title: Import of phosphatidylserine to and export of phosphatidylethanolamine molecular species from mitochondria.
abstract: Heavy isotope-labeled ethanolamine and serine as well as exogenous PE and PS species were used to study trafficking of phosphatidylethanolamine (PE) and -serine (PS) molecular species between the endoplasmic reticulum (ER) and mitochondria in HeLa cells. Import of both endogenous and exogenous PS to IMM was a relatively slow process (T1/2=several hours), but depended on the acyl chains. In particular, the 38:4 and 38:5 species were imported more efficiently compared to the other PS species. Knock-down of Mitofusin 2 or Mitostatin had no detectable effect on PS import to mitochondria, suggesting that the ER-mitochondria contacts regulated by these proteins are not essential. Knock-down of PS synthase 1 inhibited PS decarboxylation, suggesting that import of PS to mitochondria is coupled to its synthesis. Also the export of PE from IMM to microsomes is a relatively slow process, but again depends markedly on the acyl chain structure. Most notably, the polyunsaturated 38:4 and 38:5 PE species were less efficiently exported, which together with rapid import of the PS precursors most probably explains their enrichment in IMM. PE synthesized via the CDP-ethanolamine was also imported to IMM, but most of the PE in this membrane derives from imported PS. In contrast to PS, all PC species made in Golgi/ER translocated similarly and rapidly to IMM. In conclusion, selective translocation of PS species and PS-derived PE species between ER and mitochondria plays a major role in phospholipid homeostasis of these organelles.
authors.affiliation: Institute of Biomedicine, Department of Biochemistry and Developmental Biology, University of Helsinki, Helsinki, Finland.
authors.forename: Ville
authors.initials: V
authors.lastname: Kainu
authors.forename: Martin
authors.initials: M
authors.lastname: Hermansson
authors.forename: Satu
authors.initials: S
authors.lastname: Hänninen
authors.forename: Kati
authors.initials: K
authors.lastname: Hokynar
authors.forename: Pentti
authors.initials: P
authors.lastname: Somerharju
mesh_terms: D001692:Biological Transport; D006367:HeLa Cells; D006801:Humans; D013058:Mass Spectrometry; D008928:Mitochondria / Q000378:metabolism*; D010714:Phosphatidylethanolamines / Q000378:metabolism*; D010718:Phosphatidylserines / Q000378:metabolism*
chemical_list: D010714:Phosphatidylethanolamines; D010718:Phosphatidylserines