Confocal microscope image of embryonic mouse forepaw

This project is now closed

Functional analysis of NOD-like receptors that detect cytosolic microbial pathogens

Project supervisor – Katrin Rittinger

Division of Molecular Structure

The innate immune system constitutes the first line of defense against infection. Innate immune receptors detect molecular patterns conserved in a wide range of pathogens and activate signalling pathways that induce inflammatory responses and trigger adaptive immunity. NOD-like receptors (NLRs) are a family of intracellular pattern recognition receptors (PRRs) that detect cytosolic pathogens and endogenous danger signals. All members of the NLR family share a tripartite domain structure that is composed of  a C-terminal ligand-sensing leucine-rich repeat (LRR) domain, a central oligomerisation domain (NACHT domain) that mediates ligand and nucleotide-induced self-oligomerisation and an N-terminal effector domain that promotes interaction with downstream targets and often contains a caspase recruitment domain (CARD) or pyrin domain (PYD).

NLRs exist in an inactive, autoinhibited state in the absence of a signal. Interaction with a bacterial ligand is believed to release autoinhibition and trigger self-oligomerisation to form large multi-protein assemblies, such as inflammasomes, that activate a specific cellular response.

Our aim is to provide a detailed structural and mechanistic characterisation of the oligomerisation process of NLRs and their subsequent interaction with downstream ligands, which is mediated by homotypic interactions between CARDs and PYDs that are present in NLRs and their ligands. The student working on this project will express and purify the NACHT domains of different NLRs and investigate their nucleotide-dependent oligomerisation behavior using a wide range of biochemical and biophysical methods, including analytical ultracentrifugation AUC, multi angle light scattering (MALS) and fluorescence spectroscopy. In addition, there is potential to probe the structure of the monomeric and oligomeric forms of the NLRs under investigation by X-ray crystallography. The information gained from these studies will feed into our parallel studies of the interaction with downstream effectors which are recognized by the active, oligomeric form of the NLR.

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