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Modulation of cellular glycosidase activity by hyperthermia
K J Henle1, R J Shmookler Reis, C K Lumpkin
1Department of Medicine, University of Arkansas for Medical Sciences, Little Rock 72205-5484.
Summary
Mild heat stress (hyperthermia) selectively impacts lysosomal enzymes in CHO cells. Alpha-mannosidase activity significantly increases, while other glycosidases show minimal changes, suggesting distinct cellular responses to heat.
Area of Science:
- Cell Biology
- Biochemistry
- Enzymology
Background:
- Lysosomes are key organelles involved in cellular degradation.
- Glycosidases are enzymes crucial for breaking down complex molecules within lysosomes.
- Cellular responses to environmental stressors like heat are critical for survival.
Purpose of the Study:
- To investigate the impact of hyperthermia on specific lysosomal glycosidases in Chinese Hamster Ovary (CHO) cells.
- To determine if heat stress affects different glycosidases (beta-galactosidase, beta-hexosaminidase, beta-glucuronidase, alpha-mannosidase) uniformly.
- To explore the role of thermotolerance in modulating heat sensitivity of these enzymes.
Main Methods:
- Exposure of CHO cells to 45°C hyperthermia for varying durations.
- Assay of specific glycosidase activities (beta-galactosidase, beta-hexosaminidase, beta-glucuronidase, alpha-mannosidase).
- Histochemical staining to assess intracellular enzyme localization and redistribution.
Main Results:
- Lysosomal alpha-mannosidase activity dramatically increased post-hyperthermia in a dose-dependent manner.
- Beta-glucuronidase, beta-galactosidase, and beta-hexosaminidase activities showed minimal alterations after heat exposure.
- Thermotolerance enhanced beta-galactosidase heat resistance but increased alpha-mannosidase heat sensitivity.
- Mild hyperthermia induced a significant redistribution of intracellular beta-galactosidase, but not beta-glucuronidase.
Conclusions:
- Hyperthermia does not non-specifically activate lysosomes; rather, it differentially affects specific lysosomal glycosidases.
- Cells possess lysosomal subpopulations with distinct heat sensitivities and glycosidase compositions.
- Alpha-mannosidase represents a heat-sensitive lysosomal enzyme with a notable response to hyperthermia.