Differential distribution of low-density lipoprotein-receptor-related protein (LRP) and megalin in polarized epithelial cells is determined by their cytoplasmic domains

María Paz Marzolo, María Isabel Yuseff, Claudio Retamal, Maribel Donoso, Fernando Ezquer, Pamela Farfán, Yonghe Li, Guojun Bu

Research output: Contribution to journalArticle

68 Scopus citations

Abstract

Megalin and the low-density lipoprotein (LDL) receptor-related protein (LRP) are two large members of the LDL receptor family that bind and endocytose multiple ligands. The molecular and cellular determinants that dictate the sorting behavior of these receptors in polarized epithelial cells are largely unknown. Megalin is found apically distributed, whereas the limited information on LRP indicates its polarity. We show here that in Madin-Darby canine kidney cells, both endogenous LRP and a mini-receptor containing the fourth ligand-binding, transmembrane and LRP cytosolic domains were basolaterally sorted. In contrast, minireceptors that either lacked the cytoplasmic domain or had the tyrosine in the NPTY motif mutated to alanine showed a preferential apical distribution. In LLC-PK1 cells, endogenous megalin was found exclusively in the apical membrane. Studies were also done using chimeric proteins harboring the cytosolic tail of megalin, one with the fourth ligand-binding domain of LRP and the other two containing the green fluorescent protein as the ectodomain and transmembrane domains of either megalin or LRP. Findings from these experiments showed that the cytosolic domain of megalin is sufficient for apical sorting, and that the megalin transmembrane domain promotes association with lipid rafts. In conclusion, we show that LRP and megalin both contain sorting information in their cytosolic domains that directs opposite polarity, basolateral for LRP and apical for megalin. Additionally, we show that the NPTY motif in LRP is important for basolateral sorting and the megalin transmembrane domain directs association with lipid rafts.

Original languageEnglish (US)
Pages (from-to)273-288
Number of pages16
JournalTraffic
Volume4
Issue number4
DOIs
StatePublished - Apr 1 2003

Keywords

  • Apical
  • Basolateral
  • Green fluorescent protein
  • LRP
  • Lipid rafts
  • Megalin
  • Polarized sorting

ASJC Scopus subject areas

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

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