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G protein-coupled receptors
🔗 G Protein-Coupled Receptors (GPCRs) are a huge family of cell surface receptors that convert outside signals → inside responses through G proteins. They regulate vision 👁️, smell 👃, mood 🧠, heart ❤️, and immunity 🦠 - making them one of the most important drug targets in medicine 💊.
🧩 Structure of GPCRs
- 7 transmembrane α-helices ➿
- Extracellular N-terminus & intracellular C-terminus
- 3 extracellular + 3 intracellular loops
⚙️ Mechanism of GPCR Activation
- 🎯 Ligand binding → hormone/neurotransmitter/drug attaches to receptor.
- 🔄 G protein activation → GDP on α-subunit swapped for GTP.
- 📡 Signal transduction → α and βγ subunits regulate enzymes/ion channels.
- 🛑 Termination → GTP hydrolysed → receptor resets.
🔬 Types of G Proteins (α-subunits)
- 📈 Gs: stimulates adenylate cyclase → ↑ cAMP
- 📉 Gi: inhibits adenylate cyclase → ↓ cAMP
- 💥 Gq: activates PLC → IP3 + DAG → Ca²⁺ signalling
- 🔧 G12/13: cytoskeletal control & migration
🌟 Functions of GPCRs
- 👁️👃👅 Sensory: vision (rhodopsin), smell (olfactory), taste receptors
- 🧠 Neurotransmission: dopamine, serotonin, acetylcholine
- 🦠 Immune response: chemokine receptors guide cell migration
- 🌱 Growth & differentiation: regulate proliferation
- ❤️ Cardiovascular: adrenergic receptors control HR & BP
🏥 Clinical Relevance
- 💊 Pharmacological targets:
- Beta-blockers → adrenergic GPCRs
- Antipsychotics → dopamine GPCRs
- Antihistamines → histamine GPCRs
- 🧬 Genetic mutations → cancer, congenital syndromes, metabolic disease
- 🚀 Drug development → ~30–40% of all drugs act on GPCRs
📌 Summary
GPCRs = the master switches of cell communication. They sense extracellular cues and trigger intracellular cascades through G proteins. Because of their central role in physiology and disease, GPCRs remain one of the hottest targets in modern therapeutics 💊🔬.
| The content on this website is provided for educational and informational purposes only to support exam preparation (e.g., MLA, MRCP, USMLE) and learning. This is NOT medical advice, diagnosis, treatment, or professional guidance. It does not replace consultation with a qualified healthcare professional, official guidelines (e.g., NICE, GMC, BNF), or supervised clinical practice. Always verify information with current, authoritative sources. Makindo and its contributors accept no liability for any reliance on this content, including errors, omissions, or any resulting harm, loss, or consequences. By using this site, you agree to these terms. |
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