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Updated: Jul 18, 2026
Spatial and Temporal Control of Murine Melanoma Initiation from Mutant Melanocyte Stem Cells
Published on: June 7, 2019
Decrease of cholesterol in mouse melanoma causes secretion of lysosomal enzymes
Akihiro Michihara1, Ken Toda, Michihisa Suenobu
1Faculty of Pharmacy and Pharmaceutical Sciences, Fukuyama University, Fukuyama, Hiroshima 729-0292, Japan. mitihara@fupharm.fukuyama-u.ac.jp
Abstract:
We examined the change in the subcellular distribution of a lysosomal enzyme, beta-glucuronidase (beta-G), caused by decreased cholesterol levels in mouse melanoma cells using an HMG-CoA reductase inhibitor, lovastatin and lipoprotein-deficient serum (LDS). There was a decrease in the cholesterol content of the cells and increased secretion of the mature form of beta-G located in lysosomes, as documented by Percoll density gradient fractionation, digitonin permeabilization and immunoprecipitation. Furthermore, another lysosomal enzyme, cathepsin H, was found to be released in the medium from cells treated with lovastatin. Both the precursor and mature forms of cathepsin H were detected in the medium of treated cells. Next, when cells were treated with LDS without lovastatin, concomitantly with the decrease in the levels of cholesterol and beta-G activity in the cells, beta-G activity in the medium increased. Also, the ratio of beta-G (3.2-fold) released in the medium from cells treated with Dulbecco's modified Eagle medium (D-MEM) containing lovastatin and LDS was higher than that (2.3-fold) on treatment with D-MEM containing LDS without lovastatin. From these results, it was suggested that the exocytosis of mature enzymes from lysosomes into the medium or mis-sorting of the lysosomal precursor forms to the medium was caused by the lovastatin- and/or LDS-induced decrease in the cholesterol content of the cells, although the mechanism of secretion by lysosomal enzymes differed somewhat.
Insights
Decreased cholesterol in mouse melanoma cells, induced by lovastatin or lipoprotein-deficient serum, increases the secretion of lysosomal enzymes like beta-glucuronidase and cathepsin H. This suggests cholesterol depletion affects enzyme release mechanisms.
Area of Science:
- Cell Biology
- Biochemistry
- Molecular Biology
Background:
- Cholesterol is crucial for cellular membrane integrity and function.
- Lysosomal enzymes play vital roles in cellular degradation processes.
- Altering cellular cholesterol levels can impact organelle function and protein trafficking.
Purpose of the Study:
- To investigate how reduced cellular cholesterol affects the subcellular distribution and secretion of lysosomal enzymes.
- To determine the role of cholesterol depletion in the release of beta-glucuronidase and cathepsin H from mouse melanoma cells.
Main Methods:
- Treatment of mouse melanoma cells with lovastatin (HMG-CoA reductase inhibitor) and/or lipoprotein-deficient serum (LDS) to decrease cholesterol levels.
- Analysis of beta-glucuronidase (beta-G) and cathepsin H secretion using Percoll density gradient fractionation, digitonin permeabilization, and immunoprecipitation.
- Quantification of enzyme activity in both cellular fractions and the culture medium.
Main Results:
- Lovastatin and LDS treatment significantly decreased cellular cholesterol content.
- Both beta-glucuronidase and cathepsin H showed increased secretion into the medium following cholesterol reduction.
- Evidence suggested both exocytosis of mature enzymes and potential mis-sorting of precursor forms from lysosomes.
Conclusions:
- A decrease in cellular cholesterol content, induced by lovastatin or LDS, triggers the release of lysosomal enzymes.
- Cholesterol depletion appears to disrupt normal lysosomal trafficking, leading to enhanced enzyme secretion.
- The findings highlight a novel mechanism linking cholesterol homeostasis to lysosomal enzyme secretion pathways.
