Platycodin D, a natural component of Platycodon grandiflorum, prevents both lysosome- and TMPRSS2-driven SARS-CoV-2 infection by hindering membrane fusion

Abstract

An ongoing pandemic of coronavirus disease 2019 (COVID-19) is now the greatest threat to global public health. Herbal medicines and their derived natural products have drawn much attention in the treatment of COVID-19, but the detailed mechanisms by which natural products inhibit SARS-CoV-2 have not been elucidated. Here, we show that platycodin D (PD), a triterpenoid saponin abundant in Platycodon grandiflorum (PG), a dietary and medicinal herb commonly used in East Asia, effectively blocks the two main SARS-CoV-2 infection routes via lysosome- and transmembrane protease serine 2 (TMPRSS2)-driven entry. Mechanistically, PD prevents host entry of SARS-CoV-2 by redistributing membrane cholesterol to prevent membrane fusion, which can be reinstated by treatment with a PD-encapsulating agent. Furthermore, the inhibitory effects of PD are recapitulated by the pharmacological inhibition or gene silencing of NPC1, which is mutated in patients with Niemann-Pick type C (NPC) displaying disrupted membrane cholesterol distribution. Finally, readily available local foods or herbal medicines containing PG root show similar inhibitory effects against SARS-CoV-2 infection. Our study proposes that PD is a potent natural product for preventing or treating COVID-19 and that briefly disrupting the distribution of membrane cholesterol is a potential novel therapeutic strategy for SARS-CoV-2 infection. COVID-19: Closing the cellular door on coronavirus A molecule derived from a traditional Korean herbal medicine can impede entry of SARS-CoV-2 into cultured cells. The coronavirus responsible for COVID-19 can enter the cell via direct fusion with the plasma membrane, or after internalization into organelles called lysosomes. South Korean researchers led by Seungtaek Kim of the Institut Pasteur Korea, Seongnam, and C. Justin Lee at the Institute for Basic Science, Daejon, have identified a compound that can thwart both modes of entry. They treated cultured human cells with platycodin D (PD), extracted from a plant used throughout East Asia as a remedy for respiratory disease. The researchers showed that PD inhibits SARS-CoV-2 fusion with the plasma membrane while also blocking lysosomal release. This mechanism appears to be mediated by PD's influence on membrane cholesterol content, suggesting a novel strategy for treating COVID-19.