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

• Published in: The Journal of immunology (1950) 2007-11, Vol.179 (10), p.6715-6724
• Main Authors: Horiuchi, Keisuke, Miyamoto, Takeshi, Takaishi, Hironari, Hakozaki, Akihiro, Kosaki, Naoto, Miyauchi, Yoshiteru, Furukawa, Mitsuru, Takito, Jiro, Kaneko, Hironori, Matsuzaki, Kenichiro, Morioka, Hideo, Blobel, Carl P, Toyama, Yoshiaki
• Format: Article
• Language: English
• Subjects: ADAM Proteins - antagonists & inhibitors; ADAM Proteins - metabolism; ADAM17 Protein; Alternative Splicing - drug effects; Alternative Splicing - physiology; Animals; Carcinogens - pharmacology; Cell Survival - drug effects; Cell Survival - physiology; Cercopithecus aethiops; Clathrin - metabolism; COS Cells; 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
• ISSN: 0022-1767; 1550-6606
• 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.