The NOD2-RICK complex signals from the plasma membrane.

Area of Science:

• Immunology
• Cell Biology
• Gastroenterology

Background:

• NOD2 is a key innate immune receptor in the gut sensing bacterial muramyl dipeptide (MDP).
• NOD2 mutations are linked to Crohn disease pathogenesis, a chronic inflammatory bowel condition.
• NOD2 localization at the plasma membrane, not just the cytoplasm, is relevant to its function.

Purpose of the Study:

• To investigate the functional consequences of NOD2 and its Crohn disease-associated mutants at the plasma membrane.
• To explore the role of NOD2 in recruiting RICK (Rip2) to the plasma membrane for NF-kappaB signaling.
• To understand how subcellular localization of RICK influences NF-kappaB pathway activation.

Main Methods:

• Utilizing cell-based assays to assess NOD2 and mutant responses to MDP at the plasma membrane.
• Investigating the interaction between NOD2 and RICK using co-localization studies.
• Employing artificial membrane localization of RICK to determine its impact on NF-kappaB signaling and cytokine production.

Main Results:

• Membrane-bound NOD2 and Crohn disease mutants (R702W, G908R) activate NF-kappaB in response to MDP.
• The 1007FS mutant shows impaired MDP response and delocalization from the plasma membrane.
• NOD2 facilitates RICK recruitment to the plasma membrane, and RICK's membrane localization drives NF-kappaB activation and IL-8 secretion.

Conclusions:

• NOD2 functions at the plasma membrane to initiate NF-kappaB signaling in response to bacterial stimuli.
• Specific NOD2 mutations disrupt membrane-associated signaling, contributing to Crohn disease.
• Regulated recruitment of RICK to the plasma membrane by NOD2 is essential for controlled inflammatory responses.