early endosome to late endosome transport

Definition

Target type: biologicalprocess

The directed movement of substances, in membrane-bounded vesicles, from the early sorting endosomes to the late sorting endosomes; transport occurs along microtubules and can be experimentally blocked with microtubule-depolymerizing drugs. [ISBN:0815316194, PMID:29980602]

Early endosome to late endosome transport is a crucial step in the endocytic pathway, responsible for delivering internalized cargo from the plasma membrane to the lysosomes for degradation or recycling. This process involves a series of intricate molecular events that ensure the efficient and selective sorting of various molecules.

The journey begins with the formation of early endosomes, small vesicles budding off from the plasma membrane. These endosomes are characterized by their relatively low pH (around 6.0-6.5) and a unique protein composition that includes Rab5, a small GTPase involved in early endosome formation and trafficking.

As the early endosomes mature, they acquire a more acidic internal environment, reaching a pH of approximately 5.5. This acidification is driven by the activity of vacuolar ATPases (V-ATPases) embedded in the endosomal membrane. The changing pH triggers a cascade of molecular events, including the recruitment of different proteins and the dissociation of others.

One of the key events during early endosome maturation is the recruitment of Rab7, another small GTPase, which is essential for late endosome formation and transport. Rab7 replaces Rab5 on the endosomal membrane, promoting the recruitment of other late endosomal proteins, such as the adaptor protein complex AP-3 and the tethering protein complex HOPS.

The transition from early to late endosomes also involves the fusion of multiple early endosomes into larger, more mature late endosomes. This fusion process is regulated by a complex interplay of proteins, including SNAREs, which mediate membrane fusion, and Rab GTPases, which orchestrate the recruitment of specific SNAREs to the endosomal membrane.

As late endosomes mature, they acquire a more densely packed appearance due to the accumulation of internalized cargo, including proteins, lipids, and even pathogens. These late endosomes are then transported to the lysosomes, where they fuse and deliver their cargo for final degradation. This final stage of the endocytic pathway ensures the efficient removal of unwanted cellular components, while also providing a mechanism for recycling valuable molecules back to the cell surface.'
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Proteins (2)

Compounds (26)