Regulatory potential and molecular determinants of nucleocapsid transport by human cytomegalovirus inner tegument protein PP150

• Applicant: Dr. Lüder Wiebusch
• Subject Area: Virology
• Term: since 2025
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 562493739

Human cytomegalovirus (HCMV) is a highly prevalent pathogen that establishes life-long infections and causes severe disease in immunocompromised individuals. Current antiviral therapies are limited by side effects and the emergence of drug-resistant strains, emphasizing the need for novel intervention strategies. This research proposal investigates the role that the essential 150-kDa phosphoprotein (PP150) of HCMV plays in the intracellular trafficking of viral nucleocapsids. PP150 has a bipartite structure. Its N-terminal domain acts as a cement protein on the capsid exterior. In contrast, the large intrinsically disordered domain (IDD) at the C-terminus of PP150 mediates critical interactions with host proteins and recruits some of them into the tegument layer of virus particles. Preliminary work revealed BICD2, a cargo adapter for dynein-driven minus-end directed microtubule transport, as a novel interactor of PP150 that is enriched in HCMV virions. Mutational analysis identified two amino acid residues in the PP150-IDD that are required for both BICD2 binding and virion incorporation. Loss of PP150-BICD2 interaction impairs the accumulation of nucleocapsids in the cytoplasmic virus assembly compartment (cVAC). Instead, capsids become deposited in aggregates at the cell periphery, indicating that plus-end directed kinesin-driven transport dominates in the absence of BICD2 binding. The ectopic localization of BICD2-binding deficient nucleocapsids causes a pronounced defect in virus growth. This study aims to further delineate the molecular mechanisms underlying PP150-mediated nucleocapsid trafficking and investigate the functional implications for virus entry and exit pathways, for the evasion of innate immune signaling and for the differentiation and cell cycle state dependency of HCMV. A particular focus of the proposed work programme will be on the systematic analysis of minimal PP150 sequence requirements for BICD2 binding. This is linked to the hope of finding a short linear sequence motif (SLiM) in the PP150-IDD that specifically interacts with BICD2 and allows the prediction of other yet unknown viral and cellular cargos of BICD2. Due to its modular composition of SLiMs, post-translational modification motifs and single alpha-helices, the PP150-IDD represents a rich target for specific loss-of-function approaches. By advancing the systematic understanding of its interaction partners and regulatory functions, we expect to significantly advance our knowledge of the HCMV biology and to identify potential vulnerabilities in the viral life cycle that could inform the development of novel antiviral therapies. Furthermore, this study provides a framework for studying similar host interactions in other pathogens.

• DFG Programme: Research Grants