receptorai

Receptorai, often called receptors in English, are cellular proteins that detect chemical signals and initiate a response in the cell. In Lithuanian usage, receptoriai refers to these proteins. Receptors bind ligands with high specificity and affinity, and the binding event triggers changes in the receptor’s activity that propagate signals inside the cell.

Location and types: Many receptors reside on the cell surface, where they interact with extracellular ligands. Key classes include ligand-gated ion channels, G protein-coupled receptors (GPCRs), and receptor tyrosine kinases and other enzyme-linked receptors. Other receptors are intracellular, located in the cytoplasm or nucleus, and bind lipophilic ligands such as steroid hormones, thyroid hormones, or other small molecules to regulate gene transcription.

Mechanism: ligand binding induces conformational changes that activate downstream pathways. Surface receptors commonly use second messengers such as cyclic AMP, calcium, or IP3/DAG, or recruit kinases like MAPK. Intracellular receptors act as transcription factors, directly altering gene expression when bound by their ligand.

Physiology and pharmacology: Receptors orchestrate virtually all physiological processes and are frequent drug targets. Ligands can be agonists, which activate receptors, or antagonists, which block them. Receptor signaling can be upregulated, downregulated, or desensitized by chronic exposure.

Examples and relevance: Notable receptors include the insulin receptor, beta-adrenergic receptors, nicotinic acetylcholine receptors, and NMDA receptors. Understanding receptor function is essential in fields ranging from endocrinology to neuroscience and pharmacology.