Project description:Immunoglobulin A (IgA) is the major secretory immunoglobulin isotype at mucosal surfaces where it regulates microbial commensalism and excludes luminal factors from contacting intestinal epithelial cells (IEC). IEC endoplasmic reticulum (ER) stress induces a polyreactive IgA response which protects from small intestinal inflammation. IEC ER stress causes expansion and activation of peritoneal B1b cells independent of microbiota and T cells that culminates in increased lamina propria and luminal IgA. Xbp1dIEC mice exhibit IEC ER stress by conditional deletion of X-box-binding protein 1 (XBP1). Here we examine single-cell transcriptomes of peritoneal cavity cells of germ-free Xbp1dIEC mice (KO) compared to littermate controls (WT).
Project description:Immunoglobulin A (IgA) is the major secretory immunoglobulin isotype at mucosal surfaces where it regulates microbial commensalism and excludes luminal factors from contacting intestinal epithelial cells (IEC). IEC endoplasmic reticulum (ER) stress induces a polyreactive IgA response which protects from small intestinal inflammation. IEC ER stress causes expansion and activation of peritoneal B1b cells independent of microbiota and T cells that culminates in increased lamina propria and luminal IgA. Xbp1dIEC mice exhibit IEC ER stress by conditional deletion of X-box-binding protein 1 (XBP1). Here we examine differentially expressed genes in peritoneal B1b cells of germ-free Xbp1dIEC mice compared to littermate (WT) controls.
Project description:Immunoglobulin A (IgA) is the major secretory immunoglobulin isotype found at mucosal surfaces, where it regulates microbial commensalism and excludes luminal factors from contacting intestinal epithelial cells (IECs). IgA is induced by both T cell-dependent and -independent (TI) pathways. However, little is known about TI regulation. We report that IEC endoplasmic reticulum (ER) stress induces a polyreactive IgA response, which is protective against enteric inflammation. IEC ER stress causes TI and microbiota-independent expansion and activation of peritoneal B1b cells, which culminates in increased lamina propria and luminal IgA. Increased numbers of IgA-producing plasma cells were observed in healthy humans with defective autophagy, who are known to exhibit IEC ER stress. Upon ER stress, IECs communicate signals to the peritoneum that induce a barrier-protective TI IgA response.
Project description:In eukaryotic cells, the spatial regulation of protein expression is frequently conferred through the coupling of mRNA localization and the local control of translation. mRNA localization to the endoplasmic reticulum (ER) is a prominent example of such regulation and serves a ubiquitous role in segregating the synthesis of secretory and integral membrane proteins to the ER. Recent genomic and biochemical studies have now expanded this view to suggest a role for the ER in global protein synthesis. We have utilized cell fractionation and ribosome profiling to obtain a genomic survey of the subcellular organization of mRNA translation and report that ribosomal loading of mRNAs, a proxy for mRNA translation, is biased to the ER. Notably, ER-associated mRNAs encoding both cytosolic and topogenic signal-encoding proteins display similar ribosome loading densities, suggesting that ER-associated ribosomes serve a global role in mRNA translation. We propose that the partitioning of mRNAs and their translation between the cytosol and ER compartments may represent a novel mechanism for the post-transcriptional regulation of gene expression. HEK293 cells were fractionated between the cytosol and endoplasmic reticulum. Within each fraction, ribosome footprints were generated and sequenced. In parallel, total mRNA was sequenced.
Project description:Tunicamycin-induced Endoplasmic Reticulum-Quality Control Pathway and Endoplasmic Reticulum-Associated Degradation Mechanism in the diatom Phaeodactylum tricornutum
Project description:In eukaryotes, up to one-third of cellular proteins are targeted to the endoplasmic reticulum, where they undergo folding, processing, sorting and trafficking to subsequent endomembrane compartments. Targeting to the endoplasmic reticulum has been shown to occur co-translationally by the signal recognition particle (SRP) pathway or post-translationally by the mammalian transmembrane recognition complex of 40 kDa (TRC40) and homologous yeast guided entry of tail-anchored proteins (GET) pathways. Despite the range of proteins that can be catered for by these two pathways, many proteins are still known to be independent of both SRP and GET, so there seems to be a critical need for an additional dedicated pathway for endoplasmic reticulum relay. We set out to uncover additional targeting proteins using unbiased high-content screening approaches. To this end, we performed a systematic visual screen using the yeast Saccharomyces cerevisiae, and uncovered three uncharacterized proteins whose loss affected targeting. We suggest that these proteins work together and demonstrate that they function in parallel with SRP and GET to target a broad range of substrates to the endoplasmic reticulum. The three proteins, which we name Snd1, Snd2 and Snd3 (for SRP-independent targeting), can synthetically compensate for the loss of both the SRP and GET pathways, and act as a backup targeting system. This explains why it has previously been difficult to demonstrate complete loss of targeting for some substrates. Our discovery thus puts in place an essential piece of the endoplasmic reticulum targeting puzzle, highlighting how the targeting apparatus of the eukaryotic cell is robust, interlinked and flexible.
Project description:We obtained transcriptional profiles of third instar eye imaginal disc nuclei with or without endoplasmic reticulum stress using next generation sequencing (NGS). We employed an isolation of nuclei tagged in specific cell type (INTACT) protocol (Ma and Weake, J. of Vis. Exp., 2014) to label nuclear membranes of GMR-GAL4-expressing cells with EGFP. The experimental group also expressed a mutant allele of the membrane visual protein rhodopsin (Rh-1(G69D)), which is known to cause endoplasmic reticulum stress and initiate Unfolded Protein Response (UPR) signaling. The goal of this study was to characterize the transcriptional changes associated with endoplasmic reticulum stress responses in a commonly used platform, the eye imaginal disc.
Project description:Mutations in the p53 tumor suppressor gene are the most frequent genetic alteration in cancer and often associated with progression from benign to invasive, metastatic stages. Mutations inactivate tumor suppression by p53 and endow the protein with novel gain-of-function (GOF) activities that actively promote tumor progression, metastasis and therapy resistance. By comparative gene expression profiling of p53-mutated and p53-depleted cancer cells we identified ectonucleoside triphosphate diphosphohydrolase 5 (ENTPD5) as a mutant p53 (mutp53) target gene. A comprehensive pan-cancer analysis revealed a highly significant correlation between GOF p53 mutations and elevated expression of ENTPD5. Mechanistically, regulation of ENTPD5 by mutp53 is mediated by the histone H3 lysine 4 (H3K4) methyltransferase COMPASS complex. ENTPD5 has been shown to function in the endoplasmic reticulum as a UDPase to promote the N-glycosylation and folding of membrane proteins such as growth factor receptors and integrins. We show ENTPD5 to be a mediator of mutp53 GOF activity in clonogenic growth, architectural tissue remodeling, migration, invasion, and lung colonization in an experimental metastasis mouse model. Our study reveals N-glycosylation in the endoplasmic reticulum as a novel mechanism underlying the progression of tumors with mutp53 that could provide new possibilities for treating cancers driven by GOF p53 mutations.