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Subcellular distribution of mouse mevalonate pyrophosphate decarboxylase
Akihiro Michihara1, Kenji Akasaki, Yukio Yamori
1Faculty of Pharmacy and Pharmaceutical Sciences, Fukuyama University, Hiroshima, Japan. mitihara@fupharm.fukuyama-u.ac.jp
Abstract:
Mevalonate pyrophosphate decarboxylase (MPD) is considered to be a cytosolic protein. Recently, other groups reported that MPD is mostly located in the peroxisomes. In this study, we examined whether the expression of MPD in mice depends on the proliferation of peroxisomes, and whether MPD is predominantly located in the peroxisomes or the cytosol of mice. No increase in the protein level of MPD was observed in the crude extract of the livers of mice administered with peroxisome proliferative drugs. The result suggests that the expression of MPD is independent of the proliferation of peroxisomes, and may be maintained via a specific regulatory mechanism, different from the regulation of the expression of peroxisome proliferator-activated receptor alpha. When the subcellular distribution of MPD in mouse melanoma (B16F10) cells was examined by cell fractionation, MPD was detected in the cytosol of B16F10 cells, but not in the peroxisomes. In permeabilized B16F10 cells treated with digitonin, which lack cytosolic enzymes, 80% and 20% of MPD, 75% and 25% of lactate dehydrogenase, or 2% and 98% of catalase, existed in the medium and in the cell, respectively. From these results, it indicated that MPD was predominantly located in the cytosol and did not exist in the peroxisomes of B16F10 cells.
Insights
Mevalonate pyrophosphate decarboxylase (MPD) is not upregulated by peroxisome proliferators in mice. Further studies confirm MPD is primarily located in the cytosol, not peroxisomes, in mouse melanoma cells.
Area of Science:
- Biochemistry
- Cell Biology
- Molecular Biology
Background:
- Mevalonate pyrophosphate decarboxylase (MPD) has been traditionally considered a cytosolic protein.
- Recent studies have suggested a predominant localization of MPD within peroxisomes.
Purpose of the Study:
- To investigate the dependence of MPD expression on peroxisome proliferation in mice.
- To determine the predominant subcellular localization of MPD in mouse tissues and cells.
Main Methods:
- Administering peroxisome proliferative drugs to mice and analyzing liver crude extracts for MPD levels.
- Employing cell fractionation techniques to isolate subcellular components of mouse melanoma (B16F10) cells.
- Utilizing digitonin permeabilization to assess the cytosolic or pellet fraction distribution of MPD, lactate dehydrogenase, and catalase.
Main Results:
- MPD protein levels in mouse liver crude extracts did not increase following administration of peroxisome proliferative drugs.
- Cell fractionation of B16F10 cells revealed MPD exclusively in the cytosol, with no detectable presence in peroxisomes.
- Digitonin permeabilization experiments showed that 80% of MPD was released into the medium, indicating a cytosolic localization, unlike catalase which remained in the cell pellet.
Conclusions:
- MPD expression is independent of peroxisome proliferation and may be regulated by distinct mechanisms.
- MPD is predominantly localized in the cytosol of mouse melanoma cells.
- The findings challenge previous reports suggesting a primary peroxisomal localization for MPD.