EndoTranszytose

EndoTranszytose, also known as transcytosis, is a cellular process that allows molecules to pass through a cell from one side to another. It is a critical mechanism for transport across epithelial and endothelial cell layers, which form the barriers of many tissues and organs. This process is distinct from endocytosis, which involves the uptake of material into a cell, and exocytosis, which involves the release of material from a cell.

Transcytosis typically involves the formation of vesicles at one membrane surface of the cell, followed by their movement across the cytoplasm, and subsequent fusion with the opposite membrane surface to release their contents. This can occur via two main pathways: the vesicular pathway and the non-vesicular pathway. The vesicular pathway, the most common, involves the formation of endocytic vesicles that internalize cargo. These vesicles then travel through the cell and fuse with the opposing plasma membrane, releasing the cargo outside. The non-vesicular pathway can involve the direct passage of certain small molecules through the cell, perhaps via specific transporters or transient pores.

This process is essential for the transport of a wide range of substances, including nutrients, antibodies, hormones, and waste products. For example, in the intestine, transcytosis is crucial for absorbing digested nutrients. In the blood-brain barrier, it allows for the regulated passage of essential molecules into the brain while preventing harmful substances from entering. Hormones like insulin also utilize transcytosis to reach target cells. The efficiency and specificity of transcytosis are tightly regulated, ensuring appropriate transport of vital compounds and maintaining tissue homeostasis.