A Gq receptor is a type of G protein-coupled receptor (GPCR) that, when activated, primarily couples to the Gq/11 subfamily of G proteins. In the context of immunology, Gq is the most studied subclass within this subfamily.
Understanding Gq-Coupled Receptors
Gq-coupled receptors are significant because of their role in cell signaling. When a ligand (such as a hormone or neurotransmitter) binds to a Gq-coupled receptor, it activates the Gq protein. This activation leads to a cascade of intracellular events, most notably the activation of phospholipase C (PLC).
Key Steps in the Gq Signaling Pathway
- Ligand Binding: A signaling molecule binds to the Gq-coupled receptor.
- Gq Activation: The receptor activates the Gq protein.
- PLC Activation: Activated Gq stimulates phospholipase C (PLC).
- PIP2 Hydrolysis: PLC hydrolyzes phosphatidylinositol bisphosphate (PIP2) into inositol trisphosphate (IP3) and diacylglycerol (DAG).
- downstream Effects:
- IP3: IP3 binds to IP3 receptors on the endoplasmic reticulum, causing the release of calcium ions (Ca2+) into the cytoplasm.
- DAG: DAG remains in the plasma membrane and activates protein kinase C (PKC).
- Cellular Response: The increase in intracellular calcium and activation of PKC leads to various cellular responses, depending on the cell type and the specific receptor involved.
Importance in Immunology
In immunology, Gq-coupled receptors play a crucial role. These receptors are mainly coupled to sex hormone receptors and certain chemokine receptors. These receptors exhibit differential expression patterns in various lymphocyte subtypes. This differential expression suggests that Gq-coupled receptors are important in regulating lymphocyte function.
Examples of Gq-Coupled Receptors
While the provided text doesn't list specific examples, generally, Gq-coupled receptors include:
- Certain subtypes of muscarinic acetylcholine receptors (e.g., M1, M3, M5)
- Alpha-1 adrenergic receptors
- Some serotonin receptors (e.g., 5-HT1C, 5-HT2A)
- Angiotensin II receptors (AT1)
- Endothelin receptors (ETA)
Role in Autoimmunity
Dysregulation of Gq-coupled receptor signaling can contribute to autoimmune diseases. The diversity of Gq-coupled receptors in various immune cells highlights their potential as therapeutic targets for modulating immune responses in autoimmune conditions.
