Crystal Structures of a Piscine Betanodavirus: Mechanisms of Capsid Assembly and Viral Infection

Betanodaviruses cause massive mortality in marine fish species with viral nervous necrosis. The structure of a T = 3 Grouper nervous necrosis virus-like particle (GNNV-LP) is determined by the ab initio method with non-crystallographic symmetry averaging at 3.6 Å resolution. Each capsid protein (CP) shows three major domains: (i) the N-terminal arm, an inter-subunit extension at the inner surface; (ii) the shell domain (S-domain), a jelly-roll structure; and (iii) the protrusion domain (P-domain) formed by three-fold trimeric protrusions. In addition, we have determined structures of the T = 1 subviral particles (SVPs) of (i) the delta-P-domain mutant (residues 35−217) at 3.1 Å resolution; and (ii) the N-ARM deletion mutant (residues 35−338) at 7 Å resolution; and (iii) the structure of the individual P-domain (residues 214−338) at 1.2 Å resolution. The P-domain reveals a novel DxD motif asymmetrically coordinating two Ca2+ ions, and seems to play a prominent role in the calcium-mediated trimerization of the GNNV CPs during the initial capsid assembly process. The flexible N-ARM (N-terminal arginine-rich motif) appears to serve as a molecular switch for T = 1 or T = 3 assembly. Finally, we find that polyethylene glycol, which is incorporated into the P-domain during the crystallization process, enhances GNNV infection. The present structural studies together with the biological assays enhance our understanding of the role of the P-domain of GNNV in the capsid assembly and viral infection by this betanodavirus

Establishment of potent and specific synthetic substrate for dipeptidyl-peptidase 7

Bacterial dipeptidyl-peptidase (DPP) 7 liberates a dipeptide with a preference for aliphatic and aromatic penultimate residues from the N-terminus. Although synthetic substrates are useful for activity measurements, those currently used are problematic, because they are more efficiently degraded by DPP5. We here aimed to develop a potent and specific substrate and found that the kcat/Km value for Phe-Met-methylcoumaryl-7-amide (MCA) (41.40?±?0.83?μM?1?s?1) was highest compared to Met-Leu-, Leu-Leu-, and Phe-Leu-MCA (1.06?3.77?μM?1?s?1). Its hydrolyzing activity was abrogated in a Porphyromonas gingivalis dpp7-knockout strain. Conclusively, we propose Phe-Met-MCA as an ideal synthetic substrate for DPP7

Association of PD‐L1 tumor proportion score ≥20% with early resistance to osimertinib in patients with EGFR‐mutated NSCLC

Abstract Background The relationship between epidermal growth factor receptor tyrosine kinase inhibitor (EGFR‐TKI) resistance, including osimertinib, and programmed cell death‐ligand 1 (PD‐L1) expression status in EGFR‐mutated non‐small cell lung carcinoma (NSCLC) remains unclear. Patients and Methods We retrospectively analyzed 64 patients with unresectable advanced or metastatic NSCLC carrying EGFR exon 19 deletions (ex19del) or EGFR exon 21 L858R substitutions (L858R) who received osimertinib as the first‐line treatment. We compared progression‐free survival (PFS) between eligible patients with PD‐L1 tumor proportion scores (TPS) ≥20% and PD‐L1 TPS <20% using the Kaplan–Meier survival plots with a log‐rank test. Multivariate analysis was performed to examine the poor prognostic factors of PFS. Results The PD‐L1 TPS ≥20% group included 22 cases (median [range] age: 70.5 [33–86] years; 10 women [45.5%]; 11 current or ex‐smokers [50%]); ECOG performance status (PS) of 0–1/2/3/4 was noted in 16/4/1/1 patients, respectively. The PD‐L1 TPS <20% group included 42 patients (median [range] age 73 [43–88] years; 29 women [69%]; 12 current or ex‐smokers [28.6%]); ECOG PS of 0–1/2/3/4 was noted in 33/6/3/0 cases, respectively. The median PFS was 9.1 and 28.1 months in the PD‐L1 TPS ≥20% and PD‐L1 TPS <20% groups, respectively (log‐rank p = 0.013). Multivariate analysis revealed that PD‐L1 TPS ≥20% was associated with PFS (hazard ratio: 2.35, 95% confidence interval: 1.09–5.08, p = 0.030). Conclusion PD‐L1 TPS ≥20% in patients with EGFR‐mutated NSCLC may be associated with early resistance to osimertinib