Conversion of Host Cell Receptor into Virus Destructor by Immunodisc to Neutralize Diverse SARS-CoV-2 Variants.

The decreasing efficacy of antiviral drugs due to viral mutations highlights the challenge of developing a single agent targeting multiple strains. Using host cell viral receptors as competitive inhibitors is promising, but their low potency and membrane-bound nature have limited this strategy. In this study, the authors show that angiotensin-converting enzyme 2 (ACE2) in a planar membrane patch can effectively neutralize all tested severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) variants that emerged during the COVID-19 pandemic. The ACE2-incorporated membrane patch implemented using nanodiscs replicated the spike-mediated membrane fusion process outside the host cell, resulting in virus lysis, extracellular RNA release, and potent antiviral activity. While neutralizing antibodies became ineffective as the SARS-CoV-2 evolved to better penetrate host cells the ACE2-incorporated nanodiscs became more potent, highlighting the advantages of using receptor-incorporated nanodiscs for antiviral purposes. ACE2-incorporated immunodisc, an Fc fusion nanodisc developed in this study, completely protected humanized mice infected with SARS-CoV-2 after prolonged retention in the airways. This study demonstrates that the incorporation of viral receptors into immunodisc transforms the entry gate into a potent virucide for all current and future variants, a concept that can be extended to different viruses.

Regulation of tyrosine hydroxylase gene expression by retinoic acid receptor.

Retinoic acid (RA), a derivative of vitamin A, critically controls brain patterning and neurogenesis during embryogenesis, and is known to regulate morphological differentiation of catecholaminergic neuronal cells. In this study, we investigated whether the retinoic acid receptor (RAR), a transcription factor specifically activated by all-trans-RA, could directly regulate transcription of tyrosine hydroxylase (TH), the first and rate-limiting step in the catecholamine biosynthesis pathway. First, treating TH-expressing human neuroblastoma SK-N-BE(2)C cells with all-trans RA resulted in an approximately 1.7-fold increase in endogenous TH mRNA expression, as determined by real-time PCR analysis. Second, when SK-N-BE(2)C cells were transiently co-transfected with the TH promoter-luciferase reporter construct, reporter gene expression was prominently activated by RAR in a ligand-dependent manner. Third, we identified a putative RAR responsive cis-regulatory element at - 1500 to - 1487 bp in the TH upstream promoter region by deletional and site-directed mutational analysis. Finally, we demonstrated that this putative motif directly interacts with RAR protein in a sequence-specific manner by means of an electrophoretic mobility shift assay. Taken together, our results indicate that the TH gene may be a direct downstream target of the RA signaling pathway and that RAR is able to activate TH transcription through interaction with an upstream sequence motif residing at - 1500 to - 1487 bp.

Regulation of the transcriptional activity of the tyrosine hydroxylase gene by androgen receptor.

Dopamine and the sex hormone testosterone are important factors regulating male sexual behavior. To investigate the possibility that these two factors are functionally interrelated, we investigated the potential role of the androgen receptor (AR) on transcriptional activity of the tyrosine hydroxylase (TH) gene that encodes the rate-limiting enzyme of the dopamine biosynthesis pathway. In this study, using transient co-transfection assays in TH-positive SK-N-BE(2)C and MN9D cells, we show that AR prominently transactivates TH promoter function in a ligand-dependent manner. Deletional and site-directed mutational analyses have mapped a putative androgen response element (ARE) in a region from -1562 to -1328 base pairs in the upstream TH promoter. We also found that DJ-1, one of recently identified genes whose mutations cause Parkinson's disease, down-regulated AR-dependent TH activation by approximately 50% in SK-N-BE(2)C cells. Based on these data, we propose that AR activates TH gene expression and that DJ-1 may modulate AR activity as a transcriptional co-repressor.

Drosophila p53 preserves genomic stability by regulating cell death.

When animal cells are exposed to stressful conditions, the tumor suppressor protein p53 restrains growth by promoting an arrested cell cycle or initiating a cell death program. How these distinct fates are specified through the action of a single protein is not known. To study its functions in vivo we produced a targeted mutation at the Drosophila p53 (Dmp53) locus. We show that Dmp53 is required for damage-induced apoptosis but not for cell-cycle arrest. Dmp53 function is also required for damage-induced transcription of two tightly linked cell death activators, reaper and sickle. When challenged by ionizing radiation, Dmp53 mutants exhibit radiosensitivity and genomic instability. Hence, elevated mutant loads were not caused by defective checkpoint functions but instead correlated with failures in p53-associated cell death. Our studies support the notion that core ancestral functions of the p53 gene family are intimately coupled to cell death as an adaptive response to maintain genomic stability.