Mitochondria can synthesize phosphatidylethanolarnine (PE) through phosphatidylserine decarboxylase (PS decarboxylase) activity or can import this lipid from the endoplasmic reticulum. In this work, we studied the factors influencing the import of PE in brain mitochondria and its utilization for the assembly of mitochondrial membranes. Incubation of rat brain homogenate with [1-3H]ethanolamine resulted in the synthesis and distribution of 3H-PE to subcellular fractions. Twenty- one percent of labeled PE was recovered in purified mitochondria. The import of PE in mitochondria was studied in a reconstituted system made of microsomes (don or particles) and purified mitochondria (acceptor particles). Ca+2 and nonspecific lipid transfer protein purified from liver tissue (nsL-TP) enhanced the translocation processo 3H_PE synthesized in membrane associated to mitochondria (MAM) could also translocate to mitochondria in the reconstituted system. Exposure of mitochondria to trinitrobenzensulfonic acid (TNBS) resulted in the reaction of more than 60% of 3H_PE imported from endoplasmic reticulum and of about 25% of 14C_PE produced in mitochondria by decarboxylation of 14C_PS. Moreover, the removal of the outer mitochondrial membrane by digitonin treatment, resulted in the loss of 3H_PE, but not 14C_PE. These results indicate that labeled PE imported in mitochondria is mainly localized in the outer mitochondrial membrane, whereas PE produced by PS decarboxylase activity is confined to the inner rnitochondrial membrane. Phospholipase C hydrolyzed 25-30% of both PE radioactivity and mass of the outer mitochondrial membrane indicating an asymmetrical distribution of this lipid across the membrane.

Import of phosphatidylethanolamine for the assembly of rat brain mitochondrial membranes

CORAZZI, Lanfranco
1995

Abstract

Mitochondria can synthesize phosphatidylethanolarnine (PE) through phosphatidylserine decarboxylase (PS decarboxylase) activity or can import this lipid from the endoplasmic reticulum. In this work, we studied the factors influencing the import of PE in brain mitochondria and its utilization for the assembly of mitochondrial membranes. Incubation of rat brain homogenate with [1-3H]ethanolamine resulted in the synthesis and distribution of 3H-PE to subcellular fractions. Twenty- one percent of labeled PE was recovered in purified mitochondria. The import of PE in mitochondria was studied in a reconstituted system made of microsomes (don or particles) and purified mitochondria (acceptor particles). Ca+2 and nonspecific lipid transfer protein purified from liver tissue (nsL-TP) enhanced the translocation processo 3H_PE synthesized in membrane associated to mitochondria (MAM) could also translocate to mitochondria in the reconstituted system. Exposure of mitochondria to trinitrobenzensulfonic acid (TNBS) resulted in the reaction of more than 60% of 3H_PE imported from endoplasmic reticulum and of about 25% of 14C_PE produced in mitochondria by decarboxylation of 14C_PS. Moreover, the removal of the outer mitochondrial membrane by digitonin treatment, resulted in the loss of 3H_PE, but not 14C_PE. These results indicate that labeled PE imported in mitochondria is mainly localized in the outer mitochondrial membrane, whereas PE produced by PS decarboxylase activity is confined to the inner rnitochondrial membrane. Phospholipase C hydrolyzed 25-30% of both PE radioactivity and mass of the outer mitochondrial membrane indicating an asymmetrical distribution of this lipid across the membrane.
1995
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Utilizza questo identificativo per citare o creare un link a questo documento: https://hdl.handle.net/11391/102645
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