A novel clathrin adaptor complex mediates basolateral targeting in polarized epithelial cells

Cell. 1999 Oct 15;99(2):189-98. doi: 10.1016/s0092-8674(00)81650-5.


Although polarized epithelial cells are well known to maintain distinct apical and basolateral plasma membrane domains, the mechanisms responsible for targeting membrane proteins to the apical or basolateral surfaces have remained elusive. We have identified a novel form of the AP-1 clathrin adaptor complex that contains as one of its subunits mu1B, an epithelial cell-specific homolog of the ubiquitously expressed mu1A. LLC-PK1 kidney epithelial cells do not express mu1B and missort many basolateral proteins to the apical surface. Stable expression of mu1B selectively restored basolateral targeting, improved the overall organization of LLC-PK1 monolayers, and had no effect on apical targeting. We conclude that basolateral sorting is mediated by an epithelial cell-specific version of the AP-1 complex containing mu1B.

Publication types

  • Research Support, Non-U.S. Gov't
  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Adaptor Protein Complex 1*
  • Adaptor Protein Complex alpha Subunits
  • Adaptor Protein Complex mu Subunits*
  • Adaptor Proteins, Vesicular Transport
  • Animals
  • Cell Line
  • Cell Membrane / physiology*
  • Cell Polarity / physiology*
  • Clathrin / metabolism*
  • Coated Pits, Cell-Membrane / physiology*
  • Dogs
  • Epithelial Cells / physiology*
  • Humans
  • Kidney
  • LLC-PK1 Cells / physiology*
  • Macromolecular Substances
  • Membrane Proteins / metabolism*
  • Receptors, Transferrin / genetics
  • Receptors, Transferrin / physiology
  • Recombinant Proteins / metabolism
  • Swine
  • Transfection


  • AP1M1 protein, human
  • AP1M2 protein, human
  • Adaptor Protein Complex 1
  • Adaptor Protein Complex alpha Subunits
  • Adaptor Protein Complex mu Subunits
  • Adaptor Proteins, Vesicular Transport
  • Clathrin
  • Macromolecular Substances
  • Membrane Proteins
  • Receptors, Transferrin
  • Recombinant Proteins
  • adaptor protein complex 1, mu 1 subunit
  • adaptor protein complex 1, mu 2 subunit