Sorting of H,K-ATPase β-subunit in MDCK and LLC-PK1 cells is independent of μ1B adaptin expression

Amy Duffield, Heike Fölsch, Ira Mellman, Michael J. Caplan*

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

22 Scopus citations


The cytoplasmic tail of the H,K-ATPase β-subunit contains a putative tyrosine-based motif that directs the β-subunit's basolateral sorting when it is expressed in Madin-Darby Canine Kidney (MDCK) cells. When expressed in LLC-PK1 cells, however, the β-subunit is localized to the apical membrane. Several proteins that contain tyrosine-based motifs, including the low-density lipoprotein and transferrin receptors, show a similar sorting 'defect' when expressed in LLC-PK1 cells. For low-density lipoprotein and transferrin receptors, this behavior is due to the differential expression of the μ1B subunit of the AP-1B clathrin adaptor complex. μ1B is expressed by MDCK cells, but not LLC-PK1 cells, and transfection of μ1B into LLC-PK1 cells restores basolateral localization of low-density lipoprotein and transferrin receptors. For the β-subunit, however, μ1B expression in LLC-PK1 cells does not induce its basolateral expression. We found that the β-subunit interacts with both μ1B and μ1A in vitro and in vivo. The capacity to participate in a μ1B interaction therefore is not sufficient to program the β-subunit's basolateral localization in MDCK cells. Our data suggest that the H,K-ATPase β -subunit's basolateral sorting signal is either masked in certain epithelial cells, or requires an interaction with sorting machinery other than AP-1B for delivery to the basolateral plasma membrane.

Original languageEnglish (US)
Pages (from-to)449-461
Number of pages13
Issue number6
StatePublished - Jun 2004


  • Adaptor protein-1 complex
  • Epithelia
  • H,K-ATPase β-subunit
  • Polarity
  • Sorting

ASJC Scopus subject areas

  • Structural Biology
  • Biochemistry
  • Molecular Biology
  • Genetics
  • Cell Biology


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