Coated vesicles

Coated vesicles are 20 to 250 nm, have a single membrane, transport proteins, lipids or secretory products between cellular compartments, and are formed of coat proteins.

There are three types, and the coat is what names each one.

Clathrin-coated vesicles are involved in receptor-mediated endocytosis. Coatomer-coated vesicles carry material between the ER and the Golgi: COP II anterograde, from ER to Golgi; COP I retrograde, from Golgi to ER. Caveolae are small invaginations of the plasma membrane, abundant in endothelial cells, involved in potocytosis.

Coated vesicles have a size of 20 to 250 nm and a single membrane.

• They transport proteins and lipids, or secretory products, between cellular compartments.
• They are formed of coat proteins.

There are three types.

Clathrin-coated vesicles are involved in receptor-mediated endocytosis.

• They contain spines, which are transmembrane proteins made up of clathrin, attached to the coated vesicle.
• They are formed by endocytosis or by the Golgi apparatus.
• Cell surface receptors form, with the coat proteins, a coated pit. Coated pits are regions of the cell membrane specialised in receptor-mediated endocytosis.

Coatomer-coated vesicles are the ones that move material between the endoplasmic reticulum and the Golgi.

• COP II is responsible for anterograde transport, from the ER to the Golgi complex.
• COP I is responsible for retrograde transport, from the Golgi to the ER. It also carries out intra-Golgi transport.

The pair is the same one that guides movement through the Golgi stack itself, and it reverses easily under pressure. COP II carries material onward; COP I brings it back.

Caveolae are small invaginations of the plasma membrane, 50 to 100 nm.

• They are abundant in endothelial cells, which are the place of exchange of metabolites between cells.
• They are involved in potocytosis, a type of receptor-mediated endocytosis.
• Potocytosis involves caveolins, which are integral membrane proteins, and cavins, which are peripheral membrane proteins.

A caveola is not a fully formed vesicle at rest; it is a dimple in the membrane, which is what the name means.