Neuropilin-1 Assists SARS-CoV-2 Infection by Stimulating the Separation of Spike Protein Domains S1 and S2

Mutating novel interaction sites in NRP1 reduces SARS-CoV-2 spike protein internalization

The global pandemic of coronavirus disease 2019 caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) virus has become a severe global health problem because of its rapid spread. Both Ace2 and NRP1 provide initial viral binding sites for SARS-CoV-2. Here, we show that cysteine residues located in the vestigial plasminogen-apple-nematode (PAN) domain of NRP1 are necessary for SARS-CoV-2 spike protein internalization. Mutating novel cysteine residues in the PAN altered NRP1 stability and downstream activation of extracellular signal-regulated kinase (ERK) signaling pathway and impaired its interaction with the spike protein. This resulted in a significant reduction in spike protein abundance in Vero-E6 cells for the original, alpha, and delta SARS-CoV-2 variants even in the presence of the Ace2. Moreover, mutating these cysteine residues in NRP1 significantly lowered its association with Plexin-A1. As the spike protein is a critical component for targeted therapy, our biochemical study may represent a distinct mechanism to develop a path for future therapeutic discovery.

Chemosensory loss in COVID ‐19

The COVID‐19 pandemic caused by SARS‐CoV‐2 virus quickly spread globally, infecting over half a billion individuals, and killing over 6 million*. One of the more unusual symptoms was patients' complaints of sudden loss of smell and/or taste, a symptom that has become more apparent as the virus mutated into different variants. Anosmia and ageusia, the loss of smell and taste, respectively, seem to be transient for some individuals, but for others persists even after recovery from the infection. Causes for COVID‐19‐associated chemosensory loss have undergone several hypotheses. These include non‐functional or destroyed olfactory neurons and gustatory receptors or of their supporting cells, disruption of the signaling protein Neuropilin‐1, and disruption in the interaction with semaphorins, key molecules in the gustatory and olfactory axon guidance. The current paper will review these hypotheses and chart out potential therapeutic avenues.

Phage-Displayed Mimotopes of SARS-CoV-2 Spike Protein Targeted to Authentic and Alternative Cellular Receptors

The evolution of the SARS-CoV-2 virus during the COVID-19 pandemic was accompanied by the emergence of new heavily mutated viral variants with increased infectivity and/or resistance to detection by the human immune system. To respond to the urgent need for advanced methods and materials to empower a better understanding of the mechanisms of virus’s adaptation to human host cells and to the immuno-resistant human population, we suggested using recombinant filamentous bacteriophages, displaying on their surface foreign peptides termed “mimotopes”, which mimic the structure of viral receptor-binding sites on the viral spike protein and can serve as molecular probes in the evaluation of molecular mechanisms of virus infectivity. In opposition to spike-binding antibodies that are commonly used in studying the interaction of the ACE2 receptor with SARS-CoV-2 variants in vitro, phage spike mimotopes targeted to other cellular receptors would allow discovery of their role in viral infection in vivo using cell culture, tissue, organs, or the whole organism. Phage mimotopes of the SARS-CoV-2 Spike S1 protein have been developed using a combination of phage display and molecular mimicry concepts, termed here “phage mimicry”, supported by bioinformatics methods. The key elements of the phage mimicry concept include: (1) preparation of a collection of p8-type (landscape) phages, which interact with authentic active receptors of live human cells, presumably mimicking the binding interactions of human coronaviruses such as SARS-CoV-2 and its variants; (2) discovery of closely related amino acid clusters with similar 3D structural motifs on the surface of natural ligands (FGF1 and NRP1), of the model receptor of interest FGFR and the S1 spike protein; and (3) an ELISA analysis of the interaction between candidate phage mimotopes with FGFR3 (a potential alternative receptor) in comparison with ACE2 (the authentic receptor).

Diabetic Nephropathy and COVID-19: The Potential Role of Immune Actors

Nowadays, type II diabetes mellitus, more specifically ensuing diabetic nephropathy, and severe COVID-19 disease are known to be closely associated. The exact mechanisms behind this association are less known. An implication for the angiotensin-converting enzyme 2 remains controversial. Some researchers have started looking into other potential actors, such as neuropilin-1, mitochondrial glutathione, vitamin D, and DPP4. In particular, neuropilin-1 seems to play an important role in the underlying mechanism linking COVID-19 and diabetic nephropathy. We suggest, based on the findings in this review, that its up-regulation in the diabetic kidney facilitates viral entry in this tissue, and that the engagement of both processes leads to a depletion of neuropilin-1, which was demonstrated to be strongly associated with the pathogenesis of DN. More studies are needed to confirm this hypothesis, and research should be directed towards elucidating the potential roles of all these suggested actors and eventually discovering new therapeutic strategies that could reduce the burden of COVID-19 in patients with diabetic nephropathy.

The Role of Neuropilin-1 (NRP-1) in SARS-CoV-2 Infection: Review

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), discovered in 2019, is responsible for the global coronavirus disease 19 (COVID-19) pandemic. The main protein that interacts with the host cell receptor is the Spike-1 (S1) subunit of the coronavirus. This subunit binds with receptors present on the host cell membrane. It has been identified from several studies that neuropilin-1 (NRP-1) is one of the co-receptors for SARS-CoV-2 entry. Therefore, in this review, we focus on the significance of NRP-1 in SARS-CoV-2 infection. MEDLINE/PubMed database was used for a search of available literature. In the current review, we report that NRP-1 plays many important functions, including angiogenesis, neuronal development, and the regulation of immune responses. Additionally, the presence of this glycoprotein on the host cell membrane significantly augments the infection and spread of SARS-CoV-2. Literature data suggest that NRP-1 facilitates entry of the virus into the central nervous system through the olfactory epithelium of the nasal cavity. Moreover, published findings show that interfering with VEGF-A/NRP-1 using NRP-1 inhibitors may produce an analgesic effect. The review describes an association between NRP-1, SARS-CoV-2 and, inter alia, pathological changes in the retina. Based on the published findings, we suggest that NRP-1 is a very important mediator implicated in, inter alia, neurological manifestations of SARS-CoV-2 infection. Additionally, it appears that the use of NRP-1 inhibitors is a promising therapeutic strategy for the treatment of SARS-CoV-2 infection.

Neuropilin 1: A Novel Entry Factor for SARS-CoV-2 Infection and a Potential Therapeutic Target

The novel coronavirus disease 2019 (COVID-19) pandemic is severely challenging the healthcare systems and economies of the world, which urgently demand vaccine and therapy development to combat severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). Hence, advancing our understanding of the comprehensive entry mechanisms of SARS-CoV-2, especially the host factors that facilitate viral infection, is crucial for the discovery of effective vaccines and antiviral drugs. SARS-CoV-2 has previously been documented to reach cells by binding with ACE2 and CD147 receptors in host cells that interact with the spike (S) protein of SARS-CoV-2. A novel entry factor, called neuropilin 1(NRP1), has recently been discovered as a co-receptor facilitating the entry of SARS-CoV-2. NRP1 is a single-pass transmembrane glycoprotein widely distributed throughout the tissues of the body and acts as a multifunctional co-receptor to bind with different ligand proteins and play diverse physiological roles as well as pathological and therapeutic roles in different clinical conditions/diseases, including COVID-19. The current review, therefore, briefly provides the overview of SARS-CoV-2 entry mechanisms, the structure of NRP1, and their roles in health and various diseases, as well as extensively discusses the current understanding of the potential implication of NRP1 in SARS-CoV-2 entry and COVID-19 treatment.