Core fucose‐specific Pholiota squarrosa lectin (PhoSL) as a potent broad‐spectrum inhibitor of SARS‐CoV‐2 infection

Abstract

Severe acute respiratory syndrome coronavirus 2 (SARS‐CoV‐2) spike protein (S protein) is highly N‐glycosylated, and a “glycan shield” is formed to limit the access of other molecules; however, a small open area coincides with the interface to the host's receptor and also neutralising antibodies. Most of the variants of concern have mutations in this area, which could reduce the efficacy of existing antibodies. In contrast, N‐glycosylation sites are relatively invariant, and some are essential for infection. Here, we observed that the S proteins of the ancestral (Wuhan) and Omicron strains bind with Pholiota squarrosa lectin (PhoSL), a 40‐amino‐acid chemically synthesised peptide specific to core‐fucosylated N‐glycans. The affinities were at a low nanomolar level, which were ~ 1000‐fold stronger than those between PhoSL and the core‐fucosylated N‐glycans at the micromolar level. We demonstrated that PhoSL inhibited infection by both strains at similar submicromolar levels, suggesting its broad‐spectrum effect on SARS‐CoV‐2 variants. Cryogenic electron microscopy revealed that PhoSL caused an aggregation of the S protein, which was likely due to the multivalence of both the trimeric PhoSL and S protein. This characteristic is likely relevant to the inhibitory mechanism. Structural modelling of the PhoSL–S protein complex indicated that PhoSL was in contact with the amino acids of the S protein, which explains the enhanced affinity with S protein and also indicates the significant potential for developing specific binders by the engineering of PhoSL.

The specific core fucose-binding lectin Pholiota squarrosa lectin (PhoSL) inhibits hepatitis B virus infection in vitro

“…Cyanovirin-N, a lectin produced by the cyanobacterium Nostoc ellipsosporum , binds to gp120, a protein on the HIV envelope, and inhibits HIV infection by HIV membrane fusion 33 , 34 . Recently, it was reported that PhoSL inhibits SARS-CoV-2 infection by binding to S protein, a protein on the SARS-CoV-2 envelope 35 . We found that PhoSL inhibited HBV infection of HepG2-hNTCP-C4 FUT8 KO cells, which cannot bind PhoSL (Fig.…”

Capture and neutralization of SARS‐CoV‐2 and influenza virus by algae‐derived lectins with high‐mannose and core fucose specificities

“…HM‐specific lectins from plants or marine red algae have been shown to inactivate (neutralize) SARS‐CoV‐2 10–15 . Regarding core fucose‐specific lectins, Yamasaki et al 34 recently reported the neutralization of SARS‐CoV‐2 by a mushroom Pholiota squarrosa –derived core fucose‐specific lectin.…”

“…HM-specific lectins from plants or marine red algae have been shown to inactivate (neutralize) SARS-CoV-2. [10][11][12][13][14][15] Regarding core fucose-specific lectins, Yamasaki et al 34 recently reported the neutralization of SARS-CoV-2 by a mushroom Pholiota squarrosa-derived core fucose-specific lectin. However, OAA, which was found to bind to SARS-CoV-2 in column experiments, showed no neutralizing activity.…”

Tandem-repeat lectins: structural and functional insights

“…PhoSL is a trimeric non-tandem repeat lectin with a fold akin to β-prism II lectins ( Yamasaki et al. 2019 , 2023 ). Interestingly, some PhoSL homologs, such as SL2-1 from the bacterium Streptomyces rapamycinicus ( Vainauskas et al.…”