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Cell specific transformation by c-fms activating loop mutations is attributable to constitutive receptor degradation
G M Morley1, M Uden, W J Gullick
1Cell Signalling Unit, Division of Paediatrics, Obstetrics and Gynaecology, Imperial College School of Medicine, Hammersmith Hospital, London, UK.
Oncogene
|May 26, 1999
Summary
A specific mutation in the macrophage-colony stimulating factor receptor (M-CSF receptor) transforms certain cells but not others. This cell-specific transformation is linked to receptor degradation, revealing a key mechanism in cell signaling.
Area of Science:
- Molecular Biology
- Cell Biology
- Biochemistry
Background:
- The macrophage-colony stimulating factor receptor (M-CSF receptor, c-FMS) plays a crucial role in hematopoietic cell development and function.
- Activating mutations in the M-CSF receptor kinase domain can lead to oncogenic transformation.
- The D802V mutation in the M-CSF receptor's activating loop is known to potently transform hematopoietic cells but not fibroblasts.
Purpose of the Study:
- To investigate the mechanism behind the cell-specific transformation induced by the D802V M-CSF receptor mutation.
- To determine the role of receptor degradation in the observed differential cellular response.
- To explore the impact of various amino acid substitutions at position 802 on receptor activity and stability.
Main Methods:
- Cassette mutagenesis was employed to substitute aspartate 802 with all other 19 amino acids in the M-CSF receptor.
- Mutant receptors were expressed and tested for their ability to transform the FDC-P1 hematopoietic cell line and Rat-2 fibroblast cell line.
- Receptor degradation was assessed for different mutant forms.
- Site-directed mutagenesis was used to introduce point mutations or deletions at Y708 within the kinase insert region of the D802V mutant.
Main Results:
- Hydrophobic amino acid substitutions at position 802 potently transformed FDC-P1 cells but failed to transform Rat-2 fibroblasts.
- These transforming substitutions were associated with increased receptor degradation in fibroblasts.
- Modifications at Y708 partially inhibited receptor degradation of the D802V mutant.
- Stabilized D802V receptor derivatives acquired the ability to transform both FDC-P1 cells and Rat-2 fibroblasts.
Conclusions:
- The cell-specific effect of the c-fmsD802V activating loop mutation is attributed to receptor degradation.
- Kinase activation coupled with receptor degradation prevents fibroblast transformation but not hematopoietic cell transformation.
- Receptor stability is a critical determinant of oncogenic potential in different cell types.