membranetrafficking

Membranetrafficking refers to the cellular process by which membranes and their cargo are moved within the cell and between compartments. It coordinates the distribution of lipids and proteins, receptor turnover, and the delivery of enzymes and signaling molecules to specific locations, supporting cellular organization, metabolism, and communication.

Core mechanisms and components involve the formation of vesicles and tubules escorted by coat proteins such as COPI, COPII, and clathrin. Coat proteins select cargo, shape membrane buds, and drive vesicle formation. Target specificity is established by Rab GTPases, tethering factors, and SNARE proteins that mediate vesicle docking and membrane fusion. Motor proteins (dynein, kinesin, and myosin) move vesicles along cytoskeletal tracks, enabling long-range transport.

Major trafficking pathways include the secretory pathway, where proteins exit the endoplasmic reticulum, progress through the Golgi apparatus, and are delivered to the plasma membrane, lysosomes, or the extracellular space. The endocytic pathway begins at the plasma membrane with internalization and sorting in endosomes, followed by recycling to the surface or degradation in lysosomes. Additional routes such as transcytosis and autophagy-related trafficking illustrate the diversity of membrane trafficking routes in different cell types.

Regulation and significance arise from quality control in the ER, sorting signals, and adaptor proteins that direct cargo to correct destinations. Proper membranetrafficking is essential for receptor signaling, nutrient uptake, immune responses, and development. Dysfunctions in trafficking components can contribute to diseases such as cystic fibrosis, lysosomal storage disorders, neurodegenerative diseases, and cancer, reflecting the central role of membrane trafficking in cellular health.