Endosomeja

Endosomeja are membrane-bound organelles within eukaryotic cells that function as central hubs in endocytosis and intracellular trafficking. They originate when vesicles carrying material from the plasma membrane fuse to form early endosomes. Early endosomes act as sorting stations, and their identity is marked by Rab5 and associated proteins such as EEA1. As they mature, endosomeja undergo acidification and biochemical changes that drive cargo sorting and trafficking decisions.

Maturation progresses from early to late endosomes, which are typically marked by Rab7 and a more acidic lumen. Late endosomes can fuse with lysosomes, where delivered materials are degraded by lysosomal hydrolases. Alternatively, some cargo is diverted into recycling pathways back to the plasma membrane via recycling endosomes, often associated with Rab11. A key mechanism within endosomeja is the ESCRT machinery, which sorts ubiquitinated cargo into intraluminal vesicles inside multivesicular bodies (MVBs). MVBs can either fuse with lysosomes for degradation or fuse with the plasma membrane to release exosomes, small vesicles that participate in intercellular communication.

Endosomeja contribute to multiple cellular processes beyond cargo degradation, including receptor downregulation, nutrient uptake, antigen presentation, and signaling modulation. Their function is tightly coordinated by a network of Rab GTPases, SNAREs, tethering factors, and lipid environments.

Dysfunction of endosomeja or related trafficking pathways has been linked to human disease. Altered endosomal pH, defective Rab or retromer function, or impaired ESCRT activity can affect receptor signaling and protein processing, with associations to neurodegenerative disorders, lysosomal storage conditions, and pathogen entry strategies that exploit endosomal routes.