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Legionella pneumophila Outer Membrane Vesicles: Isolation and Analysis of Their Pro-inflammatory Potential on Macrophages
Published on: February 22, 2017
Legionella pneumophila macrophage infectivity potentiator protein appendage domains modulate protein dynamics and
C Wiedemann1, J J Whittaker2, V H Pérez Carrillo1
1Faculty of Chemistry and Earth Sciences, Institute of Organic Chemistry and Macromolecular Chemistry, Friedrich Schiller University Jena, Jena, Germany.
Abstract:
Macrophage infectivity potentiator (MIP) proteins are widespread in human pathogens including Legionella pneumophila, the causative agent of Legionnaires' disease and protozoans such as Trypanosoma cruzi. All MIP proteins contain a FKBP (FK506 binding protein)-like prolyl-cis/trans-isomerase domain that hence presents an attractive drug target. Some MIPs such as the Legionella pneumophila protein (LpMIP) have additional appendage domains of mostly unknown function. In full-length, homodimeric LpMIP, the N-terminal dimerization domain is linked to the FKBP-like domain via a long, free-standing stalk helix. Combining X-ray crystallography, NMR and EPR spectroscopy and SAXS, we elucidated the importance of the stalk helix for protein dynamics and inhibitor binding to the FKBP-like domain and bidirectional crosstalk between the different protein regions. The first comparison of a microbial MIP and a human FKBP in complex with the same synthetic inhibitor was made possible by high-resolution structures of LpMIP with a [4.3.1]-aza-bicyclic sulfonamide and provides a basis for designing pathogen-selective inhibitors. Through stereospecific methylation, the affinity of inhibitors to L. pneumophila and T. cruzi MIP was greatly improved. The resulting X-ray inhibitor-complex structures of LpMIP and TcMIP at 1.49 and 1.34 Å, respectively, provide a starting point for developing potent inhibitors against MIPs from multiple pathogenic microorganisms.
Insights
Macrophage infectivity potentiator (MIP) proteins are crucial drug targets in pathogens. This study reveals the stalk helix
Area of Science:
- Microbiology
- Structural Biology
- Drug Discovery
Background:
- Macrophage infectivity potentiator (MIP) proteins are essential virulence factors in human pathogens like Legionella pneumophila and Trypanosoma cruzi.
- All MIP proteins possess a conserved FKBP-like prolyl-cis/trans-isomerase domain, making it a promising target for therapeutic intervention.
- Some MIPs, including Legionella pneumophila MIP (LpMIP), feature additional appendage domains with largely uncharacterized functions.
Purpose of the Study:
- To investigate the structural and dynamic role of the stalk helix in LpMIP.
- To understand the functional crosstalk between different domains of LpMIP.
- To develop potent and pathogen-selective inhibitors targeting MIPs.
Main Methods:
- X-ray crystallography
- Nuclear Magnetic Resonance (NMR) spectroscopy
- Electron Paramagnetic Resonance (EPR) spectroscopy
- Small-angle X-ray scattering (SAXS)
Main Results:
- The stalk helix is critical for LpMIP dynamics and influences inhibitor binding to the FKBP-like domain.
- Bidirectional communication exists between distinct regions of LpMIP.
- High-resolution structures of LpMIP and Trypanosoma cruzi MIP (TcMIP) complexed with novel inhibitors were determined.
- Stereospecific methylation significantly enhanced inhibitor affinity for both LpMIP and TcMIP.
Conclusions:
- The stalk helix plays a vital role in LpMIP function and inhibitor interactions.
- Structural insights enable the design of pathogen-specific inhibitors targeting MIPs.
- Optimized inhibitors show potential for combating infections caused by L. pneumophila, T. cruzi, and other pathogenic microorganisms.
