CARD15

CARD15, also known as NOD2, is a gene that plays a crucial role in the innate immune system. It is a member of the nucleotide-binding oligomerization domain (NOD)-like receptor (NLR) family of proteins. CARD15 is primarily expressed in immune cells, particularly monocytes and macrophages. Its main function is to detect intracellular bacterial components, specifically muramyl dipeptide (MDP), a molecule found in the peptidoglycan of bacterial cell walls.

Upon sensing MDP, CARD15 undergoes conformational changes and recruits other signaling molecules, including receptor-interacting serine/threonine-protein kinase 1 (RIPK1) and CARD9. This complex initiates downstream signaling pathways that lead to the activation of nuclear factor kappa B (NF-κB) and mitogen-activated protein kinases (MAPKs). These pathways ultimately result in the production of pro-inflammatory cytokines, such as tumor necrosis factor-alpha (TNF-α) and interleukin-1 beta (IL-1β), as well as antimicrobial peptides. This inflammatory response is essential for clearing bacterial infections and maintaining gut homeostasis.

Mutations in the CARD15 gene are strongly associated with an increased risk of developing Crohn's disease, a chronic inflammatory bowel disease. These mutations can lead to a dysfunctional CARD15 protein, impairing the immune system's ability to properly recognize and respond to gut bacteria. This dysregulation of immune responses is thought to contribute to the chronic inflammation characteristic of Crohn's disease. Research into CARD15 continues to explore its precise mechanisms and potential therapeutic targets for inflammatory conditions.

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