response through activation of Eiger/TNF signaling, which leads to Toll pathway upregulation in adipocytes. Reciprocally, Toll elicits a non-tissue-autonomous program in adipocytes, which drives tumor cell death. Hemocytes play a critical role in this system by producing the ligands Spätzle and Eiger, which are required for Toll activation in the fat body and tumor cell death. Altogether, our results provide a paradigm for a long-range tumor suppression function of adipocytes in Drosophila, which may represent an evolutionarily conserved mechanism in the organismal response to solid tumors

Oxidation of SQSTM1/p62 mediates the link between redox state and protein homeostasis.

Cellular homoeostatic pathways such as macroautophagy (hereinafter autophagy) are regulated by basic mechanisms that are conserved throughout the eukaryotic kingdom. However, it remains poorly understood how these mechanisms further evolved in higher organisms. Here we describe a modification in the autophagy pathway in vertebrates, which promotes its activity in response to oxidative stress. We have identified two oxidation-sensitive cysteine residues in a prototypic autophagy receptor SQSTM1/p62, which allow activation of pro-survival autophagy in stress conditions. The Drosophila p62 homologue, Ref(2)P, lacks these oxidation-sensitive cysteine residues and their introduction into the protein increases protein turnover and stress resistance of flies, whereas perturbation of p62 oxidation in humans may result in age-related pathology. We propose that the redox-sensitivity of p62 may have evolved in vertebrates as a mechanism that allows activation of autophagy in response to oxidative stress to maintain cellular homoeostasis and increase cell survival

Inducible progenitor-derived Wingless regulates adult midgut regeneration in Drosophila

The ability to regenerate following stress is a hallmark of self-renewing tissues. However, little is known about how regeneration differs from homeostatic tissue maintenance. Here, we study the role and regulation of Wingless (Wg)/Wnt signalling during intestinal regeneration using the Drosophila adult midgut. We show that Wg is produced by the intestinal epithelial compartment upon damage or stress and it is exclusively required for intestinal stem cell (ISC) proliferation during tissue regeneration. Reducing Wg or downstream signalling components from the intestinal epithelium blocked tissue regeneration. Importantly, we demonstrate that Wg from the undifferentiated progenitor cell, the enteroblast, is required for Myc-dependent ISC proliferation during regeneration. Similar to young regenerating tissues, ageing intestines required Wg and Myc for ISC hyperproliferation. Unexpectedly, our results demonstrate that epithelial but not mesenchymal Wg is essential for ISC proliferation in response to damage, while neither source of the ligand is solely responsible for ISC maintenance and tissue self-renewal in unchallenged tissues. Therefore, fine-tuning Wnt results in optimal balance between the ability to respond to stress without negatively affecting organismal viability

Ubiquitous expression of dp120ctn-GFP or relish heterozygosity rescues aberrant gene expression in <i>dp120ctn</i> mutant flies.

<p>(A-E) qPCR analysis of the selected genes in (i) <i>w¹¹¹⁸</i>, (ii) <i>w¹¹¹⁸</i>; <i>p120³⁰⁸</i>, (iii) <i>w¹¹¹⁸</i>; <i>p120³⁰⁸</i>; <i>ubi-p120-GFP</i> and (iv) <i>w¹¹¹⁸</i>; <i>p120³⁰⁸</i>; <i>relE20/</i>+ flies (one-way ANOVA with Bonferroni posttest correction, ***p<0.001****p<0.0001). Note that restoring p120ctn expression or halving the genetic dose of relish rescued the deregulated expression of these genes in <i>dp120ctn</i> mutants. (All error bars denote standard error of the mean).</p

Transcriptomic analysis of <i>dp120ctn</i> mutants reveals differential gene expression.

<p>(A) Averaged expression profile (<i>log2</i> expression values) of selected genes in <i>w¹¹¹⁸</i> and <i>w¹¹¹⁸</i>; <i>p120³⁰⁸</i> flies before (<i>w¹¹¹⁸</i>, <i>w¹¹¹⁸</i>; <i>p120³⁰⁸</i>) and after 1hr of heat shock (<i>w¹¹¹⁸</i>-HS, <i>w¹¹¹⁸</i>; <i>p120³⁰⁸</i>-HS). Some of the genes selected for qPCR analysis are boxed in red. (B-C) Diagrams showing the number of genes up-regulated and down-regulated in <i>w¹¹¹⁸</i> and <i>w¹¹¹⁸</i>; <i>p120³⁰⁸</i> flies in response to 1hr heat shock, and their overlap. Note that there were more genes up-regulated upon heat shock in the mutants (D-H). qPCR analysis of selected targets in <i>w¹¹¹⁸</i>, <i>w¹¹¹⁸</i>; <i>p120³⁰⁸</i> and <i>w¹¹¹⁸</i>; <i>p120³⁰⁸</i>; <i>ubi-p120-GFP</i> flies before and after 1hr heat shock (one-way ANOVA with Bonferroni post test correction, ns: non-significant, * p<0.05; **p<0.005, ***p<0.001****p<0.0001). Note that the classic stress response gene <i>hsp22</i> was similarly up-regulated in all genotypes. Instead, genes previously associated with the IMD immune response such as AttC and DptB were up-regulated specifically in the mutants upon stress, and these together with other immune genes such as AttD and PGRP-LB were constitutively up-regulated in the mutations without stress challenge. (All error bars denote standard error of the mean).</p

Ubiquitous Expression of dp120ctn-GFP rescues <i>dp120ctn</i> mutants.

<p>(A-B) Survival of <i>w¹¹¹⁸</i>, <i>w¹¹¹⁸</i>; <i>p120³⁰⁸</i> and <i>w¹¹¹⁸</i>; <i>p120³⁰⁸</i>; <i>ubi-p120-GFP</i> males and females under heat shock conditions. Survival was plotted as adult survival in minutes under heat shock at 37°C. (C-F) Lifespan of <i>w¹¹¹⁸</i> and <i>w¹¹¹⁸</i>; <i>p120³⁰⁸</i> and <i>w¹¹¹⁸</i>; <i>p120³⁰⁸</i>; <i>ubi-p120-GFP</i> males and females at 25°C and 29°C. Survival was plotted as adult lifespan in days. Blue lines indicate <i>w¹¹¹⁸</i> controls, red lines <i>w¹¹¹⁸</i>; <i>p120³⁰⁸</i> and green lines <i>w¹¹¹⁸</i>; <i>p120³⁰⁸</i>; <i>ubi-p120ctn-GFP</i>. Each curve represents 100 flies. Median survival is presented for each cohort and <i>p</i> value generated using log-rank tests and refer to comparison between red lines (<i>w¹¹¹⁸</i>; <i>p120³⁰⁸</i>) and green lines (<i>w¹¹¹⁸</i>; <i>p120³⁰⁸</i>; <i>ubi-p120ctn-GFP</i>). </p

Non-autonomous crosstalk between the Jak/Stat and EGFR pathways mediates Apc1-driven intestinal stem cell hyperplasia in the Drosophila adult midgut

Inactivating mutations within adenomatous polyposis coli (APC), a negative regulator of Wnt signaling, are responsible for most sporadic and hereditary forms of colorectal cancer (CRC). Here, we use the adult Drosophila midgut as a model system to investigate the molecular events that mediate intestinal hyperplasia following loss of Apc in the intestine. Our results indicate that the conserved Wnt target Myc and its binding partner Max are required for the initiation and maintenance of intestinal stem cell (ISC) hyperproliferation following Apc1 loss. Importantly, we find that loss of Apc1 leads to the production of the interleukin-like ligands Upd2/3 and the EGF-like Spitz in a Myc-dependent manner. Loss of Apc1 or high Wg in ISCs results in non-cell-autonomous upregulation of upd3 in enterocytes and subsequent activation of Jak/Stat signaling in ISCs. Crucially, knocking down Jak/Stat or Spitz/EGFR signaling suppresses Apc1-dependent ISC hyperproliferation. In summary, our results uncover a novel non-cell-autonomous interplay between Wnt/Myc, EGFR and Jak/Stat signaling in the regulation of intestinal hyperproliferation. Furthermore, we present evidence suggesting potential conservation in mouse models and human CRC. Therefore, the Drosophila adult midgut proves to be a powerful genetic system to identify novel mediators of APC phenotypes in the intestine

Inducible progenitor-derived wingless regulates adult midgut regeneration in drosophila

The ability to regenerate following stress is a hallmark of self-renewing tissues. However, little is known about how regeneration differs from homeostatic tissue maintenance. Here, we study the role and regulation of Wingless (Wg)/Wnt signalling during intestinal regeneration using the Drosophila adult midgut. We show that Wg is produced by the intestinal epithelial compartment upon damage or stress and it is exclusively required for intestinal stem cell (ISC) proliferation during tissue regeneration. Reducing Wg or downstream signalling components from the intestinal epithelium blocked tissue regeneration. Importantly, we demonstrate that Wg from the undifferentiated progenitor cell, the enteroblast, is required for Myc-dependent ISC proliferation during regeneration. Similar to young regenerating tissues, ageing intestines required Wg and Myc for ISC hyperproliferation. Unexpectedly, our results demonstrate that epithelial but not mesenchymal Wg is essential for ISC proliferation in response to damage, while neither source of the ligand is solely responsible for ISC maintenance and tissue self-renewal in unchallenged tissues. Therefore, fine-tuning Wnt results in optimal balance between the ability to respond to stress without negatively affecting organismal viability