Identification of cytochrome c oxidase subunit 4 isoform 1 as a positive regulator of influenza virus replication

Targeted isolation of antiviral cinnamoylphloroglucinol-terpene adducts from Cleistocalyx operculatus by building blocks-based molecular networking approach

The building blocks-based molecular network (BBMN) strategy was applied to the phytochemical investigation of Cleistocalyx operculatus, leading to the targeted isolation of eighteen novel cinnamoylphloroglucinol-terpene adducts (CPTAs) with diverse skeleton types (cleistoperones A-R, 1-18). Their structures including absolute configurations were determined by extensive spectroscopic methods, quantum chemical calculations, and single-crystal X-ray crystallographic experiments. Cleistoperone A (1), consisting of a cinnamoylphloroglucinol motif and two linear monoterpene moieties, represents an unprecedented macrocyclic CPTA, whose densely functionalized tricyclo[15.3.1.03,8]heneicosane bridge ring skeleton contains an enolizable β,β'-triketone system and two different kinds of stereogenic elements (including five point and three planar chiralities). Cleistoperones B and C (2 and 3) are two new skeletal CPTAs with an unusual coupling pattern between the (nor)monoterpene moiety and the cinnamoyl chain of the cinnamoylphloroglucinol unit. Cleistoperone D (4) possesses an unprecedented cage-like 6/6/6/4/6-fused heteropentacyclic scaffold. The plausible biosynthetic pathways for 1-18 were also proposed. Notably, compounds 1, 4, 7, 8, and 18 exhibited significant antiviral activity against respiratory syncytial virus (RSV). The most potent one, cleistoperone A (1) with IC50 value of 1.71 ± 0.61 μmol/L, could effectively inhibit virus replication via affecting the Akt/mTOR/p70S6K signaling pathway.

A new mechanism of respiratory syncytial virus entry inhibition by small-molecule to overcome K394R-associated resistance

Infection with respiratory syncytial virus (RSV) is a major cause of acute lower respiratory tract disease in young children and older people. Despite intensive efforts over the past few decades, no direct-acting small-molecule agents against RSV are available. Most small-molecule candidates targeting the RSV fusion (F) protein pose a considerable risk of inducing drug-resistant mutations. Here, we explored the in vitro and in vivo virological properties of the K394R variant, a cross-resistant mutant capable of evading multiple RSV fusion inhibitors. Our results demonstrated that the K394R variant is highly fusogenic in vitro and more pathogenic than the parental strain in vivo. The small molecule (2E,2'E)-N,N'-((1R,2S,3S)-3-hydroxycyclohexane-1,2-diyl)bis(3-(2-bromo-4-fluorophenyl) acrylamide) (CL-A3-7), a structurally optimized compound derived from a natural caffeoylquinic acid derivative, substantially reduced in vitro and in vivo infections of both wild-type RSV and the K394R variant. Mechanistically, CL-A3-7 significantly inhibited virus-cell fusion during RSV entry by blocking the interaction between the viral F protein and the cellular insulin-like growth factor 1 receptor (IGF1R). Collectively, these results indicate severe disease risks caused by the K394R variant and reveal a new anti-RSV mechanism to overcome K394R-associated resistance.

IMPORTANCE

Respiratory syncytial virus (RSV) infection is a major public health concern, and many small-molecule candidates targeting the viral fusion (F) protein are associated with a considerable risk of inducing drug-resistant mutations. This study investigated virological features of the K394R variant, a mutant strain conferring resistance to multiple RSV fusion inhibitors. Our results demonstrated that the K394R variant is highly fusogenic in cell cultures and more pathogenic than the parental strain in mice. The small-molecule inhibitor CL-A3-7 substantially reduced in vitro and in vivo infections of both wild-type RSV and the K394R variant by blocking the interaction of viral F protein with its cellular receptor, showing a new mechanism of action for small-molecules to inhibit RSV infection and overcome K394R-associated resistance.

Unveiling Amaryllidaceae alkaloids: from biosynthesis to antiviral potential - a review

Covering: 2017 to 2023 (now)Amaryllidaceae alkaloids (AAs) are a unique class of specialized metabolites containing heterocyclic nitrogen bridging that play a distinct role in higher plants. Irrespective of their diverse structures, most AAs are biosynthesized via intramolecular oxidative coupling. The complex organization of biosynthetic pathways is constantly enlightened by new insights owing to the advancement of natural product chemistry, synthetic organic chemistry, biochemistry, systems and synthetic biology tools and applications. These promote novel compound identification, trace-level metabolite quantification, synthesis, and characterization of enzymes engaged in AA catalysis, enabling the recognition of biosynthetic pathways. A complete understanding of the pathway benefits biotechnological applications in the long run. This review emphasizes the structural diversity of the AA specialized metabolites involved in biogenesis although the process is not entirely defined yet. Moreover, this work underscores the pivotal role of synthetic and enantioselective studies in justifying biosynthetic conclusions. Their prospective candidacy as lead constituents for antiviral drug discovery has also been established. However, a complete understanding of the pathway requires further interdisciplinary efforts in which antiviral studies address the structure-activity relationship. This review presents current knowledge on the topic.

Tautomeric cinnamoylphloroglucinol-monoterpene adducts from Cleistocalyx operculatus and their antiviral activities

Guided by 1H NMR spectroscopic experiments using the characteristic enol proton signals as probes, three pairs of new tautomeric cinnamoylphloroglucinol-monoterpene adducts (1-3) were isolated from the buds of Cleistocalyx operculatus. Their structures with absolute configurations were established by spectroscopic analysis, modified Mosher's method, and quantum chemical electronic circular dichroism calculation. Compounds 1-3 represent a novel class of cinnamoylphloroglucinol-monoterpene adducts featuring an unusual C-4-C-1' linkage between 2,2,4-trimethyl-cinnamyl-β-triketone and modified linear monoterpenoid motifs. Notably, compounds 1-3 exhibited significant in vitro antiviral activity against respiratory syncytial virus (RSV).

Mitochondrial Oxidative Phosphorylation in Viral Infections

Mitochondria have been identified as the "powerhouse" of the cell, generating the cellular energy, ATP, for almost seven decades. Research over time has uncovered a multifaceted role of the mitochondrion in processes such as cellular stress signaling, generating precursor molecules, immune response, and apoptosis to name a few. Dysfunctional mitochondria resulting from a departure in homeostasis results in cellular degeneration. Viruses hijack host cell machinery to facilitate their own replication in the absence of a bonafide replication machinery. Replication being an energy intensive process necessitates regulation of the host cell oxidative phosphorylation occurring at the electron transport chain in the mitochondria to generate energy. Mitochondria, therefore, can be an attractive therapeutic target by limiting energy for viral replication. In this review we focus on the physiology of oxidative phosphorylation and on the limited studies highlighting the regulatory effects viruses induce on the electron transport chain.