Cell surface colony-stimulating factor 1 can be cleaved by TNF-alpha converting enzyme or endocytosed in a clathrin-dependent manner

J Immunol. 2007 Nov 15;179(10):6715-24. doi: 10.4049/jimmunol.179.10.6715.


CSF-1 is a hemopoietic growth factor, which plays an essential role in macrophage and osteoclast development. Alternative splice variants of CSF-1 are synthesized as soluble or membrane-anchored molecules, although membrane CSF-1 (mCSF-1) can be cleaved from the cell membrane to become soluble CSF-1. The activities involved in this proteolytic processing, also referred to as ectodomain shedding, remain poorly characterized. In the present study, we examined the properties of the mCSF-1 sheddase in cell-based assays. Shedding of mCSF-1 was up-regulated by phorbol ester treatment and was inhibited by the metalloprotease inhibitors GM6001 and tissue inhibitor of metalloproteases 3. Moreover, the stimulated shedding of mCSF-1 was abrogated in fibroblasts lacking the TNF-alpha converting enzyme (TACE, also known as a disintegrin and metalloprotease 17) and was rescued by expression of wild-type TACE in these cells, strongly suggesting that the stimulated shedding is TACE dependent. Additionally, we observed that mCSF-1 is predominantly localized to intracellular membrane compartments and is efficiently internalized in a clathrin-dependent manner. These results indicate that the local availability of mCSF-1 is actively regulated by ectodomain shedding and endocytosis. This mechanism may have important implications for the development and survival of monocyte lineage cells.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • ADAM Proteins / antagonists & inhibitors
  • ADAM Proteins / metabolism*
  • ADAM17 Protein
  • Alternative Splicing / drug effects
  • Alternative Splicing / physiology
  • Animals
  • COS Cells
  • Carcinogens / pharmacology
  • Cell Survival / drug effects
  • Cell Survival / physiology
  • Chlorocebus aethiops
  • Clathrin / metabolism*
  • Dipeptides / pharmacology
  • Endocytosis / physiology*
  • Macrophage Colony-Stimulating Factor / metabolism*
  • Macrophages / metabolism*
  • Membrane Proteins / metabolism
  • Mice
  • Osteoclasts / metabolism*
  • Phorbol Esters / pharmacology
  • Protease Inhibitors / pharmacology
  • Protein Structure, Tertiary / physiology
  • Tissue Inhibitor of Metalloproteinase-3 / metabolism


  • Carcinogens
  • Clathrin
  • Dipeptides
  • Membrane Proteins
  • N-(2(R)-2-(hydroxamidocarbonylmethyl)-4-methylpentanoyl)-L-tryptophan methylamide
  • Phorbol Esters
  • Protease Inhibitors
  • Tissue Inhibitor of Metalloproteinase-3
  • Macrophage Colony-Stimulating Factor
  • ADAM Proteins
  • ADAM17 Protein
  • Adam17 protein, mouse