A cytoplasmic PPPSP motif determines megalin's phosphorylation and regulates receptor's recycling and surface expression

María Isabel Yuseff, Pamela Farfan, Guojun D Bu, María P. Marzolo

Research output: Contribution to journalArticle

34 Citations (Scopus)

Abstract

Megalin is a large endocytic receptor expressed at the apical surface of several absorptive epithelia. It binds multiple ligands including apolipoproteins, vitamin and hormone carrier proteins and signaling molecules such as parathyroid hormone and the morphogen sonic hedgehog. An important characteristic of megalin is its high endocytic activity, which is mediated by tyrosine-based endocytic motifs within the receptor's cytoplasmic tail. This domain also harbors several putative consensus phosphorylation motifs for protein kinase (PK) C and casein kinase-II and one consensus motif for PKA and glycogen synthase kinase-3 (GSK3). Here we report that the cytoplasmic domain of megalin is constitutively phosphorylated depending on the integrity of a PPPSP motif, a putative GSK3 site, with a minor participation of the other phosphorylation motifs. Mutation of the serine residue within the PPPSP motif as well as blocking GSK3 activity, with two different inhibitors, significantly decreased the phosphorylation levels of the receptor. Both the megalin PPPAP mutant and the underphosphorylated wild-type receptor, by inhibition of GSK3 activity, were more expressed at the cell surface and more efficiently recycled, but they were not inhibited in their initial endocytosis rates. Altogether, these results show that the PPPSP motif and the GSK3 activity are critical to allow megalin phosphorylation and also negatively regulate the receptor's recycling.

Original languageEnglish (US)
Pages (from-to)1215-1230
Number of pages16
JournalTraffic
Volume8
Issue number9
DOIs
StatePublished - Sep 2007
Externally publishedYes

Fingerprint

Low Density Lipoprotein Receptor-Related Protein-2
Glycogen Synthase Kinase 3
Phosphorylation
Recycling
Casein Kinase II
Apolipoproteins
Cytoplasmic and Nuclear Receptors
Ports and harbors
Endocytosis
Parathyroid Hormone
Vitamins
Serine
Tyrosine
Carrier Proteins
Epithelium
Hormones
Ligands
Mutation
Molecules

Keywords

  • CK-II
  • GSK3
  • Megalin
  • PKA
  • PKC
  • Recycling

ASJC Scopus subject areas

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

Cite this

A cytoplasmic PPPSP motif determines megalin's phosphorylation and regulates receptor's recycling and surface expression. / Yuseff, María Isabel; Farfan, Pamela; Bu, Guojun D; Marzolo, María P.

In: Traffic, Vol. 8, No. 9, 09.2007, p. 1215-1230.

Research output: Contribution to journalArticle

Yuseff, María Isabel ; Farfan, Pamela ; Bu, Guojun D ; Marzolo, María P. / A cytoplasmic PPPSP motif determines megalin's phosphorylation and regulates receptor's recycling and surface expression. In: Traffic. 2007 ; Vol. 8, No. 9. pp. 1215-1230.
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