C5a receptor

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Diagram of the C5a receptor structure

The C5a receptor, also known as CD88, is a G protein-coupled receptor (GPCR) that binds to the complement component 5a (C5a), a potent anaphylatoxin involved in the immune response. The C5a receptor plays a crucial role in mediating the inflammatory response and is expressed on various immune cells, including neutrophils, macrophages, and mast cells.

Structure

The C5a receptor is a member of the rhodopsin-like receptors family, characterized by seven transmembrane alpha helices. The receptor has an extracellular N-terminus, which is important for ligand binding, and an intracellular C-terminus, which interacts with G proteins to initiate signal transduction.

Function

The primary function of the C5a receptor is to mediate the effects of C5a, which include:

• Chemotaxis of immune cells to sites of infection or injury.
• Activation of neutrophils, leading to the release of reactive oxygen species and proteolytic enzymes.
• Induction of cytokine and chemokine production.
• Enhancement of vascular permeability, contributing to the inflammatory response.

Signaling Pathway

Upon binding of C5a, the C5a receptor undergoes a conformational change that activates associated G proteins. This activation leads to the initiation of several downstream signaling pathways, including the phospholipase C pathway, which results in the production of inositol trisphosphate (IP3) and diacylglycerol (DAG), and the activation of protein kinase C (PKC).

Clinical Significance

The C5a receptor is implicated in various inflammatory diseases, such as rheumatoid arthritis, sepsis, and asthma. Therapeutic targeting of the C5a receptor is being explored to modulate the immune response in these conditions. Antagonists of the C5a receptor have shown promise in reducing inflammation and tissue damage in preclinical models.

Related Pages

• Complement system
• G protein-coupled receptor
• Anaphylatoxin
• Immune response