Inorganic polyphosphates in mitochondria |
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Authors: | T V Kulakovskaya L P Lichko V M Vagabov I S Kulaev |
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Institution: | 1.Skryabin Institute of Biochemistry and Physiology of Microorganisms,Russian Academy of Sciences,Pushchino, Moscow Region,Russia |
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Abstract: | Current data concerning the crucial role of inorganic polyphosphates (polyP) in mitochondrial functions and dysfunctions in
yeast and animal cells are reviewed. Biopolymers with short chain length (∼15 phosphate residues) were found in the mitochondria
of Saccharomyces cerevisiae. They comprised 7–10% of the total polyP content of the cell. The polyP are located in the membranes and intermembrane space
of mitochondria. The mitochondrial membranes possess polyP/Ca2+/polyhydroxybutyrate complexes. PolyP accumulation is typical of promitochondria but not of functionally active mitochondria.
Yeast mitochondria possess two exopolyphosphatases splitting Pi from the end of the polyP chain. One of them, encoded by the PPX1 gene, is located in the matrix; the other one, encoded by the PPN1 gene, is membrane-bound. Formation of well-developed mitochondria in the cells of S. cerevisiae after glucose depletion is accompanied by decrease in the polyP level and the chain length. In PPN1 mutants, the polyP chain length increased under glucose consumption, and the formation of well-developed mitochondria was
blocked. These mutants were defective in respiration functions and consumption of oxidizable carbon sources such as lactate
and ethanol. Since polyP is a compound with high-energy bonds, its metabolism vitally depends on the cell bioenergetics. The
maximal level of short-chain acid-soluble polyP was observed in S. cerevisiae under consumption of glucose, while the long-chain polyP prevailed under ethanol consumption. In insects, polyP in the mitochondria
change drastically during ontogenetic development, indicating involvement of the polymers in the regulation of mitochondrial
metabolism during ontogenesis. In human cell lines, specific reduction of mitochondrial polyP under expression of yeast exopolyphosphatase
PPX1 significantly modulates mitochondrial bioenergetics and transport. |
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