Cytoplasmic signals mediate apical early endosomal targeting of endotubin in MDCK cells

K. E. Gokay, R. S. Young, Jean Wilson

Research output: Contribution to journalArticle

11 Citations (Scopus)

Abstract

Endotubin is an integral membrane protein that targets into apical endosomes in polarized epithelial cells. Although the role of cytoplasmic targeting signals as mediators of basolateral targeting and endocytosis is well established, it has been suggested that apical targeting requires either N-glycosylation of the ectoplasmic domains or partitioning of macromolecules into glycolipid-rich rafts. However, we have previously shown that the cytoplasmic portion of endotubin possesses signals that are necessary for its proper sorting into the apical early endosomes. To further define the targeting signals involved in this apically directed event, as well as to determine if the cytoplasmic domain was sufficient to mediate apical endosomal targeting, we generated a panel of endotubin and Tac-antigen chimeras and expressed them in Madin-Darby canine kidney cells. We show that both the apically targeting wild-type endotubin and a basolaterally targeted cytoplasmic domain mutant do not associate with rafts and are TX-100 soluble. The cytoplasmic tail of endotubin is sufficient for apical endosomal targeting, as chimeras with the endotubin cytoplasmic domain and Tac transmembrane and extracellular domains are efficiently targeted to the apical endosomal compartment. Furthermore, we show that overexpression of these chimeras results in their missorting to the basolateral membrane, indicating that the apical sorting process is a saturable event. These results show that cells contain machinery in both the biosynthetic and endosomal compartments that recognize cytoplasmic apical sorting signals.

Original languageEnglish (US)
Pages (from-to)487-500
Number of pages14
JournalTraffic
Volume2
Issue number7
DOIs
StatePublished - 2001

Fingerprint

Madin Darby Canine Kidney Cells
Sorting
Endosomes
Glycosylation
Glycolipids
Endocytosis
Macromolecules
Machinery
Membrane Proteins
Epithelial Cells
Membranes
Antigens

Keywords

  • Apical
  • Brefeldin-A
  • Endosomes
  • Epithelia
  • Membrane trafficking

ASJC Scopus subject areas

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

Cite this

Cytoplasmic signals mediate apical early endosomal targeting of endotubin in MDCK cells. / Gokay, K. E.; Young, R. S.; Wilson, Jean.

In: Traffic, Vol. 2, No. 7, 2001, p. 487-500.

Research output: Contribution to journalArticle

Gokay, K. E. ; Young, R. S. ; Wilson, Jean. / Cytoplasmic signals mediate apical early endosomal targeting of endotubin in MDCK cells. In: Traffic. 2001 ; Vol. 2, No. 7. pp. 487-500.
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