Clathrin Coated Pit Endocytosis - How Does It Occur?

  • Most common and well understood route of entry into the cell.
  • Clathrin coated pits form when clathrin triskelions interdigitate together forming a hexadedral cage like structure.A Single Triskelion And A Cage Like Structure Of Many
  • In order for cargo to be incorporated into the coated pits, clathrin adaptor molecules are required.
  • The adaptor molecule AP2 is recruited to the plasma membrane through its PI2P domain.
  • The β subunit binds clathrin and the μ subunit binds cargo.
  • The μ subunit therefore has to recognise cargo. It does this by recognising a variety of sorting signals, including the tyrosine based YTRF signal found on the Transferrin recptor.
  • Cargo therefore becomes concentrated in the pits, and under the correct circumstances, the pits will undergo fission.
  • Formation Of Clathrin Coated Vesicles With CargoFisson is catalysed by Dynamin. Two non cytosloic leaflets of the membrane are brought close together and fuse, sealing off the membrane. Dynamin, and other proteins which it recruits help to bend the membrane causing the vesicle to be released.
  • Within seconds of the vesicle having formed and undergone fission, vesicles undergo uncoating so that they can fuse with the early endsome.
  • The early endosome is where all cargo is initially delivered to.

 

Image 1 courtesey of Wikimedia Commons under Creative Commons License (Public Domain)

Image 2 courtesey of 2006 Barth D. Grant and Miyuki Sato under  Creative Commons License