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Microtubule targeting agents (MTAs) have been exploited mainly as anti-cancer drugs because of their impact on cellular division and angiogenesis. Additionally, microtubules (MTs) are key structures for intracellular transport, which is frequently hijacked during viral infection. We have analyzed the antiviral activity of clinically used MTAs in the infection of DNA and RNA viruses, including SARS-CoV-2, to find that MT destabilizer agents show a higher impact than stabilizers in the viral infections tested, and FDA-approved anti-helminthic benzimidazoles were among the most active compounds. In order to understand the reasons for the observed antiviral activity, we studied the impact of these compounds in motor proteins-mediated intracellular transport. To do so, we used labeled peptide tools, finding that clinically available MTAs impaired the movement linked to MT motors in living cells. However, their effect on viral infection lacked a clear correlation to their effect in motor-mediated transport, denoting the complex use of the cytoskeleton by viruses. Finally, we further delved into the molecular mechanism of action of Mebendazole by combining biochemical and structural studies to obtain crystallographic high-resolution information of the Mebendazole-tubulin complex, which provided insights into the mechanisms of differential toxicity between helminths and mammalians. [ABSTRACT FROM AUTHOR]

African swine fever virus (ASFV) infectious cycle starts with the viral adsorption and entry into the host cell. Then, the virus is internalized via clathrin/dynamin mediated endocytosis and macropinocytosis. Similarly, to other viruses, ASF virion is then internalized and incorporated into the endocytic pathway. While the endosomal maturation entails luminal acidification, the decrease in pH acts on the multilayer structure of the virion dissolving the outer capsid. Upon decapsidation, the inner viral membrane is exposed to interact with the limiting membrane of the late endosome for fusion. Viral fusion is then necessary for the egress of incoming virions from endosomes into the cytoplasm, however this remains an intriguing and yet essential process for infection, specifically for the egress of viral nucleic acid into the cytoplasm for replication. ASFV proteins E248R and E199L, located at the exposed inner viral membrane, might be implicated in the fusion step. An interaction between these viral proteins and cellular endosomal proteins such as the Niemann-Pick C type 1 (NPC1) and lysosomal membrane proteins (Lamp-1 and -2) was shown. Furthermore, the silencing of these proteins impaired ASFV infection. It was also observed that NPC1 knock-out cells using CRISPR jeopardized ASFV infection and that the progression and endosomal exit of viral cores was arrested within endosomes at viral entry. These results suggest that the interactions of ASFV proteins with some endosomal proteins might be important for the membrane fusion step. In addition to this, reductions on ASFV infectivity and replication in NPC1 KO cells were accompanied by fewer and smaller viral factories. Our findings pave the way to understanding the role of proteins of the endosomal membrane in ASFV infection. Author summary: African swine fever virus (ASFV) causes a deadly disease of pigs and wild boars that was endemic in Africa but has spread in recent years to Europe, Asia and Oceania with a high socioeconomic impact. ASFV enters the cell by endocytosis and has adapted to the endosomal conditions to acquire infectivity. Fusion of the internal viral membrane with the endosomal membrane is required for the exit of viral DNA into the cytoplasm to start replication. We have found that ASF virion internal membrane proteins E248R and E199L interact with the endosomal proteins Niemann Pick C1 (NPC1) and lysosomal membrane protein (Lamp)-1 and -2. And, appear to be required for endosomal trafficking of ASF virions endosomal traffic and exit to the cytoplasm in the cell entry process. These molecules act regulating cholesterol flux from the endosome to the endoplasmic reticulum, and appear to be important for the viral infection cycle. In silenced and knockout cells, ASFV infection was affected at early and later stages. In null cells, virion entry and progression through the endosomal pathway at entry was arrested and several viral cores were retained at late endosomes without entering the fusion phase for cytoplasmic exit. These results provide new insights into the role of endosomal proteins for ASFV infection. [ABSTRACT FROM AUTHOR]

The interferon-induced transmembrane (IFITM) protein family is a group of antiviral restriction factors that impair flexibility and inhibit membrane fusion at the plasma or the endosomal membrane, restricting viral progression at entry. While IFITMs are widely known to inhibit several single-stranded RNA viruses, there are limited reports available regarding their effect in double-stranded DNA viruses. In this work, we have analyzed a possible antiviral function of IFITMs against a double stranded DNA virus, the African swine fever virus (ASFV). Infection with cell-adapted ASFV isolate Ba71V is IFN sensitive and it induces IFITMs expression. Interestingly, high levels of IFITMs caused a collapse of the endosomal pathway to the perinuclear area. Given that ASFV entry is strongly dependent on endocytosis, we investigated whether IFITM expression could impair viral infection. Expression of IFITM1, 2 and 3 reduced virus infectivity in Vero cells, with IFITM2 and IFITM3 having an impact on viral entry/uncoating. The role of IFITM2 in the inhibition of ASFV in Vero cells could be related to impaired endocytosis-mediated viral entry and alterations in the cholesterol efflux, suggesting that IFITM2 is acting at the late endosome, preventing the decapsidation stage of ASFV. [ABSTRACT FROM AUTHOR]

Niemann-Pick type C1 (NPC1) receptor is an endosomal membrane protein that regulates intracellular cholesterol traffic. This protein has been shown to play an important role for several viruses. It has been reported that SARS-CoV-2 enters the cell through plasma membrane fusion and/or endosomal entry upon availability of proteases. However, the whole process is not fully understood yet and additional viral/host factors might be required for viral fusion and subsequent viral replication. Here, we report a novel interaction between the SARS-CoV-2 nucleoprotein (N) and the cholesterol transporter NPC1. Furthermore, we have found that some compounds reported to interact with NPC1, carbazole SC816 and sulfides SC198 and SC073, were able to reduce SARS-CoV-2 viral infection with a good selectivity index in human cell infection models. These findings suggest the importance of NPC1 for SARS-CoV-2 viral infection and a new possible potential therapeutic target to fight against COVID-19. [Display omitted] • SARS-CoV-2 nucleoprotein (N) interacts with NPC1 protein. • This interaction was shown by CO-IP and reverse pull-downs. • Small molecules known to target EBOV GP interaction with NPC1 were tested as inhibitors. • These compounds inhibited SARS-CoV-2 and other CoV infections. [ABSTRACT FROM AUTHOR]