Mapping the Protein Phosphatase 1 Interactome in Human Cytomegalovirus Infection

Protein phosphorylation is a crucial regulatory mechanism in cellular homeostasis. The human cytomegalovirus (HCMV) incorporates protein phosphatase 1 (PP1) into its tegument, yet the biological relevance and mechanisms of this incorporation remain unclear. Our study offers the first characterization of the PP1 interactome during HCMV infection and its alterations. Using co-immunoprecipitation, mass spectrometry, and quantitative proteomics, we identified 159 high-confidence interacting proteins (HCIPs) in the PP1 interactome, consisting of 126 human and 33 viral proteins. We observed significant temporal changes in the PP1 interactome following HCMV infection, including the altered interactions of PP1 regulatory subunits. Further analysis highlighted the central roles of these PP1 interacting proteins in intracellular trafficking, with particular emphasis on the trafficking protein particle complex and Rab GTPases, which are crucial for the virus's manipulation of host cellular processes in virion assembly and egress. Additionally, our study on the noncatalytic PP1 inhibitor 1E7-03 revealed a decrease in PP1's interaction with key HCMV proteins, supporting its potential as an antiviral agent. Our findings suggest that PP1 docking motifs are critical in viral-host interactions and offer new insights for antiviral strategies.