Methicillin-resistant Staphylococcus aureus (MRSA) is the most frequent cause of hospital-acquired infection, which manifests as surgical site infections, bacteremia, and sepsis. Due to drug-resistance, prophylaxis of MRSA infection with antibiotics frequently fails or incites nosocomial diseases such as Clostridium difficile infection. Sortase A is a transpeptidase that anchors surface proteins in the envelope of S. aureus, and sortase mutants are unable to cause bacteremia or sepsis in mice. Here we used virtual screening and optimization of inhibitor structure to identify 3-(4-pyridinyl)-6-(2-sodiumsulfonatephenyl) [1,2,4]

Background: The molecular mechanism of ClpP dynamic switching between different conformations is poorly understood. Results: MD simulations describe the molecular pathway of the transition between three conformations of SaClpP. Conclusion: Helix unfolding/refolding characterizes the functional dynamics and mechanism of ClpP. Significance: This study provides molecular insights into the dynamics and mechanism of ClpP in general.

ATP-dependent Clp protease (ClpP), a highly conserved serine protease in vast bacteria, could be converted into a noncontrollable enzyme capable of degrading mature proteins in the presence of acyldepsipeptides (ADEPs). Here, we design such a gain-of-function mutant of Staphylococcus aureus ClpP (SaClpP) capable of triggering the same level of dysfunctional activity that occurs upon ADEPs treatment. The SaClpPY63A mutant degrades FtsZ in vivo and inhibits staphylococcal growth. The crystal structure of SaClpPY63A indicates that Asn42 would be an important domino to fall for further activation of ClpP. Indeed, the SaClpPN42AY63A mutant demonstrates promoted self-activated proteolysis, which is a result of an enlarged entrance pore as observed in cryo-electron microscopy images. In addition, the expression of the engineered clpP allele phenocopies treatment with ADEPs; inhibition of cell division occurs as does showing sterilizing with rifampicin antibiotics. Collectively, we show that the gain-of-function SaClpPN42AY63A mutant becomes a fairly nonspecific protease and kills persisters by degrading over 500 proteins, thus providing new insights into the structure of the ClpP protease.

The reagents (chemicals) were purchased from Lancaster, Alfa Aesar, J&K, Acros, and Shanghai Chemical Reagent Co. and used without further purification. Analytical thin-layer chromatography (TLC) was HSGF 254 (150-200 μm thickness; Yantai Huiyou Co., China). Yields were not optimized. Melting points were measured in capillary tube on a SGW X-4 melting point apparatus without correction. Nuclear magnetic resonance (NMR) spectroscopy was performed on a Bruker AMX-500, AMX-400 and AMX-300 NMR (IS as TMS). Chemical shifts were reported in parts per million (ppm, δ) downfield from tetramethylsilane. Proton coupling patterns were described as singlet (s), doublet (d), triplet (t), quartet (q), multiplet (m), and broad (br). Low-and high-resolution mass spectra (LRMS and HRMS) were given with electric, electrospray, and matrix-assisted laser desorption ionization (EI, ESI, and MALDI) produced by a Finnigan MAT-95, LCQ-DECA spectrometer and IonSpec 4.7 T.

The human ABH2 and ABH3 proteins are functionally complementary in the oxidative demethylation of N(1)-methyl adenine (1-meA) and N(3)-methyl cytosine (3-meC) nucleotide bases. ABH3 displays higher activities with single-stranded DNA (ssDNA) in vitro, whereas ABH2 acts as the primary housekeeping enzyme in mammals for effectively repairing endogenously formed alkylated lesions in double-stranded DNA (dsDNA). Structurally, their overall protein folding is quite similar, but the most significant differences occur in the nucleotide recognition lid and the β-hairpin motif. We present here a site-directed mutational analysis and motif-swapping study to gain mechanistic insight into DNA substrate selection by ABH2 and ABH3. A V101A-F102A double mutant notably reduced ABH2 activity in dsDNA, indicating that this hydrophobic region appears to be important for damage searching and repair. The phenylalanine finger F102 is found to be crucial for ssDNA selection and repair as well; however, V101 shows reduced demethylating activity for only ssDNA and not dsDNA. The ABH2 R110A mutant completely loses the methyl base repair activity, suggesting that R110 is likely to be involved in the base flipping process. E175 and F124 contribute to nucleotide base specific selection and stabilization in the active site for repair. Additionally, swapping the RED residues in ABH3 to equivalent VFG residues in ABH2 endows ABH3 with activity in dsDNA repair as efficient as wild-type ABH2. Surprisingly, by changing just a few residues, the ABH3 protein can have very different selectivity towards ssDNA or dsDNA. This result indicates that the RED motif most likely prevents ABH3 binding and repair of dsDNA. Consistently, swapped ABH3 cross-links with dsDNA very well, confirming the determining roles of these residues in the initial DNA strand recognition. Overall, this work has provided a detailed understanding of the structural features of the ssDNA and dsDNA preferences of ABH2 and ABH3.

Sonazoid is an ultrasound contrast agent based on microbubbles (MB) containing perfluorobutane (PFB) gas. Sonazoid is approved in Japan, Korea and Norway for contrast-enhanced ultrasonography of focal liver lesions and focal breast lesions (Japan only). The objective of this study was to determine the pharmacokinetics (PKs) and safety of Sonazoid in Chinese healthy volunteers (HVs) and to evaluate the potential for ethnic differences in PKs between Chinese and Caucasian HVs. Sonazoid was administered as an intra-venous bolus injection at the clinical dose of 0.12 μL or 0.60 μL MB/kg body weight to two groups of eight Chinese HVs. Expired air and blood samples were collected and analyzed using a validated gas chromatographic tandem mass spectrometry method, and the main PK parameters were calculated. The highest PFB concentrations in blood were observed shortly after intra-venous administration of Sonazoid, and elimination of PFB was rapid. In the 0.12 μL MB/kg body weight cohort, PFB concentrations above the limit of quantification were observed for only 10 to 15 min post-injection. In the 0.60 μL MB/kg body weight cohort, PFB concentrations above the limit of quantification were observed for 60 min post-injection, and the shape of the elimination curve suggested a biphasic elimination profile. The maximum observed concentration (C) values of PFB in blood were 2.3 ± 1.1 and 19.1 ± 9.2 ng/g for the 0.12 and 0.60 μL MB/kg body weight dose groups (mean ± standard deviation). Area under the curve values were 10.1 ± 2.7 and 90.1 ± 38.3 ng × min/g for the 0.12 and 0.60 μL MB/kg body weight dose groups. C values of PFB in exhaled air were 0.35 ± 0.2 and 2.4 ± 0.7 ng/mL for the 0.12 and 0.60 μL MB/kg body weight dose groups. Assessment of laboratory parameters, vital signs, oxygen saturation and electrocardiograms revealed no changes indicative of a concern. The PK profile and safety data generated in the Chinese HVs were comparable to previous data for Caucasian HVs.

Immunotherapy especially immune checkpoint inhibitors (ICIs) has brought favorable clinical results for numerous cancer patients. However, the efficacy of ICIs in colorectal cancer (CRC) is still unsatisfactory due to the poor median progression-free survival and overall survival. Here, based on the CRC models, we tried to elucidate novel relapse mechanisms during anti-PD-1 therapy. We found that PD-1 blockade elicited a mild antitumor effect in these tumor models with both increased CD8+ T cells and Treg cells. Gene mapping analysis indicated that proprotein convertase subtilisin/kexin type 9 (PCSK9), low-density lipoprotein receptor, transforming growth factor-β (TGF-β), and CD36 were unexpectedly upregulated during PD-1 blockade. To investigate the critical role of these proteins especially PCSK9 in tumor growth, anti-PCSK9 antibody in combination with anti-PD-1 antibody was employed to block PCSK9 and PD-1 simultaneously in CRC. Data showed that neutralizing PCSK9 during anti-PD-1 therapy elicited a synergetic antitumor effect with increased CD8+ T-cell infiltration and inflammatory cytokine releases. Moreover, the proportion of Treg cells was significantly reduced by co-inhibiting PCSK9 and PD-1. Overall, inhibiting PCSK9 can further enhance the antitumor effect of anti-PD-1 therapy in CRC, indicating that targeting PCSK9 could be a promising approach to potentiate ICI efficacy.

The overall metastatic rate of N0 GLC was 14.6%. T staging and pathological classification were the risk factors for LNM. Metastatic rates for levels II, III, and IV were 10.2%, 14.6%, and 2.5%, respectively. Approximate 4.2% of patients experienced LNM with no recurrence of laryngeal cancer. Overall 3- and 5-year survival rates were 85% and 80%, respectively, compared with 66% and 57%, respectively, among patients with LNM. The inter-group survival curve comparison was statistically significant (p = 0.012).