What proteins mediate clathrin‑dependent endocytosis?

Clathrin-dependent endocytosis is a cellular process that allows the internalization of molecules from the cell surface. It relies on a coordinated network of proteins. The key player is clathrin, a scaffolding protein that forms a coated vesicle around the cargo to be transported. This process also depends on adaptor and accessory proteins that help shape the membrane, capture cargo, and complete vesicle formation.

Key Proteins Involved

Clathrin

Acts as a scaffolding protein that assembles into a lattice-like structure on the inner surface of the cell membrane, forming the vesicle’s outer coat.

Adaptor Proteins

- AP-2

Connects clathrin to the cell membrane and cargo molecules. It binds to membrane lipids and specific cargo receptors, initiating the assembly of the clathrin coat.

- Epsin and AP180/CALM

Assist in bending the membrane and interact with both the clathrin coat and membrane lipids. These proteins promote curvature needed for vesicle formation.

- Eps15

Supports the early stages of clathrin-coated pit formation, helping recruit other components to the site.

Membrane-Deforming Proteins

- Dynamin

A GTPase enzyme responsible for the final “pinching off” step. It wraps around the neck of the budding vesicle and, upon GTP hydrolysis, constricts to release the vesicle into the cytoplasm.

Accessory Proteins

- Auxilin and Hsc70

After vesicle formation, these proteins remove the clathrin coat, preparing the vesicle for fusion with early endosomes.