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1.
Eur J Cell Biol ; 101(2): 151222, 2022 Apr.
Article in English | MEDLINE | ID: covidwho-1881962

ABSTRACT

Clathrin-mediated endocytosis (CME) is the major route through which cells internalise various substances and recycle membrane components. Via the coordinated action of many proteins, the membrane bends and invaginates to form a vesicle that buds off-along with its contents-into the cell. The contribution of the actin cytoskeleton to this highly dynamic process in mammalian cells is not well understood. Unlike in yeast, where there is a strict requirement for actin in CME, the significance of the actin cytoskeleton to mammalian CME is variable. However, a growing number of studies have established the actin cytoskeleton as a core component of mammalian CME, and our understanding of its contribution has been increasing at a rapid pace. In this review, we summarise the state-of-the-art regarding our understanding of the endocytic cytoskeleton, its physiological significance, and the questions that remain to be answered.


Subject(s)
Actin Cytoskeleton , Clathrin , Actin Cytoskeleton/metabolism , Actins/metabolism , Animals , Cell Membrane/metabolism , Clathrin/metabolism , Cytoskeleton/metabolism , Endocytosis/physiology , Mammals/metabolism , Saccharomyces cerevisiae/metabolism
2.
Cell Mol Life Sci ; 79(6): 316, 2022 May 27.
Article in English | MEDLINE | ID: covidwho-1866610

ABSTRACT

AXL, a TAM receptor tyrosine kinase (RTK), and its ligand growth arrest-specific 6 (GAS6) are implicated in cancer metastasis and drug resistance, and cellular entry of viruses. Given this, AXL is an attractive therapeutic target, and its inhibitors are being tested in cancer and COVID-19 clinical trials. Still, astonishingly little is known about intracellular mechanisms that control its function. Here, we characterized endocytosis of AXL, a process known to regulate intracellular functions of RTKs. Consistent with the notion that AXL is a primary receptor for GAS6, its depletion was sufficient to block GAS6 internalization. We discovered that upon receptor ligation, GAS6-AXL complexes were rapidly internalized via several endocytic pathways including both clathrin-mediated and clathrin-independent routes, among the latter the CLIC/GEEC pathway and macropinocytosis. The internalization of AXL was strictly dependent on its kinase activity. In comparison to other RTKs, AXL was endocytosed faster and the majority of the internalized receptor was not degraded but rather recycled via SNX1-positive endosomes. This trafficking pattern coincided with sustained AKT activation upon GAS6 stimulation. Specifically, reduced internalization of GAS6-AXL upon the CLIC/GEEC downregulation intensified, whereas impaired recycling due to depletion of SNX1 and SNX2 attenuated AKT signaling. Altogether, our data uncover the coupling between AXL endocytic trafficking and AKT signaling upon GAS6 stimulation. Moreover, our study provides a rationale for pharmacological inhibition of AXL in antiviral therapy as viruses utilize GAS6-AXL-triggered endocytosis to enter cells.


Subject(s)
Endocytosis , Intercellular Signaling Peptides and Proteins , Proto-Oncogene Proteins , Receptor Protein-Tyrosine Kinases , Antiviral Agents/pharmacology , Antiviral Agents/therapeutic use , COVID-19/metabolism , COVID-19/therapy , Clathrin/metabolism , Clathrin/physiology , Endocytosis/drug effects , Endocytosis/genetics , Endocytosis/physiology , Humans , Intercellular Signaling Peptides and Proteins/genetics , Intercellular Signaling Peptides and Proteins/physiology , Neoplasms/metabolism , Neoplasms/therapy , Proto-Oncogene Proteins/antagonists & inhibitors , Proto-Oncogene Proteins/genetics , Proto-Oncogene Proteins/metabolism , Proto-Oncogene Proteins/physiology , Proto-Oncogene Proteins c-akt/genetics , Proto-Oncogene Proteins c-akt/metabolism , Proto-Oncogene Proteins c-akt/physiology , Receptor Protein-Tyrosine Kinases/antagonists & inhibitors , Receptor Protein-Tyrosine Kinases/genetics , Receptor Protein-Tyrosine Kinases/physiology
3.
J Vis Exp ; (182)2022 04 21.
Article in English | MEDLINE | ID: covidwho-1834949

ABSTRACT

The development of new technologies for cellular fluorescence microscopy has facilitated high-throughput screening methods for drug discovery. Quantum dots are fluorescent nanoparticles with excellent photophysical properties imbued with bright and stable photoluminescence as well as narrow emission bands. Quantum dots are spherical in shape, and with the proper modification of the surface chemistry, can be used to conjugate biomolecules for cellular applications. These optical properties, combined with the ability to functionalize them with biomolecules, make them an excellent tool for investigating receptor-ligand interactions and cellular trafficking. Here, we present a method that uses quantum dots to track the binding and endocytosis of SARS-CoV-2 spike protein. This protocol can be used as a guide for experimentalists looking to utilize quantum dots to study protein-protein interactions and trafficking in the context of cellular physiology.


Subject(s)
Endocytosis , Quantum Dots , Spike Glycoprotein, Coronavirus , HEK293 Cells , Humans , SARS-CoV-2 , Spike Glycoprotein, Coronavirus/analysis
4.
Viruses ; 14(4)2022 03 29.
Article in English | MEDLINE | ID: covidwho-1798881

ABSTRACT

Integrins represent a gateway of entry for many viruses and the Arg-Gly-Asp (RGD) motif is the smallest sequence necessary for proteins to bind integrins. All Severe Acute Respiratory Syndrome Virus type 2 (SARS-CoV-2) lineages own an RGD motif (aa 403-405) in their receptor binding domain (RBD). We recently showed that SARS-CoV-2 gains access into primary human lung microvascular endothelial cells (HL-mECs) lacking Angiotensin-converting enzyme 2 (ACE2) expression through this conserved RGD motif. Following its entry, SARS-CoV-2 remodels cell phenotype and promotes angiogenesis in the absence of productive viral replication. Here, we highlight the αvß3 integrin as the main molecule responsible for SARS-CoV-2 infection of HL-mECs via a clathrin-dependent endocytosis. Indeed, pretreatment of virus with αvß3 integrin or pretreatment of cells with a monoclonal antibody against αvß3 integrin was found to inhibit SARS-CoV-2 entry into HL-mECs. Surprisingly, the anti-Spike antibodies evoked by vaccination were neither able to impair Spike/integrin interaction nor to prevent SARS-CoV-2 entry into HL-mECs. Our data highlight the RGD motif in the Spike protein as a functional constraint aimed to maintain the interaction of the viral envelope with integrins. At the same time, our evidences call for the need of intervention strategies aimed to neutralize the SARS-CoV-2 integrin-mediated infection of ACE2-negative cells in the vaccine era.


Subject(s)
COVID-19 , Vaccines , Angiotensin-Converting Enzyme 2 , Antibodies, Neutralizing , COVID-19/prevention & control , Endocytosis , Endothelial Cells/metabolism , Humans , Integrin alphaV/metabolism , Integrin beta3/metabolism , Oligopeptides , Protein Binding , SARS-CoV-2 , Spike Glycoprotein, Coronavirus/genetics
5.
Cell Rep ; 38(12): 110549, 2022 03 22.
Article in English | MEDLINE | ID: covidwho-1757198

ABSTRACT

Host interferons (IFNs) powerfully restrict viruses through the action of several hundred IFN-stimulated gene (ISG) products, many of which remain uncharacterized. Here, using RNAi screening, we identify several ISG restriction factors with previously undescribed contributions to IFN-mediated defense. Notably, RABGAP1L, a Tre2/Bub2/Cdc16 (TBC)-domain-containing protein involved in regulation of small membrane-bound GTPases, robustly potentiates IFN action against influenza A viruses (IAVs). Functional studies reveal that the catalytically active TBC domain of RABGAP1L promotes antiviral activity, and the RABGAP1L proximal interactome uncovered its association with proteins involved in endosomal sorting, maturation, and trafficking. In this regard, RABGAP1L overexpression is sufficient to disrupt endosomal function during IAV infection and restricts an early post-attachment, but pre-fusion, stage of IAV cell entry. Other RNA viruses that enter cells primarily via endocytosis are also impaired by RABGAP1L, while entry promiscuous SARS-CoV-2 is resistant. Our data highlight virus endocytosis as a key target for host defenses.


Subject(s)
Antiviral Agents , COVID-19 , Cell Line , Endocytosis , Humans , SARS-CoV-2
6.
Virol Sin ; 37(3): 380-389, 2022 Jun.
Article in English | MEDLINE | ID: covidwho-1730151

ABSTRACT

The recent COVID-19 pandemic poses a global health emergency. Cellular entry of the causative agent SARS-CoV-2 is mediated by its spike protein interacting with cellular receptor-human angiotensin converting enzyme 2 (ACE2). Here, by using lentivirus based pseudotypes bearing spike protein, we demonstrated that entry of SARS-CoV-2 into host cells was dependent on clathrin-mediated endocytosis, and phosphoinositides played essential roles during this process. In addition, we showed that the intracellular domain and the catalytic activity of ACE2 were not required for efficient virus entry. Finally, we showed that the current predominant Delta variant, although with high infectivity and high syncytium formation, also entered cells through clathrin-mediated endocytosis. These results provide new insights into SARS-CoV-2 cellular entry and present proof of principle that targeting viral entry could be an effective way to treat different variant infections.


Subject(s)
Angiotensin-Converting Enzyme 2 , COVID-19 , Clathrin/metabolism , Endocytosis , Humans , Pandemics , Peptidyl-Dipeptidase A/genetics , Peptidyl-Dipeptidase A/metabolism , Protein Binding , SARS-CoV-2 , Spike Glycoprotein, Coronavirus/genetics , Spike Glycoprotein, Coronavirus/metabolism , Virus Internalization
7.
Nature ; 603(7902): 715-720, 2022 03.
Article in English | MEDLINE | ID: covidwho-1661972

ABSTRACT

The emergence of SARS-CoV-2 variants of concern with progressively increased transmissibility between humans is a threat to global public health. The Omicron variant of SARS-CoV-2 also evades immunity from natural infection or vaccines1, but it is unclear whether its exceptional transmissibility is due to immune evasion or intrinsic virological properties. Here we compared the replication competence and cellular tropism of the wild-type virus and the D614G, Alpha (B.1.1.7), Beta (B.1.351), Delta (B.1.617.2) and Omicron (B.1.1.529) variants in ex vivo explant cultures of human bronchi and lungs. We also evaluated the dependence on TMPRSS2 and cathepsins for infection. We show that Omicron replicates faster than all other SARS-CoV-2 variants studied in the bronchi but less efficiently in the lung parenchyma. All variants of concern have similar cellular tropism compared to the wild type. Omicron is more dependent on cathepsins than the other variants of concern tested, suggesting that the Omicron variant enters cells through a different route compared with the other variants. The lower replication competence of Omicron in the human lungs may explain the reduced severity of Omicron that is now being reported in epidemiological studies, although determinants of severity are multifactorial. These findings provide important biological correlates to previous epidemiological observations.


Subject(s)
Bronchi/virology , Lung/virology , SARS-CoV-2/growth & development , Viral Tropism , Virus Replication , Angiotensin-Converting Enzyme 2/metabolism , Animals , COVID-19/epidemiology , COVID-19/transmission , COVID-19/virology , Cathepsins/metabolism , Chlorocebus aethiops , Endocytosis , Humans , In Vitro Techniques , SARS-CoV-2/immunology , Serine Endopeptidases/genetics , Serine Endopeptidases/metabolism , Tissue Culture Techniques , Vero Cells
8.
Viruses ; 14(1)2021 12 22.
Article in English | MEDLINE | ID: covidwho-1636836

ABSTRACT

Human adenoviruses (HAdV) cause a variety of infections in human hosts, from self-limited upper respiratory tract infections in otherwise healthy people to fulminant pneumonia and death in immunocompromised patients. Many HAdV enter polarized epithelial cells by using the primary receptor, the Coxsackievirus and adenovirus receptor (CAR). Recently published data demonstrate that a potent neutrophil (PMN) chemoattractant, interleukin-8 (IL-8), stimulates airway epithelial cells to increase expression of the apical isoform of CAR (CAREx8), which results in increased epithelial HAdV type 5 (HAdV5) infection. However, the mechanism for PMN-enhanced epithelial HAdV5 transduction remains unclear. In this manuscript, the molecular mechanisms behind PMN mediated enhancement of epithelial HAdV5 transduction are characterized using an MDCK cell line that stably expresses human CAREx8 under a doxycycline inducible promoter (MDCK-CAREx8 cells). Contrary to our hypothesis, PMN exposure does not enhance HAdV5 entry by increasing CAREx8 expression nor through activation of non-specific epithelial endocytic pathways. Instead, PMN serine proteases are responsible for PMN-mediated enhancement of HAdV5 transduction in MDCK-CAREx8 cells. This is evidenced by reduced transduction upon inhibition of PMN serine proteases and increased transduction upon exposure to exogenous human neutrophil elastase (HNE). Furthermore, HNE exposure activates epithelial autophagic flux, which, even when triggered through other mechanisms, results in a similar enhancement of epithelial HAdV5 transduction. Inhibition of F-actin with cytochalasin D partially attenuates PMN mediated enhancement of HAdV transduction. Taken together, these findings suggest that HAdV5 can leverage innate immune responses to establish infections.


Subject(s)
Adenoviruses, Human/pathogenicity , Epithelial Cells/virology , Leukocyte Elastase/metabolism , Neutrophils/immunology , Virus Internalization , Adenoviruses, Human/immunology , Adenoviruses, Human/physiology , Animals , Autophagy , Coxsackie and Adenovirus Receptor-Like Membrane Protein/metabolism , Cytochalasin B/pharmacology , Dogs , Endocytosis , Humans , Immunity, Innate , Macrolides/pharmacology , Madin Darby Canine Kidney Cells , Receptors, Virus/metabolism
9.
Proc Natl Acad Sci U S A ; 119(4)2022 01 25.
Article in English | MEDLINE | ID: covidwho-1621335

ABSTRACT

After binding to its cell surface receptor angiotensin converting enzyme 2 (ACE2), severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) enters the host cell through directly fusing with plasma membrane (cell surface pathway) or undergoing endocytosis traveling to lysosome/late endosome for membrane fusion (endocytic pathway). However, the endocytic entry regulation by host cell remains elusive. Recent studies show ACE2 possesses a type I PDZ binding motif (PBM) through which it could interact with a PDZ domain-containing protein such as sorting nexin 27 (SNX27). In this study, we determined the ACE2-PBM/SNX27-PDZ complex structure, and, through a series of functional analyses, we found SNX27 plays an important role in regulating the homeostasis of ACE2 receptor. More importantly, we demonstrated SNX27, together with retromer complex (the core component of the endosomal protein sorting machinery), prevents ACE2/virus complex from entering lysosome/late endosome, resulting in decreased viral entry in cells where the endocytic pathway dominates. The ACE2/virus retrieval mediated by SNX27-retromer could be considered as a countermeasure against invasion of ACE2 receptor-using SARS coronaviruses.


Subject(s)
Angiotensin-Converting Enzyme 2/metabolism , COVID-19/metabolism , Endosomes/metabolism , SARS-CoV-2 , Sorting Nexins/chemistry , COVID-19/virology , Cell Line , Cell Line, Tumor , Cell Membrane/metabolism , Crystallography, X-Ray , Cytosol/metabolism , Endocytosis , Gene Expression Profiling , HEK293 Cells , HeLa Cells , Homeostasis , Humans , Lentivirus , Lysosomes/metabolism , Peptides/chemistry , Protein Binding , Protein Conformation , Protein Domains , Sorting Nexins/metabolism , Virus Internalization
10.
Cell Commun Signal ; 20(1): 2, 2022 01 03.
Article in English | MEDLINE | ID: covidwho-1590514

ABSTRACT

Scavenger receptors belong to a superfamily of proteins that are structurally heterogeneous and encompass the miscellaneous group of transmembrane proteins and soluble secretory extracellular domain. They are functionally diverse as they are involved in various disorders and biological pathways and their major function in innate immunity and homeostasis. Numerous scavenger receptors have been discovered so far and are apportioned in various classes (A-L). Scavenger receptors are documented as pattern recognition receptors and known to act in coordination with other co-receptors such as Toll-like receptors in generating the immune responses against a repertoire of ligands such as microbial pathogens, non-self, intracellular and modified self-molecules through various diverse mechanisms like adhesion, endocytosis and phagocytosis etc. Unlike, most of the scavenger receptors discussed below have both membrane and soluble forms that participate in scavenging; the role of a potential scavenging receptor Angiotensin-Converting Enzyme-2 has also been discussed whereby only its soluble form might participate in preventing the pathogen entry and replication, unlike its membrane-bound form. This review majorly gives an insight on the functional aspect of scavenger receptors in host defence and describes their mode of action extensively in various immune pathways involved with each receptor type. Video abstract.


Subject(s)
Immunity, Innate , Toll-Like Receptors , Endocytosis , Phagocytosis , Receptors, Scavenger/metabolism
11.
Emerg Microbes Infect ; 11(1): 277-283, 2022 Dec.
Article in English | MEDLINE | ID: covidwho-1585239

ABSTRACT

The novel SARS-CoV-2 Omicron variant (B.1.1.529), first found in early November 2021, has sparked considerable global concern and it has >50 mutations, many of which are known to affect transmissibility or cause immune escape. In this study, we sought to investigate the virological characteristics of the Omicron variant and compared it with the Delta variant which has dominated the world since mid-2021. Omicron variant replicated more slowly than the Delta variant in transmembrane serine protease 2 (TMPRSS2)-overexpressing VeroE6 (VeroE6/TMPRSS2) cells. Notably, the Delta variant replicated well in Calu3 cell line which has robust TMPRSS2 expression, while the Omicron variant replicated poorly in this cell line. Competition assay showed that Delta variant outcompeted Omicron variant in VeroE6/TMPRSS2 and Calu3 cells. To confirm the difference in entry pathway between the Omicron and Delta variants, we assessed the antiviral effect of bafilomycin A1, chloroquine (inhibiting endocytic pathway), and camostat (inhibiting TMPRSS2 pathway). Camostat potently inhibited the Delta variant but not the Omicron variant, while bafilomycin A1 and chloroquine could inhibit both Omicron and Delta variants. Moreover, the Omicron variant also showed weaker cell-cell fusion activity when compared with Delta variant in VeroE6/TMPRSS2 cells. Collectively, our results suggest that Omicron variant infection is not enhanced by TMPRSS2 but is largely mediated via the endocytic pathway. The difference in entry pathway between Omicron and Delta variants may have an implication on the clinical manifestations or disease severity.


Subject(s)
COVID-19/virology , SARS-CoV-2/physiology , Serine Endopeptidases/metabolism , Virus Internalization , Virus Replication , Animals , Carcinoma, Non-Small-Cell Lung/pathology , Cell Line, Tumor , Chlorocebus aethiops , Chloroquine/pharmacology , Endocytosis/drug effects , Esters/pharmacology , Guanidines/pharmacology , Humans , Immune Evasion , Lung Neoplasms/pathology , Macrolides/pharmacology , Recombinant Proteins/metabolism , SARS-CoV-2/genetics , Vero Cells , Virus Cultivation , Virus Internalization/drug effects , Whole Genome Sequencing
12.
Biochem Biophys Res Commun ; 587: 69-77, 2022 01 08.
Article in English | MEDLINE | ID: covidwho-1540389

ABSTRACT

The clathrin coat assembly protein AP180 drives endocytosis, which is crucial for numerous physiological events, such as the internalization and recycling of receptors, uptake of neurotransmitters and entry of viruses, including SARS-CoV-2, by interacting with clathrin. Moreover, dysfunction of AP180 underlies the pathogenesis of Alzheimer's disease. Therefore, it is important to understand the mechanisms of assembly and, especially, disassembly of AP180/clathrin-containing cages. Here, we identified AP180 as a novel phosphatidic acid (PA)-binding protein from the mouse brain. Intriguingly, liposome binding assays using various phospholipids and PA species revealed that AP180 most strongly bound to 1-stearoyl-2-docosahexaenoyl-PA (18:0/22:6-PA) to a comparable extent as phosphatidylinositol 4,5-bisphosphate (PI(4,5)P2), which is known to associate with AP180. An AP180 N-terminal homology domain (1-289 aa) interacted with 18:0/22:6-PA, and a lysine-rich motif (K38-K39-K40) was essential for binding. The 18:0/22:6-PA in liposomes in 100 nm diameter showed strong AP180-binding activity at neutral pH. Notably, 18:0/22:6-PA significantly attenuated the interaction of AP180 with clathrin. However, PI(4,5)P2 did not show such an effect. Taken together, these results indicate the novel mechanism by which 18:0/22:6-PA selectively regulates the disassembly of AP180/clathrin-containing cages.


Subject(s)
Clathrin/metabolism , Docosahexaenoic Acids/metabolism , Monomeric Clathrin Assembly Proteins/metabolism , Phosphatidic Acids/metabolism , Animals , Binding Sites , Brain/metabolism , COVID-19/metabolism , COVID-19/virology , Cell Line , Clathrin/chemistry , Docosahexaenoic Acids/chemistry , Endocytosis/physiology , Host Microbial Interactions/physiology , Humans , Mice , Monomeric Clathrin Assembly Proteins/chemistry , Monomeric Clathrin Assembly Proteins/genetics , Phosphatidic Acids/chemistry , Protein Binding , Protein Interaction Domains and Motifs , Recombinant Proteins/chemistry , Recombinant Proteins/genetics , Recombinant Proteins/metabolism , SARS-CoV-2/physiology , Virus Internalization
13.
Nat Commun ; 12(1): 5739, 2021 10 19.
Article in English | MEDLINE | ID: covidwho-1475293

ABSTRACT

Protein aggregates associated with neurodegenerative diseases have the ability to transmit to unaffected cells, thereby templating their own aberrant conformation onto soluble homotypic proteins. Proteopathic seeds can be released into the extracellular space, secreted in association with extracellular vesicles (EV) or exchanged by direct cell-to-cell contact. The extent to which each of these pathways contribute to the prion-like spreading of protein misfolding is unclear. Exchange of cellular cargo by both direct cell contact or via EV depends on receptor-ligand interactions. We hypothesized that enabling these interactions through viral ligands enhances intercellular proteopathic seed transmission. Using different cellular models propagating prions or pathogenic Tau aggregates, we demonstrate that vesicular stomatitis virus glycoprotein and SARS-CoV-2 spike S increase aggregate induction by cell contact or ligand-decorated EV. Thus, receptor-ligand interactions are important determinants of intercellular aggregate dissemination. Our data raise the possibility that viral infections contribute to proteopathic seed spreading by facilitating intercellular cargo transfer.


Subject(s)
Angiotensin-Converting Enzyme 2/metabolism , Extracellular Vesicles/metabolism , Membrane Glycoproteins/metabolism , Protein Aggregation, Pathological/virology , Spike Glycoprotein, Coronavirus/metabolism , Viral Envelope Proteins/metabolism , Adult , Aged , Brain/pathology , Case-Control Studies , Cell Line , Endocytosis , Female , Humans , Intravital Microscopy , Male , Middle Aged , Prions/metabolism , Protein Aggregation, Pathological/pathology , Protein Folding , tau Proteins/metabolism
14.
mBio ; 12(5): e0254221, 2021 10 26.
Article in English | MEDLINE | ID: covidwho-1462902

ABSTRACT

Damage in COVID-19 results from both the SARS-CoV-2 virus and its triggered overactive host immune responses. Therapeutic agents that focus solely on reducing viral load or hyperinflammation fail to provide satisfying outcomes in all cases. Although viral and cellular factors have been extensively profiled to identify potential anti-COVID-19 targets, new drugs with significant efficacy remain to be developed. Here, we report the potent preclinical efficacy of ALD-R491, a vimentin-targeting small molecule compound, in treating COVID-19 through its host-directed antiviral and anti-inflammatory actions. We found that by altering the physical properties of vimentin filaments, ALD-491 affected general cellular processes as well as specific cellular functions relevant to SARS-CoV-2 infection. Specifically, ALD-R491 reduced endocytosis, endosomal trafficking, and exosomal release, thus impeding the entry and egress of the virus; increased the microcidal capacity of macrophages, thus facilitating the pathogen clearance; and enhanced the activity of regulatory T cells, therefore suppressing the overactive immune responses. In cultured cells, ALD-R491 potently inhibited the SARS-CoV-2 spike protein and human ACE2-mediated pseudoviral infection. In aged mice with ongoing, productive SARS-CoV-2 infection, ALD-R491 reduced disease symptoms as well as lung damage. In rats, ALD-R491 also reduced bleomycin-induced lung injury and fibrosis. Our results indicate a unique mechanism and significant therapeutic potential for ALD-R491 against COVID-19. We anticipate that ALD-R491, an oral, fast-acting, and non-cytotoxic agent targeting the cellular protein with multipart actions, will be convenient, safe, and broadly effective, regardless of viral mutations, for patients with early- or late-stage disease, post-COVID-19 complications, and other related diseases. IMPORTANCE With the Delta variant currently fueling a resurgence of new infections in the fully vaccinated population, developing an effective therapeutic drug is especially critical and urgent in fighting COVID-19. In contrast to the many efforts to repurpose existing drugs or address only one aspect of COVID-19, we are developing a novel agent with first-in-class mechanisms of action that address both the viral infection and the overactive immune system in the pathogenesis of the disease. Unlike virus-directed therapeutics that may lose efficacy due to viral mutations, and immunosuppressants that require ideal timing to be effective, this agent, with its unique host-directed antiviral and anti-inflammatory actions, can work against all variants of the virus, be effective during all stages of the disease, and even resolve post-disease damage and complications. Further development of the compound will provide an important tool in the fight against COVID-19 and its complications, as well as future outbreaks of new viruses.


Subject(s)
Anti-Inflammatory Agents/therapeutic use , Antiviral Agents/therapeutic use , COVID-19/drug therapy , COVID-19/metabolism , Organic Chemicals/therapeutic use , Spike Glycoprotein, Coronavirus/metabolism , Vimentin/metabolism , Animals , Endocytosis/drug effects , Endosomes/drug effects , Endosomes/metabolism , Exosomes/drug effects , Exosomes/metabolism , HEK293 Cells , Humans , Mice , RAW 264.7 Cells
15.
J Virol ; 95(24): e0134521, 2021 11 23.
Article in English | MEDLINE | ID: covidwho-1441856

ABSTRACT

Porcine deltacoronavirus (PDCoV), an emerging enteropathogenic coronavirus, causes serious diarrhea in suckling piglets and has the potential for cross-species transmission. Although extensive studies have been reported on the biology and pathogenesis of PDCoV, the mechanisms by which PDCoV enters cells are not well characterized. In this study, we investigated how PDCoV enters IPI-2I cells, a line of porcine intestinal epithelial cells derived from pig ileum. Immunofluorescence assays, small interfering RNA (siRNA) interference, specific pharmacological inhibitors, and dominant negative mutation results revealed that PDCoV entry into IPI-2I cells depended on clathrin, dynamin, and a low-pH environment but was independent of caveolae. Specific inhibition of phosphatidylinositol 3-kinase (PI3K) and the Na+/H+ exchanger (NHE) revealed that PDCoV entry involves macropinocytosis and depends on NHE rather than on PI3K. Additionally, Rab5 and Rab7, but not Rab11, regulated PDCoV endocytosis. This is the first study to demonstrate that PDCoV uses clathrin-mediated endocytosis and macropinocytosis as alternative endocytic pathways to enter porcine intestinal epithelial cells. We also discussed the entry pathways of PDCoV into other porcine cell lines. Our findings reveal the entry mechanisms of PDCoV and provide new insight into the PDCoV life cycle. IMPORTANCE An emerging enteropathogenic coronavirus, PDCoV, has the potential for cross-species transmission, attracting extensive attenuation. Characterizing the detailed process of PDCoV entry into cells will deepen our understanding of the viral infection and pathogenesis and provide clues for therapeutic intervention against PDCoV. With the objective, we used complementary approaches to dissect the process in PDCoV-infected IPI-2I cells, a line of more physiologically relevant intestinal epithelial cells to PDCoV infection in vivo. Here, we demonstrate that PDCoV enters IPI-2I cells via macropinocytosis, which does not require a specific receptor, and clathrin-mediated endocytosis, which requires a low-pH environment and dynamin, while a caveola-mediated endocytic pathway is used by PDCoV to enter swine testicular (ST) cells and porcine kidney (LLC-PK1) cells. These findings provide a molecular detail of the cellular entry pathways of PDCoV and may direct us toward novel antiviral drug development.


Subject(s)
Coronavirus Infections/virology , Deltacoronavirus/physiology , Dynamins/metabolism , Endocytosis , Epithelial Cells/virology , Animals , Cell Line , Cell Survival , Clathrin/metabolism , Coronavirus/genetics , Hydrogen-Ion Concentration , Ileum/virology , Kidney/virology , Phosphatidylinositol 3-Kinases/metabolism , Pinocytosis , RNA, Small Interfering/metabolism , Swine , Swine Diseases/virology , Virus Internalization , rab5 GTP-Binding Proteins/metabolism
16.
Front Immunol ; 12: 636966, 2021.
Article in English | MEDLINE | ID: covidwho-1438414

ABSTRACT

Since 2003, the world has been confronted with three new betacoronaviruses that cause human respiratory infections: SARS-CoV, which causes severe acute respiratory syndrome (SARS), MERS-CoV, which causes Middle East respiratory syndrome (MERS), and SARS-CoV-2, which causes Coronavirus Disease 2019 (COVID-19). The mechanisms of coronavirus transmission and dissemination in the human body determine the diagnostic and therapeutic strategies. An important problem is the possibility that viral particles overcome tissue barriers such as the intestine, respiratory tract, blood-brain barrier, and placenta. In this work, we will 1) consider the issue of endocytosis and the possibility of transcytosis and paracellular trafficking of coronaviruses across tissue barriers with an emphasis on the intestinal epithelium; 2) discuss the possibility of antibody-mediated transcytosis of opsonized viruses due to complexes of immunoglobulins with their receptors; 3) assess the possibility of the virus transfer into extracellular vesicles during intracellular transport; and 4) describe the clinical significance of these processes. Models of the intestinal epithelium and other barrier tissues for in vitro transcytosis studies will also be briefly characterized.


Subject(s)
Endocytosis , Intestinal Mucosa/virology , SARS-CoV-2/metabolism , Antibodies, Viral/metabolism , Antiviral Agents/pharmacology , Antiviral Agents/therapeutic use , COVID-19/drug therapy , COVID-19/transmission , COVID-19/virology , Clinical Trials as Topic , Endocytosis/drug effects , Humans , Intestinal Mucosa/metabolism , Models, Biological , SARS-CoV-2/drug effects , SARS-CoV-2/immunology , Tight Junctions/metabolism , Tight Junctions/virology , Transcytosis/drug effects , Virus Attachment
17.
Int J Med Sci ; 18(15): 3533-3543, 2021.
Article in English | MEDLINE | ID: covidwho-1409698

ABSTRACT

Importance: Despite the availability of a vaccine against the severe acute respiratory syndrome-coronavirus-2 (SARS-CoV-2), humans will have to live with this virus and the after-effects of the coronavirus disease 2019 (COVID-19) infection for a long time. Cholesterol plays an important role in the infection and prognosis of SARS-CoV-2, and the study of its mechanism is of great significance not only for the treatment of COVID-19 but also for research on generic antiviral drugs. Observations: Cholesterol promotes the development of atherosclerosis by activating NLR family pyrin domain containing 3 (NLRP3), and the resulting inflammatory environment indirectly contributes to COVID-19 infection and subsequent deterioration. In in vitro studies, membrane cholesterol increased the number of viral entry sites on the host cell membrane and the number of angiotensin-converting enzyme 2 (ACE2) receptors in the membrane fusion site. Previous studies have shown that the fusion protein of the virus interacts with cholesterol, and the spike protein of SARS-CoV-2 also requires cholesterol to enter the host cells. Cholesterol in blood interacts with the spike protein to promote the entry of spike cells, wherein the scavenger receptor class B type 1 (SR-B1) plays an important role. Because of the cardiovascular protective effects of lipid-lowering therapy and the additional anti-inflammatory effects of lipid-lowering drugs, it is currently recommended to continue lipid-lowering therapy for patients with COVID-19, but the safety of extremely low LDL-C is questionable. Conclusions and Relevance: Cholesterol can indirectly increase the susceptibility of patients to SARS-CoV-2 and increase the risk of death from COVID-19, which are mediated by NLRP3 and atherosclerotic plaques, respectively. Cholesterol present in the host cell membrane, virus, and blood may also directly participate in the virus cell entry process, but the specific mechanism still needs further study. Patients with COVID-19 are recommended to continue lipid-lowering therapy.


Subject(s)
COVID-19/complications , Hypercholesterolemia/complications , Angiotensin-Converting Enzyme 2/metabolism , Antiviral Agents/therapeutic use , Atherosclerosis/physiopathology , COVID-19/diagnosis , COVID-19/drug therapy , COVID-19/therapy , Cell Membrane/metabolism , Cholesterol, HDL/metabolism , Cholesterol, LDL/metabolism , Endocytosis , Humans , Hypercholesterolemia/diagnosis , Hypercholesterolemia/therapy , Inflammation , Macrophages/metabolism , NLR Family, Pyrin Domain-Containing 3 Protein/blood , Prognosis , SARS-CoV-2 , Scavenger Receptors, Class B/metabolism
18.
Int J Mol Sci ; 22(10)2021 May 17.
Article in English | MEDLINE | ID: covidwho-1383880

ABSTRACT

Numerous viruses hijack cellular protein trafficking pathways to mediate cell entry or to rearrange membrane structures thereby promoting viral replication and antagonizing the immune response. Adaptor protein complexes (AP), which mediate protein sorting in endocytic and secretory transport pathways, are one of the conserved viral targets with many viruses possessing AP-interacting motifs. We present here different mechanisms of viral interference with AP complexes and the functional consequences that allow for efficient viral propagation and evasion of host immune defense. The ubiquity of this phenomenon is evidenced by the fact that there are representatives for AP interference in all major viral families, covered in this review. The best described examples are interactions of human immunodeficiency virus and human herpesviruses with AP complexes. Several other viruses, like Ebola, Nipah, and SARS-CoV-2, are pointed out as high priority disease-causative agents supporting the need for deeper understanding of virus-AP interplay which can be exploited in the design of novel antiviral therapies.


Subject(s)
Adaptor Proteins, Vesicular Transport/metabolism , HIV-1/metabolism , Herpesviridae/metabolism , SARS-CoV-2/metabolism , Ebolavirus/metabolism , Endocytosis , Humans , Nipah Virus/metabolism , Protein Transport , Virus Release , Virus Replication
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