The LRR and RING Domain Protein LRSAM1 Is an E3 Ligase Crucial for Ubiquitin-Dependent Autophagy of Intracellular Salmonella Typhimurium

Abstract

SUMMARY Several species of pathogenic bacteria replicate within an intracellular vacuolar niche. Bacteria that escape into the cytosol are captured by the autophagic pathway and targeted for lysosomal degradation, representing a defense against bacterial exploitation of the host cytosol. Autophagic capture of Salmonella Typhimurium occurs predominantly via generation of a polyubiquitin signal around cytosolic bacteria, binding of adaptor proteins, and recruitment of autophagic machinery. However, the components mediating bacterial target selection and ubiquitination remain obscure. We identify LRSAM1 as the E3 ligase responsible for anti-Salmonella autophagy-associated ubiquitination. LRSAM1 localizes to several intracellular bacterial pathogens and generates the bacteria-associated ubiquitin signal; these functions require LRSAM1’s leucine-rich repeat and RING domains, respectively. Using cells from LRSAM1-deficient individuals, we confirm that LRSAM1 is required for ubiquitination associated with intracellular bacteria but dispensable for ubiquitination of aggregated proteins. LRSAM1 is therefore a bacterial recognition protein and ubiquitin ligase that defends the cytoplasm from invasive pathogens.

Ubiquitin systems mark pathogen-containing vacuoles as targets for host defense by guanylate binding proteins

“…The coating of intracellular pathogens with ubiquitin is indeed a conserved defense mechanism found in host organisms as diverse as fruit flies and humans (28,50). Specifically, the E3 ligases Parkin and LRSAM1 were found to be required for the ubiquitination of intracellular Mycobacterium tuberculosis and Salmonella enterica in mouse and human cells (50,51). Both of these pathogens are subjects of GBPmediated immune responses (5, 9, 10), yet the mechanisms by which the host can tag M. tuberculosis and S. enterica with GBPs are unknown.…”

Recruitment of TBK 1 to cytosol‐invading Salmonella induces WIPI 2‐dependent antibacterial autophagy

“…The bacterial ubiquitin coat that develops subsequent to SCV damage comprises another “eat‐me” signal (Perrin et al , 2004). Two E3 ligases, Parkin and LRSAM1, have been suggested to generate the bacterial ubiquitin coat, possibly in response to different bacterial species (Huett et al , 2012; Manzanillo et al , 2013). The ubiquitin “eat‐me” signal is detected by several cargo receptors, of which optineurin and NDP52 provide independent physical links to TBK1.…”

A LRSAM1 mutation links Charcot–Marie–Tooth type 2 to Parkinson's disease

“…Little is known about the specificity of noncanonical polyubiquitylation that LRSAM1 has been described to favor in vitro. It is interesting to note that parkin also mediates formation of Lys‐27‐ubiquitin chains 6. Mutations in PINK1 and parkin mediate degradation of mitochondria through mitophagy, and lead to failure of mitochondrial translocation 7.…”