Transcytosis
Transcytosis is a type of cytosis that allows particles to be shuttled from one membrane to another. An example of this would be when a receptor normally lies on the basal or lateral membrane of an epithelial cell, but needs to be trafficked to the apical side. This can only be done through transcytosis due to tight junctions, which prevent movement from one plasma membrane domain to another. This type of cytosis occurs commonly in epithelium, intestinal cells, and blood capillaries. Transcytosis can also be taken advantage of by pathogenic molecules and organisms. Several studies have shown that bacterium can easily enter intestinal lumen through transcytosis of goblet cells. Other studies, however, are exploring the idea that transcytosis may play a role in allowing medications to cross the blood-brain barrier. Exploiting this fact may allow certain drug therapies to be better utilized by the brain.
Methods of cytosis not only move substances in, out of, and through cells, but also add and subtract membrane from the cell's plasma membrane. The surface area of the membrane is determined by the balance of the two mechanisms and contribute to the homeostatic environment of the cell.
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