EMBO/soda-nel huggingface dataset:
The IKK-related kinase TBK1 activates mTORC1 directly in response to growth factors and innate immune agonists (2017)
Figure 8

Figure 8: mTOR S2159 phosphorylation promotes mTORC1 signaling, IRF3 nuclear translocation, and IFNβ production upon TLR3 activation in primary macrophages

A. Reduced TLR3-induced mTORC1 signaling in mTOR S2159A knock-in primary macrophages (mTORA/A) relative to wild type (mTOR+/+): BMDMs were pre-treated with Torin 1 [100 nM] (30 min) and stimulated -/+ poly (I:C) [30 μg/ml] for 30 min. Whole cells lysate (WCL) was immunoblotted as indicated. The graph quantitates three independent experiments each with n=1 (n=3 total). The level of P-S6K1-T389 normalized to total protein in mTOR+/+ macrophages stimulated with poly (I:C) was set at 100%. *The confidence interval at 95% (52.7-59.1) indicates statistical significance between mTOR+/+ vs. mTORA/A BMDMs.

B. Reduced TLR4-induced mTORC1 signaling in mTORA/A primary macrophages: BMDMs were treated as in A except stimulated -/+ LPS [100 ng/mL] (30 min). The graph quantitates three independent experiments each with n=1 (n=3 total). The level of P-S6K1-T389 normalized to total protein in mTOR+/+ macrophages stimulated with LPS was set at 100%. *The confidence interval at 95% (58.6-71.2%) indicates statistical significance between mTOR+/+ vs. mTORA/A BMDMs.

C. Reduced TLR3-stimulated IFNβ protein production in mTORA/A primary macrophages: BMDMs were serum starved for 6 hr. and stimulated -/+ poly (I:C) [30 μg/ml] for 6 hr. The secretion of IFNβ was measured by ELISA. Results represent the mean +/- SEM from three independent experiments, n=8 samples total. *p=.0002 relative to mTOR+/+ + Poly(I:C) by unpaired t-test (equal variance; two-tailed). **p=.0001 relative to mTOR+/+ + Poly(I:C) by paired t-test (two-tailed).

D. Reduced TLR3-stimulated IRF3 nuclear translocation in mTORA/A primary macrophages: BMDMs were treated -/+ poly (I:C) for 3 hr as in A, fixed, and processed for confocal immunofluorescence microscopy using an anti-IRF3-Alexa 488 antibody and Dapi stain. The graph represents the mean +/- SEM of at least 270 cells total from four independent experiments. *p=.001 relative to mTOR+/+ no Poly(I:C) by unpaired t-test (equal variance; two-tailed). **p=.02 relative to mTOR+/+ + Poly(I:C) by unpaired t-test (equal variance; two-tailed). Scale bar = 10 μM.

E. Model: TLR3 and TLR4 signaling increase TBK1-mediated mTOR S2159 phosphorylation, resulting in increased mTORC1 catalytic activity, mTORC1 downstream signaling, IRF3 nuclear translocation, and IFNβ production.
Transport through recycling endosomes requires EHD1 recruitment by a phosphatidylserine translocase (2014)
Figure 1

ATP8A1 regulates endosomal membrane traffic at REs

A COS‐1 cells co‐transfected with GFP‐ATP8A1 and myc‐CDC50A were stained for myc‐tag and TfnR, TGN46, GM130, VPS26, CD63, or LAMP2. mCherry‐Rab11 was expressed in a cell in the top row. Nuclei were stained with DAPI (in blue). Pearson's coefficient between GFP‐ATP8A1 and each organelle marker is shown in the merged image (mean ± SD, n > 20 cells from two experiments). Scale bars, 10 μm.
B COS‐1 cells were treated with ATP8A1 siRNAs for 72 h. Cell lysates were prepared and then immunoblotted with anti‐ATP8A1 antibody. α‐tubulin was used as a loading control.
C, D COS‐1 cells were treated with ATP8A1 siRNA1 for 72 h. siRNA‐resistant GFP‐ATP8A1 (WT or E191Q) and myc‐CDC50A were transfected 48 h after siRNA transfection. Cells were pulsed with Alexa 594‐Tfn and chased in medium with unlabeled Tfn. During the chase, cells were imaged every 6 min for 54 min. The fluorescence intensity of Alexa 594‐Tfn is shown as percentage of that at 0 min (mean ± SEM, n = 4–6; ***P 0.001; Student's t‐test). See Supplementary Fig S2 for the representative images.
E, F COS‐1 cells were treated with ATP8A1 siRNA1 for 72 h. Cells were pulsed with Alexa 594‐CTxB for 5 min and chased for 15 or 60 min. Cells were then fixed and stained for GM130. In (E), representative images are shown. In (F), the Pearson's coefficient between CTxB and GM130 after 60‐min chase is shown. Data represent mean ± SD (n > 26 cells from three independent experiments). ***P 0.001; two‐tailed Student's t‐test. Scale bars, 10 μm.
Transport through recycling endosomes requires EHD1 recruitment by a phosphatidylserine translocase (2014)
Figure 2

ATP8A1 activity is essential for fission of TfnR‐positive membrane carriers

COS‐1 cells were treated with ATP8A1 siRNA1 for 72 h and stained for TfnR. Each image represents the maximum intensity z‐projection of four confocal slices. Intensified images are shown in the bottom row. Red dashed lines and arrowheads indicate nuclei and TfnR puncta, respectively. Scale bars, 10 μm.
COS‐1 cells were treated with ATP8A1 siRNA1 for 72 h and stained for the indicated proteins. Scale bars, 10 μm.
COS‐1 cells were treated with ATP8A1 siRNA1 for 72 h. TfnR‐GFP was transfected 48 h after siRNA transfection. Cells were then imaged with an epifluorescent microscope. Selected stills from Supplementary Movie S1 are shown. The asterisks indicate the tips of the tubules of interest. Scale bars, 5 μm.
The effect of increasing levels of 1,2‐dioleoyl‐PS on the ATPase activity of purified ATP8A1 (WT and E191Q)‐CDC50A complex. The Km and Vmax for the WT complex were 59.1 ± 3.5 μM and 38.7 ± 0.8 μmol ATP/min/mg protein, respectively.
COS‐1 cells were treated with ATP8A1 siRNA1 for 72 h. siRNA‐resistant ATP8A1 (WT or E191Q), and myc‐CDC50A were transfected 48 h after siRNA transfection. Cells were then fixed and stained for TfnR. The graph shows percentages of cells showing aberrant TfnR‐positive tubules as mean ± SD of three independent experiments. At least 50 cells were counted per experiment.
Transport through recycling endosomes requires EHD1 recruitment by a phosphatidylserine translocase (2014)
Figure 3

EHD1 localizes at REs in an ATP8A1 activity‐dependent manner and is required for fission of TfnR‐positive membrane carriers

A COS‐1 cells were treated with EHD1 siRNAs for 72 h. Cell lysates were prepared and then immunoblotted with EHD1 antibody. α‐tubulin was used as a loading control.
B, C Cells were treated with EHD1 siRNA1 for 72 h. Cells were pulsed with Alexa 488‐Tfn and chased in medium with unlabeled Tfn. During the chase, cells were imaged every 3 min for 57 min. In (B), representative images of Alexa 488‐Tfn in control or EHD1‐depleted cells are shown. In (C), the fluorescence intensity of Alexa 488‐Tfn is shown as percentage of that at 0 min (mean ± SEM, n > 3 cells from three independent experiments). ***P 0.001; two‐tailed Student's t‐test. Scale bars, 10 μm.
D COS‐1 cells were treated with EHD1 siRNA1 for 72 h. Cells were pulsed with Alexa 594‐CTxB for 5 min and chased for 60 min. Cells were then fixed and stained for GM130. The Pearson's coefficient between CTxB and GM130 is shown (mean ± SD, n > 30 cells from two independent experiments). ***P 0.001; two‐tailed Student's t‐test. See Supplementary Fig S7A for the representative images.
E COS‐1 cells were treated with EHD1 siRNA1 for 72 h and stained for TfnR. The image represents the maximum intensity z‐projection of four confocal slices. Scale bar, 10 μm.
F COS‐1 cells co‐transfected with GFP‐ATP8A1 and myc‐CDC50A were stained for EHD1. Scale bar, 10 μm.
G Cells were treated with ATP8A1 siRNA1 for 72 h and stained for EHD1. For the rescue experiments, siRNA‐resistant GFP‐ATP8A1 (WT or E191Q) and myc‐CDC50A were transfected 48 h after siRNA transfection. Asterisks indicate cells with GFP‐ATP8A1 expression. The graph represents percentage of cells with perinuclear localization of EHD1 as mean ± SD of three independent experiments (at least 141 cells were counted for each condition). Scale bars, 10 μm.
Transport through recycling endosomes requires EHD1 recruitment by a phosphatidylserine translocase (2014)
Figure 4

EHD1 localization is dependent on cellular PS levels

The effect of various lipids on the ATPase activity of the purified ATP8A1‐CDC50A complex. The ATPase activity was measured in the presence of 5 mM ATP and 10 mol % of one of the following lipids: 1,2‐dioleoyl‐phosphatidycholine (PC), 1,2‐dioleoyl‐PS, 1,2‐dioleoyl‐PE, 1,2‐dioleoyl‐phosphatidylglycerol (PG), 1,2‐dioleoyl‐phosphatidylinositol (PI), 1,2‐dioleoyl‐phosphatidic acid (PA), sphingomyelin (SM), cholesterol (Chol), or brain polar lipid (BPL) and 90% PC. The activity of the ATP8A1 (E191Q)‐CDC50A in the presence of 1,2‐dioleoyl‐PS was also determined.
NBD‐labeled PS or PE transport (flippase) activity of ATP8A1 (WT and E191Q)‐CDC50A complex. The percentage of NBD‐lipid flipped was shown.
Schematic of the biosynthetic pathway of PS in mammalian cells. The impaired pathways in PSA‐3 and R‐41 cells are indicated.
PSA‐3 and R‐41 cells were transiently transfected with GFP‐EHD1 and then cultured under the indicated conditions for 72 h. Cells were then fixed, and the nuclei were strained with DAPI. Arrowheads indicate the perinuclear RE localization of GFP‐EHD1. Scale bars, 10 μm.

Data information: In (A, B), the data represent the mean ± SD of n = 3 independent experiments.
Transport through recycling endosomes requires EHD1 recruitment by a phosphatidylserine translocase (2014)
Figure 5

EHD1 binds PS in vitro

A His‐tagged EHD1 was mixed with PC‐based liposomes containing the indicated % (mol/mol) of PS or PE. After 15 min, the mixture was spun at 100,000 g for 30 min, and the resultant supernatant (S) and pellet (P) were subjected to SDS–PAGE. The proteins and lipids were then stained with Coomassie blue.
B, C The intensities of individual bands in (A) were quantified with ImageJ, and the percentage of bound proteins was calculated. In (B), the data represent the mean ± SD of n = 3 independent experiments and were analyzed with one‐way analysis of variance (ANOVA) followed by Tukey–Kramer post hoc test. *P 0.01; NS, not significant. In (C), each point represents the mean of two independent experiments with an error bar showing the range of values obtained. The sigmoidal fitting was applied.
D, E His‐tagged EHD1 was mixed with PC‐based liposomes (20, 40, or 60% PS) of decreasing size produced by extrusion through filter pores of the size indicated. After 15 min, the mixture was spun at 100,000 g for 30 min, and the resultant supernatant (S) and pellet (P) were subjected to SDS–PAGE. The proteins and lipids were then stained with Coomassie blue. In (E), the intensities of individual bands were quantified (mean ± SEM of three independent experiments). See Supplementary Fig S8 for the size distributions of the prepared liposomes.
Transport through recycling endosomes requires EHD1 recruitment by a phosphatidylserine translocase (2014)
Figure 6

ATP8A1 knockdown causes an increase in RE luminal PS levels

A His‐tagged 2xPH was mixed with liposomes that were composed of 75% (mol/mol) PE, 20% (mol/mol) PC, and 5% (mol/mol) of PS, PA, PI, PIPs, or sulfatide. In the case of PE/PC, liposomes of 80% (mol/mol) PE and 20% (mol/mol) PC were used. After 15 min, the mixture was spun at 100,000 g for 30 min, and the resultant supernatant (S) and pellet (P) were subjected to SDS–PAGE. The gels were stained with Coomassie blue.
B COS‐1 cells were incubated in medium containing Alexa 488‐Tfn for 40 min, washed, fixed, and stained with recombinant 2xPH. Magnified image is shown in the right panel. Scale bar, 10 μm.
C COS‐1 cells were transiently transfected with GFP‐lact‐C2 and stained for Rab11. Scale bar, 10 μm.
D, E COS‐1 cells were transiently transfected with GFP‐lact‐C2 and stained with recombinant 2xPH and anti‐GM130 antibody. The asterisk indicates a cell expressing GFP‐lact‐C2, and the arrowhead indicates a non‐expressing cell. The graph in (E) shows fluorescence intensity per pixel of recombinant 2xPH stain in RE area, which was delimited by GM130. Data are normalized to the 2xPH intensity in GFP‐lact‐C2 (−) cells (mean ± SD, n = 13 cells for each condition). Scale bar, 10 μm.
F–H COS‐1 cells stably expressing GFP‐lact‐C2 were treated with ATP8A1 siRNA1 or EHD1 siRNA1 for 72 h and stained with recombinant 2xPH and anti‐GM130 antibody. The intensities of 2xPH staining and GFP‐lact‐C2 in RE area were measured. The intensity of 2xPH (G) and the ratio of 2xPH to GFP‐lact‐C2 intensities (H) are shown. In (H), data are normalized to that of control cells. Data represent mean ± SD and were analyzed with two‐tailed Student's t‐test (n > 26 cells from three independent experiments). **P 0.01; ***P 0.001; NS, not significant. Scale bars, 10 μm.
Transport through recycling endosomes requires EHD1 recruitment by a phosphatidylserine translocase (2014)
Figure 7

Wild‐type ATP8A2, but not a disease‐associated mutant, can compensate for the loss of ATP8A1 function

A COS‐1 cells co‐transfected with GFP‐ATP8A2 (WT) and myc‐CDC50A were stained for myc‐tag and TfnR. Scale bar, 10 μm.
B The effect of increasing levels of PS on the ATPase activity of ATP8A2 (WT and I376M)‐CDC50A complex.
C NBD‐labeled PS transport (flippase) activity of ATP8A2 (WT and I376M)‐CDC50A complex. The percentage of NBD‐lipid flipped was shown.
D Cells were treated with ATP8A1 siRNA1 for 72 h. ATP8A2‐1D4 (WT or mutants) and myc‐CDC50A were transfected 48 h after siRNA transfection. The cells were then stained for EHD1 and 1D4‐tag. Scale bars, 10 μm.
E Quantification of percentages of cells with perinuclear EHD1 localization. Data represent mean ± SD of three or four independent experiments. At least 20 cells were counted per experiment.
F Cells were treated with ATP8A1 siRNA for 72 h. GFP‐ATP8A2 (WT or mutant) and myc‐CDC50A were transfected 48 h after siRNA transfection. The cells were then stained for TfnR. Data represent mean ± SD of three or four independent experiments. At least 20 cells were counted per experiment.
G, H Surface biotinylation assay with Atp8a2+/+ or Atp8a2−/− cortical neurons. The ratio of surface to total TfnR was quantified and normalized to Atp8a2+/+. Data represent mean value (2 mice for each genotype).
SUMO-2 and PIAS1 modulate insoluble mutant huntingtin protein accumulation. (2013)
Figure 1

K6 and K9 Are Primary Sites for HTTex1p In Vitro SUMOylation

(A) Schematic illustration of the SUMOylation pathway. SUMO is expressed as a precursor protein (SUMO-X) that is processed by SUMO-specific proteases (SENPs) to expose a C-terminal diglycine motif (-GG). Enzymatic reactions are similar to ubiquitination and include activation by the SUMO E1-activating enzyme (SAE1/UBA2), to the SUMO E2-conjugating enzyme (Ubc9), and transfer of SUMO to target lysines with or without the assistance of the SUMO E3-ligating enzymes.

(B) Time course of SUMO-1 modification of His-tagged HTTex1p (25Q)-purified proteins (WT, K6R, K9R, K6,9R, K6,9,15R, and S13,16D) was performed in vitro. SUMOylation was visualized using anti-His antibody. WT HTTex1p is SUMOylated within 16 min, K6R or K9R mutations delay SUMOylation, and combined mutations (K6,9R or K6,9,15R) greatly reduce SUMOylation. Mutations that mimic phosphorylation (S13,16D) alter kinetics of SUMO-1 modification with SUMO modification observed beginning by 4 min.

See also Figure S1.
SUMO-2 and PIAS1 modulate insoluble mutant huntingtin protein accumulation. (2013)
Figure 2

SUMO-1 and SUMO-2 Are Differentially Expressed in HD Mice versus Control

(A) qRT-PCR analysis of SUMO-modifying proteins and enzymes in cortex and striata of WT mice at 12 weeks. Relative expression for all the SUMO enzymes is normalized to mouse β-actin.

(B and C) qRT-PCR of SUMO mRNAs from 12-week-old WT and R6/2 mouse cortex (B) and striatum (C). SUMO enzyme mRNAs are differentially expressed in R6/2 versus control with statistically significant increases in SENP1 (p = 0.01), SENP3 (p = 0.02), and SUMO-1 (p = 0.003) in cortex and SENP1 (p = 0.02), SENP6 (p = 0.04), PIAS3 (p = 0.007), SUMO-1 (p = 0.02), and SUMO-2 (p = 0.02) in striatum. Samples were analyzed in quadruplicate and normalized to mouse β-actin. Data are shown as R6/2 expression relative to WT levels set at 1 for each enzyme with ± SD (n = 4). *p < 0.05. n.s., not significant.

(D and E) Western blot analysis of SUMO-2 in 14-week R6/2 cortex (D) and striatum (E) versus aged-matched controls. SUMO-2 is upregulated in R6/2 striatum versus control (p = 0.026; n = 4). Protein is normalized to α-tubulin and quantitated using ImageJ.

Note that only the 12-week time point is shown in (B) and (C). Please see 4- and 8-week time points in Figures S2A and S2B.
SUMO-2 and PIAS1 modulate insoluble mutant huntingtin protein accumulation. (2013)
Figure 3

HTT Is Modified by Both SUMO-1 and SUMO-2

(A) HeLa cells transfected with His-tagged HTTex1p (46Q) or 46QP-K6,9,15R (3R) along with GFP-SUMO-1 or GFP-SUMO-2, lysed under denaturing conditions, and nickel purified (Ni-NTA). Unmodified HTT-46Q is indicated by the arrow and SUMO-modified HTT by the boxed region. The lysine mutant (3R) serves as a negative control. Ni-NTA represents nickel-purified His-tagged HTT, and WC TCA represents 10% of the whole-cell lysate expression of HTT and myc-actin (transfection control). HTT is modified by SUMO-1 (left) and SUMO-2 (right).

(B) SUMO isopeptidases (SENP1, SENP2, SENP3, SENP5, and SENP6) modulate SUMO-modified HTT when overexpressed together with HTT (46QP-H4 or 3R) and SUMO-1 (GFP-SUMO-1). SENP1, SENP2, and SENP6 decrease HTT SUMOylation. Graph depicts quantitation of western blot using the Odyssey Infrared Imaging System (LI-COR) to calculate the ratio of HTT purified versus the HTT modified by SUMO multiplied by 100.

(C) Titration of SUMO-1. Denaturing nickel purification of HTTex1p (46QP-H4) following transfection with decreasing amounts of SUMO-1 reduces the amount of SUMO-modified HTT to undetectable levels. The Ni-NTA blot displayed in the gray scale shows purified HTTex1 and SUMO-modified HTTex1 using HTT antibody. Note that 0.5 μg of SUMO-1 (¼ the amount of SUMO-1 cDNA ) was used for identifying the SUMO-1 E3 ligase for HTTex1p. Graph depicts quantitation of western blot using the Odyssey Infrared Imaging System to calculate the ratio of HTT purified versus the HTT modified by SUMO multiplied by 100. Note that all experiments were performed in triplicate, and a representative figure is shown.

See also Figure S3A.
SUMO-2 and PIAS1 modulate insoluble mutant huntingtin protein accumulation. (2013)
Figure 4

PIAS1 Is a SUMO E3 Ligase for HTT

(A) Under limiting SUMO conditions (1/4 SUMO-1, lanes 3–9), PIAS1 increases HTT-SUMO modification above 1/4 SUMO alone. Purified HTT (arrow) and SUMO-HTT (boxed region) were detected using anti-HTT. Graph depicts quantitation of the Ni-NTA western blot using the Odyssey Infrared Imaging Software (LI-COR) to calculate the ratio of HTT purified versus the HTT modified by SUMO multiplied by 100.

(B) Western analysis of overexpression of HTTex1 (46QP-H4 or 3R), SUMO-2 (GFP-SUMO-2), and all the PIAS proteins (PIAS1, PIASxα, PIASxβ, PIAS3, and PIASy). Under nonlimiting SUMO-2 conditions, PIAS1 enhances SUMO modification of HTT. WC TCA shows overall myc-actin (transfection control) and HTT levels. Graph quantitating the ratio of HTT purified versus the HTT modified using the Odyssey (LICOR).

(C) Left panel is the autoradiography results of a GST pull-down assay showing that radiolabeled human PIAS1 interacts with HTTex1p. Right panel is a phosphorimager analysis of GST pull-downs, performed in triplicate, showing the percentage of 35S-labeled PIAS protein that bound the GST proteins: GST alone, unexpanded HTT with and without the proline-rich region (20QP and 20Q), expanded HTT with and without the proline-rich region (51QP and 51Q), and the proline-rich region alone (Pro). Error bars were calculated as an estimate of SE = STDEV(n)/SQRT(n-1).
SUMO-2 and PIAS1 modulate insoluble mutant huntingtin protein accumulation. (2013)
Figure 6

SUMO-2 Causes Mutant HTT to Accumulate

(A) Western analysis of whole-cell lysates from HeLa cells transfected with His-SUMO-1 or SUMO-2 and/or 97Q-HTT exon 1 and treated with 5 μM MG132 for 18 hr. Lysates were separated using differential centrifugation into a detergent-soluble fraction (SOLUBLE) with 1% Triton X-100 and a detergent-insoluble fraction (INSOLUBLE) with 4% SDS. Western blot probed with anti-HTT shows full-length endogenous HTT in the SOLUBLE fraction (upper arrow) and 97Q-HTTex1 (lower arrow) (left panel). In the INSOLUBLE fraction, HTT HMW species are indicated by the bracket and asterisks (right panel).

(B) MG132 and SUMO-2 cause mutant HTT to accumulate as HMW species (bracke and asterisk). Western blot showing IP with HTT antibody crosslinked beads from the detergent-insoluble fraction probed with the anti-HTT antibody.

(C) Mutant HTT (97Q-Httex1) fibrils are detected with anti-HTT in the insoluble fraction with treatment of MG132 or addition of exogenous SUMO-2.

(D) Western blot with increasing concentrations of SUMO-2 detected with anti-His antibody (left panel). Middle panel is the same western blot probed with anti-HTT showing soluble forms of HTT. Right panel presents western blot from detergent-insoluble fraction with monomeric HTT (97Q) at 55 kDa, and the asterisk (*) indicates the HMW species. Note that all experiments were performed in triplicate; representative figures are shown.
SUMO-2 and PIAS1 modulate insoluble mutant huntingtin protein accumulation. (2013)
Figure 7

SUMO-2 Proteins Accumulate in HD Brain

(A) Western blot analysis of HeLa cells over-expressing exogenous PIAS1 in the presence of mutant HTT (97Q) when separated into detergent-soluble and detergent-insoluble fractions. No difference is detected in monomeric HTT (top panel, Soluble), but HMW HTT levels increase with PIAS1 overexpression. Anti-PIAS1 antibody (Invitrogen) was used to detect PIAS1.

(B) Acute knockdown of PIAS1 decreases HMW HTT species in the detergent-insoluble fraction. PIAS1 knockdown is detected in detergent-soluble and -insoluble fractions using anti-PIAS1 antibody.

(C) Drosophila melanogaster expressing mutant HTTex1p (93Q) in a reduced Su(var)2-10/dPIAS genetic background exhibits statistically significantly reduced photoreceptor neuron degeneration (left panel, p = 0.033) when comparing dPIAS/+ to +/+ flies and increased overall survival (right panel, p = 0.047) when comparing dPIAS1/+ to +/+ flies. Significance was measured by Student’s t test.

(D) HMW SUMO-2 accumulates in postmortem HD striata. Western blot analysis of the insoluble fraction from three control and three HD postmortem striata as described (Experimental Procedures).