An inter-chromosomal transcription hub activates the unfolded protein response in plasma cells
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ABSTRACT:
ORGANISM(S): Mus musculus
PROVIDER: GSE113014 | GEO | 2019/04/10
REPOSITORIES: GEO
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Project description:Antibody-secreting plasma cells are the terminal stage of the B-cell lineage. Plasma cell differentiation requires a major resetting of gene expression to silence the B cell transcriptional program, whilst establishing secretory function and long-term survival. The transcription factors Blimp1 and Irf4 are essential for the initial differentiation of activated B cells to antibody-secreting cells, however their function in mature plasma cells remains elusive. We have found that while Irf4 was essential for plasma cell survival, Blimp1 was dispensable. Blimp1-deficient cells retained the unique plasma cell transcriptional signature, but lost the ability to secrete antibody or to maintain the characteristic size and ultrastructure of plasma cells. Blimp1 was required for full expression of many components of the unfolded protein response (UPR), including Xbp1 and Atf6, as well as for the appropriate processing of Igh mRNA. The overlap of Blimp1 and Xbp1 function was restricted to the UPR genes, with Blimp1 uniquely regulating activity of the mTOR pathway, plasma cell size and morphology. These studies establish Blimp1 as a major regulator of the UPR pathway that is also required for the unique metabolic requirements of plasma cells enabling the secretion of protective antibody. RNA-seq was performed on wild type, Blimp1-/- and Xbp1-/- mouse plasma cells. Between two to four biological replicates were generated and sequenced for each sample.
2016-01-18 | E-GEOD-70981 | biostudies-arrayexpress
Project description:Though it is known that plasma cells utilize the unfolded protein response to remodel their ER it is generally believed that this follows Blimp1-mediated transcriptional and translational increases in immunoglobulin protein. In this study we utilize Blimp1 reporter mice to examine the earliest activation of UPR-affiliated gene expression in plasma cell inductive stimulation of B cells. We combine in-vivo gene expression of follicular B cells, marginal zone B cells from spleen and short and long lived plasma cells from bone marrow with in-vivo generated activated B cells and plasma cells from the same mice to examine gene expression before and after Blimp1-upregulation. Using a novel in-vitro stimulation approach we separate those UPR-affiliated genes activated by B cell activation and those requiring a plasma cell inductive stimulus. We report here that these plasma cell specific UPR-affiliated genes are activated in absence of ER-stress prior to upregulation of Blimp1.
2019-12-05 | GSE141419 | GEO
Project description:Antibody-secreting plasma cells are the terminal stage of the B-cell lineage. Plasma cell differentiation requires a major resetting of gene expression to silence the B cell transcriptional program, whilst establishing secretory function and long-term survival. The transcription factors Blimp1 and Irf4 are essential for the initial differentiation of activated B cells to antibody-secreting cells, however their function in mature plasma cells remains elusive. We have found that while Irf4 was essential for plasma cell survival, Blimp1 was dispensable. Blimp1-deficient cells retained the unique plasma cell transcriptional signature, but lost the ability to secrete antibody or to maintain the characteristic size and ultrastructure of plasma cells. Blimp1 was required for full expression of many components of the unfolded protein response (UPR), including Xbp1 and Atf6, as well as for the appropriate processing of Igh mRNA. The overlap of Blimp1 and Xbp1 function was restricted to the UPR genes, with Blimp1 uniquely regulating activity of the mTOR pathway, plasma cell size and morphology. These studies establish Blimp1 as a major regulator of the UPR pathway that is also required for the unique metabolic requirements of plasma cells enabling the secretion of protective antibody.
2016-01-18 | GSE70981 | GEO
Project description:During plasma cell differentiation there is activation of UPR gene expression that has been termed the physiological UPR of plasma cell differentiation. This is canonically thought to be downstream of Blimp1-mediated increases in immunoglobulin gene production and activation of the Xbp1 transcription factor by the RNA splicing activity of the ER-stress sensor IRE1α. Having observed UPR-affiliated gene expression prior to upregulation of Blimp1 as reported in the companion linked series, we endeavored to determine the necessity of Xbp1 activity in the early remodeling of the ER in nascent plasma cells. To this end, we mated mice harboring a floxed exon 2 of the Xbp1 gene (Xbp1flox) to mice expressing a tamoxifen-inducible cre recombinase under the control of the human CD20 promoter (hCD20-TamCre). These mice and their hCD20-TamCre-Xbp1wt litermates were fed oral tamoxifen in their diet for two weeks and follicular B cells were prepared for in-vitro plasma cell differentiation studies. We report here that prior to plasma cell differentiation as measured by CD138 expression, which coincides temporally with Blimp1 expression, there is no defect in UPR-affiliated gene expression in cells lacking Xbp1.
2019-12-05 | GSE141422 | GEO
Project description:Early UPR-affiliated gene expression occurs before Blimp1 upregulation and independent of canonical ER-stress activated Xbp1. In linked companion studies we detailed how Xbp1-independent activation of early plasma cell specific UPR-affiliated gene expression occurs prior to Blimp1 upregulation. Having observed that these genes overlapped with canonical mTORC1 signature genes and that PC-poised marginal zone B cells have higher base line mTORC1 signaling we designed this experiment to assess the dependence of early ER-remodeling on mTORC1 signaling in plasma cell differentiation. To this end we mated mice harboring a floxed allele for the mTORC1 adapter Raptor (B6.Rptor-flox) to mice expressing a tamoxifen-inducible cre recombinase under the control of the human CD20 promoter (B6.hCD20-TamCre). These mice and their hCD20-TamCre-Rptor-wt litermates were fed oral tamoxifen in their diet for two weeks and follicular B cells were prepared for in-vitro plasma cell differentiation studies. We report here that as early as 24 hours of stimulation in culture we see a marked defect in the ability of Rptor null B cells to upregulate UPR-affiliated genes associated with plasma cell differentiation.
2019-12-05 | GSE141421 | GEO
Project description:Little is known about the earliest transcriptomic events in plasma cell differentiation. Indeed, activation of UPR-affiliated gene expression is seen in in-vitro plasma cell differentiation prior to Blimp1 upregulation and in the absence of Xbp1 as we show in linked companion series. In this study, Blimp1 reporter mice were immunized with the T-independent antigen NP-LPS four days prior to spleen harvest and naïve B cells, NP-binding activated B cells and NP-binding plasma cells were analyzed by bulk RNA-seq. Here we report the activation of ER remodeling gene expression in antigen-specific activated B cells in-vivo prior to upregulation of Blimp1 transcription.
2019-12-05 | GSE141420 | GEO
Project description:Homeostatic control mechanisms are essentil to life. One such mechanism, the unfolded protein response (UPR) operates in all eukarytic cells to adjust protein folding capacity of the endoplasmic reticulum (ER) according to need. UPR induction in all eurkarytic cells to date involves Ire1 (kinase/endonuclease transmembrane protein) mediated a non-convential splicing of Hac1/XBP1 mRNA, encoding for a potent transcription factor. UPR induction causes a comprehensive transcriptional upregulation of the folding capacity in the ER. Here we studied the global transcriptional profile of the UPR in fission yeast. Fission yeast lacks a clear homolog of Hac1/XBP1. Instead Ire1 maintains ER homeostasis through two post-transciptional programs: selective mRNA decay and processing of Bip1 mRNA (encoding for a major HS70-familiy member in the ER) thereby stabilizing it.
2012-11-21 | GSE40298 | GEO
Project description:The unfolded protein response (UPR) couples cellular translation rates and gene expression to the protein folding status of the endoplasmic reticulum (ER). Upon activation, the UPR machinery elicits a general suppression of protein synthesis and activation of stress gene expression, which act coordinately to restore protein folding homeostasis. We report here that UPR activation promotes the release of signal sequence-encoding mRNAs from the ER to the cytosol as a mechanism to decrease protein influx into the ER. This release of mRNA begins rapidly, then gradually recovers with ongoing stress. Upon release into the cytosol, these mRNAs have divergent fates: some synthesize full-length proteins, while others are translationally inactive and retain nascent protein chains. Together, these findings identify the dynamic subcellular localization of mRNAs and translation as a regulatory feature of the cellular response to protein folding stress. Cells were treated with a timecourse of Thapsigargin or DTT, then fractionated and analyzed by mRNA-seq or ribosome profiling
2014-08-28 | E-GEOD-53743 | biostudies-arrayexpress
Project description:The ARV1-encoded protein mediates sterol transport from the endoplasmic reticulum (ER) to the plasma membrane. Yeast ARV1 mutants accumulate multiple lipids in the ER and are sensitive to pharmacological modulators of both sterol and sphingolipid metabolism. Using fluorescent and electron microscopy, we demonstrate sterol accumulation, subcellular membrane expansion, elevated lipid droplet formation and vacuolar fragmentation in ARV1 mutants. Motif-based regression analysis of ARV1 deletion transcription profiles indicates activation of Hac1p, an integral component of the UPR. Accordingly, we show constitutive splicing of HAC1 transcripts, induction of a UPR reporter and elevated expression of UPR targets in ARV1 mutants. IRE1, encoding the unfolded protein sensor in the ER lumen, exhibits a lethal genetic interaction with ARV1, indicating a viability requirement for the UPR in cells lacking ARV1. Surprisingly, ARV1 mutants expressing a variant of Ire1p defective in sensing unfolded proteins are viable. Moreover these strains also exhibit constitutive HAC1 splicing that interacts with DTT-mediated perturbation of protein folding. These data suggest a component of UPR induction in arv1? strains is distinct from protein misfolding. Decreased ARV1 expression in murine macrophages also results in UPR induction, particularly up-regulation of activating transcription factor-4, C/EBP homologous protein (CHOP) and apoptosis. Cholesterol loading or inhibition of cholesterol esterification further elevated CHOP expression in ARV1 knockdown cells. Thus, loss or down-regulation of ARV1 disturbs membrane and lipid homeostasis resulting in a disruption of ER integrity, one consequence of which is induction of the UPR. Yeast strains were grown to mid-logarithmic stage (A600=0.5-0.6) for RNA extraction and hybridization on Ye6100 or S98 Affymetrix gene chips. The control array (sample name C) was carried out in duplicate. The ARV1 mutant array (sample name A) was carried out in triplicate. Both ARV1 mutants Ye6100 arrays were compared to the same control Ye6100 array. Strains represent different isolates of the same genotype, mating type and genetic background (w303). Sturley lab collection (SCY) strains include SCY328 and SCY2004 for controls and SCY820 and SCY840 for ARV1 mutants.
2011-02-17 | E-GEOD-26801 | biostudies-arrayexpress
Project description:The ARV1-encoded protein mediates sterol transport from the endoplasmic reticulum (ER) to the plasma membrane. Yeast ARV1 mutants accumulate multiple lipids in the ER and are sensitive to pharmacological modulators of both sterol and sphingolipid metabolism. Using fluorescent and electron microscopy, we demonstrate sterol accumulation, subcellular membrane expansion, elevated lipid droplet formation and vacuolar fragmentation in ARV1 mutants. Motif-based regression analysis of ARV1 deletion transcription profiles indicates activation of Hac1p, an integral component of the UPR. Accordingly, we show constitutive splicing of HAC1 transcripts, induction of a UPR reporter and elevated expression of UPR targets in ARV1 mutants. IRE1, encoding the unfolded protein sensor in the ER lumen, exhibits a lethal genetic interaction with ARV1, indicating a viability requirement for the UPR in cells lacking ARV1. Surprisingly, ARV1 mutants expressing a variant of Ire1p defective in sensing unfolded proteins are viable. Moreover these strains also exhibit constitutive HAC1 splicing that interacts with DTT-mediated perturbation of protein folding. These data suggest a component of UPR induction in arv1? strains is distinct from protein misfolding. Decreased ARV1 expression in murine macrophages also results in UPR induction, particularly up-regulation of activating transcription factor-4, C/EBP homologous protein (CHOP) and apoptosis. Cholesterol loading or inhibition of cholesterol esterification further elevated CHOP expression in ARV1 knockdown cells. Thus, loss or down-regulation of ARV1 disturbs membrane and lipid homeostasis resulting in a disruption of ER integrity, one consequence of which is induction of the UPR.
2011-02-17 | GSE26801 | GEO