Cellular receptor for urokinase plasminogen activator. Carboxyl-terminal processing and membrane anchoring by glycosyl-phosphatidylinositol

J Biol Chem. 1991 Jan 25;266(3):1926-33.

Abstract

The cellular receptor for human urokinase-type plasminogen activator (u-PAR) is shown by several independent criteria to be a true member of a family of integral membrane proteins, anchored to the plasma membrane exclusively by a COOH-terminal glycosyl-phosphatidylinositol moiety. 1) Amino acid analysis of u-PAR after micropurification by affinity chromatography and N-[2-hydroxy-1,1-bis(hydroxymethyl)-ethyl]glycine-sodium dodecyl sulfate-polyacrylamide gel electrophoresis revealed the presence of 2-3 mol of ethanolamine/mol protein. 2) Membrane-bound u-PAR is efficiently released from the surface of human U937 cells by trace amounts of purified bacterial phosphatidylinositol-specific phospholipase C. This soluble form of u-PAR retains the binding specificity toward both u-PA and its amino-terminal fragment holding the receptor-binding domain. 3) Treatment of purified u-PAR with phosphatidylinositol-specific phospholipase C or mild alkali completely alters the hydrophobic properties of the receptor as judged by temperature-induced detergent-phase separation and charge-shift electrophoresis. 4) Biosynthetic labeling of u-PAR was obtained with [3H]ethanolamine and myo-[3H]inositol. 5) Finally, comparison of amino acid compositions derived from cDNA sequence and amino acid analysis shows that a polypeptide of medium hydrophobicity is excised from the COOH terminus of the nascent u-PAR. A similar proteolytic processing has been reported for other proteins that are linked to the plasma membrane by a glycosyl-phosphatidylinositol membrane anchor.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Amino Acids / analysis
  • Ethanolamine
  • Ethanolamines / metabolism
  • Glycolipids / metabolism
  • Glycosylphosphatidylinositols
  • Humans
  • In Vitro Techniques
  • Membrane Glycoproteins / metabolism*
  • Molecular Weight
  • Phosphatidylinositol Diacylglycerol-Lyase
  • Phosphatidylinositols / metabolism
  • Phosphoinositide Phospholipase C
  • Phosphoric Diester Hydrolases / metabolism
  • Polysaccharides / metabolism
  • Protein Processing, Post-Translational
  • Receptors, Cell Surface / metabolism*
  • Receptors, Urokinase Plasminogen Activator
  • Solubility
  • Tumor Cells, Cultured
  • Urokinase-Type Plasminogen Activator / metabolism*

Substances

  • Amino Acids
  • Ethanolamines
  • Glycolipids
  • Glycosylphosphatidylinositols
  • Membrane Glycoproteins
  • PLAUR protein, human
  • Phosphatidylinositols
  • Polysaccharides
  • Receptors, Cell Surface
  • Receptors, Urokinase Plasminogen Activator
  • Ethanolamine
  • Phosphoric Diester Hydrolases
  • Phosphoinositide Phospholipase C
  • Urokinase-Type Plasminogen Activator
  • Phosphatidylinositol Diacylglycerol-Lyase