Sorting of H,K-ATPase beta-subunit in MDCK and LLC-PK cells is independent of mu 1B adaptin expression

Traffic. 2004 Jun;5(6):449-61. doi: 10.1111/j.1398-9219.2004.00192.x.

Abstract

The cytoplasmic tail of the H,K-ATPase beta-subunit contains a putative tyrosine-based motif that directs the beta-subunit's basolateral sorting when it is expressed in Madin-Darby Canine Kidney (MDCK) cells. When expressed in LLC-PK(1) cells, however, the beta-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-PK(1) cells. For low-density lipoprotein and transferrin receptors, this behavior is due to the differential expression of the mu 1B subunit of the AP-1B clathrin adaptor complex. mu 1B is expressed by MDCK cells, but not LLC-PK(1) cells, and transfection of mu 1B into LLC-PK(1) cells restores basolateral localization of low-density lipoprotein and transferrin receptors. For the beta-subunit, however, mu B expression in LLC-PK(1) cells does not induce its basolateral expression. We found that the beta-subunit interacts with both mu 1B and mu 1A in vitro and in vivo. The capacity to participate in a mu 1B interaction therefore is not sufficient to program the beta-subunit's basolateral localization in MDCK cells. Our data suggest that the H,K-ATPase beta-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.

Publication types

  • Comparative Study
  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Adaptor Protein Complex mu Subunits / metabolism*
  • Adaptor Proteins, Vesicular Transport / chemistry
  • Adaptor Proteins, Vesicular Transport / metabolism
  • Amino Acid Motifs
  • Animals
  • Cell Line
  • Cytoplasm / chemistry
  • Dogs
  • Epithelial Cells / metabolism*
  • Glutathione Transferase / metabolism
  • H(+)-K(+)-Exchanging ATPase / chemistry
  • H(+)-K(+)-Exchanging ATPase / metabolism
  • LLC-PK1 Cells
  • Membrane Proteins / metabolism
  • Protein Subunits / chemistry*
  • Protein Subunits / genetics
  • Protein Subunits / metabolism*
  • Protein Transport*
  • Receptors, LDL / metabolism
  • Receptors, Transferrin / metabolism
  • Recombinant Fusion Proteins / metabolism
  • Swine
  • Transfection
  • Tyrosine / chemistry
  • Tyrosine / metabolism*

Substances

  • Adaptor Protein Complex mu Subunits
  • Adaptor Proteins, Vesicular Transport
  • Membrane Proteins
  • Protein Subunits
  • Receptors, LDL
  • Receptors, Transferrin
  • Recombinant Fusion Proteins
  • Tyrosine
  • Glutathione Transferase
  • H(+)-K(+)-Exchanging ATPase