Phosphatidylserine flipping by the P4-ATPase ATP8A2 is electrogenic.

Autor:	Tadini-Buoninsegni F; Department of Chemistry Ugo Schiff, University of Florence, 50019 Sesto Fiorentino, Italy., Mikkelsen SA; Department of Biomedicine, Aarhus University, DK-8000 Aarhus C, Denmark., Mogensen LS; Department of Biomedicine, Aarhus University, DK-8000 Aarhus C, Denmark., Molday RS; Department of Biochemistry and Molecular Biology, University of British Columbia, Vancouver, BC V6T 1Z3, Canada.; Department of Ophthalmology and Visual Sciences, Centre for Macular Research, University of British Columbia, Vancouver, BC V5Z 3N9, Canada., Andersen JP; Department of Biomedicine, Aarhus University, DK-8000 Aarhus C, Denmark; jpa@biomed.au.dk.
Jazyk:	angličtina
Zdroj:	Proceedings of the National Academy of Sciences of the United States of America [Proc Natl Acad Sci U S A] 2019 Aug 13; Vol. 116 (33), pp. 16332-16337. Date of Electronic Publication: 2019 Aug 01.
DOI:	10.1073/pnas.1910211116
Abstrakt:	Phospholipid flippases (P4-ATPases) utilize ATP to translocate specific phospholipids from the exoplasmic leaflet to the cytoplasmic leaflet of biological membranes, thus generating and maintaining transmembrane lipid asymmetry essential for a variety of cellular processes. P4-ATPases belong to the P-type ATPase protein family, which also encompasses the ion transporting P2-ATPases: Ca 2+ -ATPase, Na + ,K + -ATPase, and H + ,K + -ATPase. In comparison with the P2-ATPases, understanding of P4-ATPases is still very limited. The electrogenicity of P4-ATPases has not been explored, and it is not known whether lipid transfer between membrane bilayer leaflets can lead to displacement of charge across the membrane. A related question is whether P4-ATPases countertransport ions or other substrates in the opposite direction, similar to the P2-ATPases. Using an electrophysiological method based on solid supported membranes, we observed the generation of a transient electrical current by the mammalian P4-ATPase ATP8A2 in the presence of ATP and the negatively charged lipid substrate phosphatidylserine, whereas only a diminutive current was generated with the lipid substrate phosphatidylethanolamine, which carries no or little charge under the conditions of the measurement. The current transient seen with phosphatidylserine was abolished by the mutation E198Q, which blocks dephosphorylation. Likewise, mutation I364M, which causes the neurological disorder cerebellar ataxia, mental retardation, and disequilibrium (CAMRQ) syndrome, strongly interfered with the electrogenic lipid translocation. It is concluded that the electrogenicity is associated with a step in the ATPase reaction cycle directly involved in translocation of the lipid. These measurements also showed that no charged substrate is being countertransported, thereby distinguishing the P4-ATPase from P2-ATPases. Competing Interests: The authors declare no conflict of interest.
Databáze:	MEDLINE
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