TRAP complex is essential for coronavirus replication and glycoprotein biogeneses

Abstract Coronaviruses remodel the endoplasmic reticulum (ER) to build replication organelles while producing heavily glycosylated membrane proteins, but the mechanisms coordinating these demands are unclear. Here, we describe the ER-resident translocon-associated protein (TRAP/SSR) complex as a conserved host dependency across diverse coronaviruses. Using porcine hemagglutinating encephalomyelitis virus (PHEV) as a model, we identify TRAPγ in a genome-wide CRISPR-Cas9 screen as essential for productive viral infection. TRAPγ depletion suppresses viral replication, disrupts canonical replication organelle formation, and amplifies innate immune signaling. Viral glycoproteins (nsp4, Spike, and hemagglutinin-esterase) selectively engage specific TRAP subunits (α, β, γ, and δ), and reducing their signal-sequence hydrophobicity compromises glycoprotein production and N-glycosylation, consistent with impaired co-translational ER targeting or translocation. Inhibition of the oligosaccharyltransferase (OST) complex recapitulates these defects, supporting a sequential signal recognition particle (SRP)–TRAP–OST axis. Thus, our findings reveal an essential role for the TRAP complex in viral subversion of ER proteostasis, highlighting ER co‑translational translocation machinery as a pivotal host-pathogen interface during the viral lifecycle.