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Inhibition of epithelial cell death in the secondary palate in vitro by alteration of lysosome function
Abstract:
The secondary palate in vivo and in vitro exhibits selective cell death at its medialedge epithelium (MEE) at a precise developmental age. This epithelial degeneration is mediated, in part, by MEE lysosomes. Previous studies in vitro (27) showed that the glutamine analogue, diazo-oxo-norleucine (DON), prevented MEE cell death by inhibiting glucosamine synthesis and thereby the glycosylation of proteins without affecting either the synthesis or activity of palatal lysosomal enzymes. In the present study, histochemical examination of MEE from DON treated day-15 rat palates demonstrated that acid phosphatase activity was restricted to Golgi saccules and associated vesicles as well as to lysosomes. Control MEE had reaction product in these structures and distributed diffusely throughout the cytoplasm of degenerating cells. DON treatment therefore appears to alter the intracellular distribution of lysosomal enzymes. Since DON treatment appears to have prevented MEE cell death by inhibiting glycosylation of proteins, glycosylation of lysosomal membranes or lysosomal enzymes may be essential for its role in programmed cell death.
Insights
Diazo-oxo-norleucine (DON) prevents programmed cell death in medial edge epithelium (MEE) by inhibiting protein glycosylation. This suggests glycosylation is crucial for lysosomal function in programmed cell death during palate development.
Area of Science:
- Developmental Biology
- Cell Biology
- Biochemistry
Background:
- Programmed cell death in the medial edge epithelium (MEE) is essential for secondary palate fusion.
- Lysosomes play a role in MEE cell death.
- Inhibition of glucosamine synthesis by diazo-oxo-norleucine (DON) prevents MEE cell death in vitro.
Purpose of the Study:
- To investigate the effect of DON on lysosomal enzyme distribution in MEE in vivo.
- To explore the role of protein glycosylation in MEE programmed cell death.
Main Methods:
- Histochemical examination of medial edge epithelium (MEE) from day-15 rat palates.
- Treatment with diazo-oxo-norleucine (DON) to inhibit glucosamine synthesis.
Main Results:
- DON treatment restricted acid phosphatase activity to Golgi saccules, vesicles, and lysosomes in MEE.
- Control MEE showed diffuse acid phosphatase distribution throughout the cytoplasm.
- DON altered the intracellular distribution of lysosomal enzymes.
Conclusions:
- DON treatment prevents MEE cell death, likely by inhibiting protein glycosylation.
- Glycosylation of lysosomal membranes or enzymes may be essential for their role in programmed cell death during palate development.