Porcine Enteric Alphacoronavirus Entry through Multiple Pathways (Caveolae, Clathrin, and Macropinocytosis) Requires Rab GTPases for Endosomal Transport.

Porcine enteric alphacoronavirus (PEAV) is a new bat HKU2-like porcine coronavirus, and its endemic outbreak has caused severe economic losses to the pig industry. Its broad cellular tropism suggests a potential risk of cross-species transmission. A limited understanding of PEAV entry mechanisms may hinder a rapid response to potential outbreaks. This study analyzed PEAV entry events using chemical inhibitors, RNA interference, and dominant-negative mutants. PEAV entry into Vero cells depended on three endocytic pathways: caveolae, clathrin, and macropinocytosis. Endocytosis requires dynamin, cholesterol, and a low pH. Rab5, Rab7, and Rab9 GTPases (but not Rab11) regulate PEAV endocytosis. PEAV particles colocalize with EEA1, Rab5, Rab7, Rab9, and Lamp-1, suggesting that PEAV translocates into early endosomes after internalization, and Rab5, Rab7, and Rab9 regulate trafficking to lysosomes before viral genome release. PEAV enters porcine intestinal cells (IPI-2I) through the same endocytic pathway, suggesting that PEAV may enter various cells through multiple endocytic pathways. This study provides new insights into the PEAV life cycle. IMPORTANCE Emerging and reemerging coronaviruses cause severe human and animal epidemics worldwide. PEAV is the first bat-like coronavirus to cause infection in domestic animals. However, the PEAV entry mechanism into host cells remains unknown. This study demonstrates that PEAV enters into Vero or IPI-2I cells through caveola/clathrin-mediated endocytosis and macropinocytosis, which does not require a specific receptor. Subsequently, Rab5, Rab7, and Rab9 regulate PEAV trafficking from early endosomes to lysosomes, which is pH dependent. The results advance our understanding of the disease and help to develop potential new drug targets against PEAV.

Differences in endosomal Rab gene expression between positive and negative COVID-19 patients.

OBJECTIVE: SARS CoV-2, the etiologic agent of coronavirus disease-2019 (COVID-19) is well-known to use ACE2 to begin internalization. Some viruses enter the host cell through the endocytosis process and involve some endocytosis proteins, such as the Rab family. However, the relationship between SARS CoV-2 infection with endocytic mRNA RAB5, RAB7, and RAB11B is unknown. This study aims to compare the expression of RAB5, RAB7, and RAB11B between positive and negative COVID-19 patient groups. RESULTS: Both viral and human epithelial RNA Isolation and RT-PCR were performed from 249 samples. The genes expression was analysed using appropriate statistical tests. We found the Median (inter-quartile range/IQR) of RAB5, RAB7, and RAB11B expression among the COVID-19 patient group was 2.99 (1.88), 0.17 (0.47), 0.47 (1.49), and 1.60 (2.88), 1.05 (2.49), 1.10 (3.96) among control group respectively. We proceeded with Mann Whitney U Test and found that RAB5 expression was significantly increased (P < 0.001), and RAB7 and RAB11B expression was significantly decreased (P < 0.001 and P = 0.036) in the COVID-19 patient group compared to the control group. This first report showed significant differences in RAB5, RAB7, and RAB11B exist between COVID-19 positive and negative patients.

In-silico Studies of Phytochemicals of Ashwagandha, Harsingar, Meethi neem and Tulsi Against Covid-19

The ongoing coronavirus disease 2019 (COVID-19) has become a global pandemic and risk to the healthcare system of almost every nation around the world. The endocytic pathway has been considered as a key factor in viral infection. In the case of CoVs, several investigations have shown that these viruses mainly follow the clathrin-mediated endocytic pathway. As a result, inhibiting the clathrin-mediated endocytic pathway might be a useful therapeutic approach. In this study, bioactive components of Harsingar, Meethi neem, Tulsi and Ashwagandha extract was analyzed by HR-LCMS and among them 55 phytochemical compounds were selected based on antiviral and steroidal properties. 55 phytochemical compounds of four Indian herbal plants were used to analyze their binding with clathrin protein associated with COVID-19. Based on the molecular docking as well as ADMET analysis, Ashwagandha, Harsingar, Meethi neem and Tulsi were identified as potential herbal medicine candidates. We have found that the inhibition potentials of the Ashwagandha, Harsingar, Meethi neem and Tulsi are very promising with no side effects.

Dynamic Dissection of the Endocytosis of Porcine Epidemic Diarrhea Coronavirus Cooperatively Mediated by Clathrin and Caveolae as Visualized by Single-Virus Tracking.

Coronaviruses (CoVs) have caused severe diseases in humans and animals. Endocytic pathways, such as clathrin-mediated endocytosis (CME) and caveolae-mediated endocytosis (CavME), play an important role for CoVs to penetrate the cell membrane barrier. In this study, a novel CoV entry manner is unraveled in which clathrin and caveolae can cooperatively mediate endocytosis of porcine epidemic diarrhea coronavirus (PEDV). Using multicolor live-cell imaging, the dynamics of the fluorescently labeled clathrin structures, caveolae structures, and PEDV were dissected. During CavME of PEDV, we found that clathrin structures can fuse with caveolae near the cell plasma membrane, and the average time of PEDV penetrating the cell membrane was within ∼3 min, exhibiting a rapid course of PEDV entry. Moreover, based on the dynamic recruitment of clathrin and caveolae structures and viral motility, the direct evidence also shows that about 20% of PEDVs can undergo an abortive entry via CME and CavME. Additionally, the dynamic trafficking of PEDV from clathrin and caveolae structures to early endosomes, and from early endosomes to late endosomes, and viral fusion were directly dissected, and PEDV fusion mainly occurred in late endosomes within ∼6.8 min after the transport of PEDV to late endosomes. Collectively, this work systematically unravels the early steps of PEDV infection, which expands our understanding of the mechanism of CoV infection.IMPORTANCE Emerging and re-emerging coronaviruses cause serious human and animal epidemics worldwide. For many enveloped viruses, including coronavirus, it is evident that breaking the plasma membrane barrier is a pivotal and complex process, which contains multiple dynamic steps. Although great efforts have been made to understand the mechanisms of coronavirus endocytic pathways, the direct real-time imaging of individual porcine epidemic diarrhea coronavirus (PEDV) internalization has not been achieved yet. In this study, we not only dissected the kinetics of PEDV entry via clathrin-mediated endocytosis and caveolae-mediated endocytosis and the kinetics of endosome trafficking and viral fusion but also found a novel productive coronavirus entry manner in which clathrin and caveolae can cooperatively mediate endocytosis of PEDV. Moreover, we uncovered the existence of PEDV abortive endocytosis. In summary, the productive PEDV entry via the cooperation between clathrin and caveolae structures and the abortive endocytosis of PEDV provide new insights into coronavirus penetrating the plasma membrane barrier.

Targeting the Endocytic Pathway and Autophagy Process as a Novel Therapeutic Strategy in COVID-19.

Coronaviruses (CoVs) are a group of enveloped, single-stranded positive genomic RNA viruses and some of them are known to cause severe respiratory diseases in human, including Severe Acute Respiratory Syndrome (SARS), Middle East Respiratory Syndrome (MERS) and the ongoing coronavirus disease-19 (COVID-19). One key element in viral infection is the process of viral entry into the host cells. In the last two decades, there is increasing understanding on the importance of the endocytic pathway and the autophagy process in viral entry and replication. As a result, the endocytic pathway including endosome and lysosome has become important targets for development of therapeutic strategies in combating diseases caused by CoVs. In this mini-review, we will focus on the importance of the endocytic pathway as well as the autophagy process in viral infection of several pathogenic CoVs inclusive of SARS-CoV, MERS-CoV and the new CoV named as severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), and discuss the development of therapeutic agents by targeting these processes. Such knowledge will provide important clues for control of the ongoing epidemic of SARS-CoV-2 infection and treatment of COVID-19.