vesicle

A vesicle is a small, membrane-bound compartment that encloses a volume of fluid and substances for transport within a cell or between cells. Vesicles are bounded by a lipid bilayer and often carry proteins, lipids, and other cargo.

Vesicle formation typically involves budding from a donor membrane, aided by coat proteins such as clathrin or caveolin. Fission, cargo selection, and targeting are coordinated by small GTPases and SNARE proteins that mediate docking and fusion with recipient membranes.

Within the cell, vesicles participate in endocytosis, trafficking through the endomembrane system, and exocytosis. Transport vesicles move cargo from the endoplasmic reticulum to the Golgi apparatus and from the Golgi to various destinations, including the plasma membrane and lysosomes. Secretory vesicles store and release hormones, neurotransmitters, or enzymes in response to signals. Synaptic vesicles in neurons release neurotransmitters at synapses.

In addition to intracellular vesicles, extracellular vesicles are released from cells and include exosomes and microvesicles, which carry lipids, proteins, and nucleic acids that can influence recipient cells. Exosomes originate from multivesicular bodies, while microvesicles bud directly from the plasma membrane.

Abnormal vesicle trafficking is linked to various diseases, including neurodegenerative disorders, immune dysfunction, and lysosomal storage diseases. Vesicle biology is a central aspect of cellular organization and intercellular communication.