Heparin and heparan sulfate (HS) glycosaminoglycans (GAGs) are essential regulators of neurotrophic signaling. However, their therapeutic applications are hindered by structural heterogeneity, batch variability, and anticoagulant activity. Thus, there is a need for well-defined glycomimetics that replicate the function of native HS in regenerative medicine. Here, we synthesized HS glycomimetics through a modular strategy that enables the installation of sulfate groups at the designated positions along the sugar backbone. These glycomimetics selectively bind and stabilize neurotrophins, such as fibroblast growth factors (FGF-1, FGF-2) and nerve growth factor (NGF), in a sulfation-dependent manner with dissociation constants in the low micromolar range. They exhibit no anticoagulant activity, a crucial prerequisite for clinical translation. We show that our lead compound has neuritogenic ability because in two neuronal cell models, PC12 and SH-SY5Y, it enhances NGF-mediated neural maturation when immobilized on a surface. Furthermore, in primary rat hippocampal neurons, it promotes FGF-2-mediated neurite outgrowth and spontaneous synaptic activity. Our findings show that HS glycomimetics have the potential for regenerative therapies.

Extracellular vesicles are produced in all three domains of life, and their biogenesis has common ancient origins in eukaryotes and archaea. Although bacterial vesicles were discovered several decades ago and multiple roles have been attributed to them, no mechanism has been established for vesicles biogenesis in bacteria. For this reason, there is a significant level of skepticism about the biological relevance of bacterial vesicles. Bacteroides thetaiotaomicron (Bt), a prominent member of the human intestinal microbiota, produces significant amounts of outer membrane vesicles (OMVs) which have been proposed to play key physiological roles. Here, we employed a dual marker system, consisting of outer membrane- and OMV-specific markers fused to fluorescent proteins to visualize OMV biogenesis by time-lapse microscopy. Furthermore, we performed comparative proteomic analyses to show that, in Bt, the OMV cargo is adapted for the optimal utilization of different polysaccharides. We also show that a negatively charged N-terminal motif acts as a signal for protein sorting into OMVs irrespective of the nutrient availability. Our results demonstrate that OMV production is the result of a highly regulated process in Bt.

The COVID-19 pandemic caused by the severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) has emphasized the serious threat to human health posed by emerging coronaviruses. Effective broadly-acting antiviral countermeasures are urgently needed to prepare for future emerging CoVs, as vaccine development is not compatible with a rapid response to a newly emerging virus. The green tea catechin, epigallocatechin gallate (EGCG), has broad-spectrum antiviral activity, although its mechanisms against coronavirus (CoV) infection have remained unclear. Here, we show that EGCG prevents human and murine CoV infection and blocks the entry of lentiviral particles pseudotyped with spike proteins from bat or highly pathogenic CoVs, including SARS-CoV-2 variants of concern, in lung epithelial cells. Mechanistically, EGCG treatment reduces CoV attachment to target cell surfaces by interfering with attachment to cell-surface glycans. Heparan sulfate proteoglycans are a required attachment factor for SARS-CoV-2 and are shown here to be important in endemic HCoV-OC43 infection. We show that EGCG can compete with heparin, a heparan sulfate analog, for virion binding. Our results highlight heparan sulfate as a conserved cell attachment factor for CoVs, and demonstrate the potential for the development of pan-coronavirus attachment inhibitors, which may be useful to protect against future emerging CoVs.
© 2022. The Author(s).

CD4 and chemokine receptors mediate HIV-1 attachment and entry. They are, however, insufficient to explain the preferential viral infection of central memory T cells. Here, we identify L-selectin (CD62L) as a viral adhesion receptor on CD4+ T cells. The binding of viral envelope glycans to L-selectin facilitates HIV entry and infection, and L-selectin expression on central memory CD4+ T cells supports their preferential infection by HIV. Upon infection, the virus downregulates L-selectin expression through shedding, resulting in an apparent loss of central memory CD4+ T cells. Infected effector memory CD4+ T cells, however, remain competent in cytokine production. Surprisingly, inhibition of L-selectin shedding markedly reduces HIV-1 infection and suppresses viral release, suggesting that L-selectin shedding is required for HIV-1 release. These findings highlight a critical role for cell surface sheddase in HIV-1 pathogenesis and reveal new antiretroviral strategies based on small molecular inhibitors targeted at metalloproteinases for viral release.