Hyperon Polarization along the Beam Direction Relative to the Second and Third Harmonic Event Planes in Isobar Collisions at sqrt[s_{NN}]=200 GeV

The polarization of Λ and Λ[over ¯] hyperons along the beam direction has been measured relative to the second and third harmonic event planes in isobar Ru+Ru and Zr+Zr collisions at sqrt[s_{NN}]=200  GeV. This is the first experimental evidence of the hyperon polarization by the triangular flow originating from the initial density fluctuations. The amplitudes of the sine modulation for the second and third harmonic results are comparable in magnitude, increase from central to peripheral collisions, and show a mild p_{T} dependence. The azimuthal angle dependence of the polarization follows the vorticity pattern expected due to elliptic and triangular anisotropic flow, and qualitatively disagrees with most hydrodynamic model calculations based on thermal vorticity and shear induced contributions. The model results based on one of existing implementations of the shear contribution lead to a correct azimuthal angle dependence, but predict centrality and p_{T} dependence that still disagree with experimental measurements. Thus, our results provide stringent constraints on the thermal vorticity and shear-induced contributions to hyperon polarization. Comparison to previous measurements at RHIC and the LHC for the second-order harmonic results shows little dependence on the collision system size and collision energy.

Tumor Treatment Response Assessed During the Concurrent Chemoradiotherapy for Nasopharyngeal Patients

PURPOSE/OBJECTIVE(S)

To evaluate intratumoral treatment response distribution with using FDG-PET/CT during the chemoradiotherapy of nasopharyngeal patients (NPC).

MATERIALS/METHODS

A total of 5 of 30 patients with stage III-IVA NPC were enrolled in the institutional protocol for induction/concurrent chemoradiotherapy with radiation dose of 70 Gy in 33 fractions. For each patient, a pre-radiation treatment FDG-PET/MRI image (SUV0) and a mid-treatment image (SUVm) at the treatment dose of 31.8 Gy were obtained. Followed by deformable PET/MRI registration between SUV0 and SUVm, the tumor voxel SUV reduction ratio was obtained to construct a tumor dose response matrix (DRM). Tumor SUVavid was also constructed by limiting tumor voxel SUVm > a given value. Spatial correlations of the tumor SUV0, SUVm, SUVavid and DRM were determined.

RESULTS

The mean and coefficient variation (CV) of the SUV0, SUVm and DRM for all tumors were 5.05 (52%), 2.72 (49%) and 0.64 (63%) (Table contains the individual data), which were smaller than those on the SUVs of head-n-neck HPV+ patients reported previously due to the induction chemotherapy, but had much larger DRM mean and CV. The inter-tumoral CVs of SUV0 and DRM were 29% and 27%, which were much lower than those of the intra-tumoral CVs 43% and 57%. Meanwhile, the intra-tumoral variations on SUV0 was smaller than the one of head-neck HPV+ patients, but the DRM intra-variation was much larger. There was a weak correlation between SUV0 and SUVm with the correlation coefficient 0.13, a medium correlation of -0.55 between SUV0 and DRM, but a strong correlation, 0.72, between SUVm and DRM. However, the spatial correlation between tumor DRM and SUVavid was getting weaker as the SUVavid value increasing and equal 0.47 with SUVavid value > 3.

CONCLUSION

The spatial dose response DRM for NPC in the concurrent chemoradiotherapy was relatively high, while had relatively low baseline tumor metabolic activity SUV0. It was most likely due to the induction chemotherapy. In addition, the tumor dose response showed vary large intra-tumoral variation. The high correlations between DRM and SUVm imply that SUVavid could be used partially to guide adaptive modification of NPC treatment with carefully selected boundary value.

Structure of the Schizosaccharomyces pombe Gtr-Lam complex reveals evolutionary divergence of mTORC1-dependent amino acid sensing

mTORC1 is a protein kinase complex that controls cellular growth in response to nutrient availability. Amino acid signals are transmitted toward mTORC1 via the Rag/Gtr GTPases and their upstream regulators. An important regulator is LAMTOR, which localizes Rag/Gtr on the lysosomal/vacuole membrane. In human cells, LAMTOR consists of five subunits, but in yeast, only three or four. Currently, it is not known how variation of the subunit stoichiometry may affect its structural organization and biochemical properties. Here, we report a 3.1 Å-resolution structural model of the Gtr-Lam complex in Schizosaccharomyces pombe. We found that SpGtr shares conserved architecture as HsRag, but the intersubunit communication that coordinates nucleotide loading on the two subunits differs. In contrast, SpLam contains distinctive structural features, but its GTP-specific GEF activity toward SpGtr is evolutionarily conserved. Our results revealed unique evolutionary paths of the protein components of the mTORC1 pathway.

Redundant electrostatic interactions between GATOR1 and the Rag GTPase heterodimer drive efficient amino acid sensing in human cells

Cells need to coordinate nutrient availability with their growth and proliferation. In eukaryotic cells, this coordination is mediated by the mechanistic target of the rapamycin complex 1 (mTORC1) pathway. mTORC1 activation is regulated by two GTPase units, the Rag GTPase heterodimer and the Rheb GTPase. The RagA-RagC heterodimer controls the subcellular localization of mTORC1, and its nucleotide loading states are strictly controlled by upstream regulators including amino acid sensors. A critical negative regulator of the Rag GTPase heterodimer is GATOR1. In the absence of amino acids, GATOR1 stimulates GTP hydrolysis by the RagA subunit to turn off mTORC1 signaling. Despite the enzymatic specificity of GATOR1 to RagA, a recent cryo-EM structural model of the human GATOR1-Rag-Ragulator complex reveals an unexpected interface between Depdc5, a subunit of GATOR1, and RagC. Currently, there is no functional characterization of this interface, nor do we know its biological relevance. Here, combining structure-function analysis, enzymatic kinetic measurements, and cell-based signaling assays, we identified a critical electrostatic interaction between Depdc5 and RagC. This interaction is mediated by the positively charged Arg-1407 residue on Depdc5 and a patch of negatively charged residues on the lateral side of RagC. Abrogating this interaction impairs the GAP activity of GATOR1 and cellular response to amino acid withdrawal. Our results reveal how GATOR1 coordinates the nucleotide loading states of the Rag GTPase heterodimer, and thus precisely controls cellular behavior in the absence of amino acids.

Measurements of the Elliptic and Triangular Azimuthal Anisotropies in Central ^{3}He+Au, d+Au and p+Au Collisions at sqrt[s_{NN}]=200 GeV

The elliptic (v_{2}) and triangular (v_{3}) azimuthal anisotropy coefficients in central ^{3}He+Au, d+Au, and p+Au collisions at sqrt[s_{NN}]=200  GeV are measured as a function of transverse momentum (p_{T}) at midrapidity (|η|<0.9), via the azimuthal angular correlation between two particles both at |η|<0.9. While the v_{2}(p_{T}) values depend on the colliding systems, the v_{3}(p_{T}) values are system independent within the uncertainties, suggesting an influence on eccentricity from subnucleonic fluctuations in these small-sized systems. These results also provide stringent constraints for the hydrodynamic modeling of these systems.

Observation of Directed Flow of Hypernuclei _{Λ}^{3}H and _{Λ}^{4}H in sqrt[s_{NN}]=3 GeV Au+Au Collisions at RHIC

We report here the first observation of directed flow (v_{1}) of the hypernuclei _{Λ}^{3}H and _{Λ}^{4}H in mid-central Au+Au collisions at sqrt[s_{NN}]=3  GeV at RHIC. These data are taken as part of the beam energy scan program carried out by the STAR experiment. From 165×10^{6} events in 5%-40% centrality, about 8400 _{Λ}^{3}H and 5200 _{Λ}^{4}H candidates are reconstructed through two- and three-body decay channels. We observe that these hypernuclei exhibit significant directed flow. Comparing to that of light nuclei, it is found that the midrapidity v_{1} slopes of _{Λ}^{3}H and _{Λ}^{4}H follow baryon number scaling, implying that the coalescence is the dominant mechanism for these hypernuclei production in the 3 GeV Au+Au collisions.

Beam Energy Dependence of Triton Production and Yield Ratio (N_{t}×N_{p}/N_{d}^{2}) in Au+Au Collisions at RHIC

We report the triton (t) production in midrapidity (|y|<0.5) Au+Au collisions at sqrt[s_{NN}]=7.7-200  GeV measured by the STAR experiment from the first phase of the beam energy scan at the Relativistic Heavy Ion Collider. The nuclear compound yield ratio (N_{t}×N_{p}/N_{d}^{2}), which is predicted to be sensitive to the fluctuation of local neutron density, is observed to decrease monotonically with increasing charged-particle multiplicity (dN_{ch}/dη) and follows a scaling behavior. The dN_{ch}/dη dependence of the yield ratio is compared to calculations from coalescence and thermal models. Enhancements in the yield ratios relative to the coalescence baseline are observed in the 0%-10% most central collisions at 19.6 and 27 GeV, with a significance of 2.3σ and 3.4σ, respectively, giving a combined significance of 4.1σ. The enhancements are not observed in peripheral collisions or model calculations without critical fluctuation, and decreases with a smaller p_{T} acceptance. The physics implications of these results on the QCD phase structure and the production mechanism of light nuclei in heavy-ion collisions are discussed.

Detergent modulates the conformational equilibrium of SARS-CoV-2 Spike during cryo-EM structural determination

The Spike glycoprotein of SARS-CoV-2 mediates viral entry into the host cell via the interaction between its receptor binding domain (RBD) and human angiotensin-converting enzyme 2 (ACE2). Spike RBD has been reported to adopt two primary conformations, a closed conformation in which the binding site is shielded and unable to interact with ACE2, and an open conformation that is capable of binding ACE2. Many structural studies have probed the conformational space of the homotrimeric Spike from SARS-CoV-2. However, how sample buffer conditions used during structural determination influence the Spike conformation is currently unclear. Here, we systematically explored the impact of commonly used detergents on the conformational space of Spike. We show that in the presence of detergent, the Spike glycoprotein predominantly occupies a closed conformational state during cryo-EM structural determination. However, in the absence of detergent, such conformational compaction was neither observed by cryo-EM, nor by single-molecule FRET designed to visualize the movement of RBD in solution in real-time. Our results highlight the highly sensitive nature of the Spike conformational space to buffer composition during cryo-EM structural determination, and emphasize the importance of orthogonal biophysical approaches to validate the structural models obtained.

S:D614G and S:H655Y are gateway mutations that act epistatically to promote SARS-CoV-2 variant fitness

SARS-CoV-2 variants bearing complex combinations of mutations that confer increased transmissibility, COVID-19 severity, and immune escape, were first detected after S:D614G had gone to fixation, and likely originated during persistent infection of immunocompromised hosts. To test the hypothesis that S:D614G facilitated emergence of such variants, S:D614G was reverted to the ancestral sequence in the context of sequential Spike sequences from an immunocompromised individual, and within each of the major SARS-CoV-2 variants of concern. In all cases, infectivity of the S:D614G revertants was severely compromised. The infectivity of atypical SARS-CoV-2 lineages that propagated in the absence of S:D614G was found to be dependent upon either S:Q613H or S:H655Y. Notably, Gamma and Omicron variants possess both S:D614G and S:H655Y, each of which contributed to infectivity of these variants. Among sarbecoviruses, S:Q613H, S:D614G, and S:H655Y are only detected in SARS-CoV-2, which is also distinguished by a polybasic S1/S2 cleavage site. Genetic and biochemical experiments here showed that S:Q613H, S:D614G, and S:H655Y each stabilize Spike on virions, and that they are dispensable in the absence of S1/S2 cleavage, consistent with selection of these mutations by the S1/S2 cleavage site. CryoEM revealed that either S:D614G or S:H655Y shift the Spike receptor binding domain (RBD) towards the open conformation required for ACE2-binding and therefore on pathway for infection. Consistent with this, an smFRET reporter for RBD conformation showed that both S:D614G and S:H655Y spontaneously adopt the conformation that ACE2 induces in the parental Spike. Data from these orthogonal experiments demonstrate that S:D614G and S:H655Y are convergent adaptations to the polybasic S1/S2 cleavage site which stabilize S1 on the virion in the open RBD conformation and act epistatically to promote the fitness of variants bearing complex combinations of clinically significant mutations.

Measurement of Sequential ϒ Suppression in Au+Au Collisions at sqrt[s_{NN}]=200 GeV with the STAR Experiment

We report on measurements of sequential ϒ suppression in Au+Au collisions at sqrt[s_{NN}]=200  GeV with the STAR detector at the Relativistic Heavy Ion Collider (RHIC) through both the dielectron and dimuon decay channels. In the 0%-60% centrality class, the nuclear modification factors (R_{AA}), which quantify the level of yield suppression in heavy-ion collisions compared to p+p collisions, for ϒ(1S) and ϒ(2S) are 0.40±0.03(stat)±0.03(sys)±0.09(norm) and 0.26±0.08(stat)±0.02(sys)±0.06(norm), respectively, while the upper limit of the ϒ(3S) R_{AA} is 0.17 at a 95% confidence level. This provides experimental evidence that the ϒ(3S) is significantly more suppressed than the ϒ(1S) at RHIC. The level of suppression for ϒ(1S) is comparable to that observed at the much higher collision energy at the Large Hadron Collider. These results point to the creation of a medium at RHIC whose temperature is sufficiently high to strongly suppress excited ϒ states.

Beam Energy Dependence of Fifth- and Sixth-Order Net-Proton Number Fluctuations in Au+Au Collisions at RHIC

We report the beam energy and collision centrality dependence of fifth and sixth order cumulants (C_{5}, C_{6}) and factorial cumulants (κ_{5}, κ_{6}) of net-proton and proton number distributions, from center-of-mass energy (sqrt[s_{NN}]) 3 GeV to 200 GeV Au+Au collisions at RHIC. Cumulant ratios of net-proton (taken as proxy for net-baryon) distributions generally follow the hierarchy expected from QCD thermodynamics, except for the case of collisions at 3 GeV. The measured values of C_{6}/C_{2} for 0%-40% centrality collisions show progressively negative trend with decreasing energy, while it is positive for the lowest energy studied. These observed negative signs are consistent with QCD calculations (for baryon chemical potential, μ_{B}≤110  MeV) which contains the crossover transition range. In addition, for energies above 7.7 GeV, the measured proton κ_{n}, within uncertainties, does not support the two-component (Poisson+binomial) shape of proton number distributions that would be expected from a first-order phase transition. Taken in combination, the hyperorder proton number fluctuations suggest that the structure of QCD matter at high baryon density, μ_{B}∼750  MeV at sqrt[s_{NN}]=3  GeV is starkly different from those at vanishing μ_{B}∼24  MeV at sqrt[s_{NN}]=200  GeV and higher collision energies.

[Efficacy and safety of daratumumab in patients with relapsed/refractory multiple myeloma]

Objective: To investigate the efficacy and safety of daratumumab in relapsed/refractory multiple myeloma (RRMM) patients. Methods: Fifty-two RRMM patients treated with daratumumab from September 2019 to November 2021 in West China Hospital were retrospectively enrolled, including 31 males and 21 females. The mean age of these patients at the first diagnosis of multiple myeloma was (58±10) years. According to the dosage of daratumumab, patients were divided into low dosage group (n=10) and high dosage group (n=42). Overall response rate (ORR), progression-free survival (PFS), overall survival (OS), and adverse event rates were investigated. Univariate and multivariate analysis of potential factors were conducted. Results: Of the 52 patients, 8 received daratumumab monotherapy, 27 received daratumumab plus immuno-modulatory drug (IMiD) treatment, 4 received daratumumab plus proteosome inhibitor (PI) treatment, and 11 received daratumumab plus dexamethasone treatment. The diagnosis age of high dosage group patients was (57±9) years, which was significantly younger than that of low dosage group [(66±10) years] (P=0.009). The baseline creatinine level of high dosage group patients [M (Q₁, Q₃)] was 91 (68, 196) μmol/L, which was significantly higher than that of low dosage group [66 (51, 76) μmol/L] (P=0.021). There was no significant difference in other baseline clinical characteristics, previous treatment regimens, previous lines of treatment, and regimen and cycles of daratumumab between the high dosage group and low dosage group (all P>0.05). The ORR for the 52 patients was 71.2% (37/52). The ORR for daratumumab plus IMiD group was 81.5% (22/27), which was significantly higher than that in monotherapy or dexamethasone group [ORR: 52.6% (10/19), P=0.036). With a median follow-up [M (Q₁, Q₃)] of 7 (5, 26) months, the median PFS for overall cohort was 17 (95%CI: 9.6-24.4) months. The median PFS for daratumumab plus IMiD group was 26 (95%CI: 6.0-46.0) months, which was significantly better than that in monotherapy or dexamethasone group [12 (95%CI: 3.5-20.5) months] (HR=0.231, 95%CI: 0.075-0.715, P=0.011). Higher diagnosis age was the risk factor of progression (HR=1.085, 95%CI: 1.016-1.158, P=0.014), while more cycles of daratumumab treatment was the protective factor of progression (HR=0.669, 95%CI: 0.495-0.904, P=0.009). There was no significant influence of daratumumab dosage on progression (high dosage vs low dosage, HR=1.016, 95%CI: 0.221-4.668, P=0.984). The median OS for overall cohort was 26 (95%CI: 13.1-38.9) months. Higher serum calcium was the independent risk factor of death (HR=12.190, 95%CI: 1.170-127.048, P=0.037). There was no significant influence of daratumumab dosage on death (high dosage vs low dosage, HR=0.818, 95%CI: 0.171-3.917, P=0.802). Adverse events included infections (43.2%, 16/37), infusion-associated reactions (29.7%, 11/37), and thrombocytopenia (27.0%, 10/37). Conclusions: Daratumumab is effective to treat RRMM. The dosage of daratumumab has no significant influence on prognosis when used in combined treatment. The incidence of adverse events is relatively low, with a favorable safety profile.

Purification and biochemical characterization of the Rag GTPase heterodimer

The mechanistic target of rapamycin complex 1 (mTORC1) senses nutrient levels in the cell and based on the availability, regulates cellular growth and proliferation. Its activity is tightly modulated by two GTPase units, the Rag GTPases and the Rheb GTPase. The Rag GTPases are the central hub of amino acid sensing as they summarize the amino acid signals from upstream regulators and control the subcellular localization of mTORC1. Unique from canonical signaling GTPases, the Rag GTPases are obligatory heterodimers, and the two subunits coordinate their nucleotide loading states to regulate their functional states. Robust biochemical analysis is indispensable to understanding the molecular mechanism governing the GTPase cycle. This chapter discusses protocols for purifying and biochemically characterizing the Rag GTPase heterodimer. We described two purification protocols to recombinantly produce the Rag GTPase heterodimer in large quantities. We then described assays to quantitatively measure the nucleotide binding and hydrolysis by the Rag GTPases. These assays allow for a thorough investigation of this unique heterodimeric GTPase, and they could be applicable to investigations of other noncanonical GTPases.

[Clinical characteristics and prognosis of lymphoma-associated hemophagocytic syndrome]

Subjective To investigate clinical characteristics, treatment, and prognosis of lymphoma-associated hemophagocytic syndrome (LAHS) patients. Methods: The clinical data of patients diagnosed with LAHS from January 2010 to October 2021 in West China Hospital were retrospectively analyzed. Clinical characteristics, treatment, overall response rate (ORR), and overall survival (OS) were investigated. Univariate and multivariate analysis of potential factors were conducted. Results: Of all 94 patients included, 59 were male and 35 were female. The age at hemophagocytic lymphohistiocytosis (HLH) diagnosis was (40.5±17.3) years. Seventy-four cases were T/NK cell lymphoma; 15 were B cell lymphoma; 5 were Hodgkin lymphoma. The age at HLH diagnosis of T/NK cell LAHS patients was (37.9±16.2) years, while that of B cell LAHS patients was (55.9±14.0) years. T/NK cell LAHS patients were significantly younger than B cell LAHS patients (P<0.001). Baseline fibrinogen of T/NK cell LAHS patients was 1.34 (0.86, 2.44) g/L, while that of B cell LAHS patients was 2.20 (1.75, 4.25) g/L. T/NK cell LAHS patients showed significantly lower fibrinogen levels than B cell LAHS patients (P=0.008). Combined treatment of anti-HLH and anti-lymphoma treatment was conducted in 35 patients; anti-HLH treatment was conducted in 31 patients; anti-lymphoma treatment was conducted in 8 patients; glucocorticoid treatment was conducted in 7 patients. ORR was 49.4%, and the median OS was 61 days for overall patients. Patients who received anti-HLH treatment and turned to anti-lymphoma treatment early displayed the best ORR and OS, significantly higher than those of anti-HLH patients (69.0 vs 38.7%, P=0.019, and 192.0 vs 24.5 days, P=0.028, respectively), which were also insignificantly higher than those of anti-lymphoma patients. Extranodal NK/T-cell lymphoma or aggressive natural killer cell leukemia was the risk factor of LAHS prognosis (HR=0.113, 95%CI: 0.018-0.728, P=0.022). Conclusions: Prognosis of LAHS patients is poor. Anti-lymphoma treatment should be initiated as soon as HLH is rapidly controlled.

Cryo-EM structures of the human GATOR1-Rag-Ragulator complex reveal a spatial-constraint regulated GAP mechanism

mTORC1 controls cellular metabolic processes in response to nutrient availability. Amino acid signals are transmitted to mTORC1 through the Rag GTPases, which are localized on the lysosomal surface by the Ragulator complex. The Rag GTPases receive amino acid signals from multiple upstream regulators. One negative regulator, GATOR1, is a GTPase activating protein (GAP) for RagA. GATOR1 binds to the Rag GTPases via two modes: an inhibitory mode and a GAP mode. How these two binding interactions coordinate to process amino acid signals is unknown. Here, we resolved three cryo-EM structural models of the GATOR1-Rag-Ragulator complex, with the Rag-Ragulator subcomplex occupying the inhibitory site, the GAP site, and both binding sites simultaneously. When the Rag GTPases bind to GATOR1 at the GAP site, both Rag subunits contact GATOR1 to coordinate their nucleotide loading states. These results reveal a potential GAP mechanism of GATOR1 during the mTORC1 inactivation process.

Conformational dynamics and allosteric modulation of the SARS-CoV-2 spike

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infects cells through binding to angiotensin-converting enzyme 2 (ACE2). This interaction is mediated by the receptor-binding domain (RBD) of the viral spike (S) glycoprotein. Structural and dynamic data have shown that S can adopt multiple conformations, which controls the exposure of the ACE2-binding site in the RBD. Here, using single-molecule Förster resonance energy transfer (smFRET) imaging, we report the effects of ACE2 and antibody binding on the conformational dynamics of S from the Wuhan-1 strain and in the presence of the D614G mutation. We find that D614G modulates the energetics of the RBD position in a manner similar to ACE2 binding. We also find that antibodies that target diverse epitopes, including those distal to the RBD, stabilize the RBD in a position competent for ACE2 binding. Parallel solution-based binding experiments using fluorescence correlation spectroscopy (FCS) indicate antibody-mediated enhancement of ACE2 binding. These findings inform on novel strategies for therapeutic antibody cocktails.

[Effects of exosomes from human adipose-derived mesenchymal stem cells on inflammatory response of mouse RAW264.7 cells and wound healing of full-thickness skin defects in mice]

Objective: To investigate the effects of exosomes from human adipose-derived mesenchymal stem cells (ADSCs) on inflammatory response of mouse RAW264.7 cells and wound healing of full-thickness skin defects in mice. Methods: The experimental research methods were adopted. The discarded adipose tissue was collected from 3 female patients (aged 10-25 years) who underwent abdominal surgery in the First Affiliated Hospital of Air Force Medical University. ADSCs were extracted from the adipose tissue by collagenase Ⅰ digestion and identified with flow cytometry. Exosomes were extracted from the human ADSCs by differential ultracentrifugation, the morphology of the exosomes was observed by transmission electron microscopy, the particle diameter of the exosomes was detected by nanoparticle tracking analyzer, and the protein expressions of CD9, CD63, tumor susceptibility gene 101 (TSG101), and β-actin were detected by Western blotting. The human ADSCs exosomes (ADSCs-Exos) and RAW264.7 cells were co-cultured for 12 h, and the uptake of RAW264.7 cells for human ADSCs-Exos was observed. The RAW264.7 cells were divided into phosphate buffer solution (PBS) group stimulated with PBS for suitable time, endotoxin/lipopolysaccharide (LPS) stimulation 2 h group, LPS stimulation 4 h group, LPS stimulation 6 h group, LPS stimulation 12 h group, and LPS stimulation 24 h group stimulated with LPS for corresponding time, with 3 wells in each group, and the mRNA expressions of interleukin 1β (IL-1β), tumor necrosis factor α (TNF-α), IL-6, and IL-10 were detected by real-time fluorescence quantitative reverse transcription polymerase chain reaction (RT-PCR) method. The RAW264.7 cells were divided into PBS group, LPS alone group, and LPS+ADSCs-Exos group, with 3 wells in each group, which were dealt correspondingly for the time screened out in the previous experiment, the mRNA expressions of IL-1β, TNF-α, IL-6, IL-10, trasforming growth factor β (TGF-β,) and vascular endothelial growth factor (VEGF) were detected by real time fluorescence quantitative RT-PCR method, and the protein expressions of inducible nitric oxide synthase (iNOS) and arginase 1 (Arg1) were detected by Western blotting. Twenty-four 8-week-old male BALB/c mice were divided into PBS group and ADSCs-Exos group according to the random number table, with 12 mice in each group, and a full-thickness skin defect wound with area of 1 cm×1 cm was inflicted on the back of each mouse. Immediately after injury, the wounds of mice in the two groups were dealt correspondingly. On post injury day (PID) 1, the concentration of IL-1β and TNF-α in serum were detected by enzyme-linked immunosorbent assay, and the mRNA expressions of IL-1β, TNF-α, and IL-6 were detected by real time fluorescence quantitative RT-PCR method. On PID 3, 6, 9, 12, and 15, the wound healing was observed and the wound non-healing rate was calculated. On PID 15, the defect length of skin accessory and collagen volume fraction (CVF) were detected by hematoxylin eosin staining and Masson staining, respectively, the CD31 expression and neovascularization were detected by immunohistochemistry, and the ratio of Ki67 positive cells, the ratio of iNOS and Arg1 double positive cells, and the ratio of iNOS positive cells to Arg1 positive cells and their fluorescence intensities were detected by immunofluorescence method. The number of samples in animal experiments was 6. Data were statistically analyzed with analysis of variance for repeated measurement, one-way analysis of variance, and independent sample t test. Results: At 12 h of culture, the cells exhibited a typical spindle shape, which were verified as ADSCs with flow cytometry. The exosomes with a vesicular structure and particle diameters of 29-178 nm, were positively expressed CD9, CD63, and TSG101 and negatively expressed β-actin. After 12 h of co-culture, the human ADSCs-Exos were endocytosed into the cytoplasm by RAW264.7 cells. The mRNA expressions of IL-1β, TNF-α, IL-6, and IL-10 of RAW264.7 cells in LPS stimulation 2 h group, LPS stimulation 4 h group, LPS stimulation 6 h group, LPS stimulation 12 h group, and LPS stimulation 24 h group were significantly higher than those in PBS group (with t) values of 39.10, 14.55, 28.80, 4.74, 48.80, 22.97, 13.25, 36.34, 23.12, 18.71, 29.19, 41.08, 11.68, 18.06, 8.54, 43.45, 62.31, 22.52, 21.51, and 37.13, respectively, P<0.01). The stimulation 12 h with significant expressions of all the inflammatory factors was selected as the time point in the following experiment. After stimulation of 12 h, the mRNA expressions of IL-1β, TNF-α, IL-6, and IL-10 of RAW264.7 cells in LPS alone group were significantly higher than those in PBS group (with t values of 44.20, 51.26, 14.71, and 8.54, respectively, P<0.01); the mRNA expressions of IL-1β, TNF-α, and IL-6 of RAW264.7 cells in LPS+ADSCs-Exos group were significantly lower than those in LPS alone group (with t values of 22.89, 25.51, and 8.03, respectively, P<0.01), while the mRNA expressions of IL-10, TGF-β, and VEGF were significantly higher than those in LPS alone group (with t values of 9.89, 13.12, and 7.14, respectively, P<0.01). After stimulation of 12 h, the protein expression of iNOS of RAW264.7 cells in LPS alone group was significantly higher than that in PBS group and LPS+ADSCs-Exos group, respectively (with t values of 11.20 and 5.06, respectively, P<0.05 or P<0.01), and the protein expression of Arg1 was significantly lower than that in LPS+ADSCs-Exos group (t=15.01, P<0.01). On PID 1, the serum concentrations of IL-1β and TNF-α and the mRNA expressions of IL-1β, TNF-α, and IL-6 in wound tissue of mice in ADSCs-Exos group were significantly those in lower than PBS group (with t values of 15.44, 12.24, 9.24, 7.12, and 10.62, respectively, P<0.01). On PID 3, 6, 9, 12, and 15 d, the wound non-healing rates of mice in ADSCs-Exos group were (73.2±4.1)%, (53.8±3.8)%, (42.1±5.1)%, (24.1±2.8)%, and 0, which were significantly lower than (82.5±3.8)%, (71.2±4.6)%, (52.9±4.1)%, (41.5±3.6)%, and (14.8±2.5)% in PBS group, respectively (with t values of 4.77, 8.93, 5.54, 7.63, and 7.59, respectively, P<0.01). On PID 15, the defect length of skin accessory in wounds of mice in PBS group was significantly longer than that in ADSCs-Exos group (t=9.50, P<0.01), and the CVF was significantly lower than that in ADSCs-Exos group (t=9.15, P<0.01). On PID 15, the CD31 expression and the number of new blood vessels (t=12.99, P<0.01), in wound tissue of mice in ADSCs-Exos group were significantly more than those in PBS group, and the ratio of Ki67 positive cells was significantly higher than that in PBS group (t=7.52, P<0.01). On PID 15, the ratio of iNOS and Arg1 double positive cells in wound tissue of mice in PBS group was (12.33±1.97)%, which was significantly higher than (1.78±0.29)% in ADSCs-Exos group (t=13.04, P<0.01), the ratio of iNOS positive cells and the fluorescence intensity of iNOS were obviously higher than those of ADSCs-Exos group, and the ratio of Arg1 positive cells and the fluorescence intensity of Arg1 were obviously lower than those of ADSCs-Exos group. Conclusions: The human ADSCs-Exos can alleviate inflammatory response of mouse RAW264.7 cells, decrease macrophage infiltration and secretion of the pro-inflammatory cytokines, increase the secretion of anti-inflammatory cytokines to promote neovascularization and cell proliferation in full-thickness skin defect wounds of mice, hence accelerating wound healing.

[Effects of exosomes from human adipose-derived mesenchymal stem cells on pulmonary vascular endothelial cells injury in septic mice and its mechanism]

Objective: To investigate the effects of exosomes from human adipose-derived mesenchymal stem cells (ADSCs) on pulmonary vascular endothelial cells (PMVECs) injury in septic mice and its mechanism. Methods: The experimental research method was adopted. The primary ADSCs were isolated and cultured from the discarded fresh adipose tissue of 3 patients (female, 10-25 years old), who were admitted to the First Affiliated Hospital of Air Force Medical University undergoing abdominal surgery, and the cell morphology was observed by inverted phase contrast microscope on the 5th day. The expressions of CD29, CD34, CD44, CD45, CD73, and CD90 of ADSCs in the third passage were detected by flow cytometry. The third to the fifth passage of ADSCs were collected, and their exosomes from the cell supernatant were obtained by differential ultracentrifugation, and the shape, particle size, and the protein expressions of CD9, CD63, tumor susceptibility gene 101 (TSG101), and β-actin of exosomes were detected, respectively, by transmission electron microscopy, nano-particle tracking analysis and Western blotting. Twenty-four adult male BALB/c mice were adopted and were divided into normal control group, caecal ligation perforation (CLP) alone group, and CLP+ADSC-exosome group with each group of 8 according to random number table (the same grouping method below) and were treated accordingly. At 24 h after operation, tumor necrosis factor (TNF-α) and interleukin 1β (IL-1β) levels of mice serum were detected by enzyme-linked immunosorbent assay, and lung tissue morphology of mice was detected by hematoxylin-eosin and myeloperoxidase staining, and the expression of 8-hydroxy-deoxyguanosine (8-OHdG) of mouse lung cells was detected by immunofluorescence method. Primary PMVECs were obtained from 1-month-old C57 mice regardless gender by tissue block method. The expression of CD31 of PMVECs was detected by immunofluorescence and flow cytometry. The third passage of PMVECs was co-cultured with ADSCs derived exosomes for 12 h, and the phagocytosis of exosomes by PMVECs was detected by PKH26 kit. The third passage of PMVECs were adopted and were divided into blank control group, macrophage supernatant alone group, and macrophage supernatant+ADSC-exosome group, with 3 wells in each group, which were treated accordingly. After 24 h, the content of reactive oxygen species in cells was detected by flow cytometry, the expression of 8-OHdG in cells was detected by immunofluorescence, and Transwell assay was used to determine the permeability of cell monolayer. The number of samples in above were all 3. Data were statistically analyzed with one-way analysis of variance and least significant difference t test. Results: The primary ADSCs were isolated and cultured to day 5, growing densely in a spindle shape with a typical swirl-like. The percentages of CD29, CD44, CD73 and CD90 positive cells of ADSCs in the third passage were all >90%, and the percentages of CD34 and CD45 positive cells were <5%. Exosomes derived from ADSCs of the third to fifth passages showed a typical double-cavity disc-like structure with an average particle size of 103 nm, and the protein expressions of CD9, CD63 and TSG101 of exosomes were positive, while the protein expression of β-actin of exosomes was negative. At 24 h after operation, compared with those in normal control group, both the levels of TNF-α and IL-1β of mice serum in CLP alone group were significantly increased (with t values of 28.76 and 29.69, respectively, P<0.01); compared with those in CLP alone group, both the content of TNF-α and IL-1β of mice serum in CLP+ADSC-exosome group was significantly decreased (with t values of 9.90 and 4.76, respectively, P<0.05 or P<0.01). At 24 h after surgery, the pulmonary tissue structure of mice in normal control group was clear and complete without inflammatory cell infiltration; compared with those in normal control group, the pulmonary tissue edema and inflammatory cell infiltration of mice in CLP alone group were more obvious; compared with those in CLP alone group, the pulmonary tissue edema and inflammatory cell infiltration of mice in CLP+ADSC-exosome group were significantly reduced. At 24 h after operation, endothelial cells in lung tissues of mice in 3 groups showed positive expression of CD31; compared with that in normal control group, the fluorescence intensity of 8-OHdG positive cells of the lung tissues of mice in CLP alone group was significantly increased, and compared with that in CLP alone group, the fluorescence intensity of 8-OHdG positive cells in the lung tissues of mice in CLP+ADSC-exosome group was significantly decreased. The PMVECs in the 3rd passage showed CD31 positive expression by immunofluorescence, and the result of flow cytometry showed that CD31 positive cells accounted for 99.5%. At 12 h after co-culture, ADSC-derived exosomes were successfully phagocytose by PMVECs and entered its cytoplasm. At 12 h after culture of the third passage of PMVECs, compared with that in blank control group, the fluorescence intensity of reactive oxygen species of PMVECs in macrophage supernatant alone group was significantly increased (t=15.73, P<0.01); compared with that in macrophage supernatant alone group, the fluorescence intensity of reactive oxygen species of PMVECs in macrophage supernatant+ADSC-exosome group was significantly decreased (t=4.72, P<0.01). At 12 h after culture of the third passage of PMVECs, and the 8-OHdG positive fluorescence intensity of PMVECs in macrophage supernatant alone group was significantly increased; and compared with that in blank control group, the 8-OHdG positive fluorescence intensity of PMVECs in macrophage+ADSC-exosome supernatant group was between blank control group and macrophage supernatant alone group. At 12 h after culture of the third passage PMVECs, compared with that in blank control group, the permeability of PMVECs monolayer in macrophage supernatant alone group was significantly increased (t=6.34, P<0.01); compared with that in macrophage supernatant alone group, the permeability of PMVECs monolayer cells in macrophage supernatant+ADSC-exosome group was significantly decreased (t=2.93, P<0.05). Conclusions: Exosomes derived from ADSCs can ameliorate oxidative damage in mouse lung tissue, decrease the level of reactive oxygen species, 8-OHdG expression, and permeability of PMVECs induced by macrophage supernatant.

Ribosome profiling reveals novel regulation of C9ORF72 GGGGCC repeat-containing RNA translation

GGGGCC (G₄C₂) repeat expansion in the first intron of C9ORF72 causes amyotrophic lateral sclerosis and frontotemporal dementia. Repeat-containing RNA is translated into dipeptide repeat (DPR) proteins, some of which are neurotoxic. Using dynamic ribosome profiling, we identified three translation initiation sites in the intron upstream of (G₄C₂) repeats; these sites are detected irrespective of the presence or absence of the repeats. During translocation, ribosomes appear to be stalled on the repeats. An AUG in the preceding C9ORF72 exon initiates a uORF that inhibits downstream translation. Polysome isolation indicates that unspliced (G₄C₂) repeat-containing RNA is a substrate for DPR protein synthesis. (G₄C₂) repeat-containing RNA translation is 5' cap-independent but inhibited by the initiation factor DAP5, suggesting an interplay with uORF function. These results define novel translational mechanisms of expanded (G₄C₂) repeat-containing RNA in disease.

A New Crosslinking Assay to Study Guanine Nucleotide Binding in the Gtr Heterodimer of S. cerevisiae

The mechanistic target of rapamycin (mTOR) complex is responsible for coordinating nutrient availability with eukaryotic cell growth. Amino acid signals are transmitted towards mTOR via the Rag/Gtr heterodimers. Due to the obligatory heterodimeric architecture of the Rag/Gtr GTPases, investigating their biochemical properties has been challenging. Here, we describe an updated assay that allows us to probe the guanine nucleotide-binding affinity and kinetics to the Gtr heterodimers in Saccharomyces cerevisiae. We first identified the structural element that Gtr2p lacks to enable crosslinking. By using a sequence conservation-based mutation, we restored the crosslinking between Gtr2p and the bound nucleotides. Using this construct, we determined the nucleotide-binding affinities of the Gtr heterodimer, and found that it operates under a different form of intersubunit communication than human Rag GTPases. Our study defines the evolutionary divergence of the Gtr/Rag-mTOR axis of nutrient sensing.

Conformational dynamics and allosteric modulation of the SARS-CoV-2 spike

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infects cells through binding to angiotensin-converting enzyme 2 (ACE2). This interaction is mediated by the receptor-binding domain (RBD) of the viral spike (S) glycoprotein. Structural and dynamic data have shown that S can adopt multiple conformations, which controls the exposure of the ACE2-binding site in the RBD. Here, using single-molecule Förster resonance energy transfer (smFRET) imaging we report the effects of ACE2 and antibody binding on the conformational dynamics of S from the Wuhan-1 strain and the B.1 variant (D614G). We find that D614G modulates the energetics of the RBD position in a manner similar to ACE2 binding. We also find that antibodies that target diverse epitopes, including those distal to the RBD, stabilize the RBD in a position competent for ACE2 binding. Parallel solution-based binding experiments using fluorescence correlation spectroscopy (FCS) indicate antibody-mediated enhancement of ACE2 binding. These findings inform on novel strategies for therapeutic antibody cocktails.

mTOR-Activating Mutations in RRAGD Are Causative for Kidney Tubulopathy and Cardiomyopathy

BACKGROUND

Over the last decade, advances in genetic techniques have resulted in the identification of rare hereditary disorders of renal magnesium and salt handling. Nevertheless, approximately 20% of all patients with tubulopathy lack a genetic diagnosis.

METHODS

We performed whole-exome and -genome sequencing of a patient cohort with a novel, inherited, salt-losing tubulopathy; hypomagnesemia; and dilated cardiomyopathy. We also conducted subsequent in vitro functional analyses of identified variants of RRAGD, a gene that encodes a small Rag guanosine triphosphatase (GTPase).

RESULTS

In eight children from unrelated families with a tubulopathy characterized by hypomagnesemia, hypokalemia, salt wasting, and nephrocalcinosis, we identified heterozygous missense variants in RRAGD that mostly occurred de novo. Six of these patients also had dilated cardiomyopathy and three underwent heart transplantation. We identified a heterozygous variant in RRAGD that segregated with the phenotype in eight members of a large family with similar kidney manifestations. The GTPase RagD, encoded by RRAGD, plays a role in mediating amino acid signaling to the mechanistic target of rapamycin complex 1 (mTORC1). RagD expression along the mammalian nephron included the thick ascending limb and the distal convoluted tubule. The identified RRAGD variants were shown to induce a constitutive activation of mTOR signaling in vitro.

CONCLUSIONS

Our findings establish a novel disease, which we call autosomal dominant kidney hypomagnesemia (ADKH-RRAGD), that combines an electrolyte-losing tubulopathy and dilated cardiomyopathy. The condition is caused by variants in the RRAGD gene, which encodes Rag GTPase D; these variants lead to an activation of mTOR signaling, suggesting a critical role of Rag GTPase D for renal electrolyte handling and cardiac function.

Efficacy of utidelone plus capecitabine versus capecitabine for heavily pretreated, anthracycline- and taxane-refractory metastatic breast cancer: final analysis of overall survival in a phase III randomised controlled trial

BACKGROUND

Primary analysis of the phase III trial BG01-1323L demonstrated that utidelone plus capecitabine significantly improved progression-free survival (PFS) and overall response rate (ORR) versus capecitabine alone in heavily-pretreated patients with metastatic breast cancer (MBC). Here, we report the final overall survival (OS) analysis and updates of other endpoints.

PATIENTS AND METHODS

In total, 405 patients were randomised 2:1 to receive utidelone (30 mg/m² IV daily, days 1-5, over 90 min) plus capecitabine (1000 mg/m² orally b.i.d., days 1-14) or capecitabine alone (1250 mg/m² orally b.i.d., days 1-14) every 21 days. The secondary endpoint, OS, was estimated using the Kaplan-Meier product-limit approach at a two-sided alpha level of 0.05 after the prespecified 310 death events had been reached. Exploratory analyses of the primary endpoint, PFS, and the secondary endpoint, ORR, were also done. Safety was analysed in patients who had at least one dose of study drug.

RESULTS

At the final OS analysis, the median duration of follow-up was 19.6 months in the utidelone plus capecitabine group and 15.4 months in the capecitabine alone group. In the intention-to-treat population, 313 deaths had occurred at data cut-off, 203 of 270 patients in the combination group and 110 of 135 in the monotherapy group. Median OS in the combination group was 19.8 months compared with 16.0 months in the monotherapy group [hazard ratio (HR) = 0.75, 95% confidence intervals (CI) 0.59-0.94, P = 0.0142]. The updated analysis of PFS and ORR showed that the combination therapy remained superior to monotherapy. Safety results were similar to those previously reported with respect to incidence, severity and specificity. No late-emerging toxicities or new safety concerns occurred.

CONCLUSIONS

For heavily-pretreated, anthracycline- and taxane-resistant MBC patients, utidelone plus capecitabine significantly improved OS versus capecitabine alone. These results support the use of utidelone plus capecitabine as a novel therapeutic regimen for patients with MBC.

[Clinicopathological features and prognosis in patients with presacral recurrent rectal cancer]

Objective: To investigate the clinicopathological features and prognostic factors in patients with presacral recurrent rectal cancer (PRRC). Methods: PRRC was defined as recurrence of rectal cancer after radical surgery involving posteriorly the presacral soft tissue, the sacrum/coccyx, and/or sacral nerve root. The diagnosis is confirmed with clinical symptoms (pain of pelvis/back/lower limb, bloody stools, increased frequency of defecation, and abnormal secretions), physical examination of perineal or pelvic masses, radiological findings, colonoscopy with histopathological biopsy, and the evaluation by multi-disciplinary team (MDT). Inclusion criteria: (1) primary rectal cancer undergoing radical surgery without distant metastasis; (2) PRRC was diagnosed; (3) complete inpatient, outpatient and follow-up data. According to the above criteria, clinical data of 72 patients with PRRC in Peking University People's Hospital from January 2008 to December 2017 were retrospectively analyzed. The clinicopathological features and follow-up data were summarized. Cox proportional hazard models was used to analyze the prognostic factors of PRRC. Results: Among 72 patients, 45 were male and 27 were female with a male-to-female ratio of 1.7:1.0. The median age at recurrence was 58 (34 to 83) years and the median interval from surgery to recurrence was 2.0 (0.2 to 17.0) years. The main symptom was pain in 48.6% (35/72) of patients. In addition, gastrointestinal symptoms were found in 25.0% (18/72) of patients. The presacral recurrent sites were presacral fascia in 36 (50.0%) patients, lower sacrum (S3~S5 or coccyx) in 25 (34.7%) patients, and higher sacrum (S1~S2) in 11 (15.3%) patients. Forty-seven (65.3%) patients underwent radical surgery (abdominal resection, abdominoperineal resection, sacrectomy, abdominosacral resection), 12 (16.7%) underwent non-radical surgery (colostomy, cytoreductive surgery), and 13 (18.1%) did not undergo any surgery but only receive palliative chemoradiotherapy and nutritional support treatment. Thirty-three (45.8%) patients received radiotherapy and/or chemotherapy (oxaliplatin, 5-fluorouracil, capecitabine, irinotecan, etc.). All the patients received follow-up, and the median follow-up time was 19 (2 to 72) months. The median overall survival time was 14 (1 to 65) months. The 1- and 3-year overall survival rates were 67.1% and 32.0%, respectively. Univariate analysis showed that age at recurrence (P=0.031) and radical resection (P<0.001) were associated with prognosis. Multivariate analysis demonstrated that radical resection was independent factor of good prognosis (RR=0.140, 95%CI: 0.061-0.322, P<0.001). Conclusions: Patients tend to develop presacral recurrent rectal cancer within 2 years after primary surgery. The main symptom is pain. Patients undergoing radical resection have a relatively good prognosis.

[Comparison of clinical efficacy among different surgical methods for presacral recurrent rectal cancer]

Objective: To investigate the efficacy and prognosis of three surgical methods for presacral recurrent rectal cancer (PRRC). Methods: A retrospective cohort study was carried out. Case inclusion criteria: (1) primary rectal cancer without distant metastasis and undergoing radical surgery; (2) patients undergoing radical surgery after the diagnosis of PRRC; (3) complete inpatient, outpatient and follow-up data. Clinical data of 47 patients meeting the above criteria who underwent operation at the Department of Gastrointestinal Surgery, The Peking University People's Hospital from January 2008 to December 2017 were reviewed and analyzed retrospectively. Of the 47 patients, 31 were male and 16 were female; the mean age was 57 years old; 9 (19.1%) were low differentiation or signet ring cell carcinoma, 38 (80.9%) were medium differentiation; 19 (40.4%) received neoadjuvant therapy. According to operative procedure, 22 patients were in the abdominal/abdominoperineal resection group, 15 in the sacrectomy group and 10 in the abdominosacral resection group. The operative data, postoperative data and prognosis were compared among the three groups. Survival curve was conducted using the Kaplan-Meier method, and log-rank test was used to compare survival difference among three groups. Results: There were no significant differences in baseline data among three groups (all P>0.05). All the 47 patients completed the radical resection successfully. The mean operation time was (4.7±2.1) hours, the median intraoperative blood loss was 600 ml, and the median postoperative hospitalization time was 17 days. Fifteen cases (31.9%) had perioperative complications, of which 3 cases were grade III-IV. There was no perioperative death. The mean operative time was (7.4±1.6) hours in the abdominosacral resection group, (4.9±1.6) hours in the abdominal/abdominoperineal resection group, and (3.0±1.1) hours in the sacroectomy group, with a significant difference (F=25.071, P<0.001). There were no significant differences in intraoperative blood loss, postoperative hospitalization days and perioperative complications among the three groups (all P>0.05). The median follow-up period of all the patients was 24 months, 12 cases (25.5%) developed postoperative dysfunction. The incidence of postoperative dysfunction in the abdominosacral resection group was 5/10, which was higher than 4/15 in the sacrectomy group and 3/22 (13.6%) in the abdominoperineal resection group with statistically significant difference (χ(2)=9.307, P=0.010). The 1-year and 3-year overall survival rates were 86.1% and 40.2% respectively. The 1-year overall survival rates were 86.0%, 86.7% and 83.3%, and the 3-year overall survival rates were 33.2%, 40.0% and 62.5% in the abdominal/abdominoperineal resection group, sacrectomy group and abdominosacral resection group, respectively, whose difference was not statistically significant (χ(2)=0.222, P=0.895). Conclusions: Abdominal/abdominoperineal resection, sacrectomy and abdominosacral resection are all effective for PRRC. Intraoperative function protection should be concerned for patients undergoing abdominosacral resection.

Abstract PR02: Structural and functional analyses of GATOR1, a negative regulator of the mTORC1 pathway

mTORC1 is a major regulator for cell growth and proliferation that coordinates nutrient inputs, such as amino acids, glucose, and growth factor, with anabolic and catabolic processes in cells. Amino acid signals are transmitted towards mTORC1 through the Rag GTPases, which directly recruit mTORC1 onto the lysosomal membrane. The Rag GTPase heterodimer has a unique architecture that consists of two GTPase subunits, RagA or RagB bound to RagC or RagD. Their nucleotide loading states are strictly controlled by several lysosomal or cytosolic protein complexes that directly process the amino acid signal. One such complex is GATOR1, a negative regulator on the cytosolic branch of the amino acid sensing pathway. GATOR1 comprises three subunits, Depdc5, Nprl2, and Nprl3, and is a GTPase Activating Protein (GAP) for RagA. It functions through a noncanonical GAP mechanism in which GATOR1 binds the Rag GTPases with two modes, an inhibitory mode that holds the Rag GTPase heterodimer and has been captured by structural determination, and a GAP mode that actually stimulates GTP hydrolysis by RagA but remains elusive. Here, we used biochemical approaches to probe the GAP mode of GATOR1 and found that a critical arginine finger on Nprl2, Arg78, is the catalytic residue, while a loop localized close to it provides the binding site for the Rag GTPases. Furthermore, we used cryo-EM to resolve the structure of the GATOR1-Rag-Ragulator complex at 4.1A resolution, which represents the architecture of the mTORC1-inhibiting complex on the lysosomal surface. Our results revealed the molecular bases for mTORC1 inactivation in human cells.

This abstract is also being presented as Poster B10.

Citation Format: Kuang Shen, Rick Huang, Zhiheng Yu, David M. Sabatini. Structural and functional analyses of GATOR1, a negative regulator of the mTORC1 pathway [abstract]. In: Proceedings of the AACR Special Conference on Targeting PI3K/mTOR Signaling; 2018 Nov 30-Dec 8; Boston, MA. Philadelphia (PA): AACR; Mol Cancer Res 2020;18(10_Suppl):Abstract nr PR02.

[Effects and mechanism of pyrroloquinoline quinine on mitochondrial function and cell survival of rat bone marrow mesenchymal stem cells under oxidative stress]

Objective: To observe the effects of pyrroloquinoline quinine (PQQ) on the mitochondrial function and cell survival of rat bone marrow mesenchymal stem cells (BMSCs) under oxidative stress, and to explore its mechanism. Methods: BMSCs of rats were cultured in vitro with Dulbecco's minimum essential medium/F12 medium containing fetal bovine serum in the volume fraction of 10% (hereinafter referred to as normal medium). The rat BMSCs of third to fifth passages in logarithmic growth phase were selected for the following experiments. (1) The cells were divided into normal control group, normal control+ PQQ group, hydrogen peroxide (H(2)O(2)) alone group, and H(2)O(2)+ PQQ group. The cells in normal control group were cultured in normal medium for 24 hours; the cells in normal control+ PQQ group were cultured in normal medium containing 100 μmol/L PQQ for 24 hours; the cells in H(2)O(2) alone group were cultured in normal medium containing 200 μmol/L H(2)O(2) for 24 hours; the cells in H(2)O(2)+ PQQ group were pre-incubated with normal medium containing 100 μmol/L PQQ for 2 hours, and then with H(2)O(2) added to the concentration of 200 μmol/L and cultured for 24 hours. The cell morphology of each group was observed under the inverted phase contrast microscope, and the cell survival rate was detected by cell count kit 8 method. (2) Five batches of cells were collected, and the cells of each batch were divided into normal control group, H(2)O(2) alone group, and H(2)O(2)+ PQQ group. The cells in each group received the same treatment as that in the corresponding group of experiment (1). After 24 hours of culture, one batch of cells was collected for apoptosis detection by flow cytometry, and the apoptosis rate was calculated. One batch of cells was subjected to mitochondrial membrane potential assay and JC-1 fluorescent staining observation using the JC-1 mitochondrial membrane potential detection kit and the inverted phase contrast fluorescence microscope, respectively. One batch of cells was collected for mitochondrial morphology observation under the transmission electron microscope. One batch of cells was subjected to catalase (CAT) and superoxide dismutase (SOD) activity assay by CAT activity assay kit and SOD activity assay kit, respectively. One batch of cells was subjected to Western blotting for determination of protein level of Epac1, adenine monophosphate activated protein kinase (AMPK), phosphorylated AMPK, cysteinyl aspartate-specific proteinase 3 (caspase-3), and cleaved caspase-3, and the phosphorylation level of AMPK and cleaved caspase-3/caspase-3 ratio were calculated. Six replicates were measured in each group for each index except for morphological observation. Data were statistically analyzed with one-way analysis of variance and independent sample equal variance t test. Results: (1) After 24 hours of culture, compared with those in normal control group (the cell survival rate was set to 100.0%), there was an increase in cell vacuole and a decrease in cell number in H(2)O(2) alone group, and the cell survival rate was significantly reduced to (74.3±2.9)% (t=6.39, P<0.01). Compared with those in H(2)O(2) alone group, the cell morphology of H(2)O(2)+ PQQ group was significantly improved, and the cell survival rate was significantly increased to (116.9±4.2)% (t=6.92, P<0.01); the cell survival rate in normal control+ PQQ group was (101.2±1.1)%, close to that of control group (t=1.06, P>0.05). (2) After 24 hours of culture, compared with (13.6±1.0)% in normal control group, the apoptosis rate of cells in H(2)O(2) alone group was significantly increased to (37.1±2.0)% (t=10.57, P<0.01). Compared with that in H(2)O(2) alone group, the apoptosis rate of cells in H(2)O(2)+ PQQ group was significantly declined to (17.0±0.7)% (t=9.49, P<0.01). (3) After 24 hours of culture, compared with those in normal control group, the mitochondrial membrane potential of cells in H(2)O(2) alone group was depolarized, the JC-1 fluorescent dye mainly existed in the cytoplasm in the form of monomer, which emitted green fluorescence, and a significant decrease in mitochondrial membrane potential was shown (t=4.18, P<0.01). Compared with those in H(2)O(2) alone group, the mitochondrial membrane potential of cells in H(2)O(2)+ PQQ group was increased to normal level (t=4.43, P<0.01), and the JC-1 fluorescent dye accumulated in mitochondria following the polarized mitochondrial membrane potential and emitted red fluorescence. (4) After 24 hours of culture, compared with that in normal control group, the mitochondrial structure of cells in H(2)O(2) alone group was disordered, with disappeared mitochondrial cristae and decreased mitochondrial matrix density. Compared with that in H(2)O(2) alone group, the mitochondrial structure of cells in H(2)O(2)+ PQQ group was regular and intact, with clearly visible mitochondrial cristae and increased mitochondrial matrix density. (5) After 24 hours of culture, compared with those in normal control group, the CAT activity of cells in H(2)O(2) alone group was significantly increased (t=4.54, P<0.05), and the SOD activity was significantly decreased (t=3.93, P<0.05). Compared with those in H(2)O(2) alone group, the CAT activity of cells in H(2)O(2)+ PQQ group was obviously increased (t=8.65, P<0.01), while there was no significant change in the SOD activity (t=0.72, P>0.05). (6) After 24 hours of culture, compared with those in normal control group, the protein expression of Epac1 of cells in H(2)O(2) alone group was significantly decreased (t=4.67, P<0.01), while the AMPK phosphorylation level and the cleaved caspase-3/caspase-3 ratio were significantly increased (t=7.88, 3.62, P<0.01). Compared with those in H(2)O(2) alone group, the protein expression of Epac1 and the AMPK phosphorylation level of cells in H(2)O(2)+ PQQ group were both significantly increased (t=4.34, 16.37, P<0.01), while the cleaved caspase-3/caspase-3 ratio was significantly declined (t=3.17, P<0.05). Conclusions: Pretreatment with PQQ can improve the mitochondrial function, reduce cell apoptosis rate, and enhance cell survival rate of rat BMSCs under oxidative stress, which may be related to the up-regulation of Epac1 protein expression, activation of AMPK signaling pathway, and down-regulation of cleaved caspase-3 protein level.

Structural and Functional Analysis of the D614G SARS-CoV-2 Spike Protein Variant

The SARS-CoV-2 spike (S) protein variant D614G supplanted the ancestral virus worldwide in a matter of months. Here we show that D614G was more infectious than the ancestral form on human lung cells, colon cells, and cells rendered permissive by ectopic expression of various mammalian ACE2 orthologs. Nonetheless, D614G affinity for ACE2 was reduced due to a faster dissociation rate. Assessment of the S protein trimer by cryo-electron microscopy showed that D614G disrupts a critical interprotomer contact and that this dramatically shifts the S protein trimer conformation toward an ACE2-binding and fusion-competent state. Consistent with the more open conformation, neutralization potency of antibodies targeting the S protein receptor-binding domain was not attenuated. These results indicate that D614G adopts conformations that make virion membrane fusion with the target cell membrane more probable but that D614G retains susceptibility to therapies that disrupt interaction of the SARS-CoV-2 S protein with the ACE2 receptor.

[Procedure for prolapse and hemorrhoids versus stapled transanal rectal resection in the treatment of grade IV hemorrhoids]

Objective: To compare the efficacy and safety of two procedures in the treatment of hemorrhoid: the procedure for prolapse and hemorrhoids (PPH) and stapled transanal rectal resection (STARR). Methods: A retrospective cohort research was conducted. Clinical data of 263 patients undergoing the first elective surgery for grade IV hemorrhoids by the same team of surgeons at our department from January 2015 to December 2016 were analyzed retrospectively, while those had other anorectal diseases, emergency surgery, inflammatory bowel disease, tumor and incomplete clinical data were excluded. PPH was performed in 129 patients and STARR was performed in 134 patients. PPH procedure: a circular purse 2-0 string suture was made at 4 cm above the dentate line; in accordance with the standard protocol, the PPH circular stapling devicewas introduced; the suture was closed, and a pull-through followed; the traction was continued; the stapler was fired; the prolapsed mucosa and submucosa were removed. STARR procedure: 3-5 needles were sutured in the anterior rectal mucosa, protecting the posterior wall mucosa; with the help of a finger the PPH stapler was inserted into the vaginal lumen; the sutures were hooked from both sides of the stapler to maintain traction; according to the disease condition, the suturewas tightened appropriately; stapler was screwed and activated; the anterior wall mucosa was removed; the joint of the both ends of anastomosis was cut; the posterior wall mucosa was removed as well. The short-term efficacy, surgical safety and prognosis of the two groups were compared. Results: There were 67 males (51.9%) in the PPH group and 57 (42.5%) males in the STARR group. The median age of the two groups was 51.0 (22.0, 80.0) years and 49.0 (24.0, 74.0) years, respectively. There were no significant differences in the baseline data between the two groups (all P>0.05). No significant differences in the intraoperative bleeding, length of hospital stay, postoperative analgesic drug use, postoperative bleeding, postoperative infection, etc. were found between two groups (all P>0.05). As compared to PPH group, STAAR group had longer operation time and higher hospitalization cost with significant differences [(44.0±19.3) minutes vs. (26.3±8.5) minutes, t=9.701, P=0.001; (11 047±473) yuan vs. (7674±309) yuan, t=32.826, P=0.001]. One case in STAAR group developed rectovaginal fistula. The median follow-up period of the whole group was 40 (33, 52) months. A total of 108 cases in STARR group and 114 cases in PPH group completed the follow-up. The 3-year disease-relapse rate was 0 in STARR group and 4.2% in PPH group (P=0.042). Conclusion: STARR procedure can improve the prognosis in the treatment of grade IV hemorrhoid, but attention should be paid to the development of complications.

Cryo-EM Structure of the Human FLCN-FNIP2-Rag-Ragulator Complex

mTORC1 controls anabolic and catabolic processes in response to nutrients through the Rag GTPase heterodimer, which is regulated by multiple upstream protein complexes. One such regulator, FLCN-FNIP2, is a GTPase activating protein (GAP) for RagC/D, but despite its important role, how it activates the Rag GTPase heterodimer remains unknown. We used cryo-EM to determine the structure of FLCN-FNIP2 in a complex with the Rag GTPases and Ragulator. FLCN-FNIP2 adopts an extended conformation with two pairs of heterodimerized domains. The Longin domains heterodimerize and contact both nucleotide binding domains of the Rag heterodimer, while the DENN domains interact at the distal end of the structure. Biochemical analyses reveal a conserved arginine on FLCN as the catalytic arginine finger and lead us to interpret our structure as an on-pathway intermediate. These data reveal features of a GAP-GTPase interaction and the structure of a critical component of the nutrient-sensing mTORC1 pathway.

Hollow core-shell structured TS-1@S-1 as an efficient catalyst for alkene epoxidation

Hollow core-shell structured TS-1@S-1 zeolite (HCS-TS) was prepared successfully for the first time, which exhibited excellent activity in the epoxidation of alkenes. Combining TEM, UV-vis, UV-Raman, pyridine-IR, solid-state MAS NMR, XPS and so on characterization, the improvement in the catalytic performance of hollow core-shell structured TS-1@S-1 zeolite was credited to the newly formed superior active sites: defective Ti(OSi)₃(OH) species in HCS-TS and six-coordinated titanium active species in uncalcined HCS-TS (HCS-TS^P). Interestingly, these two different titanium active species in the samples could be constructed through calcination or not in the same synthesis process. A possible formation mechanism was investigated in detail; it indicated that the hollowing treatment of TS-1 in the first step was conducive to the construction of the new superior active sites in the samples, and there was a synergistic effect on the formation of these active sites between TPAOH and TEOS in the second step of the synthesis process. This strategy is feasible to enhance the catalytic performance of TS-1, and is suitable for the synthesis of TS-1 on an industrial scale.

Low temperature hidden Fermi-liquid charge transport in under doped La x Sr1-x CuO2 infinite layer electron-doped thin films

We have studied the low temperature electrical transport properties of La _x Sr_1-x CuO₂ thin films grown by oxide molecular beam epitaxy on (1 1 0) GdScO₃ and TbScO₃ substrates. The transmission electron microscopy measurements and the x-ray diffraction analysis confirmed the epitaxy of the obtained films and the study of their normal state transport properties, removing the ambiguity regarding the truly conducting layer, allowed to highlight the presence of a robust hidden Fermi liquid charge transport in the low temperature properties of infinite layer electron doped cuprate superconductors. These results are in agreement with recent observations performed in other p  and n doped cuprate materials and point toward a general description of the superconducting and normal state properties in these compounds.

C7orf59/LAMTOR4 phosphorylation and structural flexibility modulate Ragulator assembly

Ragulator is a pentamer composed of p18, MP1, p14, C7orf59, and hepatitis B virus X‐interacting protein (HBXIP; LAMTOR 1—5) which acts as a lysosomal scaffold of the Rag GTPases in the amino acid sensitive branch of TORC1 signaling. Here, we present the crystal structure of human HBXIP‐C7orf59 dimer (LAMTOR 4/5) at 2.9 Å and identify a phosphorylation site on C7orf59 which modulates its interaction with p18. Additionally, we demonstrate the requirement of HBXIP‐C7orf59 to stabilize p18 and allow further binding of MP1‐p14. The structure of the dimer revealed an unfolded N terminus in C7orf59 (residues 1–15) which was shown to be essential for p18 binding. Full‐length p18 does not interact stably with MP1‐p14 in the absence of HBXIP‐C7orf59, but deletion of p18 residues 108–161 rescues MP1‐p14 binding. C7orf59 was phosphorylated by protein kinase A (PKA) in vitro and mutation of the conserved Ser67 residue to aspartate prevented phosphorylation and negatively affected the C7orf59 interaction with p18 both in cell culture and in vitro. C7orf59 Ser67 was phosphorylated in human embryonic kidney 293T cells. PKA activation with forskolin induced dissociation of p18 from C7orf59, which was prevented by the PKA inhibitor H‐89. Our results highlight the essential role of HBXIP‐C7orf59 dimer as a nucleator of pentameric Ragulator and support a sequential model of Ragulator assembly in which HBXIP‐C7orf59 binds and stabilizes p18 which allows subsequent binding of MP1‐p14.

[Clinicopathological features and prognosis of patients in endometrial cancer with bone metastases]

Objective: To analyze the clinicopathological features and prognosis of patients in endometrial cancer with bone metastases. Methods: A retrospective review of medical records was performed to analyze patients with endometrial cancer who developed bone metastases at Peking Union Medical College Hospital (PUMCH) from January 2004 to December 2017, including patients with bone metastases at the diagnosis of endometrial cancer and at recurrence of endometrial cancer. The patient's clinicopathological features, bone metastasis characteristics, treatment process and prognoses were also analyzed. Results: The incidence of bone metastasis of endometrial cancer in PUMCH from 2004 to 2017 was 0.57% (14/2 458). (1) General clinical pathological features: the median age of the 7 patients with bone metastases diagnosed at the time of initial diagnosis was 50 years old, and the main pathological type was endometrioid carcinoma (n=5). The median age of the other 7 patients was 57 years old, with no significant difference comparing to the former groups (P=0.559). (2) The majority site of bone metastasis in endometrial cancer were discovered in pelvic bones, followed by the tibia. (3) Treatment: according to the staging of endometrial cancer, a comprehensive treatment based on surgery was performed, and one patient with isolated bone metastases underwent resection of bone metastasis. (4) Prognosis: nine out of the 14 patients died during the follow-up period. The median over all survival time was 25.5 months (range: 7.7-258.0 months). The median survival of population after diagnosis of bone metastases was 15.0 months (range: 3.0-51.0 months). The survival rate of endometrial cancer at 1-year after diagnosis of bone metastasis was 71.4%. The 2-year survival rate was 40.8%. (5) No independent prognostic factors affecting survival was found (P>0.05). Conclusions: The incidence of bone metastasis in endometrial cancer is less than 1%. Bone metastasis could occur at the diagnosis of endometrial cancer or recurrence of endometrial cancer. Bone metastasis suggests a poor prognosis. There is no standard follow-up and treatment protocols so that individualized treatment is needed.

Abstract P3-03-08: Not presented

This abstract was not presented at the conference.

Citation Format: Liang Y, Chen X, Zhan W, Zhu Y, Wu J, Huang O, He J, Zhu L, Li Y, Chen W, Shen K. Not presented [abstract]. In: Proceedings of the 2018 San Antonio Breast Cancer Symposium; 2018 Dec 4-8; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2019;79(4 Suppl):Abstract nr P3-03-08.