Biology subjects

Li, T.-N.

Publications and source records attributed to Li, T.-N..

4 recordsLinked to original sources

bioRxiv2022

Chemical-induced degradation of PreS2 mutant surface antigen reverses HBV- mediated hepatocarcinogenesis

Naturally evolved immune-escape PreS2 mutant is an oncogenic caveat of liver cirrhosis and hepatocellular carcinoma (HCC) during chronic hepatitis B virus (HBV) infection. Notably, PreS2 mutants is prevalent in above 50% of patients with HCC. Intrahepatic expression of PreS2 mutant large surface antigen (PreS2-LHBS) induces endoplasmic reticulum stress, mitochondria dysfunction, cytokinesis failure and subsequent chromosome hyperploidy. In this study, we ask if long-term inhibition of PreS2-LHBS may act to reverse HBV-mediated hepatocarcinogenesis. We set up a stability reporter platform and identified ABT199 as an inhibitor of PreS2-LHBS from a library of 1068 FDA-approved drugs. Treatment of ABT199 induced PreS2-LHBS degradation without affecting the general cell viability, as shown in hepatoma and immortalized hepatocyte cell lines. We found that ABT199 induced the recruitment of PreS2-LHBS to ring-shaped structures in close proximity to lysosomal marker Lamp1 and multivesicular body marker Rab7. Simultaneously, inhibitions of lysosomal degradation or microautophagy restored the expression of PreS2-LHBS. Specifically, a 24-hr treatment of ABT199 reduced DNA damages and cytokinesis failure induced by PreS2-LHBS. Persistent treatment of ABT199 for 3 weeks reversed chromosome hyperploidy in PreS2-LHBS cells and suppressed anchorage-independent growth of HBV-positive hepatoma cell line. Together, we showed that ABT199 provoked selective degradation of PreS2-LHBS through the induction of microautophagy, and a long-term treatment of ABT199 reversed oncogenic mechanisms induced by HBV. Our results indicate that long-term degradation of PreS2-LHBS may serve as a novel therapeutic strategy to constrain HBV-mediated hepatocarcinogenesis. Graphical abstract O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=66 SRC="FIGDIR/small/477454v1_ufig1.gif" ALT="Figure 1"> View larger version (16K): org.highwire.dtl.DTLVardef@1720c85org.highwire.dtl.DTLVardef@943121org.highwire.dtl.DTLVardef@1257a22org.highwire.dtl.DTLVardef@1756348_HPS_FORMAT_FIGEXP M_FIG C_FIG Author summaryHBV PreS2 mutant large surface antigen (PreS2-LHBS) is an oncoprotein that induces liver cirrhosis and liver cancer. This study identified ABT199 as a potential inhibitor of PreS2-LHBS. We found that ABT199 could trigger the degradation of PreS2-LHBS through the induction of microautophagy. Moreover, a long-term treatment of ABT199 significantly reversed LHBS-induced oncogenic events including DNA damage, mitotic failure, chromosome hyperploidy, and anchorage-independent growth. This study not only identifies a specific inhibitor of PreS2-LHBS but also highlights a plausible strategy to constrain HBV-mediated hepatocarcinogenesis through targeting the degradation of PreS2-LHBS.

microbiology↗

bioRxiv2020

Aerobic glycolysis supports hepatitis B virus biosynthesis through interaction between viral surface antigen and pyruvate kinase isoform M2

As an intracellular pathogen, the reproduction of hepatitis B virus (HBV) depends on the occupancy of host metabolism machinery. Here we test a hypothesis if HBV may govern intracellular biosynthesis to achieve a productive reproduction. To test this hypothesis, we set up an affinity purification screen for host factors that interact with viral large surface antigen (LHBS). This identified pyruvate kinase isoform M2 (PKM2), a key regulator of glucose metabolism, as a binding partner of LHBS. We showed that the expression of LHBS affected oligomerization of PKM2 in hepatocytes, and thereby increased glucose consumption and lactate production, a phenomenon known as aerobic glycolysis. Interestingly, recovering PKM2 activity in hepatocytes by chemical activators, TEPP-46 or DASA-58, reduced biosynthesis of viral surface and core antigens. In addition, reduction of glycolysis by culturing in low-glucose condition or treatment with 2-deoxyglucose also decreased biosynthesis of viral surface antigen, without affecting general host proteins. Finally, TEPP-46 largely suppressed proliferation of LHBS-positive cells on 3-dimensional agarose plates, but showed no effect on the traditional 2-dimensional cell culture. Taken together, these results indicate that virus-induced metabolic switch may support de novo biosynthesis of HBV in hepatocytes. In addition, aerobic glycolysis is likely essential for LHBS-mediated oncogenesis. Accordingly, restriction of glucose metabolism may be considered as a novel strategy to restrain viral mediated biosynthesis and oncogenesis during chronic HBV infection. Author summaryChronic HBV infection is a life-long threat of patients, with a 25~40% increased risk of developing liver cirrhosis and cancer. Persistent expression of oncogenic viral products in the liver, especially LHBS, is an oncogenic caveat and resistant to current antiviral agents. Here we show that viral LHBS binds to host PKM2 and diminishes its kinase activity. This virus-host interaction induces metabolic switch from oxidative phosphorylation to aerobic glycolysis, with increased glucose consumption and lactate production. We show that such metabolic switch not only favors biosynthesis of HBV but also provokes hepatocarcinogenesis. Notably, restoration of PKM2 activity by chemical activators decreases expressions of viral products and largely suppresses virus-mediated hepatocarcinogenesis. This study highlights the importance of host metabolism in supporting viral biosynthesis and indicates a novel therapeutic approach to control chronic HBV infection via modulating host metabolic switch.

microbiology↗

bioRxiv2020

Flower initiates a positive feedback loop upon PIP2 enrichment at periactive zones to control bulk endocytosis

Synaptic vesicle (SV) endocytosis is coupled to exocytosis to maintain SV pool size and thus neurotransmitter release. Intense stimulation induces activity-dependent bulk endocytosis (ADBE) to recapture large quantities of SV constituents in large endosomes from which SVs reform. How these consecutive processes are spatiotemporally coordinated remains unknown. Here, we show that the Flower Ca2+ channel-dependent phosphatidylinositol 4,5-bisphosphate (PIP2) compartmentalization governs such control. Strong stimuli trigger PIP2 microdomain formation at periactive zones. Upon exocytosis Flower translocates from SVs to periactive zones, where it increases PIP2 levels via Ca2+ influxes. Remarkably, PIP2 directly enhances Flower channel activity, thereby establishing a positive feedback loop for PIP2 microdomain compartmentalization. The PIP2 microdomains drive ADBE and SV reformation from bulk endosomes. PIP2 further sorts Flower to bulk endosomes, thereby terminating endocytosis. Hence, we propose that the interplay between Flower and PIP2 is the crucial spatiotemporal cue that couples exocytosis to ADBE and subsequent SV reformation.

neuroscience↗

bioRxiv2020

Dynamin-2 regulates synaptic podosome maturation to facilitate neuromuscular junction development

Neuromuscular junctions (NMJs) govern rapid and efficient neuronal communication with muscle cells, which relies on the proper architecture of specialized postsynaptic compartments. However, the intrinsic mechanism in muscle cells contributing to elaborate NMJ development has been unclear. In this study, we reveal that the GTPase dynamin-2 (Dyn2), best-known for catalyzing synaptic vesicle endocytosis at the presynaptic membrane, is also involved in postsynaptic morphogenesis. We demonstrate that Dyn2 is enriched in the postsynaptic membrane of muscle cells and is involved in the maturation of neurotransmitter receptor clusters via its actin bundling ability. Dyn2 functions as a molecular girdle to regulate synaptic podosome turnover and promote morphogenesis of the postsynaptic apparatus. In Drosophila NMJs, Dyn2 is required to organize the postsynaptic actin cytoskeleton and to mediate its electrophysiological activities. Mechanistically, the actin binding, self-assembly, GTP hydrolysis ability, and Y597 phosphorylation of Dyn2 all regulate its actin bundling activity. Together, our study uncovers a role for Dyn2 in cytoskeleton remodeling and organization at the postsynaptic membrane of NMJs.

molecular biology↗