The predominant secreted protein of transformed murine fibroblasts carries the lysosomal mannose 6-phosphate recognition marker

J Biol Chem. 1982 Sep 25;257(18):11145-50.

Abstract

We have found that the major excreted protein (MEP) of transformed mouse fibroblasts, a phosphoglycoprotein of Mr = 35,000, carries the mannose 6-phosphate recognition marker. MEP secreted by Kirsten virus-transformed NIH 3T3 cells binds to a purified preparation of lysosomal enzyme phosphomannosyl receptor, and this binding is specifically inhibited by mannose 6-phosphate. 32Pi introduced into MEP by metabolic labeling of intact cells is exclusively associated with asparagine-linked oligosaccharides as indicated by sensitivity to endohexosaminidase H. Labeling studies utilizing [2-3H]mannose indicate that approximately one-fifth of the mannose residues of MEP are phosphorylated. Comparative studies of the synthesis, secretion, and uptake of MEP and the lysosomal enzyme beta-galactosidase indicate that MEP made by Kirsten virus-transformed NIH 3T3 cells is not handled in the same manner as are other lysosomal enzymes. MEP may be an unusual lysosomal protein, or both.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Cathepsin L
  • Cathepsins
  • Cell Transformation, Neoplastic*
  • Cells, Cultured
  • Cysteine Endopeptidases
  • Endopeptidases*
  • Glycoproteins / isolation & purification
  • Glycoproteins / metabolism*
  • Hexosaminidases
  • Hexosephosphates / metabolism*
  • Hexosephosphates / pharmacology*
  • Kirsten murine sarcoma virus / genetics*
  • Lysosomes / metabolism*
  • Mannosephosphates / metabolism*
  • Mannosephosphates / pharmacology*
  • Mannosyl-Glycoprotein Endo-beta-N-Acetylglucosaminidase
  • Mice
  • Oligosaccharides / analysis
  • Receptor, IGF Type 2
  • Receptors, Cell Surface / metabolism*
  • Sarcoma Viruses, Murine / genetics*
  • beta-Galactosidase / metabolism

Substances

  • Glycoproteins
  • Hexosephosphates
  • Mannosephosphates
  • Oligosaccharides
  • Receptor, IGF Type 2
  • Receptors, Cell Surface
  • mannose-6-phosphate
  • Hexosaminidases
  • beta-Galactosidase
  • Mannosyl-Glycoprotein Endo-beta-N-Acetylglucosaminidase
  • Cathepsins
  • Endopeptidases
  • Cysteine Endopeptidases
  • Cathepsin L
  • Ctsl protein, mouse