Proteomic analysis of human lysosomes: application to monocytic and breast cancer cells

Proteomics. 2002 Aug;2(8):1026-40. doi: 10.1002/1615-9861(200208)2:8<1026::AID-PROT1026>3.0.CO;2-I.


To date, about fifty lysosomal hydrolases have been identified, and most of them are targeted towards the lysosomes through a specific mannose-6-phosphate (M-6-P) tag. As more lysosomal hydrolases were expected to be discovered, we performed a proteomic study of soluble lysosomal proteins. Human cells were induced to secrete M-6-P proteins which were affinity purified on immobilized M-6-P receptor. The purified proteins were resolved by two-dimensional electrophoresis and analyzed by mass spectrometry. Twenty-two proteins were identified, among which 16 were well-known lysosomal hydrolases. The remaining species distributed as follows: epididymis-specific alpha-mannosidase is a new mannosidase homolog, cystatin F and CREG (cellular repressor of E1A-stimulated genes) were previously identified as M-6-P proteins (Journet et al., Electrophoresis 2000, 21, 3411-3419), and the last three, which are not hydrolases, were up to now considered as nonlysosomal. This two-dimensional reference map of human U937 M-6-P proteins was afterwards used for comparison with M-6-P proteins purified either from U937 differentiated into macrophage-like cells, or from human breast cancer MCF7 cells. Phorbol ester induced differentiation of U937 cells led to limited proteolytic cleavage or maturation of a discrete number of hydrolases. Five additional lysosomal hydrolases were identified from MCF7 samples. These results prove the usefulness of such a procedure to analyze the lysosomal content of various cell lines, to discover new M-6-P proteins, as well as to point towards unknown biological processes.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Breast Neoplasms / chemistry*
  • Cell Differentiation / physiology
  • Cell Line
  • Electrophoresis, Gel, Two-Dimensional
  • Female
  • Humans
  • Lysosomes / chemistry*
  • Lysosomes / enzymology
  • Mannosephosphates / chemistry
  • Mass Spectrometry
  • Molecular Sequence Data
  • Monocytes / chemistry*
  • Proteins / analysis*
  • Proteome / analysis*
  • Sequence Analysis, Protein
  • Tetradecanoylphorbol Acetate / metabolism


  • Mannosephosphates
  • Proteins
  • Proteome
  • lysosomal proteins
  • mannose-6-phosphate
  • Tetradecanoylphorbol Acetate