The AP-1A and AP-1B clathrin adaptor complexes define biochemically and functionally distinct membrane domains

Heike Fölsch*, Marc Pypaert, Sandra Maday, Laurence Pelletier, Ira Mellman

*Corresponding author for this work

Research output: Contribution to journalArticle

158 Scopus citations

Abstract

Most epithelial cells contain two AP-1 clathrin adaptor complexes. AP-1A is ubiquitously expressed and involved in transport between the TGN and endosomes. AP-1B is expressed only in epithelia and mediates the polarized targeting of membrane proteins to the basolateral surface. Both AP-1 complexes are heterotetramers and differ only in their 50-kD μ1A or μ1B subunits. Here, we show that AP-1A and AP-1B, together with their respective cargoes, define physically and functionally distinct membrane domains in the perinuclear region. Expression of AP-1B (but not AP-1A) enhanced the recruitment of at least two subunits of the exocyst complex (Sec8 and Exo70) required for basolateral transport. By immunofluorescence and cell fractionation, the exocyst subunits were found to selectively associate with AP-1B-containing membranes that were both distinct from AP-1A-positive TGN elements and more closely apposed to transferrin receptor-positive recycling endosomes. Thus, despite the similarity of the two AP-1 complexes, AP-1A and AP-1B exhibit great specificity for endosomal transport versus cell polarity.

Original languageEnglish (US)
Pages (from-to)351-362
Number of pages12
JournalJournal of Cell Biology
Volume163
Issue number2
DOIs
StatePublished - Oct 27 2003

Keywords

  • Basolateral sorting
  • Epithelial cells
  • Exocyst
  • Exocytosis
  • TGN

ASJC Scopus subject areas

  • Cell Biology

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