VIsekretion

VIsekretion, often equated with vesicle secretion or exocytosis, is the process by which cells export substances that are stored in intracellular secretory vesicles. Contents released include neurotransmitters, hormones, enzymes, and mucus. The term covers regulated and constitutive routes, and is essential for intercellular communication and extracellular matrix modulation.

Mechanism: cargo packaged in vesicles formed at endoplasmic reticulum and Golgi; vesicles travel along cytoskeletal tracks to the plasma membrane; docking and priming involve SNARE proteins (v-SNAREs on vesicle, t-SNAREs on target membrane); triggered by intracellular Ca2+ in regulated secretion; fusion of vesicle and plasma membranes releases cargo to outside; vesicle membranes are retrieved by endocytosis and recycled.

Types of secretion: constitutive secretion is continuous and unregulated; regulated secretion stores cargo in dense-core or large granules and releases upon specific stimuli; many cell types secrete via both routes depending on physiological state.

Examples: neurons release neurotransmitters via rapid exocytosis across synapses; endocrine cells release hormones like insulin; exocrine glands secrete enzymes and mucus; alveolar cells in lungs secrete surfactant.

Clinical relevance: disruptions can contribute to diseases such as diabetes (insufficient insulin secretion), neurodegenerative conditions, or toxin-mediated paralysis (botulinum and tetanus toxins cleave SNAREs).