Xun, J. | bioRxiv Science

bioRxiv2023

A conserved ion channel function of STING mediates non-canonical autophagy and cell death

The cGAS/STING pathway triggers inflammation in response to diverse cellular stresses such as infection, cellular damage, senescence, normal aging, and age-related disease. Besides inflammation, STING also triggers non-canonical autophagy and cell death, the former of which requires the proton pump V-ATPase- mediated LC3 lipidation to single membrane STING vesicles. V-ATPase is known to sense organelle de- acidification in other contexts and recruits the ATG16L1 complex for direct conjugation of LC3/ATG8 to single membranes (CASM). However, it is unclear how STING activates V-ATPase for non-canonical autophagy. Here we report that upon STING activation, the transmembrane domain (TMD) of STING significantly reorganizes and forms an electron-sparse pore in the center. Cellular imaging and in vitro ion flux assays revealed that STING is critical for proton efflux and pH neutralization of Golgi-derived STING vesicles. A chemical ligand of STING, C53, which binds to and blocks the channel of STING strongly inhibited STING-mediated proton flux in vitro and vesicular de-acidification in cells. C53 also abolished STING-dependent LC3 lipidation and cell death. Thus, the ion channel function of STING activates non-canonical autophagy and cell death through vesicle de-acidification.

biochemistry↗

bioRxiv2022

ASGR1 is a candidate receptor for SARS-CoV-2 that promotes infection of liver cells

Backgroud & AimsCurrently, the COVID-19 pandemic, caused by SARS-CoV-2 infection, represents a serious public health problem worldwide. Although it has been shown that ACE2 serves as the main receptor for SARS-CoV-2 entry into host cells, studies have shown that ACE2 is expressed at extremely low levels in various tissues, especially in some organs where virus particles have been found, such as the heart and liver. Therefore, these organs potentially express additional SARS-CoV-2 receptors that have not yet been discovered. Methods & ResultsHere, by a genome-wide CRISPR-Cas9 activation library screening, we found that ASGR1 promoted SARS-CoV-2 infection of 293T cells. In Huh-7 and HepG2 cell lines, simultaneous knock out of ACE2 and ASGR1 prevented SARS-CoV-2 pseudovirus infection. In the immortalized THLE-2 hepatocyte cell line and primary liver parenchymal cells, both of which hardly express ACE2, SARS-CoV-2 could successfully establish an infection. After treatment with ASGR1 antibody, the infection rate significantly reduced. This suggests that SARS-CoV-2 infects liver cells mainly through an ASGR1-dependent mechanism. Finally, we also found that the soluble ASGR1 could not only prevent the SARS-CoV-2 pseudovirus, which binds to the ASGR1 receptors, from infecting host liver cells, but also had a protective effect on those expressing ACE2, indicating that administration of soluble ASGR1 protein may represent a new treatment approach. ConclusionsColletively, these findings indicate that ASGR1 is a candidate receptor for SARS-CoV-2 that promotes infection of liver cells. Lay SummaryWe show that ASGR1 is a candidate receptor for SARS-CoV-2 to infect liver cells.

microbiology↗