Vaccinia virus growth factor induces divergent signaling programs and biological outcomes from cellular epidermal growth factor

Epidermal growth factor receptor (EGFR) signaling is a major pathway that controls cellular growth, survival, proliferation, and differentiation. Viruses often hijack this pathway to create a favorable environment to support their replication. Vaccinia virus (the prototype member of poxviridae) encodes its own viral growth factor (VGF). VGF is a secreted viral polypeptide with sequence and structural homology to the cellular EGF, which binds to and activates EGFR signaling. Studies from our lab and others have shown that VGF promotes metabolic reprogramming, cell motility, virulence, and spread during VACV infection. However, it remains unclear whether VGF fully mimics EGF signaling or selectively rewires downstream pathways to meet the specific demands of viral replication. To address this question, we used quantitative global phosphoproteomics to systematically compare signaling programs induced by EGF and VGF in primary human foreskin fibroblasts. By analyzing global phosphorylation patterns, kinase activity inference, and motif enrichment, we found that although both peptides engage the same EGFR receptor, EGF and VGF induce distinct downstream phosphorylation and bias downstream kinase activities. Transcriptomic analysis provided a complementary view of the cellular responses to the ligand treatment. Moreover, we found that VGF is more effective at promoting VACV plaque formation than EGF, thereby providing functional support to the VGF-biased EGFR signaling nodes important for viral spread. These findings highlight differences in how viral and cellular growth factors activate EGFR signaling and position poxviral growth factors as powerful tools for examining the fundamental principles of cellular signaling.