The spike protein (S) of SARS-CoV-2 mediates entry into human cells by interacting with human angiotensin-converting enzyme 2 (ACE2) through its receptor-binding domain (RBD). Here, we report identification of CD209L/L-SIGN and a related protein, CD209/DSIGN as alternative receptors capable of mediating SARS-CoV-2 entry into human cells. Immunofluorescence staining of human tissues revealed a prominent expression of CD209L in the lung and kidney epithelial and endothelial cells of small and medium-sized vessels, whereas CD209 was detected only in a limited number of cell types. Biochemical assays revealed that ectopically expressed CD209L and CD209 bind to S-RBD and mediate SARS-CoV-2 Spseudotyped virus entry. Furthermore, we demonstrate that human endothelial cells endogenously express CD209L and are permissive to SARS-CoV-2 infection. Soluble CD209L-Fc neutralized virus entry.Our observations show that CD209L and CD209 serve as alternative receptors for SARS-CoV-2 in diseaserelevant cell types, including the vascular system. This may have implications for antiviral drug development.

As the COVID-19 pandemic continues to spread, investigating the processes underlying the interactions between SARS-CoV-2 and its hosts is of high importance. Here, we report the identification of CD209L/L-SIGN and the related protein CD209/DC-SIGN as receptors capable of mediating SARS-CoV-2 entry into human cells. Immunofluorescence staining of human tissues revealed prominent expression of CD209L in the lung and kidney epithelia and endothelia. Multiple biochemical assays using a purified recombinant SARS-CoV-2 spike receptor-binding domain (S-RBD) or S1 encompassing both N termal domain and RBD and ectopically expressed CD209L and CD209 revealed that CD209L and CD209 interact with S-RBD. CD209L contains two N -glycosylation sequons, at sites N92 and N361, but we determined that only site N92 is occupied. Removal of the N -glycosylation at this site enhances the binding of S-RBD with CD209L. CD209L also interacts with ACE2, suggesting a role for heterodimerization of CD209L and ACE2 in SARS-CoV-2 entry and infection in cell types where both are present. Furthermore, we demonstrate that human endothelial cells are permissive to SARS-CoV-2 infection, and interference with CD209L activity by a knockdown strategy or with soluble CD209L inhibits virus entry. Our observations demonstrate that CD209L and CD209 serve as alternative receptors for SARS-CoV-2 in disease-relevant cell types, including the vascular system. This property is particularly important in tissues where ACE2 has low expression or is absent and may have implications for antiviral drug development.

Exosomes can be efficiently isolated in a short period of time by the specific interaction of titanium dioxide with the phosphate groups on the surface of phospholipid bilayer.

SARS-CoV-2 entry into host cells is a crucial step for virus tropism, transmission, and pathogenesis. Angiotensin-converting enzyme 2 (ACE2) has been identified as the primary entry receptor for SARS-CoV-2; however, the possible involvement of other cellular components in the viral entry has not yet been fully elucidated. Here we describe the identification of vimentin (VIM), an intermediate filament protein widely expressed in cells of mesenchymal origin, as an important attachment factor for SARS-CoV-2 on human endothelial cells. Using liquid chromatography–tandem mass spectrometry, we identified VIM as a protein that binds to the SARS-CoV-2 spike (S) protein. We showed that the S-protein receptor binding domain (RBD) is sufficient for S-protein interaction with VIM. Further analysis revealed that extracellular VIM binds to SARS-CoV-2 S-protein and facilitates SARS-CoV-2 infection, as determined by entry assays performed with pseudotyped viruses expressing S and with infectious SARS-CoV-2. Coexpression of VIM with ACE2 increased SARS-CoV-2 entry in HEK-293 cells, and shRNA-mediated knockdown of VIM significantly reduced SARS-CoV-2 infection of human endothelial cells. Moreover, incubation of A549 cells expressing ACE2 with purified VIM increased pseudotyped SARS-CoV-2-S entry. CR3022 antibody, which recognizes a distinct epitope on SARS-CoV-2-S-RBD without interfering with the binding of the spike with ACE2, inhibited the binding of VIM with CoV-2 S-RBD, and neutralized viral entry in human endothelial cells, suggesting a key role for VIM in SARS-CoV-2 infection of endothelial cells. This work provides insight into the pathogenesis of COVID-19 linked to the vascular system, with implications for the development of therapeutics and vaccines.

Mass spectrometry (MS)-based glycoproteomics research requires highly efficient sample preparation to eliminate interference from non-glycopeptides and to improve the efficiency of glycopeptide detection. In this work, a novel MoS/Au-NP (gold nanoparticle)-L-cysteine nanocomposite was prepared for glycopeptide enrichment. The two-dimensional (2D) structured MoS nanosheets served as a matrix that could provide a large surface area for immobilizing hydrophilic groups (such as L-cysteine) with low steric hindrance between the materials and the glycopeptides. As a result, the novel nanomaterial possessed an excellent ability to capture glycopeptides. Compared to commercial zwitterionic hydrophilic interaction liquid chromatography (ZIC-HILIC) materials, the novel nanomaterials exhibited excellent enrichment performance with ultrahigh selectivity and sensitivity (approximately 10 fmol), high binding capacity (120 mg g), high enrichment recovery (more than 93%), satisfying batch-to-batch reproducibility, and good universality for glycopeptide enrichment. In addition, its outstanding specificity and efficiency for glycopeptide enrichment was confirmed by the detection of glycopeptides from an human serum immunoglobulin G (IgG) tryptic digest in quantities as low as a 1:1250 molar ratio of IgG tryptic digest to bovine serum albumin tryptic digest. The novel nanocomposites were further used for the analysis of complex samples, and 1920 glycopeptide backbones from 775 glycoproteins were identified in three replicate analyses of 50 μg of proteins extracted from HeLa cell exosomes. The resulting highly informative mass spectra indicated that this multifunctional nanomaterial-based enrichment method could be used as a promising tool for the in-depth and comprehensive characterization of glycoproteomes in MS-based glycoproteomics.

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Due to its key roles in regulating the occurrence and development of cancer, protein histidine phosphorylation has been increasingly recognized as an important form of post-translational modification in recent years. However, large-scale analysis of histidine phosphorylation is much more challenging than that of serine/threonine or tyrosine phosphorylation, mainly because of its acid lability. In this study, MoS 2 −Ti 4+ nanomaterials were synthesized using a solvothermal method and taking advantage of the electrostatic adsorption between MoS 2 nanosheets and Ti 4+ . The MoS 2 −Ti 4+ nanomaterials have the advantage of the combined affinity of Ti 4+ and Mo toward phosphorylation under medium acidic conditions (pH = 3), which is crucial for preventing hydrolysis and loss of histidine phosphorylation during enrichment. The feasibility of using the MoS 2 − Ti 4+ nanomaterial for phosphopeptide enrichment was demonstrated using mixtures of βcasein and bovine serum albumin (BSA). Further evaluation revealed that the MoS 2 −Ti 4+ nanomaterial is capable of enriching synthetic histidine phosphopeptides from 1000 times excess tryptic-digested HeLa cell lysate. Application of the MoS 2 −Ti 4+ nanomaterials for large-scale phosphopeptide enrichment results in the identification of 10 345 serine, threonine, and tyrosine phosphosites and the successful mapping of 159 histidine phosphosites in HeLa cell lysates, therefore indicating great potential for deciphering the vital biological roles of protein (histidine) phosphorylation.