Accelerated urokinase-receptor protein turnover triggered by interference with the addition of the glycolipid anchor

Biochem J. 2011 Mar 1;434(2):233-42. doi: 10.1042/BJ20101573.


u-PAR (urokinase-type plasminogen activator receptor), anchored to the cell surface via a glycolipid moiety, drives tumour progression. We previously reported that colon cancer cells (RKO clone 2 FS2), attenuated for in vivo tumorigenicity, are diminished >15-fold for u-PAR display when compared with their tumorigenic isogenic counterparts (RKO clone 2), this disparity not reflecting altered transcription/mRNA stability. FACS, confocal microscopy and Western blotting using a fused u-PAR-EGFP (enhanced green fluorescent protein) cDNA revealed a >14-fold differential in the u-PAR-EGFP signal between the isogenic cells, ruling out alternate splicing as a mechanism. Although metabolic labelling indicated similar synthesis rates, pulse-chase revealed accelerated u-PAR-EGFP turnover in the RKO clone 2 FS2 cells. Expression in RKO clone 2 cells of a u-PAR-EGFP protein unable to accept the glycolipid moiety yielded diminished protein amounts, thus mirroring the low endogenous protein levels evident with RKO clone 2 FS2 cells. Transcript levels for the phosphatidylglycan anchor biosynthesis class B gene required for glycolipid synthesis were reduced by 65% in RKO clone 2 FS2 cells, and forced overexpression in these cells partially restored endogenous u-PAR. Thus attenuated u-PAR levels probably reflects accelerated turnover triggered by inefficient addition of the glycolipid moiety.

Publication types

  • Research Support, N.I.H., Extramural

MeSH terms

  • Alternative Splicing
  • Colonic Neoplasms / metabolism
  • DNA, Complementary / metabolism
  • Glycolipids / metabolism
  • Green Fluorescent Proteins / genetics
  • Green Fluorescent Proteins / metabolism
  • Humans
  • Signal Transduction
  • Transfection
  • Tumor Cells, Cultured
  • Urokinase-Type Plasminogen Activator / genetics
  • Urokinase-Type Plasminogen Activator / metabolism*


  • DNA, Complementary
  • Glycolipids
  • enhanced green fluorescent protein
  • Green Fluorescent Proteins
  • Urokinase-Type Plasminogen Activator