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1.
Glycobiology ; 31(9): 1080-1092, 2021 09 20.
Article in English | MEDLINE | ID: covidwho-1434394

ABSTRACT

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), which causes coronavirus disease 2019 (COVID-19), started in 2019 in China and quickly spread into a global pandemic. Nucleocapsid protein (N protein) is highly conserved and is the most abundant protein in coronaviruses and is thus a potential target for both vaccine and point-of-care diagnostics. N Protein has been suggested in the literature as having posttranslational modifications (PTMs), and accurately defining these PTMs is critical for its potential use in medicine. Reports of phosphorylation of N protein have failed to provide detailed site-specific information. We have performed comprehensive glycomics, glycoproteomics and proteomics experiments on two different N protein preparations. Both were expressed in HEK293 cells; one was in-house expressed and purified without a signal peptide (SP) sequence, and the other was commercially produced with a SP channeling it through the secretory pathway. Our results show completely different PTMs on the two N protein preparations. The commercial product contained extensive N- and O-linked glycosylation as well as O-phosphorylation on site Thr393. Conversely, the native N Protein model had O-phosphorylation at Ser176 and no glycosylation, highlighting the importance of knowing the provenance of any commercial protein to be used for scientific or clinical studies. Recent studies have indicated that N protein can serve as an important diagnostic marker for COVID-19 and as a major immunogen by priming protective immune responses. Thus, detailed structural characterization of N protein may provide useful insights for understanding the roles of PTMs on viral pathogenesis, vaccine design and development of point-of-care diagnostics.


Subject(s)
Coronavirus Nucleocapsid Proteins/metabolism , Protein Processing, Post-Translational/physiology , SARS-CoV-2/metabolism , Amino Acid Motifs , Amino Acid Sequence , Binding Sites , Coronavirus Nucleocapsid Proteins/chemistry , Glycosylation , HEK293 Cells , Humans , Phosphorylation , SARS-CoV-2/chemistry
2.
Anal Bioanal Chem ; 413(29): 7179-7193, 2021 Dec.
Article in English | MEDLINE | ID: covidwho-1300454

ABSTRACT

The COVID-19 pandemic is caused by the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). Similar to other coronaviruses, its particles are composed of four structural proteins: spike (S), envelope (E), membrane (M), and nucleocapsid (N) proteins. S, E, and M proteins are glycosylated, and the N protein is phosphorylated. The S protein is involved in the interaction with the host receptor human angiotensin-converting enzyme 2 (hACE2), which is also heavily glycosylated. Recent studies have revealed several other potential host receptors or factors that can increase or modulate the SARS-CoV-2 infection. Interestingly, most of these molecules bear carbohydrate residues. While glycans acquired by the viruses through the hijacking of the host machinery help the viruses in their infectivity, they also play roles in immune evasion or modulation. Glycans play complex roles in viral pathobiology, both on their own and in association with carrier biomolecules, such as proteins or glycosaminoglycans (GAGs). Understanding these roles in detail can help in developing suitable strategies for prevention and therapy of COVID-19. In this review, we sought to emphasize the interplay of SARS-CoV-2 glycosylated proteins and their host receptors in viral attachment, entry, replication, and infection. Moreover, the implications for future therapeutic interventions targeting these glycosylated biomolecules are also discussed in detail.


Subject(s)
COVID-19/virology , SARS-CoV-2/metabolism , Angiotensin-Converting Enzyme 2/metabolism , Carbohydrate Conformation , Glycosylation , Humans , Polysaccharides/chemistry , Polysaccharides/metabolism , Protein Conformation , SARS-CoV-2/physiology , Spike Glycoprotein, Coronavirus/chemistry , Spike Glycoprotein, Coronavirus/metabolism
3.
Glycobiology ; 31(9): 1080-1092, 2021 09 20.
Article in English | MEDLINE | ID: covidwho-1231033

ABSTRACT

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), which causes coronavirus disease 2019 (COVID-19), started in 2019 in China and quickly spread into a global pandemic. Nucleocapsid protein (N protein) is highly conserved and is the most abundant protein in coronaviruses and is thus a potential target for both vaccine and point-of-care diagnostics. N Protein has been suggested in the literature as having posttranslational modifications (PTMs), and accurately defining these PTMs is critical for its potential use in medicine. Reports of phosphorylation of N protein have failed to provide detailed site-specific information. We have performed comprehensive glycomics, glycoproteomics and proteomics experiments on two different N protein preparations. Both were expressed in HEK293 cells; one was in-house expressed and purified without a signal peptide (SP) sequence, and the other was commercially produced with a SP channeling it through the secretory pathway. Our results show completely different PTMs on the two N protein preparations. The commercial product contained extensive N- and O-linked glycosylation as well as O-phosphorylation on site Thr393. Conversely, the native N Protein model had O-phosphorylation at Ser176 and no glycosylation, highlighting the importance of knowing the provenance of any commercial protein to be used for scientific or clinical studies. Recent studies have indicated that N protein can serve as an important diagnostic marker for COVID-19 and as a major immunogen by priming protective immune responses. Thus, detailed structural characterization of N protein may provide useful insights for understanding the roles of PTMs on viral pathogenesis, vaccine design and development of point-of-care diagnostics.


Subject(s)
Coronavirus Nucleocapsid Proteins/metabolism , Protein Processing, Post-Translational/physiology , SARS-CoV-2/metabolism , Amino Acid Motifs , Amino Acid Sequence , Binding Sites , Coronavirus Nucleocapsid Proteins/chemistry , Glycosylation , HEK293 Cells , Humans , Phosphorylation , SARS-CoV-2/chemistry
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