Vesikkelitoiminnan

Vesikkelitoiminnan, or vesicle activity, refers to the dynamic processes by which tiny membrane-bound compartments known as vesicles transport and deliver molecules within cells and between cells. Vesicles originate from the endomembrane system, comprising the endoplasmic reticulum, Golgi apparatus, endosomes, lysosomes, and plasma membrane. They carry proteins, lipids, and signaling molecules, ensuring that materials reach their appropriate destinations for secretion, recycling, or degradation.

The formation of a vesicle begins with membrane curvature induced by adaptor proteins, coat protein complexes such as clathrin or COPI/COPII, and lipid composition. After budding, vesicles are coated and then shed to become secretory or transport vesicles. Small GTPases, particularly the Rab family, assign vesicles to specific target compartments by controlling tethering, docking, and fusion. SNARE proteins mediate the final membrane merging that releases vesicle contents. Defects in these proteins or in the vesicular machinery can lead to a variety of diseases, including neurodegenerative conditions, metabolic disorders, and immune deficiencies.

Vesicle activity is essential for many cellular functions beyond trafficking. It facilitates signal transduction by delivering neurotransmitters at synaptic clefts, participates in antigen presentation by moving peptides to the cell surface, and mediates cell–cell communication through exosomes. The study of vesicle dynamics has been propelled by advanced imaging techniques such as fluorescence microscopy, cryo-electron microscopy, and single-molecule assays, providing detailed insights into vesicle life cycles and their coordination within the cellular network.