EMBO/soda-nel huggingface dataset:
Prdx4 limits caspase-1 activation and restricts inflammasome-mediated signaling by extracellular vesicles (2019)
Figure 4

Figure 4. Prdx4 interacts with C397 of caspase-1 to block its function.

A Western blot analysis of rPRDX4, rCASP-1 and co-incubated rPRDX4 and rCASP-1 after non-reducing SDS-PAGE. Black arrows at 250 kDa indicate the corresponding molecular weights of rCASP-1 and rPRDX4 oligomers and decrease of the Prdx4 band intensity upon co-incubation with rCASP-1. Black arrow at approx. 50 kDa indicates the appearance of an additional rPRDX4 band which corresponds to the molecular weight of a Prdx4 dimer.

B Western blot analysis of rPRDX4 (=P) and rCASP-1 (=C) after alkylation (=A) and non-reducing SDS-PAGE. Black arrows indicate the termination of the integration of rCASP-1 into the rPRDX4 decamer/HMWC upon alkylation.

C Rate of caspase-1 activity in the presence of non-reduced decameric rPrdx4, reduced dimeric and monomeric rPRDX4, YVAD or control.

D Foldchange in IL-1β concentration in supernatants of HEK293 cells transfected with plasmids for NLRP3, ASC, IL-1β and caspase-1 WT or Cys-to-Ser mutants C362S or C397S and co-transfected with Prdx4 or control. Cells were stimulated with 2.5 mM ATP for 30 min before analysis.

E Western blot analysis of non-reducing SDS-PAGE of cell lysates from HEK293 cells transfected with caspase-1 WT, C362S, C397S, or C362S plus C397S mutants and co-transfected with Prdx4-GFP or GFP as control.

F Western blot analysis of co-immunoprecipitation using HA-magnetic beads from cell lysates of HEK293 cells transfected with HA-tagged caspase-1 WT, C362S, C397S, or C362S plus C397S mutants and co-transfected with Prdx4-GFP or GFP as control.

G IL-1β concentration in supernatants of HEK293 cells transfected with plasmids for NLRP3, ASC, IL-1β and caspase-1 and co-transfected with Prdx4 WT or Cys-to-Ala mutants C51A, C124A, C245A or DM C124A/C245A or control. Cells were stimulated with 2.5 mM ATP for 30 min before analysis.

H Western blot analysis of co-immunoprecipitation using HA-magnetic beads from cell lysates of HEK293 cells transfected with HA-tagged caspase-1 WT or control and co-transfected with Prdx4 WT or Cys-to-Ala mutants C51A, C124A, C245A or DM C124A/C245A.

Data information: Data are representative of two (B, E, F) or three (A, C, D, G, H) independent experiments. Each bar represents a mean of triplicate wells, error bars indicate SD. *, p < 0.05; **, p < 0.01; n.s. not significant (two-tailed t-test).
Prdx4 limits caspase-1 activation and restricts inflammasome-mediated signaling by extracellular vesicles (2019)
Figure 5

Figure 5: Prdx4 is secreted upon activation of the NLRP3 inflammasome and co-localizes with caspase-1 in MVBs

A Western blot analysis of Prdx4, pro-caspase‑1, Gapdh and E-Cadherin from the cytosolic and insoluble cell fraction of LPS and/or ATP-stimulated BMDMs or untreated controls.

B Prdx4 concentration in supernatants of Prdx4 WT or KO BMDMs, primed for 6 h with LPS and pulsed for indicated time points with 5 mM ATP. Each circle represents a mean of n=3 mice, vertical lines indicate SD. **, p < 0.01; n.s. not significant (two-tailed t-test).

C Concentration of Prdx4 in the serum of WT mice, injected with LPS (4.5 mg/kg BW) for the time points indicated. Each dot represents an individual mouse. Horizontal lines indicate mean. *, p < 0.05; **, p < 0.01; ***, p < 0.001; n.s. not significant (two-tailed t-test).

D Concentration of Prdx4 in supernatants of Prdx4 WT and KO BMDMs. Cells were primed with LPS (100 ng/ml) for 6 h, followed by pretreatment with 20 µM YVAD or DMSO as control for 30 min and stimulated with 5 mM ATP for 4 h or no further stimulation. Each bar represents a mean of n=3 mice, vertical lines indicate SD. **, p < 0.01; n.s. not significant (two-tailed t-test).

E Schematic illustration of selected mechanisms that were targeted by either Glycine, Necrosulfonamide (NSA) or GW4869 to study LPS+ATP-induced Prdx4 secretion.

F Relative levels of Prdx4 secretion in response to LPS+ATP stimulation and pretreatment with either Glycine, NSA or GW4869 and relative levels of caspase-1 secretion in response to LPS+ATP stimulation and pretreatment with in response to LPS+ATP stimulation and pretreatment with GW4869. Each bar represents a mean of n=3 biological with 2 technical replicates, vertical lines indicate SD. *, p < 0.05; **, p < 0.01; n.s. not significant (two-tailed t-test).

G Western blot analysis of subcellular organelle fractions. OptiPrep density gradient ultracentrifugation was used to fractionate subcellular organelles from Prdx4 WT BMDMs that were primed with LPS (100 ng/ml) for 12 h and stimulated with 5 mM ATP for 4 h.

Data information: Data are representative of two (A, B, D, E) or three (G) independent experiments.
Prdx4 limits caspase-1 activation and restricts inflammasome-mediated signaling by extracellular vesicles (2019)
Figure 6

Figure 6: ATP-induced NLRP3 inflammasome activation leads to secretion of distinct EVs from BMDMs.

A Schematic illustration of workflow for EV isolation and characterization (panels B-G) from BMDMs that were left untreated or LPS-primed in the presence or absence of either ATP, Nigericin, poly(dA:dT) or Flagellin.

B BCA analysis of EV protein concentration in EVs isolates. Each bar represents a mean of n=3 technical replicates, vertical lines indicate SD. *, p < 0.05; **, p < 0.01; ***, p < 0.001; n.s. not significant (two-tailed t-test).

C Exocet quantification assay of EVs particle numbers. Each bar represents a mean of n=3 technical replicates, vertical lines indicate SD. *, p < 0.05; ***, p < 0.001; n.s. not significant (two-tailed t-test).

D Transmission electron microscopy (TEM) of EV isolates. Three representative pictures are displayed. Scale bar indicates 200 nm.

E Analysis of size distribution of EVs. Each dot indicates the diameter in nm of an individual vesicle. SD. ***, p < 0.001; n.s. not significant (one-way ANOVA, followed by a Tukey multiple comparison test).

F Prdx4 concentration in EV lysates. Each bar represents a mean of n= 2 technical replicates, vertical lines indicate SD. **, p < 0.01; ***, p < 0.001; n.s. not significant (two-tailed t-test).

G Caspase-1 and IL-1β concentration in EV lysates. Each bar represents a mean of n= 2 technical replicates, vertical lines indicate SD. **, p < 0.01; ***, p < 0.001; n.s. not significant (two-tailed t-test).

Data information: Data are representative of two (D,E) or three (B,C,F,G) independent experiments.
Prdx4 limits caspase-1 activation and restricts inflammasome-mediated signaling by extracellular vesicles (2019)
Figure 7

Figure 7: Prdx4 controls caspase-1 cleavage and IL-1β maturation in extracellular vesicles.

A Western blot analysis of Prdx4, NLRP3, ASC, caspase‑1, IL-1β and CD63 from EV lysates (upper panel) or caspase-1 after immunoprecipitation against caspase-1 (lower panel).

B EVs isolated from donor BMDMs were transferred to recipient cells or mice followed by subsequent readout of inflammatory response markers.

C Cxcl1 concentration in supernatants of caspase-1-deficient BMDMs stimulated with EVs from LPS, LPS and ATP or control-treated Prdx4 WT or KO BMDMs, as well as caspase-1-deficient BMDMs pre-treated with Anakinra and stimulated with EVs from LPS and ATP-treated Prdx4 WT or KO BMDMs. Each bar represents a mean of n=3 biological with 2 technical replicates, vertical lines indicate SD. *, p < 0.05; **, p < 0.01; n.s. not significant (two-tailed t-test).

D Serum Cxcl1 in C57Bl6/N mice injected with either PBS or EVs from LPS and ATP or control-treated Prdx4 WT or KO or ASC KO BMDMs. Each dot represents an individual mouse. Horizontal lines indicate mean.

Data information: Data are representative of two (C, D) or three (A) independent experiments.

Expanded View:
Peroxisome degradation by microautophagy in Pichia pastoris: identification of specific steps and morphological intermediates. (1998)
Figure 7

Microautophagic degradation of peroxisomes is not observed in a vacuolar protease-negative strain (STK7) of P. pastoris. Kinetics of morphological changes in vacuoles and peroxisomal GFP-SKL during (a) glucose adaptation and (b) ethanol adaptation. (c) Fluorescence images taken after 2 h of glucose adaptation. Arrows show GFP-SKL in vacuolar matrix. Some cells showed diffusion of GFP-SKL into the vacuolar matrix.
Peroxisome degradation by microautophagy in Pichia pastoris: identification of specific steps and morphological intermediates. (1998)
Figure 8

(a) Visualization of alcohol oxidase activity in colonies after (a) glucose adaptation for 8 h and ethanol adaptation for 24 h in wild-type (strain PPY12) and pag mutant cells (strains STK1-STK6, Materials and Methods) of P. pastoris. (b) Western-blot analysis of samples taken from cultures shifted from methanol to glucose for the indicated time. Antibodies used were AOX, alcohol oxidase; F1, mitochondrial F1β subunit; G6PDH, glucose-6-phosphate dehydrogenase. Growth curve of the wild-type strain PPY12 and the pag4 mutant (strain STK4) after shift from methanol to glucose.
Peroxisome degradation by microautophagy in Pichia pastoris: identification of specific steps and morphological intermediates. (1998)
Figure 9

Fluorescence images of (a) pag2 (strain STK2) and (b) pag3 (strain STK3) mutants of P. pastoris after a 3 h shift to glucose. (b) Arrows show deeply invaginated structures of vacuolar membranes surrounding peroxisomes in the pag3 mutant.
Peroxisome degradation by microautophagy in Pichia pastoris: identification of specific steps and morphological intermediates. (1998)
Figure 11

Microautophagy of peroxisomes in a pex1-ts mutant (strain SJH242) of P. pastoris expressing GFP-SKL from the constitutive glyceraldehyde-3-phosphate dehydrogenase (GAPDH) promoter at the restrictive temperature for peroxisome assembly (34°C). (a) Kinetics of peroxisome degradation at 34°C. Strain SJH242 was induced on methanol at 23°C, and glucose adaptation was performed at 34°C. (b) Changes in vacuole morphology were seen even in the absence of normal peroxisomes. At 0 h, SJH242 cells were grown at 34°C when GFP-SKL was diffuse in the cytosol and many vacuoles showed spherical morphologies. After 2 h, ∼20–30% vacuoles showed complicated membrane structures representative of stage 2 cells.
The unique histidine in OSCP subunit of F-ATP synthase mediates inhibition of the permeability transition pore by acidic pH (2017)
Figure 1

Figure 1. Effect of acidic pH and DPC on the interactions of CyPD with F-ATP synthase at OSCP and carbethoxylation of OSCP H112.

Bovine heart mitochondria were incubated at the indicated pH in absence or presence of 200 μM DPC, treated with 1% (w/v) digitonin and F-ATP synthase was immunoprecipitated with an anti-F-ATP synthase Ab followed by 15% SDS-PAGE. β subunit and CyPD content were detected by Western blotting. The ratio between CyPD and the corresponding β subunit is reported in the lower part of the panel, referring to pH 7.4 values as 100%. Data are an average ± s.e. of 3 independent experiments.

B,C EDTA-SMP were solubilized at the indicated pH values, extracted with 1% (w/v) digitonin and subjected to BN-PAGE in order to separate dimers (Vd) and monomers (Vm), which were identified by Coomassie blue (panel B) or in-gel activity staining (panel C) and analyzed by densitometry, which is reported in the bottom part of each panel. Values report the dimer/monomer ratio, where the ratio at pH 7.4 was taken as 100%. Data are an average ± s.e. of 3 independent experiments. The p-values calculated with the Student t test are shown * p≤0.05 *** p≤0.001.

D Sequence of peptides 95-113 of OSCP before (left panel) and after reaction with DPC (right panel) obtained from tryptic digests of the SDS-PAGE band corresponding to the expected molecular mass of OSCP in immunoprecipitated F-ATP synthase. Fragments of the series b and y identified in the LC-MS/MS analysis are indicated on the sequence of the peptides. H112 and H112CeT are indicated in red boldface. Ions y4-y17 show a mass shift of +72 Da in the modified peptide.
The unique histidine in OSCP subunit of F-ATP synthase mediates inhibition of the permeability transition pore by acidic pH (2017)
Figure 2

Figure 2. The PTP cannot be inhibited by acidic pH in cells with OSCP H112Q and H112Y replacements.

Permeabilized HEK293T cells expressing wild type (WT) or edited (H112Q or H112Y) OSCP subunit were suspended in KSCN-based media at pH 7.4 (left traces) or pH 6.5 (right traces) and PTP opening was measured as the decrease in absorbance at 540 nm. Where indicated (arrows) 0.1 mM Ca2+ in the absence of further additions (black traces) or in the presence of 0.5 mM DPC (red traces) or 2 µM CsA (blue traces) was added. The bottom panel reports the difference between the absorbance readings before the addition of Ca2+ and at the end of the swelling phase. Data are mean ± s.e. of 5 experiments (triplicate samples) for Ca2+ alone (black bars) and Ca2+ + DPC (red bars) and of 3 experiments (duplicate samples) for Ca2+ + CsA (blue bars). Solid bars, pH 7.4, hatched bars, pH 6.5.

Mitochondria were prepared from cells, suspended in sucrose buffer at pH 7.4 (solid bars) or 6.5 (hatched bars) in the absence (black bars) or presence (blue bars) of 1.6 µM CsA, extracted with 1% (w/v) digitonin and immunoprecipitated with an F-ATP synthase antibody. The immunoprecipitates were subjected to 12% SDS-PAGE followed by Western blotting for CyPD and α subunit of F-ATP synthase. Each immunodetected band was analyzed by densitometry, the ratio between CyPD and α subunit was measured and expressed relative to the ratio obtained in absence of CsA at pH 7.4, which was taken as 100%. Data are average ± s.e. of 6 independent experiments.

HEK293T cells were incubated in a balanced salt solution containing 2-deoxyglucose at pH 7.4 (solid bars) or 6.5 (hatched bars) and anoxia induced by incubation in a BD GasPak EZ Anaerobe Gas-generating Pouch System (BD Biosciences). Cell death was measured based on LDH release (average ± s.e. from 8 independent experiments). In all panels the p values calculated with the Student t test are shown (*p ≤ 0.05, **p ≤ 0.01, ***p ≤ 0.001).
The unique histidine in OSCP subunit of F-ATP synthase mediates inhibition of the permeability transition pore by acidic pH (2017)
Figure 3

Figure 3. H112Q replacement in OSCP does not affect single channel features of the MMC in mitoplasts but renders it insensitive to acidification.

Representative current traces recorded at V(pipette) +10 mV from mitoplasts derived from wild type (WT) or H112Q OSCP mutation-harboring cells.

Channel activity (top) and corresponding amplitude histograms (bottom) recorded in wild type mitochondria before (WT pH 7.3) and after acidification to pH 6.5 (WT pH 6.5). Amplitude histograms were obtained from 120 second-long current traces for the corresponding pH values and the panels are from the same experiment.

Recordings as in panel B from mitoplasts of cells harboring the OSCP H112Q replacement. Left panel, pH 7.3; middle panel, 440 seconds after acidification to pH 6,5; right panel, 30 seconds after the addition of 5 mM Ba2+ at pH 6.5. Amplitude histograms were obtained from 100 second-long segments and the panels are from the same experiment. Note that both in panels B and C well-visible subconductance states can be detected in the amplitude histograms (peaks between open levels o2 and o3 on left panels). Gaussian fitting has been obtained using the Origin Program set. In all panels c, closed; o1, o2, o3 open states with discrete subconductance.
The unique histidine in OSCP subunit of F-ATP synthase mediates inhibition of the permeability transition pore by acidic pH (2017)
Figure 4

Figure 4. Effect of H112 protonation on OSCP molecular dynamics and sequence comparison of OSCP across species.

The left panel depicts a cryo-EM based atomic model of monomeric bovine F-ATP synthase (pdb 5ara) (excluding subunits e, f, g, DAPIT, 6.8PL and A6L) with OSCP (cyan) and subunit b (yellow) highlighted on the structure of F-ATP synthase in the lower part of the panel. The region H112-E115 is shown as van der Waals spheres (inflated for better visibility). The backbone of the stretch T130-K135 is shown in red van der Waals spheres. The top part of the panel shows the results of restrained molecular dynamics simulations of the isolated lateral stalk (OSCP and subunits b, d, F6) displaying a large number of conformations in this region. Snapshots taken at 1 ns intervals along the last 15 ns of the trajectory are shown for the fragment 112-HRGE-115 for the deprotonated (HIS) and the protonated form (HIS+). Only for protonated H112 a salt bridge with a well defined turn or helix arrangement at H112-E115 is found in a large number of MD conformations. The larger conformational variability of the deprotonated form can also be appreciated. The right panel reports a sequence comparison of OSCP across 16 out of 197 species (HRGE is boxed in red; Sauria sequences are in the thin black box). Conservation, quality of the aligment and consensus at each position in the alignment of all vertebrate sequences in RefSeq, excluding Sauria and most divergent sequences, are described in the documentation of the program JalView [67].
ERp18 regulates activation of ATF6α during unfolded protein response (2019)
Figure 1

Figure 1: Validation of ATF6 Partner Proteins

Schematic of the ATF6α constructs used in this study. The N- terminus of ATF6α is tagged with a HA epitope or GFP as indicated. The C-terminus is V5-epitope-tagged. The region N-terminal to the transmembrane domain is localised in the cytosol whereas the region C-terminal is localised to the ER (lumenal domain). The positions of the cysteine residues and mutations are as indicated as well as the S1P cleavage site mutation (R415A/R416A). TAD: transactivation domain.

Immunofluorescence microscopy of HEK293T exogenously expressing ATF6α-V5 tagged. Cells were fixed and stained with anti-calnexin (green) or anti-V5 (red). An overlay of the cells is presented in the third panel. Bar = 10 µm.

Whole cell lysates from HEK293T cells, with or without stable expression of ATF6α (as indicated) were immunoisolated with mouse anti-V5. RCN1 was transiently transfected into both cell lines in the experiment depicted in panel 3. Immunoisolated material was separated by SDS-PAGE under reducing conditions followed by western blotting to determine the co-isolation of ER proteins with ATF6α. Ig-HC (anti-BiP blot) indicates immunoglobulin heavy chains.

Whole cell lysates from HEK293T cells stably expressing ATF6α were either untreated (-) or treated (+) with 5 µM thapsigargin (TG) for 1 h. THBS4 was transiently transfected into cells in the experiment depicted in panel 2. ATF6α was either immunoisolated with anti-V5 (panel 1 and 3) or anti-HA (panel 2). For the experiment in panel 3 the cells were cross-linked prior to immunoisolation. Samples were separated by SDS-PAGE under reducing conditions followed by western blots to determine co-isolation of endogenous PDIR, ERp18 or exogenously expressed THBS4 with ATF6α. HC indicates immunoglobulin heavy chain.
ERp18 regulates activation of ATF6α during unfolded protein response (2019)
Figure 2

Figure 2: PDI Family Substrate-trapping Mutants form Mixed-disulfide Complexes with ATF6

HEK293T cells stably expressing ATF6α were either left untransfected (UT) or transfected with substrate-trapping mutants of PDI oxidoreductases. ATF6α was immunoisolated from cell lysates with mouse anti-ATF6α, separated by SDS-PAGE under non-reducing conditions and ATF6α detected by western blotting using rabbit anti-HA. Blots confirm mixed-disulfide complexes between ATF6α and ERp18, ERp57, and PDIR indicated with arrows (lanes 2, 4, 5). M, D and O refer to ATF6α monomer, dimer and oligomer respectively.

Whole cell lysates of HEK293T cells expressing an ATF6α mutant containing cysteine to alanine mutations in the lumenal domain (ATF6 DM) were transfected with PDI substrate-trapping mutants. ATF6α was immunoisolated with mouse anti-ATF6α, separated by SDS-PAGE under non-reducing conditions, and ATF6α detected with rabbit anti-HA.
ERp18 regulates activation of ATF6α during unfolded protein response (2019)
Figure 3

Figure 3: ER Stress Modulates ATF6α-PDI Mixed-disulfide Complexes

A-D HEK293T cells were co-transfected with ATF6α S1P and PDI substrate-trapping mutants and either left untreated (-) or treated (+) for 1 h with 5 µM TG (A), 5 µg/ml tunicamycin (B) or 20 µM MG132 (C) to induce ER stress. ATF6α was immunoisolated from cell lysates with mouse anti-ATF6α, separated by SDS-PAGE under non-reducing conditions and ATF6α detected by western blotting using rabbit anti-HA. Blots indicate that mixed-disulfide complexes between ATF6α and PDI enzymes are regulated by ER stress. M, D and O refer to ATF6α monomer, dimer and oligomer respectively. Samples from (A) were rerun and probed with anti-sera raised against respective PDI enzymes as indicated (D). *indicates positions of the ATF6α-PDI enzymes mixed-disulfide complexes. ** indicates hypoglycosylated ATF6α. Data shown are representative of three independent experiments.
ERp18 regulates activation of ATF6α during unfolded protein response (2019)
Figure 4

Figure 4: ATF6α C467 forms a Stable Mixed-disulfide Complex with the ERp18 Substrate-trapping Mutant

HEK293T cells were co-transfected with the ERp18 substrate-trapping mutant and the indicated ATF6α constructs. Cell were allowed to recover for 24 h post-transfection before being either left untreated (-) or treated (+) for 1 h with 5 µM TG to induce ER stress. ATF6α was immunoisolated from cell lysates with mouse anti-ATF6α, separated by SDS-PAGE under non-reducing conditions and ATF6α detected by western blotting using rabbit anti-HA. The blot confirms that ATF6α C618A forms a stable complex with ERp18 trapping mutant following ER stress. M, D and O refer to ATF6 monomer, dimer and oligomer respectively. *indicates positions of the ATF6-ERp18 mixed-disulfide complexes.

HEK293T cells were co-transfected with GFP-ATF6α and ERp18 trapping mutant constructs as indicated. GFP-ATF6α complexes were immunoisolated using GFP-trap. Immunoisolated material was separated by SDS-PAGE under non-reducing conditions and silver stained to detect ATF6α disulfide-linked complexes. MS analyses confirmed that protein bands indicated by black arrows are a complex comprising ATF6α and ERp18, whilst bands marked as monomer (M) and oligomer (O) contain ATF6α only.

Cartoon depicting the presumed composition of the ATF6α disulfide-linked complexes and dimers indicating their respective apparent molecular weight.