Pezacki, J. P. | bioRxiv Science

bioRxiv2019

In vitro hepatitis C virus infection and hepatic choline metabolism

Choline is an essential nutrient required for normal neuronal and muscular development, as well as homeostatic regulation of hepatic metabolism. In the liver, choline is incorporated into the main eukaryotic phospholipid, phosphatidylcholine (PC) and can enter one carbon metabolism via mitochondrial oxidation. Hepatitis C virus (HCV) is a hepatotropic positive-strand RNA virus that similar to other positive-strand RNA viruses can impact phospholipid metabolism. In the current study we sought to interrogate the link between choline transport and early HCV infection. Namely, we aimed to investigate how HCV modulates markers of choline metabolism following in vitro infection, while subsequently assessing how the inhibition of choline uptake and metabolism upon concurrent HCV infection may alter early viral replication. Finally, we assessed whether these parameters were consistent between cells cultured in fetal bovine serum (FBS) or human serum (HS), conditions known to differentially affect in vitro HCV infection. We observed that choline transport in FBS-cultured Huh7.5 cells is facilitated by the intermediate affinity transporter choline transporter-like family (CTL), and that CTL1 expression and the incorporation of choline into PC is diminished in 24 h infected FBS-cultured cells. Reciprocally, limiting the availability of choline for PC synthesis resulted in increased HCV replication at this early stage. In chronically HS-cultured Huh7.5 cells, there were no differences in the expression of choline transporters upon HCV infection or alterations to viral replication when choline transport was inhibited compared to control treatments. However, inhibiting choline uptake and metabolism in this system significantly impaired the production of infectious virions in HS-cultured cells. These results suggest that in addition to a known role of choline kinase, the transport of choline, potentially via CTL1, might also represent an important and regulated process during HCV infection.\n\n\n\nO_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=107 SRC=\"FIGDIR/small/746776v1_ufig1.gif\" ALT=\"Figure 1\">\nView larger version (56K):\norg.highwire.dtl.DTLVardef@133a652org.highwire.dtl.DTLVardef@1ec8fa8org.highwire.dtl.DTLVardef@1cb7626org.highwire.dtl.DTLVardef@b9bbc2_HPS_FORMAT_FIGEXP M_FIG C_FIG

cell biology↗

bioRxiv2019

Armeniaspirols inhibit the ATP-dependent proteases ClpYQ and ClpXP in Gram-positive bacteria, dysregulating the divisome

Multi-drug resistant bacteria present an urgent threat to modern medicine, creating a desperate need for the discovery of antibiotics with new modes of action. Natural products whose unique highly diverse structures have been shaped by evolution to possess biologically relevant activity are an ideal discovery ground for new antibiotics with new mechanisms of action. In this study we elucidate the mechanism of action of the Gram-positive antibiotic armeniaspirol, a compound for which resistant bacteria could not be selected for. We show that armeniaspirol inhibits the ATP-dependent proteases ClpXP and ClpYQ in biochemical assays and in the Gram-positive bacteria Bacillus subtilis. We then show that this activity dysregulates key proteins involved in the divisome and elongasome including FtsZ, DivIVA, and MreB all of which are known to inhibit cell division when upregulated. Inhibition of ClpXP and ClpYQ leading to dysregulation of the divisome and elongasome represents a new mechanism of action and armeniaspirol is the first known natural product inhibitor of the coveted anti-virulence target ClpP. Thus armeniaspirol is the lead compound for a promising new class of antibiotics with a unique pharmacology and a novel mechanism for combating antimicrobial resistance, making it a highly promising candidate for further development.

microbiology↗