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Appropriate glycosylation of the fms gene product is a prerequisite for its transforming potency
Abstract:
Processing inhibitors of N-linked glycans were used to determine whether correct glycosylation of the oncogene product gp140v-fms, encoded by the McDonough strain of feline sarcoma virus (SM-FeSV), is required to maintain the oncogenic properties of v-fms. SM-FeSV-transformed cells treated with the glucosidase-I inhibitors N-methyldeoxynojirimycin (MdN) or castanospermine synthesized predominantly a gp125v-fms species which had a normal half life. The molecule was transported to the plasma membrane and exhibited normal kinase activity as determined by autophosphorylation. However, although no significant change in cell morphology of the SM-FeSV-transformed cells was observed in the presence of castanospermine, growth of these cells became strictly serum-dependent. In addition, growth in soft agar was drastically retarded despite the presence of 10% calf serum, indicating that the transformed properties of the cells were altered. In contrast, swainsonine, an inhibitor of the processing alpha-mannosidase-II, had no effect. Cells transformed by the Snyder Theilen strain of FeSV were used to demonstrate that the altered proliferative properties were directly linked to the modified structure of the fms gene product. Our data suggest that the extracellular domain of gp140v-fms plays a role in regulating cell proliferation.
Insights
Correct glycosylation of the feline sarcoma virus (SM-FeSV) v-fms oncogene product is crucial for maintaining oncogenic properties. Inhibiting specific N-linked glycan processing alters cell proliferation and serum dependence.
Area of Science:
- Molecular Biology
- Virology
- Cell Biology
Background:
- The oncogene product gp140v-fms, encoded by the McDonough strain of feline sarcoma virus (SM-FeSV), is critical for cell transformation.
- N-linked glycosylation is a key post-translational modification affecting protein function and localization.
Purpose of the Study:
- To investigate the role of correct N-linked glycan processing of gp140v-fms in maintaining the oncogenic properties of SM-FeSV.
- To determine if alterations in glycosylation affect the protein's stability, localization, kinase activity, and transforming potential.
Main Methods:
- Treatment of SM-FeSV-transformed cells with glucosidase-I inhibitors (N-methyldeoxynojirimycin and castanospermine) and alpha-mannosidase-II inhibitor (swainsonine).
- Analysis of gp125v-fms species synthesis, half-life, plasma membrane transport, and kinase activity.
- Assessment of cell morphology, serum dependence, and soft agar growth.
Main Results:
- Glucosidase-I inhibition resulted in a gp125v-fms species with normal half-life, membrane transport, and kinase activity.
- Castanospermine treatment led to serum-dependent growth and significantly reduced soft agar colony formation, indicating altered transformed properties.
- Swainsonine had no discernible effect on the transformed cells.
Conclusions:
- Correct N-linked glycosylation of gp140v-fms, specifically processing by glucosidase-I, is essential for full expression of oncogenic properties.
- The extracellular domain of gp140v-fms appears to play a regulatory role in cell proliferation, influenced by its glycosylation status.