An alternative mechanism of clathrin-coated pit closure revealed by ion conductance microscopy

J Cell Biol. 2012 May 14;197(4):499-508. doi: 10.1083/jcb.201109130. Epub 2012 May 7.

Abstract

Current knowledge of the structural changes taking place during clathrin-mediated endocytosis is largely based on electron microscopy images of fixed preparations and x-ray crystallography data of purified proteins. In this paper, we describe a study of clathrin-coated pit dynamics in living cells using ion conductance microscopy to directly image the changes in pit shape, combined with simultaneous confocal microscopy to follow molecule-specific fluorescence. We find that 70% of pits closed with the formation of a protrusion that grew on one side of the pit, covered the entire pit, and then disappeared together with pit-associated clathrin-enhanced green fluorescent protein (EGFP) and actin-binding protein-EGFP (Abp1-EGFP) fluorescence. This was in contrast to conventionally closing pits that closed and cleaved from flat membrane sheets and lacked accompanying Abp1-EGFP fluorescence. Scission of both types of pits was found to be dynamin-2 dependent. This technique now enables direct spatial and temporal correlation between functional molecule-specific fluorescence and structural information to follow key biological processes at cell surfaces.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • COS Cells
  • Chlorocebus aethiops
  • Clathrin / chemistry
  • Clathrin / metabolism*
  • Coated Pits, Cell-Membrane / metabolism*
  • Dynamin II / metabolism
  • Endocytosis
  • Green Fluorescent Proteins / genetics
  • Green Fluorescent Proteins / metabolism
  • Microscopy

Substances

  • Clathrin
  • enhanced green fluorescent protein
  • Green Fluorescent Proteins
  • Dynamin II