๐ G Protein-Coupled Receptors (GPCRs) are a huge family of cell surface receptors that convert outside signals โ inside responses through G proteins.
They regulate vision ๐๏ธ, smell ๐, mood ๐ง , heart โค๏ธ, and immunity ๐ฆ โ making them one of the most important drug targets in medicine ๐.
๐งฉ Structure of GPCRs
- 7 transmembrane ฮฑ-helices โฟ
- Extracellular N-terminus & intracellular C-terminus
- 3 extracellular + 3 intracellular loops
โ๏ธ Mechanism of GPCR Activation
- ๐ฏ Ligand binding โ hormone/neurotransmitter/drug attaches to receptor.
- ๐ G protein activation โ GDP on ฮฑ-subunit swapped for GTP.
- ๐ก Signal transduction โ ฮฑ and ฮฒฮณ subunits regulate enzymes/ion channels.
- ๐ Termination โ GTP hydrolysed โ receptor resets.
๐ฌ Types of G Proteins (ฮฑ-subunits)
- ๐ Gs: stimulates adenylate cyclase โ โ cAMP
- ๐ Gi: inhibits adenylate cyclase โ โ cAMP
- ๐ฅ Gq: activates PLC โ IP3 + DAG โ Caยฒโบ signalling
- ๐ง G12/13: cytoskeletal control & migration
๐ Functions of GPCRs
- ๐๏ธ๐๐
Sensory: vision (rhodopsin), smell (olfactory), taste receptors
- ๐ง Neurotransmission: dopamine, serotonin, acetylcholine
- ๐ฆ Immune response: chemokine receptors guide cell migration
- ๐ฑ Growth & differentiation: regulate proliferation
- โค๏ธ Cardiovascular: adrenergic receptors control HR & BP
๐ฅ Clinical Relevance
- ๐ Pharmacological targets:
- Beta-blockers โ adrenergic GPCRs
- Antipsychotics โ dopamine GPCRs
- Antihistamines โ histamine GPCRs
- ๐งฌ Genetic mutations โ cancer, congenital syndromes, metabolic disease
- ๐ Drug development โ ~30โ40% of all drugs act on GPCRs
๐ 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 ๐๐ฌ.
