Abstract
The product of the open reading frame YPL206c, Pgc1p, of the yeast Saccharomyces cerevisiae displays homology to bacterial and mammalian glycerophosphodiester phosphodiesterases. Deletion of PGC1 causes an accumulation of the anionic phospholipid, phosphatidylglycerol (PG), especially under conditions of inositol limitation. This PG accumulation was not caused by increased production of phosphatidyl-glycerol phosphate or by decreased consumption of PG in the formation of cardiolipin, the end product of the pathway. PG accumulation in the pgc1Delta strain was caused rather by inactivation of the PG degradation pathway. Our data demonstrate an existence of a novel regulatory mechanism in the cardiolipin biosynthetic pathway in which Pgc1p is required for the removal of excess PG via a phospholipase C-type degradation mechanism.
Highlights
Cardiolipin (CL)2 is a major mitochondrial anionic phospholipid with important functions in promoting cell growth, anaerobic metabolism, mitochondrial function, and biogenesis [1, 2]
The use of osmotic stabilizers in the growth medium alleviated reported inability of pgs1⌬ mutant to grow in the presence of ethidium bromide [27], demonstrating that mitochondrial anionic phospholipids and functional mitochondria are required for cell wall biogenesis [28]
Degradation of PG to DAG and Glycerophosphate Is Decreased upon Deletion of PGC1—Because deletion of PGC1 had no effect upon CL formation or in vitro measured Phosphatidylglycerol phosphate (PGP) synthase activity, we explored the possibility that the PGC1 gene product is involved in PG turnover
Summary
It is believed that PG can substitute for CL in most cellular functions in yeast, as demonstrated by the absence of any gross mitochondrial dysfunction in crd1⌬ mutant [5, 8, 9]. Not all CL functions can be substituted for by PG, because a CL-deficient mutant has decreased mitochondrial membrane potential, decreased maximum respiratory rate, and decreased ATPase and cytochrome c activities [25] Absence of both PG and CL, as occurs in a PGS1/PEL1 deletion mutant, causes more severe phenotypes: dependence on a fermentable carbon source for growth, temperature sensitivity, and “petite lethality” [7, 26]. In this study we report that the product of ORF YPL206c (here named PGC1 for phosphatidylglycerol phospholipase C) controls the PG content of membranes via a phospholipase C-type degradation mechanism. This conclusion is based on the following observations. Nor formation of CL from PG are changed. (ii) An in vitro assay to monitor PG degradation products shows that yeast extracts devoid of Pgc1p exhibit much less PG-oriented phospholipase C activity compared with wild-type yeast extracts
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