Multiple post-translational modifications of mouse insulin-like growth factor binding protein-6 expressed in epithelial Madin-Darby canine kidney cells

Mol Cell Endocrinol. 2008 Nov 25;295(1-2):18-23. doi: 10.1016/j.mce.2008.08.034. Epub 2008 Sep 10.

Abstract

Insulin-like growth factors (IGFs), IGF receptors and IGF binding proteins (IGFBPs) participate in the regulation of proliferation and differentiation of epithelial cells. Expression of the growth-inhibitory murine IGFBP-6 in epithelial Madin-Darby canine kidney (MDCK) cells followed by 2D analysis revealed the presence of multiple isoforms. Metabolic labelling experiments showed that several IGFBP-6 isoforms are modified by phosphate and sulfate groups. Expression analysis of mutant IGFBP-6 further demonstrated that serine residue 143 is O-glycosylated. Substitution of serine 143 by alanine did slightly reduce the preferential sorting of mIGFBP-6 to the apical site in MDCK cells grown on semipermeable filters. Both the presence of multiple and heterogeneously modified isoforms of murine IGFBP-6 in MDCK cells, and the preferential secretion of non-glycosylated IGFBP-6 mutants to the apical side suggest that the major apical sorting signal is the protein moiety.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Cell Line
  • Dogs
  • Epithelial Cells / metabolism*
  • Glycosylation
  • Insulin-Like Growth Factor Binding Protein 6 / genetics
  • Insulin-Like Growth Factor Binding Protein 6 / metabolism*
  • Kidney / cytology
  • Kidney / metabolism*
  • Mice
  • Mutation
  • Phosphorylation
  • Protein Isoforms
  • Protein Processing, Post-Translational*
  • Protein Sorting Signals
  • Protein Transport
  • Sulfates / metabolism
  • Transfection

Substances

  • Insulin-Like Growth Factor Binding Protein 6
  • Protein Isoforms
  • Protein Sorting Signals
  • Sulfates