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OPA1 disease alleles causing dominant optic atrophy have defects in cardiolipin-stimulated GTP hydrolysis and membrane tubulation.

Ban T, Heymann JA, Song Z, Hinshaw JE, Chan DC - Hum. Mol. Genet. (2010)

Bottom Line: The dynamin-related GTPase OPA1 is mutated in autosomal dominant optic atrophy (DOA) (Kjer type), an inherited neuropathy of the retinal ganglion cells.The membrane tubulation activity of OPA1 is suppressed by GTPgammaS.OPA1 disease alleles associated with DOA display selective defects in several activities, including cardiolipin association, GTP hydrolysis and membrane tubulation.

View Article: PubMed Central - PubMed

Affiliation: Division of Biology, California Institute of Technology, Pasadena, CA 91125, USA.

ABSTRACT
The dynamin-related GTPase OPA1 is mutated in autosomal dominant optic atrophy (DOA) (Kjer type), an inherited neuropathy of the retinal ganglion cells. OPA1 is essential for the fusion of the inner mitochondrial membranes, but its mechanism of action remains poorly understood. Here we show that OPA1 has a low basal rate of GTP hydrolysis that is dramatically enhanced by association with liposomes containing negative phospholipids such as cardiolipin. Lipid association triggers assembly of OPA1 into higher order oligomers. In addition, we find that OPA1 can promote the protrusion of lipid tubules from the surface of cardiolipin-containing liposomes. In such lipid protrusions, OPA1 assemblies are observed on the outside of the lipid tubule surface, a protein-membrane topology similar to that of classical dynamins. The membrane tubulation activity of OPA1 is suppressed by GTPgammaS. OPA1 disease alleles associated with DOA display selective defects in several activities, including cardiolipin association, GTP hydrolysis and membrane tubulation. These findings indicate that interaction of OPA1 with membranes can stimulate higher order assembly, enhance GTP hydrolysis and lead to membrane deformation into tubules.

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Effects of DOA disease mutations in liposome-binding and GTP hydrolysis activity. (A) Liposome binding was measured by a liposome co-sedimentation assay, as in Fig. 2A. (B–D) GTP hydrolysis activity was measured at 300 mm NaCl (B), 0 mm NaCl (C) and 300 mm NaCl with cardiolipin-containing liposomes (D).
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DDQ088F6: Effects of DOA disease mutations in liposome-binding and GTP hydrolysis activity. (A) Liposome binding was measured by a liposome co-sedimentation assay, as in Fig. 2A. (B–D) GTP hydrolysis activity was measured at 300 mm NaCl (B), 0 mm NaCl (C) and 300 mm NaCl with cardiolipin-containing liposomes (D).

Mentions: To understand the molecular basis of these severe in vivo defects, we studied these alleles in vitro using the biochemical assays detailed earlier (Figs 6 and 7 and Supplementary Material, Fig. S4). Two alleles (V910D and L939P) were found to be almost completely insoluble when expressed in bacteria (data not shown), in contrast to wild-type OPA1-S1. These two alleles likely have a folding defect and were not studied further.


OPA1 disease alleles causing dominant optic atrophy have defects in cardiolipin-stimulated GTP hydrolysis and membrane tubulation.

Ban T, Heymann JA, Song Z, Hinshaw JE, Chan DC - Hum. Mol. Genet. (2010)

Effects of DOA disease mutations in liposome-binding and GTP hydrolysis activity. (A) Liposome binding was measured by a liposome co-sedimentation assay, as in Fig. 2A. (B–D) GTP hydrolysis activity was measured at 300 mm NaCl (B), 0 mm NaCl (C) and 300 mm NaCl with cardiolipin-containing liposomes (D).
© Copyright Policy - creative-commons
Related In: Results  -  Collection

License 1 - License 2
Show All Figures
getmorefigures.php?uid=PMC2865371&req=5

DDQ088F6: Effects of DOA disease mutations in liposome-binding and GTP hydrolysis activity. (A) Liposome binding was measured by a liposome co-sedimentation assay, as in Fig. 2A. (B–D) GTP hydrolysis activity was measured at 300 mm NaCl (B), 0 mm NaCl (C) and 300 mm NaCl with cardiolipin-containing liposomes (D).
Mentions: To understand the molecular basis of these severe in vivo defects, we studied these alleles in vitro using the biochemical assays detailed earlier (Figs 6 and 7 and Supplementary Material, Fig. S4). Two alleles (V910D and L939P) were found to be almost completely insoluble when expressed in bacteria (data not shown), in contrast to wild-type OPA1-S1. These two alleles likely have a folding defect and were not studied further.

Bottom Line: The dynamin-related GTPase OPA1 is mutated in autosomal dominant optic atrophy (DOA) (Kjer type), an inherited neuropathy of the retinal ganglion cells.The membrane tubulation activity of OPA1 is suppressed by GTPgammaS.OPA1 disease alleles associated with DOA display selective defects in several activities, including cardiolipin association, GTP hydrolysis and membrane tubulation.

View Article: PubMed Central - PubMed

Affiliation: Division of Biology, California Institute of Technology, Pasadena, CA 91125, USA.

ABSTRACT
The dynamin-related GTPase OPA1 is mutated in autosomal dominant optic atrophy (DOA) (Kjer type), an inherited neuropathy of the retinal ganglion cells. OPA1 is essential for the fusion of the inner mitochondrial membranes, but its mechanism of action remains poorly understood. Here we show that OPA1 has a low basal rate of GTP hydrolysis that is dramatically enhanced by association with liposomes containing negative phospholipids such as cardiolipin. Lipid association triggers assembly of OPA1 into higher order oligomers. In addition, we find that OPA1 can promote the protrusion of lipid tubules from the surface of cardiolipin-containing liposomes. In such lipid protrusions, OPA1 assemblies are observed on the outside of the lipid tubule surface, a protein-membrane topology similar to that of classical dynamins. The membrane tubulation activity of OPA1 is suppressed by GTPgammaS. OPA1 disease alleles associated with DOA display selective defects in several activities, including cardiolipin association, GTP hydrolysis and membrane tubulation. These findings indicate that interaction of OPA1 with membranes can stimulate higher order assembly, enhance GTP hydrolysis and lead to membrane deformation into tubules.

Show MeSH
Related in: MedlinePlus