ABSTRACT
Objective: COVID-19 has emerged as a significant global health crisis causing devastating effects on world population accounting for over 6 million deaths worldwide. Although acute RTI is the prevalent cause of morbidity, kidney outcomes centered on a spectrum of AKI have evolved over the course of the pandemic. Especially the emerging variants have posed a daunting challenge to the scientific communities, prompting an urging requirement for global contributions in understanding the viral dynamics. In addition to canonical genes, several subgroup- specific accessory genes are located between the S and E genes of coronaviruses regarding which little is known. Previous studies have shown that accessory proteins (aps) in viruses function as viroporins that regulate viral infection, propagation and egress [1]. In this study we attempted to characterize the function of aps of coronavirus variants as ion channels. Furthermore, we also probed the interaction of ap4 with the host system. Method(s): Serial passaging (selection pressure), growth kinetics, confocal imaging, genome sequence analysis and proteomics were performed in Huh-7, MRC5 cells and/or human monocyte derived macrophages. Potassium uptake assay was performed in a Saccharo myces cerevisiae strain, which lacks the potassium transporters trk1 and trk2. Ion conductivity experiments were performed in Xenopus laevis oocytes using Two Electrode Voltage Clamp (TEVC) method. Result(s): Serial passaging demonstrated the acquisition of several frameshift mutations in ORF4 resulting in C-terminally truncated protein versions (ap4 and ap4a) and indicate a strong selection pressure against retaining a complete ORF4 in vitro. Growth kinetics in primary cells illustrated a reduction of viral titers when the full-length ap4 was expressed compared to the C-terminally truncated protein ap4a. Confocal imaging showed that ap4 and ap4a are not exclusively located in a single cellular compartment. Potassium uptake assay in yeast and TEVC analyses in Xenopus oocytes showed that ap4 and ap4a act as a weak K+ selective ion channel. In addition, accessory proteins of other virus variants also elicited microampere range of currents. Conclusion(s): Our study provides the first evidence that ap4 and other accessory proteins of coronavirus variants act as viroporins. Future studies are aimed at demonstrating the role of ap4 during the viral life cycle by modulating ion homeostasis of host cell in vivo (interacting proteins obtained from proteomic studies) and thereby serve as a tool for potential drug target.
ABSTRACT
Researches aimed at finding effective means of pathogenic therapy for this viral infection are extremely relevant. Researches of the last three years have established that some human pathogenic coronaviruses - MERS, SARS-CoV and SARS-CoV-2, contain aliphatic polyamines in their structure, which participate in the packaging of genetic material (DNA, RNA), as well as the nucleocapsid. Virus-host cell interactions also provide adhesion processes on the surface of the cytoplasmic membrane of target cells. In the intra-cellular space, aliphatic polyamines actively affect the translation and replication processes of the genetic material and necessary proteins of the virus itself, as well as the formation of daughter viruses. Long-term persistence in the SARS-CoV-2 infected organism is largely due to the absorption of polyamines by corona-virus localized in target cells of the blood and parenchymatous organs. Unfortunately, the above new facts did not serve as a prerequisite for finding effective means of pathogenetic therapy for COVID-19, based on the inhibition of polyamine-dependent processes that ensure long-term persistence of SARS-CoV-2 in the infected organism. We are talking about specific drugs such as alpha-difluoromethylornithine and its ana-logues, which are successfully used in oncology in the complex treatment of malignant neoplasms with the aim of lowering the level of aliphatic polyamines in the affected areas of malignantly transformed organs. We recommend the use of polyamine-free and polyamine-deficient diets for COVID-19 for the first time. In the planned study, we will present tables with food products of animal and vegetable origin, characterized by extremely low content and/or absence of aliphatic polyamines in them. At the same time, food products with a high content of aliphatic polyamines should be excluded from the general list of products recommended for COVID-19 patients. We also recommend the use of a polyamine-deficient diet (with a preventive purpose) during the COVID-19 pandemic to a wide contingent of practically healthy individuals, convalescents, medical staff of specialized infectious disease clinics, as well as family members of SARS-CoV-2 infected patients. Copyright © 2022, Yerevan State Medical University. All rights reserved.