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Phosphatidic acid synthesis in mitochondria. Topography of formation and transmembrane migration
T R Chakraborty1, A Vancura, V S Balija
1Department of Biological Sciences, St. John's University, Jamaica, New York 11439, USA.
Abstract:
The topography of formation and migration of phosphatidic acid (PA) in the transverse plane of rat liver mitochondrial outer membrane (MOM) were investigated. Isolated mitochondria and microsomes, incubated with sn-glycerol 3-phosphate and an immobilized substrate palmitoyl-CoA-agarose, synthesized both lyso-PA and PA. The mitochondrial and microsomal acylation of glycerophosphate with palmitoyl-CoA-agarose was 80-100% of the values obtained in the presence of free palmitoyl-CoA. In another series of experiments, both free polymyxin B and polymyxin B-agarose stimulated mitochondrial glycerophosphate acyltransferase activity approximately 2-fold. When PA loaded mitochondria were treated with liver fatty acid binding protein, a fifth of the phospholipid left the mitochondria. The amount of exportable PA reduced with the increase in the time of incubation. In another approach, PA-loaded mitochondria were treated with phospholipase A(2). The amount of phospholipase A(2)-sensitive PA reduced when the incubation time was increased. Taken together, the results suggest that lysophosphatidic acid (LPA) and PA are synthesized on the outer surface of the MOM and that PA moves to the inner membrane presumably for cardiolipin formation.
Insights
Phosphatidic acid (PA) and lysophosphatidic acid (LPA) are synthesized on the outer mitochondrial membrane. PA then moves inward, likely for cardiolipin synthesis, with export influenced by incubation time.
Area of Science:
- Biochemistry
- Cell Biology
- Mitochondrial Research
Background:
- Phosphatidic acid (PA) is a key lipid intermediate.
- Mitochondrial membranes play crucial roles in cellular metabolism and signaling.
- Understanding lipid synthesis and trafficking within mitochondria is essential.
Purpose of the Study:
- To investigate the formation and migration of phosphatidic acid (PA) in rat liver mitochondrial outer membrane (MOM).
- To determine the localization of PA synthesis and its subsequent movement within the mitochondria.
Main Methods:
- Incubation of isolated mitochondria and microsomes with sn-glycerol 3-phosphate and immobilized palmitoyl-CoA-agarose.
- Assay of mitochondrial glycerophosphate acyltransferase activity using free and immobilized substrates.
- Treatment of PA-loaded mitochondria with liver fatty acid binding protein and phospholipase A(2).
Main Results:
- Mitochondria and microsomes synthesized lyso-PA and PA using immobilized palmitoyl-CoA-agarose.
- Acylation activity with immobilized substrate was comparable to free palmitoyl-CoA.
- Polymyxin B, free or immobilized, stimulated mitochondrial glycerophosphate acyltransferase activity.
- PA export from mitochondria decreased with increased incubation time.
- Phospholipase A(2)-sensitive PA also decreased with increased incubation time.
Conclusions:
- Lysophosphatidic acid (LPA) and PA are synthesized on the outer surface of the mitochondrial outer membrane (MOM).
- Synthesized PA translocates to the inner mitochondrial membrane.
- This translocation is presumed to be for cardiolipin formation.