Label-free quantitative proteomics reveals the Steap3-Gm2a axis inhibiting the phagosomal escape of Listeria monocytogenes.

As a pathogenic microorganism, Listeria monocytogenes is widely used in the research of bacterial pathogenesis and host defense. The phagosomal escape of L. monocytogenes is essential for its replication in the cytoplasm of the host. Here, we reported that the protein abundance of the Six-transmembrane epithelial antigen of the prostate 3 (Steap3) was decreased upon L. monocytogenes infection compared to uninfected cells in macrophages. However, the decreased Steap3 abundance was not regulated by the host but was caused by LLO secreted by L. monocytogenes. Functional experiments showed that deletion of Steap3 facilitated entry of L. monocytogenes from the phagosome into the cytoplasm. Then, the comprehensive proteomic analysis revealed that the deletion of Steap3 could affect the proteins abundance of the lysosomal signaling pathway in macrophages. Among these proteins affected by Steap3, we discovered that only the Ganglioside GM2 activator (Gm2a) inhibited the phagosomal escape of L. monocytogenes as Steap3. In summary, we found that the Steap3-Gm2a axis could restrict the phagosomal escape of L. monocytogenes and serve the potential molecular drug targets for antibacterial treatment.