Single amino acid substitution at position 614 in SARS-CoV-2 Spike Protein alters viral assembly and infectivity

The emergence of SARS-CoV-2 has posed a substantial global public - health threat and has led to the emergence of diverse variant strains. A prevalent mutation, D614G, is commonly detected in the spike glycoprotein (S) of successive SARS- CoV-2 variants, which enhances viral infectivity. Here, the objective was to examine the influence of mutations on the synthesis and processing of the S protein, virus assembly, and infectivity. This was achieved by artificially substituting the aspartic acid at position 614 of the S protein with 19 distinct amino acids, including glycine, via codon modification. Pseudoviruses and virus-like particles were employed as models for this investigation. The results demonstrated that the expression characteristics of the modified S proteins diverged from those of the original D614 variant. Moreover, pseudoviruses with various mutations displayed different efficiencies in entering cells expressing ACE2. Significantly, the D614P and D614C mutations disrupted the production and processing of the S protein, exerting a notable impact on virus assembly. However, co-immunoprecipitation analysis indicated that D614 mutations did not hinder the interaction between the S protein and the ACE2 receptor. These findings emphasize the significance of D614 or G614 in S protein expression and virus assembly, providing novel targets and perspectives for the progress of research on spike-based vaccines and antiviral therapeutics.