Project description:<p>Porcine epidemic diarrhea virus (PEDV) causes acute intestinal disease in pigs and remains a major threat to the global swine industry due to its high morbidity and mortality in neonatal piglets. To investigate host metabolic alterations upon PEDV infection, we performed untargeted metabolomic profiling in LLC-PK1 and Vero E6 cells. Pathway enrichment analysis revealed significant changes in nucleotide metabolism, cofactor biosynthesis, amino acid biosynthesis, and purine metabolism. Notably, PEDV infection led to divergent regulation of purine metabolism in the two cell types—upregulation in Vero E6 cells and downregulation in LLC-PK1 cells at 18 hours post-infection. We further identified inosine monophosphate dehydrogenase (IMPDH), the rate-limiting enzyme in guanine nucleotide biosynthesis, as a critical host factor for PEDV replication. Both genetic knockdown of IMPDH2 and pharmacological inhibition using merimepodib (VX-497, MMPD) significantly reduced viral RNA levels and impaired replication. These treatments also suppressed host nucleotide biosynthetic activity. Together, our findings demonstrate that PEDV hijacks the IMPDH-dependent guanosine biosynthesis pathway to support its replication, and identify IMPDH as a promising host-directed antiviral target against PEDV.</p>
Project description:A key organismal response to overnutrition involves the development of new adipocytes through the process of adipogenesis. Preadipocytes sense changes in the systemic nutrient status and metabolites can directly modulate adipogenesis. We previously identified a role of de novo nucleotide biosynthesis in adipogenesis induction, whereby inhibition of nucleotide biosynthesis suppresses the expression of the transcriptional regulators PPARg and C/EBPa. Here, we set out to identify the global transcriptomic changes associated with the inhibition of nucleotide biosynthesis. Through RNA sequencing (RNAseq), we discovered that mitochondria were the most altered transcriptional signature in response to inhibition of nucleotide biosynthesis. Blocking nucleotide biosynthesis induced rounded mitochondrial morphology, and altered mitochondrial function, and metabolism, reducing levels of tricarboxylic acid cycle intermediates, and increasing fatty acid oxidation (FAO). The loss of mitochondrial function induced by suppression of nucleotide biosynthesis was rescued by exogenous expression of PPARg. Moreover, inhibition of FAO restored PPARg expression, mitochondrial protein expression, and adipogenesis in the presence of nucleotide biosynthesis inhibition, suggesting a regulatory role of nutrient oxidation in differentiation. Collectively, our studies shed light on the link between substrate oxidation and transcription in cell fate determination.
Project description:Fundamental cellular processes including replication, transcription, and repair rely on both an adequate nucleotide supply and sufficient availability of new histones. Chromatin disassembly and reassembly is crucial to maintain genome stability, and is regulated by the orderly engagement of histones with a series of histone chaperones that guide newly synthesized histones from ribosomes to DNA. Although the synthesis of nucleotides and the histone proteins are the two major biosynthetic processes to complete the formation of chromatin, our knowledge about the coordination of these processes is limited. Phosphoribosyl pyrophosphate synthetases (PRPSs) catalyze the rate-limiting step in the nucleotide biosynthesis pathway. PRPS enzymes form a complex with PRPS-associated proteins (PRPSAPs). In the present study, we discover that PRPS-PRPSAP enzyme complex are part of the histone chaperone network involving HSP70/90, NASP, HAT1/RBBP7 and importin-4 to regulate chromatin assembly. We show PRPS enzymes are essential not only for nucleotide biogenesis, but together with PRPSAP also play a key role in the heterodimerization of H3-H4 and posttranslational modification of nascent histones, early steps in the process of histone maturation. Depletion of PRPS proteins leads to limited histone availability and therefore to impaired chromatin assembly. Our discovery bridges nucleotide metabolism and chromatin regulation and provides first evidence on how nucleotide biogenesis and chromatin dynamics work in synchrony.