reseptor

A reseptor is a molecule that receives signals from outside or inside a cell by binding a ligand, and translates that binding into a cellular response. Most reseptorerer are proteins, though some RNA-based systems exist. They can be located on the cell surface or inside the cell, depending on where their ligands operate.

Reseptorer come in several major classes based on location and mechanism. Cell-surface reseptorer include G-protein-coupled reseptorer (GPCRs), ligand-gated ion channels, and enzyme-linked reseptorer such as receptor tyrosine kinases. Intracellular reseptorer include nuclear reseptorer that bind lipophilic ligands and regulate gene transcription. Ligand binding typically induces a conformational change in the reseptor, triggering a signaling cascade or transcriptional response.

Mechanisms of action vary by type. GPCRs activate heterotrimeric G proteins and downstream effectors; enzyme-linked reseptorer activate kinases; ligand-gated ion channels alter ion flux across membranes; nuclear reseptorer modulate gene expression directly after ligand binding. Examples include beta-adrenergic GPCRs, the insulin receptor, and glucocorticoid receptor.

Regulation of reseptorer function is common and important. Cells can adjust reseptor number on the surface (upregulation or downregulation), desensitize reseptorer to persistent stimulation, or internalize them. Many drugs target reseptorer to treat disease, functioning as agonists that activate, antagonists that block, or modulators that alter signaling strength.

Reseptorer are central to physiology, mediating senses, neurotransmission, hormonal signaling, and immune responses, and they are a primary focus in pharmacology and biomedical research.