AP-4 binds basolateral signals and participates in basolateral sorting in epithelial MDCK cells

Nat Cell Biol. 2002 Feb;4(2):154-9. doi: 10.1038/ncb745.


Adaptors are heterotetrameric complexes that mediate the incorporation of cargo into transport vesicles by interacting with sorting signals present in the cytosolic domain of transmembrane proteins. Four adaptors, AP-1 (beta 1, gamma, mu 1A or mu 1B, sigma 1), AP-2 (beta 2, alpha, mu 2, sigma 2), AP-3 (beta 3 , delta, mu 3, sigma 3) or AP-4 (beta 4, epsilon, mu 4, sigma 4), have been characterized. AP-1 and AP-3 mediate sorting events at the level of the TGN and/or endosomes, whereas AP-2 functions in endocytic clathrin coated vesicle formation; no function is known so far for AP-4. Here, we show that AP-4 can bind different types of cytosolic signals known to mediate basolateral transport in epithelial cells. Furthermore, in MDCK cells with depleted mu 4 protein levels, several basolateral proteins are mis-sorted to the apical surface, showing that AP-4 participates in basolateral sorting in epithelial cells.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adaptor Proteins, Vesicular Transport
  • Amino Acid Sequence
  • Animals
  • Carrier Proteins / genetics
  • Carrier Proteins / metabolism*
  • Cell Fractionation
  • Cell Line
  • Cell Polarity
  • Dogs
  • Epithelial Cells / metabolism*
  • Epithelial Cells / ultrastructure
  • Humans
  • Kidney / cytology
  • Membrane Proteins / genetics
  • Membrane Proteins / metabolism*
  • Molecular Sequence Data
  • Monomeric Clathrin Assembly Proteins*
  • Protein Binding
  • Protein Subunits
  • Protein Transport / physiology*
  • Proto-Oncogene Proteins c-myc / genetics
  • Proto-Oncogene Proteins c-myc / metabolism
  • Recombinant Fusion Proteins / genetics
  • Recombinant Fusion Proteins / metabolism


  • Adaptor Proteins, Vesicular Transport
  • Carrier Proteins
  • Membrane Proteins
  • Monomeric Clathrin Assembly Proteins
  • Protein Subunits
  • Proto-Oncogene Proteins c-myc
  • Recombinant Fusion Proteins
  • clathrin assembly protein AP180