Bacterial esterases reverse lipopolysaccharide ubiquitylation to block host immunity

Area of Science:

• Microbiology
• Immunology
• Structural Biology

Background:

• Burkholderia pathogens evade host immune responses, but mechanisms for cytosolic replication remain unclear.
• Ring finger protein 213 (RNF213) initiates antibacterial autophagy via lipopolysaccharide (LPS) ubiquitylation.

Purpose of the Study:

• To elucidate Burkholderia strategies for evading RNF213-mediated immune surveillance.
• To investigate the molecular mechanisms by which Burkholderia blocks antibacterial autophagy.

Main Methods:

• Structural analysis of bacterial components and host immune factors.
• Biochemical assays to assess protein-protein interactions and enzymatic activities.
• Functional studies in bacterial infection models.

Main Results:

• Burkholderia employs a polysaccharide capsule to prevent RNF213 binding to bacterial LPS.
• The Burkholderia deubiquitylase (DUB) TssM reverses RNF213 activity via a novel esterase function.
• Structural data reveals TssM's uncoupled esterase activity against ubiquitylated LPS, a key virulence mechanism.

Conclusions:

• Burkholderia utilizes a dual strategy involving capsule shielding and TssM-mediated deubiquitylation to evade RNF213-dependent autophagy.
• TssM's esterase activity represents a novel bacterial immune evasion tactic targeting LPS ubiquitylation.
• Understanding these mechanisms is crucial for developing therapeutics against Burkholderia infections.