PFN1 inhibits lytic replication of Kaposi sarcoma-associated herpesvirus through SQSTM1/p62-mediated selective autophagy targeting the KSHV helicase

Kaposi sarcoma-associated herpesvirus (KSHV), an oncogenic virus associated with several malignancies, including Kaposi sarcoma (KS), primary effusion lymphoma (PEL), and multicentric Castleman disease, harbors a DNA replication helicase encoded by ORF44 that is crucial for viral replication and pathogenesis. In this study, we identified the host PFN1 (profilin 1), a well-known actin-binding factor, as an inhibitor of KSHV lytic replication functioning via the macroautophagy/autophagy-lysosomal degradation pathway targeting ORF44. Mechanistic analyses revealed that PFN1 interacts with ORF44, leading to enhanced polyubiquitination of PFN1. Notably, the E3 ubiquitin Ligase TRIM37 (tripartite motif containing 37) facilitates the polyubiquitination of lysine residues at position 116 of PFN1, which serves as a critical recognition motif for the cargo receptor SQSTM1/p62 (sequestosome 1), which is pivotal for the subsequent autophagic degradation of ORF44. Overall, our findings revealed a previously uncharacterized Antiviral function of PFN1, highlighting its potential as a novel therapeutic avenue for the treatment of KSHV-associated malignancies.Abbreviations: ALS: amyotrophic lateral sclerosis; Baf A1: bafilomycin A₁; co-IP: co-immunoprecipitation; KSHV: Kaposi sarcoma-associated herpes virus; LIR: LC3-interacting region; PFN1: profilin 1; SQSTM1/p62: sequestosome 1; TRIM37: tripartite motif containing 37; UBA: ubiquitin-associated domain.