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p150Ship, a signal transduction molecule with inositol polyphosphate-5-phosphatase activity
M N Lioubin1, P A Algate, S Tsai
1Fred Hutchinson Cancer Research Center, Seattle, Washington 98104, USA.
Abstract:
The production, survival, and function of monocytes and macrophages is regulated by the macrophage colony-stimulating factor (M-CSF or CSF-1) through its tyrosine kinase receptor Fms. Binding of M-CSF to Fms induces the tyrosine phosphorylation and association of a 150-kD protein with the phosphotyrosine-binding (PTB) domain of Shc. We have cloned p150 using a modified yeast two-hybrid screen. p150 contains one SH2 domain, two potential PTB-binding sites, an ATP/GTP-binding domain, several potential SH3-binding sites, and a domain with homology to inositol polyphosphate-5-phosphatases. p150 antibodies detect this protein in FDC-P1 myeloid cells, but the same protein is not detectable in fibroblasts. The antibodies immunoprecipitate a 150-kD protein from quiescent or M-CSF-stimulated FDC-P1 cells that hydrolyzes PtdIns(3,4,5)P3, to PtdIns(3,4)P2. This activity is observed in Shc immunoprecipitates only after M-CSF stimulation. Retroviral expression of p15O in FD-Fms cells results in strong inhibition of cell growth in M-CSF and a lesser inhibition in IL-3. Ectopic expression of p150 in fibroblasts does not inhibit growth. This novel protein, p150(ship) (SH2-containing inositol phosphatase), identifies a component of a new growth factor-receptor signaling pathway in hematopoietic cells.
Insights
Macrophage colony-stimulating factor (M-CSF) signaling involves a novel protein, p150(ship), an inositol phosphatase. This protein regulates hematopoietic cell growth, identifying a new signaling pathway.
Area of Science:
- Hematopoiesis
- Cell Signaling
- Molecular Biology
Background:
- Macrophage colony-stimulating factor (M-CSF) regulates monocyte and macrophage production, survival, and function via its receptor, Fms.
- M-CSF binding to Fms triggers tyrosine phosphorylation and association of a 150-kD protein with the Shc phosphotyrosine-binding (PTB) domain.
Purpose of the Study:
- To clone and characterize the novel 150-kD protein involved in M-CSF/Fms signaling.
- To elucidate the function and cellular localization of this protein in hematopoietic cells.
Main Methods:
- Yeast two-hybrid screening to clone the p150 protein.
- Antibody generation and immunoprecipitation to detect and assay protein activity.
- Retroviral expression in cell lines (FDC-P1, FD-Fms) to assess growth effects.
Main Results:
- Cloned p150, containing SH2, PTB-binding, ATP/GTP-binding, SH3-binding sites, and inositol polyphosphate-5-phosphatase homology.
- p150 protein detected in myeloid cells (FDC-P1) but not fibroblasts.
- p150 exhibits phosphatidylinositol 3,4,5-trisphosphate 3-phosphatase activity, hydrolyzing PtdIns(3,4,5)P3 to PtdIns(3,4)P2.
- This enzymatic activity is M-CSF-dependent and associated with Shc immunoprecipitates.
- p150 expression inhibits M-CSF-induced growth in FD-Fms cells and IL-3-induced growth to a lesser extent.
Conclusions:
- Identified a novel protein, p150(ship) (SH2-containing inositol phosphatase), as a key component in M-CSF/Fms signaling.
- p150(ship) possesses inositol phosphatase activity crucial for regulating hematopoietic cell growth.
- This discovery reveals a new growth factor-receptor signaling pathway in hematopoietic cells.