Dataset Information

Sec62 regulates ER-phagy during recovery from ER stress

ABSTRACT: Perturbing ER homeostasis activates stress programs collectively called the unfolded protein response (UPR). The UPR enhances production of ER-resident chaperones and enzymes to reduce the burden of misfolded proteins. Upon resolution of ER stress, excess ER material is removed by ill-defined, selective autophagic programs. Here, using biochemical and cell-based essays, we identify a novel ER-resident autophagy receptor, Sec62, which is activated during recovery from ER stress to selectively deliver ER fragments to the autolysosomal system for clearance. Quantitative mass spectrometry analyses of autolysosomal fractions upon selective inactivation of the Sec62-regulated pathway inform on the selectivity of Sec62-regulated ER-phagy.

INSTRUMENT(S): Q Exactive

ORGANISM(S): Homo Sapiens (human)

TISSUE(S): Permanent Cell Line Cell, Cell Culture

SUBMITTER: Manfredo Quadroni

LAB HEAD: Maurizio Molinari

PROVIDER: PXD003961 | Pride | 2016-10-11

REPOSITORIES: Pride

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			Action	DRS
	20151127_Molinari_7926B.raw	Raw
	20151127_Molinari_7926C.raw	Raw
	20151127_Molinari_7926D.raw	Raw
	20151127_Molinari_7926E.raw	Raw
	20151127_Molinari_7926F.raw	Raw

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Publications

Translocon component Sec62 acts in endoplasmic reticulum turnover during stress recovery.

Fumagalli Fiorenza F Noack Julia J Bergmann Timothy J TJ Cebollero Eduardo E Pisoni Giorgia Brambilla GB Fasana Elisa E Fregno Ilaria I Galli Carmela C Loi Marisa M Soldà Tatiana T D'Antuono Rocco R Raimondi Andrea A Jung Martin M Melnyk Armin A Schorr Stefan S Schreiber Anne A Simonelli Luca L Varani Luca L Wilson-Zbinden Caroline C Zerbe Oliver O Hofmann Kay K Peter Matthias M Quadroni Manfredo M Zimmermann Richard R Molinari Maurizio M

Nature cell biology 20161017 11

The endoplasmic reticulum (ER) is a site of protein biogenesis in eukaryotic cells. Perturbing ER homeostasis activates stress programs collectively called the unfolded protein response (UPR). The UPR enhances production of ER-resident chaperones and enzymes to reduce the burden of misfolded proteins. On resolution of ER stress, ill-defined, selective autophagic programs remove excess ER components. Here we identify Sec62, a constituent of the translocon complex regulating protein import in the ...[more]

PMID: 27749824

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Project description:The unfolded protein response (UPR) maintains endoplasmic reticulum (ER) proteostasis through the activation of transcription factors such as XBP1s and ATF6. The functional consequences of these transcription factors for ER proteostasis remain poorly defined. Here, we describe methodology that enables orthogonal, small molecule-mediated activation of the UPR-associated transcription factors XBP1s and/or ATF6 in the same cell independent of stress. We employ transcriptomics and quantitative proteomics to evaluate ER proteostasis network remodeling owing to the XBP1s and/or ATF6 transcriptional programs. Furthermore, we demonstrate that the three ER proteostasis environments accessible by activating XBP1s and/or ATF6 differentially influence the folding, trafficking, and degradation of destabilized ER client proteins without globally affecting the endogenous proteome. Our data reveal how the ER proteostasis network is remodeled by the XBP1s and/or ATF6 transcriptional programs at the molecular level and demonstrate the potential for selectively restoring aberrant ER proteostasis of pathologic, destabilized proteins through arm-selective UPR-activation. The unfolded protein response adapts endoplasmic reticulum (ER) proteostasis via stress-responsive transcription factors including XBP1s and ATF6. Here, R. Luke Wiseman and colleagues implement technology for the orthogonal, ligand-dependent activation of XBP1s and/or ATF6 in a single cell. They characterize how XBP1s and/or ATF6 activation impacts ER proteostasis pathway composition and function. Adapted ER environments influence the proteostasis of destabilized protein variants without affecting the endogenous proteome. The work informs the development of proteostasis environment-adapting therapeutics for protein misfolding-related diseases. In order to activate both XBP1s and ATF6 in the same cell, we incorporated DHFR.ATF6 and tet-inducible XBP1s into a HEK293T-REx cell line stably expressing the tet-repressor. The HEK293DYG control cell line expresses tet-inducible eGFP and DHFR.YFP and is used as a control to demonstrate that the addition of doxycycline (dox) and trimethoprim (TMP) do not induce UPR genes. HEK293DYG cells were treated for 12 h with vehicle or 1 μg/mL dox and 10 μM TMP in biological triplicate. Cells were harvested and RNA was extracted using the RNeasy Mini Kit (Qiagen). Genomic DNA was removed by on-column digestion using the RNase-free DNase Set (Qiagen). Data from HEK293DYG cells showed no significant overlap in the ligand-treated transcriptomes obtained from HEK293DAX cells.

Project description:Bronchopulmonary dysplasia (BPD), a chronic lung disease of prematurity, has been linked to endoplasmic reticulum (ER) stress. To investigate a causal role for ER stress in BPD pathogenesis, we generated mice (cGrp78f/f) with lung epithelial cell-specific knockout (KO) of Grp78, a gene encoding the ER chaperone 78-kDa glucose-regulated protein (GRP78), a master regulator of ER homeostasis and the unfolded protein response (UPR). Lung epithelial-specific Grp78 KO disrupted lung morphogenesis, causing developmental arrest, increased alveolar epithelial type II cell apoptosis and decreased surfactant protein and type I cell marker expression in perinatal lungs. cGrp78f/f pups died immediately after birth, likely due to respiratory distress. Importantly, Grp78 KO triggered UPR activation with marked induction of pro-apoptotic transcription factor C/EBP homologous protein (CHOP). Increased expression of genes involved in oxidative stress and cell death and decreased expression of genes encoding antioxidant enzymes suggest a role for oxidative stress in alveolar epithelial cell (AEC) apoptosis. Increased Smad3 phosphorylation and expression of transforming growth factor-Î² (TGF-Î²)/Smad3 targets Cdkn1a (encoding p21) and Gadd45a suggest that interactions among the apoptotic arm of the UPR, oxidative stress and TGF-Î²/Smad signaling pathways contribute to Grp78 KO-induced AEC apoptosis and developmental arrest. Chemical chaperone taursodeoxycholic acid reduced UPR activation and apoptosis in cGrp78f/f lungs cultured ex vivo, confirming a role for ER stress in observed AEC abnormalities. These results demonstrate a key role for GRP78 in AEC survival and gene expression during lung development through modulation of ER stress and suggest the UPR as a potential therapeutic target in BPD. Whole-genome expression profiling was performed using MouseRef-8 v2.0 Expression BeadChips (Illumina) on RNA isolated from lungs of four Grp78f/f and three cGrp78f/f mice at E18.