SARS-CoV-2 SPIKE PROTEIN INTERACTIONS WITH ACE2-DERIVED PEPTIDES IN LANGMUIR MONOLAYERS

The ongoing evolution of SARS-CoV-2 challenges COVID-19 treatments and threatens public health. The Omicron variant carries over 30 mutations in the spike protein, which mediates binding to the angiotensin-converting enzyme 2 (ACE2) receptor and fusion with the host cell membrane. Although significant progress has been made in understanding the structure, function, and interactions of the SARS-CoV-2 spike protein, the role of the membrane environment remains poorly characterized. In this work, we investigated the interactions of the recombinant Omicron SARS-CoV-2 spike ectodomain (S protein) with Langmuir monolayers composed of phosphatidylcholine, phosphatidylethanolamine, and phosphatidylserine containing saturated (18:0) or unsaturated (18:1) acyl chains. Two ACE2-derived peptides (P1 and P2) were further included to evaluate their interactions with the S protein at lipid monolayers. Surface pressure measurements were used to determine binding parameters, including maximum insertion pressure (MIP) and synergy, for the S protein, the ACE2-derived peptides, and the combined S protein-peptide systems. The S protein exhibited higher binding parameters for saturated phosphatidylserine monolayers, indicating a more favorable interaction with negatively charged and condensed lipid monolayers. Peptide binding was affected by both peptide structural features and lipid composition. For the combined S protein-peptide systems, increased MIP values were observed, particularly for S protein-P2 in saturated phosphatidylserine monolayers, which exhibited a higher MIP than the S protein and P2 individually, indicating a synergistic effect. This behavior suggests that the S protein may enhance peptide binding through S protein-peptide interactions, as well as changes in the physicochemical properties of the monolayer induced by S protein incorporation. These findings provide insights into the influence of membrane composition on SARS-CoV-2 spike protein interactions.

This work was supported by the São Paulo Research Foundation (FAPESP; grants 24/19172-0 and 23/13811-9), the National Institute for Science and Technology on Organic Electronics (INEO), and the National Council for Scientific and Technological Development (CNPq).