The two-component dengue virus NS2B-NS3 protease (NS2B-NS3pro) is an established drug target but inhibitor design is hampered by uncertainties about its 3D structure in solution. Crystal structures reported very different conformations for the functionally important C-terminal segment of the NS2B cofactor (NS2Bc), indicating open and closed conformations in the absence and presence of inhibitors, respectively. An earlier NMR study in solution indicated that a closed state is the preferred conformation in the absence of an artificial linker engineered between NS2B and NS3pro. To obtain direct structural information on the fold of unlinked NS2B-NS3pro in solution, we tagged NS3pro with paramagnetic tags and measured pseudocontact shifts by NMR to position NS2Bc relative to NS3pro. NS2Bc was found to bind to NS3pro in the same way as reported in a previously published model and crystal structure of the closed state. The structure is destabilized, however, by high ionic strength and basic pH, showing the importance of electrostatic forces to tie NS2Bc to NS3pro. Narrow NMR signals previously thought to represent the open state are associated with protein degradation. In conclusion, the closed conformation of the NS2B-NS3 protease is the best model for structure-guided drug design.

The C-terminal β-hairpin of NS2B (NS2Bc) in the dengue virus NS2B-NS3 protease is required for full enzymatic activity. In crystal structures without inhibitor and in the complex with bovine pancreatic trypsin inhibitor (BPTI), NS2Bc is displaced from the active site. In contrast, nuclear magnetic resonance (NMR) studies in solution only ever showed NS2Bc in the enzymatically active closed conformation. Here we demonstrate by pseudocontact shifts from a lanthanide tag that NS2Bc remains in the closed conformation also in the complex with BPTI. Therefore, the closed conformation is the best template for drug discovery.

Structure-guided drug design relies on detailed structural knowledge of protein-ligand complexes, but crystallization of cocomplexes is not always possible. Here we present a sensitive nuclear magnetic resonance (NMR) approach to determine the binding mode of tightly binding lead compounds in complex with difficult target proteins. In contrast to established NMR methods, it does not depend on rapid exchange between bound and free ligand or on stable isotope labeling, relying instead on a tert-butyl group as a chemical label. tert-Butyl groups are found in numerous protein ligands and deliver an exceptionally narrow and tall (1)H NMR signal. We show that a tert-butyl group also produces outstandingly intense intra- and intermolecular NOESY cross-peaks. These enable measurements of pseudocontact shifts generated by lanthanide tags attached to the protein, which in turn allows positioning of the ligand on the protein. Once the ligand has been located, assignments of intermolecular NOEs become possible even without prior resonance assignments of protein side chains. The approach is demonstrated with the dengue virus NS2B-NS3 protease in complex with a high-affinity ligand containing a tert-butyl group.

Although FTY720 may alter migration and homing of lymphocytes via sphingosine-1-phosphate (S1P) receptors, our recent studies indicated that FTY720 directly controls the differentiation of Th1 cells to regulatory T cells (Tregs) by targeting S1P1. However, the pharmacological function of FTY720 in immunological hepatic injury remains unknown. In this study, the role and regulatory signaling pathway of S1P receptor were investigated using a pharmacological approach in immune-mediated hepatic injury (IMH). In the context of IMH, FTY720 significantly ameliorated mortality and hepatic pathology. In FTY720-treated mice, recruited CD11b+Gr1+ myeloid-derived suppressor cells (MDSCs) mediate protection against IMH and are functional suppressive immune modulators that result in fewer IFN-γ–producing Th1 cells and more Foxp3+ Tregs. In agreement, FTY720-treated MDSCs promote the reciprocal differentiation between Th1 cells and Tregs in vitro and in vivo. Mechanistically, FTY720 treatment induced inducible NO synthase expression and NO production in MDSCs. Pharmacologic inhibition of inducible NO synthase completely eliminates MDSC suppressive function and eradicates their inducible effects on T cell differentiation. Finally, the mTOR inhibitor, rapamycin, photocopies the effects of FTY720 on MDSCs, implicating mTOR as a downstream effector of S1P1 signaling. This study identifies MDSCs as an essential component that provides protection against IMH following FTY720 or rapamycin treatment, validating the S1P1–mTOR signaling axis as a potential therapeutic target in hepatic injury.

O-tert-Butyltyrosine (Tby) is an unnatural amino acid that can be site-specifically incorporated into proteins using established orthogonal aminoacyl-tRNA synthetase/tRNA systems. Here we show that the tert-butyl group presents an outstanding NMR tag that can readily be observed in one-dimensional 1 H NMR spectra without any isotope labeling. Owing to rapid bond rotations and the chemical equivalence of the protons of a solvent-exposed tert-butyl group from Tby, the singlet resonance from the tert-butyl group generates an easily detectable narrow signal in a spectral region with limited overlap with other methyl resonances. The potential of the tert-butyl 1 H NMR signal in protein research is illustrated by the observation and assignment of two resonances in the Bacillus stearothermophilus DnaB hexamer (320 kDa), demonstrating that this protein preferentially assumes a 3-fold rather than 6-fold symmetry in solution, and by the quantitative measurement of the submicromolar dissociation constant K d (0.2 μM) of the complex between glutamate and the Escherichia coli aspartate/ glutamate binding protein (DEBP, 32 kDa). The outstanding signal height of the 1 H NMR signal of the Tby tert-butyl group allows K d measurements using less concentrated protein solutions than usual, providing access to K d values 1 order of magnitude lower than established NMR methods that employ direct protein detection for K d measurements.

IMPORTANCEOwing to the good prognosis of differentiated thyroid cancer (DTC), guidelines recommend total thyroidectomy (TT) or thyroid lobectomy (TL) as surgical treatment for DTC with low to intermediate risk of recurrence. However, the association of these surgeries with the health-related quality of life (HRQOL) of patients with DTC with low to intermediate risk of recurrence is unclear.OBJECTIVE To longitudinally compare the HRQOL of patients with DTC undergoing different surgeries. DESIGN, SETTING, AND PARTICIPANTSThis prospective observational longitudinal cohort study enrolled patients diagnosed with DTC with low to intermediate risk of recurrence at the First Affiliated Hospital, Sun Yat-sen University, China, from October 1, 2018, to September 31, 2019. Eligible patients were categorized into TL and TT groups according to the surgery they underwent. They were evaluated preoperatively and followed up at 1, 3, 6, and 12 months postoperatively using 3 HRQOL-related questionnaires (European Organization for Research and Treatment of Cancer Quality of Life Questionnaire, version 3.0; Hospital Anxiety and Depression Scale; and Thyroid Cancer-Specific Quality of Life Questionnaire); serum thyrotropin levels, complications, and patient satisfaction were also monitored. Data were analyzed to compare the HRQOL of patients undergoing different surgeries at different time points.EXPOSURES Total thyroidectomy or TL. MAIN OUTCOMES AND MEASURESThe primary end point was HRQOL (European Organization for Research and Treatment of Cancer Quality of Life Questionnaire, version 3.0; Hospital Anxiety and Depression Scale; and Thyroid Cancer-Specific Quality of Life Questionnaire) at different time points, and the secondary end points were postoperative complications, thyrotropin level, and patient satisfaction. RESULTS Of the 1060 eligible patients, 563 underwent TL (438 women [77.8%]; median [IQR] age, 38 [31-45] years), and 497 underwent TT (390 women [78.5%]; median [IQR] age, 38 [32-48] years). Compared with the TL group, including the 1-to 4-cm tumor subgroup, the TT group experienced more postoperative HRQOL problems at 1 and 3 months postoperatively. However, nearly all the differences disappeared at 6 and 12 months postoperatively. CONCLUSIONS AND RELEVANCEResults of this study suggest that HRQOL of patients with DTC with low to intermediate risk of recurrence is not associated with the extent of surgery, and HRQOL may not be an important consideration when making surgical decisions. If better HRQOL is requested in the short term, TL may be preferred.

Solute carrier family members control essential physiological functions and are tightly linked to human diseases. Solute carrier family 35 member F2 (SLC35F2) is aberrantly activated in several malignancies. However, the biological function and molecular mechanism of SLC35F2 in papillary thyroid carcinoma (PTC) are yet to be fully explored. Here, we showed that SLC35F2 was prominently upregulated in PTC tissues at both protein and mRNA expression level compared with matched adjacent normal tissues. Besides, the high expression of SLC35F2 was significantly associated with lymph node metastasis in patients with PTC. CRISPR/Cas9‐mediated knockout of SLC35F2 attenuated the tumorigenic properties of PTC, including cell proliferation, migration and invasion and induced G1 phase arrest. In contrast, ectopic expression of SLC35F2 brought about aggressive malignant phenotypes of PTC cells. Moreover, SLC35F2 expedited the proliferation and migration of PTC cells by targeting transforming growth factor‐β type I receptor (TGFBR1) and phosphorylation of apoptosis signal‐regulating kinase 1 (p‐ASK‐1), thereby activating the mitogen‐activated protein kinase signaling pathway. The malignant behaviors induced by overexpression of SLC35F2 could be abrogated by silencing of TGFBR1 using a specific inhibitor. We conducted the first study on SLC35F2 in thyroid cancer with the aim of elucidating the functional significance and molecular mechanism of SLC35F2. Our findings suggest that SLC35F2 exerts its oncogenic effect on PTC progression through the mitogen‐activated protein kinase pathway, with dependence on activation of TGFBR‐1 and apoptosis signal‐regulating kinase 1.

No abstract