Multiple post-translational modifications of mouse insulin-like growth factor binding protein-6 expressed in epithelial Madin-Darby canine kidney cells.
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.
Shalamanova
L
L
University Medical Center Hamburg-Eppendorf, Department Biochemistry, Children's Hospital, Martinistrasse 52, D-20246 Hamburg, Germany.
Kübler
B
B
Storch
S
S
Scharf
J-G
JG
Braulke
T
T
D000818:Animals; D002460:Cell Line; D004285:Dogs; D004847:Epithelial Cells / Q000378:metabolism*; D006031:Glycosylation; D018976:Insulin-Like Growth Factor Binding Protein 6 / Q000235:genetics / Q000378:metabolism*; D007668:Kidney / Q000166:cytology / Q000378:metabolism*; D051379:Mice; D009154:Mutation; D010766:Phosphorylation; D020033:Protein Isoforms; D011499:Protein Processing, Post-Translational; D021382:Protein Sorting Signals; D021381:Protein Transport; D013431:Sulfates / Q000378:metabolism; D014162:Transfection
D018976:Insulin-Like Growth Factor Binding Protein 6; D020033:Protein Isoforms; D021382:Protein Sorting Signals; D013431:Sulfates