Pestiviruses utilize pyrimidine metabolism to regulate mitophagy for viral replication.

DHODH (dihydroorotate dehydrogenase (quinone)) has been demonstrated as a critical regulator of programmed cell death, yet its role in macroautophagy/autophagy remains poorly defined. Flaviviridae pose a significant threat to global public health, and their replication is closely associated with autophagy. Building upon our previous findings that DHODH was a broad-spectrum target for Flaviviridae and a key regulator of Pestiviruses replication, this study employed RNA-seq screening coupled with functional validation to demonstrate that DHODH affected Pestiviruses replication by regulating mitophagy. Notably, we observed remarkable virus genus specificity in this regulatory mechanism. For autophagy-dependent Pestiviruses, DHODH deficiency impaired autophagosome-lysosome fusion, thereby suppressing viral replication. Conversely, in autophagy-inhibiting Flaviviruses, the blockade of autophagy flux facilitated viral replication. These observations underscore the specificity of DHODH-mediated viral replication regulation. Additionally, compound supplementation assays indicated that DHODH regulated autophagy via pyrimidine nucleotide metabolism, as exogenous pyrimidine precursors restored autophagosome-lysosome fusion. Furthermore, our research uncovered a novel mechanism whereby classical swine fever virus (CSFV) non-structural protein 4A (NS4A) recruited DHODH to mitochondria, facilitating its interaction with MAP1LC3/LC3 (microtubule associated protein 1 light chain 3) through the LC3-interacting region (LIR) domain to activate mitophagy. Collectively, our findings highlight DHODH as a promising antiviral target within the metabolism-autophagy axis, providing novel insights for antiviral drug development.Abbreviation: AMPK: AMP-activated protein kinase; ATF4: activating transcription factor 4; ATG5: autophagy related 5; BafA1: bafilomycin A1; BNIP3L/NIX: BCL2 interacting protein 3 like; BVDV: bovine viral diarrhea virus; CALCOCO2/NDP52: calcium binding and coiled-coil domain 2; CCCP: carbonyl cyanide 3-chlorophenylhydrazone; co-IP: co-immunoprecipitation; COX4: cytochrome c oxidase subunit 4; CQ: chloroquine; CSFV: classical swine fever virus; DAPI: 4',6-diamidino-2-phenylindole; DEGs: differentially expressed genes; DHO: DHODH substrate dihydroorotate; DHODH: dihydroorotate dehydrogenase; DTMUV: duck tembusu virus; FIS1: fission mitochondrial 1; FUNDC1: FUN14 domain containing 1; GAPDH: glyceraldehyde-3-phosphate dehydrogenase; GFP: green fluorescent protein; GO: gene ontology; HSPA/HSP70: heat shock protein family A (Hsp70); JEV: Japanese encephalitis virus; KEGG: kyoto encyclopedia of genes and genomes; LIR: LC3-interacting region; MAP1LC3/LC3: microtubule associated protein 1 light chain 3; Mdivi-1: mitochondrial division inhibitor 1; MFF: mitochondrial fission factor; MFN1: mitofusin 1; MFN2: mitofusin 2; MITO: mitochondria; MOI: multiplicity of infection; MTOR: mechanistic target of rapamycin kinase; MTS: mitochondrial targeting signal; OPTN: optineurin; ORO: DHODH product orotate; PBS: phosphate-buffered saline; PRKN: parkin RBR E3 ubiquitin protein ligase; PYR: pyrazofurin; RAPA: rapamycin; RFP: red fluorescent protein; RNA-seq: RNA sequencing; RT-qPCR: reverse transcription-quantitative real-time polymerase chain reaction; SD: standard deviation; siRNA: small interfering RNA; SQSTM1/p62: sequestosome 1; TOMM20: translocase of outer mitochondrial membrane 20; UMP: uridine monophosphate; VDAC1: voltage dependent anion channel 1.