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Sulfur-containing macromolecules in cultured monocyte-like cells
1Department of Tumour Biology, Norwegian Cancer Society, University of Tromsø, Norway.
Acta Histochemica
|January 1, 1988
Summary
U-937 cells, a monocytic cell line, do not store proteoglycans intracellularly, even when induced to differentiate. These cells release newly synthesized proteoglycans into the surrounding medium.
Area of Science:
- Cell Biology
- Biochemistry
- Electron Microscopy
Background:
- The monocytic cell line U-937 is a model for studying monocyte/macrophage differentiation.
- Mastocytoma cells are known to produce heparin and contain sulfur-rich granules.
Purpose of the Study:
- To investigate the intracellular storage of proteoglycans in U-937 cells.
- To compare proteoglycan synthesis and storage in U-937 cells versus mastocytoma cells.
Main Methods:
- U-937 cells were cultured in vitro with or without phorbol myristate acetate (PMA) to induce differentiation.
- Transmission scanning electron microscopy was used to examine intracellular structures.
- Cells were pulsed with 35S-sulfate and chased to track proteoglycan synthesis and release.
Main Results:
- U-937 cells, both control and PMA-treated, lacked the electron-dense, sulfur-containing granules observed in mastocytoma cells.
- 35S-proteoglycans increased in the culture medium of U-937 cells over time.
- No significant intracellular accumulation of 35S-proteoglycans was detected.
Conclusions:
- U-937 cells do not appear to store proteoglycans intracellularly.
- Synthesized proteoglycans are released into the extracellular medium by U-937 cells, regardless of differentiation status.
- This suggests a distinct mechanism of proteoglycan handling compared to cell types with intracellular storage granules.