Vesicular Trafficking

Abstract

Normal cell function depends on the appropriate synthesis, maturation, sorting, and delivery of fully processed proteins and other macromolecules to specific intracellular compartments; uptake of material from the cell exterior; and regulated intracellular processing and degradation of proteins, lipids, complex carbohydrates, abnormal aggregates, and senescent organelles. These fundamental functions involve secretory, endocytic, and autophagic pathways. The secretory pathway is responsible for protein maturation, sorting, and delivery of transmembrane and secreted proteins from their site of synthesis to their final destinations. Synaptic vesicle exocytosis is a special form of secretion that allows rapid communication between neurons. The endocytic pathway starts with the internalization of material via endosomes. Endosomal content can be transported back to the cell body, recycled to cell compartments, or delivered for degradation by the lysosome. Abnormal protein aggregates or damaged organelles undergo autophagy, which involves formation of an autophagosome and degradation by the lysosome. Impaired vesicular trafficking is a fundamental mechanism in a large number of neurodegenerative disorders, including hereditary spastic paraplegia, lower motor neuron syndromes, and Parkinson disease.