TGF-β sensitivity is determined by N-linked glycosylation of the type II TGF-β receptor

Biochem J. 2012 Aug 1;445(3):403-11. doi: 10.1042/BJ20111923.

Abstract

N-linked glycosylation is a critical determinant of protein structure and function, regulating processes such as protein folding, stability and localization, ligand-receptor binding and intracellular signalling. TβRII [type II TGF-β (transforming growth factor β) receptor] plays a crucial role in the TGF-β signalling pathway. Although N-linked glycosylation of TβRII was first demonstrated over a decade ago, it was unclear how this modification influenced TβRII biology. In the present study, we show that inhibiting the N-linked glycosylation process successfully hinders binding of TGF-β1 to TβRII and subsequently renders cells resistant to TGF-β signalling. The lung cancer cell line A549, the gastric carcinoma cell line MKN1 and the immortal cell line HEK (human embryonic kidney)-293 exhibit reduced TGF-β signalling when either treated with two inhibitors, including tunicamycin (a potent N-linked glycosylation inhibitor) and kifunensine [an inhibitor of ER (endoplasmic reticulum) and Golgi mannosidase I family members], or introduced with a non-glycosylated mutant version of TβRII. We demonstrate that defective N-linked glycosylation prevents TβRII proteins from being transported to the cell surface. Moreover, we clearly show that not only the complex type, but also a high-mannose type, of TβRII can be localized on the cell surface. Collectively, these findings demonstrate that N-linked glycosylation is essentially required for the successful cell surface transportation of TβRII, suggesting a novel mechanism by which the TGF-β sensitivity can be regulated by N-linked glycosylation levels of TβRII.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Alkaloids / pharmacology
  • Amino Acid Sequence
  • Amino Acid Substitution
  • Asparagine / chemistry
  • Cell Line
  • Cell Membrane / metabolism
  • Conserved Sequence
  • Glycosylation / drug effects
  • HEK293 Cells
  • HeLa Cells
  • Hep G2 Cells
  • Humans
  • Molecular Sequence Data
  • Mutagenesis, Site-Directed
  • Protein Serine-Threonine Kinases / chemistry
  • Protein Serine-Threonine Kinases / genetics
  • Protein Serine-Threonine Kinases / metabolism*
  • Receptor, Transforming Growth Factor-beta Type II
  • Receptors, Transforming Growth Factor beta / chemistry
  • Receptors, Transforming Growth Factor beta / genetics
  • Receptors, Transforming Growth Factor beta / metabolism*
  • Recombinant Proteins / chemistry
  • Recombinant Proteins / genetics
  • Recombinant Proteins / metabolism
  • Sequence Homology, Amino Acid
  • Signal Transduction / drug effects
  • Transforming Growth Factor beta / metabolism*
  • Tunicamycin / pharmacology

Substances

  • Alkaloids
  • Receptors, Transforming Growth Factor beta
  • Recombinant Proteins
  • Transforming Growth Factor beta
  • kifunensine
  • Tunicamycin
  • Asparagine
  • Protein Serine-Threonine Kinases
  • Receptor, Transforming Growth Factor-beta Type II