Legionella effectors SidC/SdcA ubiquitinate multiple small GTPases and SNARE proteins to promote phagosomal maturation

• DOI: 10.1007/s00018-024-05271-7
• Publication Date: 2024-06-05T11:54:14Z
• Authors: Kelong Ma; Rundong Shu; Hongtao Liu; Jinli Ge; Jiayang Liu; Qian Lu; Jiaqi Fu; Xiaoyun Liu; Jiazhang Qiu
• Keywords: 0301 basic medicine; Qa-SNARE Proteins; Ubiquitin-Protein Ligases; Ubiquitination; rab7 GTP-Binding Proteins; Endoplasmic Reticulum; Legionella pneumophila; Mice; 03 medical and health sciences; HEK293 Cells; Bacterial Proteins; rab GTP-Binding Proteins; Phagosomes; Vacuoles; Humans; Animals; Original Article; SNARE Proteins; Monomeric GTP-Binding Proteins

AbstractProtein ubiquitination is one of the most important posttranslational modifications (PTMs) in eukaryotes and is involved in the regulation of almost all cellular signaling pathways. The intracellular bacterial pathogenLegionella pneumophilatranslocates at least 26 effectors to hijack host ubiquitination signaling via distinct mechanisms. Among these effectors, SidC/SdcA are novel E3 ubiquitin ligases with the adoption of a Cys-His-Asp catalytic triad. SidC/SdcA are critical for the recruitment of endoplasmic reticulum (ER)-derived vesicles to theLegionella-containingvacuole (LCV). However, the ubiquitination targets of SidC/SdcA are largely unknown, which restricts our understanding of the mechanisms used by these effectors to hijack the vesicle trafficking pathway. Here, we demonstrated that multiple Rab small GTPases and target soluble N-ethylmaleimide-sensitive factor attachment protein receptors (SNARE) proteins arebona fideubiquitination substrates of SidC/SdcA. SidC/SdcA-mediated ubiquitination of syntaxin 3 and syntaxin 4 promotes their unconventional pairing with the vesicle-SNARE protein Sec22b, thereby contributing to the membrane fusion of ER-derived vesicles with the phagosome. In addition, our data reveal that ubiquitination of Rab7 by SidC/SdcA is critical for its association with the LCV membrane. Rab7 ubiquitination could impair its binding with the downstream effector Rab-interacting lysosomal protein (RILP), which partially explains why LCVs avoid fusion with lysosomes despite the acquisition of Rab7. Taken together, our study reveals the biological mechanisms employed by SidC/SdcA to promote the maturation of the LCVs.