Angiotensin Peptides and SARS-CoV-2: Mechanistic Insights into Spike–Receptor Binding Enhancement

Study Background and Research Question

The renin–angiotensin system (RAS), and its constituent peptides such as Angiotensin (1-7) (Asp-Arg-Val-Tyr-Ile-His-Pro), play pivotal roles in cardiovascular, renal, and metabolic regulation. With the emergence of COVID-19, attention has focused on how SARS-CoV-2 leverages host proteins—including ACE2, neuropilin-1 (NRP1), and the lesser-studied AXL receptor—for cell entry. While ACE2 is widely recognized as the principal receptor for the viral spike protein, AXL has emerged as an alternative mediator, particularly in cell types with low ACE2 expression. The reference study (Oliveira et al., 2025) addresses a crucial knowledge gap: how do endogenous angiotensin peptides modulate the interaction between the SARS-CoV-2 spike protein and its cellular receptors, especially AXL?

Key Innovation from the Reference Study

The central innovation is the discovery that several naturally occurring angiotensin peptides—including Angiotensin (1-7)—can markedly enhance the binding of the SARS-CoV-2 spike protein to AXL, independent of their classical vasoactive roles. Notably, the study demonstrates that not only Angiotensin II (1–8), but also its C- and N-terminal truncated forms (including Angiotensin (1-7), Angiotensin (1-6), Angiotensin III, and Angiotensin IV), promote spike–AXL binding, with some truncated peptides showing even greater enhancement than the parent molecule. These findings bridge the fields of peptide hormone biology and viral pathogenesis, suggesting that RAS peptides may influence susceptibility to SARS-CoV-2 infection and disease progression through modulation of alternative viral entry pathways.

Methods and Experimental Design Insights

The research team employed antibody-based binding assays to quantify the effect of various angiotensin peptides on the interaction between the SARS-CoV-2 spike protein and its known receptors: ACE2, NRP1, and AXL. Peptides tested included full-length Angiotensin I (1–10), Angiotensin II (1–8), Angiotensin (1-7), Angiotensin (1-6), and several N-terminally truncated forms (Angiotensin III (2–8), Angiotensin IV (3–8), Angiotensin (2–7), Angiotensin (5–7)). Additionally, the study examined the impact of amino acid substitutions and post-translational modifications (e.g., tyrosine phosphorylation or substitution at position 4) on spike–AXL binding. The use of these systematically truncated and modified peptides allowed for precise mapping of sequence determinants underpinning the spike–receptor interaction enhancement.

Core Findings and Why They Matter

Key results from the study include:

• Angiotensin II (1–8) caused a two-fold increase in spike–AXL binding, but did not affect spike–ACE2 or spike–NRP1 interactions (Oliveira et al., 2025).
• Truncation of Angiotensin II to Angiotensin (1-7) or Angiotensin (1-6) preserved the ability to enhance spike–AXL binding, indicating that the C-terminal Phe residue is not essential for this effect.
• N-terminal truncation (e.g., Angiotensin III, Angiotensin IV) further increased spike–AXL binding (up to 2.7-fold with Angiotensin IV), suggesting that specific sequence motifs are critical for maximal enhancement.
• Peptides with tyrosine substitutions or phosphorylation at position 4 also enhanced spike–AXL binding, implicating this residue as a functional determinant.
• Angiotensin IV exhibited broader effects, enhancing spike protein binding not only to AXL but also to ACE2 and NRP1, raising the possibility that certain angiotensin fragments may influence multiple viral entry routes.

These findings are significant for several reasons. First, they imply that endogenous peptides—traditionally studied in hemodynamic and fibrotic contexts—may modulate viral infectivity by altering the affinity of SARS-CoV-2 for alternative host receptors. Second, the data suggest that the RAS system's peptide milieu, including Angiotensin (1-7), could influence tissue tropism and disease severity, particularly in organs where AXL is highly expressed and ACE2 is less abundant. This mechanistic insight may help explain clinical heterogeneity in COVID-19 and supports further investigation into RAS modulation as a therapeutic or preventive strategy.

Why this cross-domain matters, maturity, and limitations

The cross-domain implication—spanning peptide hormone biology and viral pathogenesis—is supported here by direct experimental evidence that angiotensin fragments modulate viral receptor engagement. However, these findings are based on in vitro binding assays. Although the enhancement of spike–AXL binding is robust, the study does not address whether these interactions increase viral entry or replication in full cellular or in vivo systems. Thus, while the mechanistic bridge is plausible and relevant, the translational maturity is limited: direct effects on infection rates, pathogenesis, or patient outcomes remain to be validated in future studies.

Comparison with Existing Internal Articles

Internal literature available from APExBIO and partner resources has previously emphasized the utility of Angiotensin (1-7) as an anti-fibrotic and anti-inflammatory agent, with proven modulation of PI3K/AKT and ERK pathways (see Mechanistic Benchmarks). These applications extend to cardiovascular, renal, neuroprotective, and oncological models, where Angiotensin (1-7)'s Mas receptor agonism underpins its biological effects (Mechanistic Leverage). The reference study by Oliveira et al. adds a new dimension by revealing a virological interface, demonstrating that Angiotensin (1-7)'s sequence (Asp-Arg-Val-Tyr-Ile-His-Pro) not only regulates host signaling pathways but also influences viral spike–receptor interactions. While prior internal articles focus on disease model modulation and reproducibility in signaling assays, the current study uniquely highlights a potential role for Angiotensin (1-7) and related fragments in modulating viral entry mechanisms—an aspect previously unaddressed in these resources.

Limitations and Transferability

Several caveats must be considered. The reference study's findings, while mechanistically robust in vitro, require validation in physiologically relevant infection models. The concentrations of angiotensin peptides used in the assays may not fully reflect endogenous levels during disease states, and the in vivo consequences of spike–AXL binding enhancement are not delineated. Moreover, while the data support a role for sequence-specific modulation, the broader implications for RAS-targeted therapies or peptide analogs in COVID-19 prevention or treatment remain speculative. Transferability to clinical or in vivo antiviral contexts should be approached cautiously until further empirical evidence is available.

Protocol Parameters

• Peptide application in binding assays: Angiotensin (1-7) and related peptides were used at concentrations sufficient to elicit measurable changes in spike–AXL binding; exact concentrations should be titrated based on assay sensitivity and pilot experiments.
• Peptide sequence selection: Use Asp-Arg-Val-Tyr-Ile-His-Pro for Angiotensin (1-7), and consider testing N- or C-terminal truncations to delineate sequence specificity in receptor modulation.
• Functional validation: Where possible, supplement binding data with cell-based viral entry assays to confirm biological relevance.
• Workflow recommendations: For mechanistic studies of PI3K/AKT or ERK pathway regulation, validated concentrations of Angiotensin (1-7) (e.g., 100 nM in cell models) may be adapted from disease model protocols (product information).

Research Support Resources

For researchers aiming to extend these findings or to probe the dual roles of Angiotensin (1-7) in both signaling and viral receptor modulation, high-purity, protocol-ready reagents are essential. Angiotensin (1-7) (SKU A1041) is available as a research-grade peptide, with validated solubility and purity supporting reliable in vitro and in vivo applications. Its sequence (Asp-Arg-Val-Tyr-Ile-His-Pro) and well-characterized Mas receptor activity make it suitable for studies of PI3K/AKT and ERK pathway modulation, as well as for emerging investigations into viral spike–receptor interactions. Researchers can leverage existing protocol benchmarks from APExBIO’s internal resources to optimize their experimental designs while exploring new translational frontiers in viral pathogenesis and host response.