Metalloprotease-mediated OPA1 processing is modulated by the mitochondrial membrane potential.
BACKGROUND
Human OPA1 (optic atrophy type 1) is a dynamin-related protein of the mitochondrial IMS (intermembrane space) involved in membrane fusion and remodelling. Similarly to its yeast orthologue Mgm1p that exists in two isoforms generated by the serine protease Pcp1p/Rbd1p, OPA1 exists in various isoforms generated by alternative splicing and processing. In the present paper, we focus on protease processing of OPA1.


RESULTS
We find that various mammalian cell types display a similar pattern of OPA1 isoforms [two L-OPA1 (long isoforms of OPA1) and three S-OPA1 (short isoforms of OPA1)] and that loss of the inner membrane potential, but not inhibition of oxidative phosphorylation or glycolysis, induces rapid and complete processing of L-OPA1 to S-OPA1. In isolated mitochondria, OPA1 processing was inhibited by heavy-metal chelators, pointing to processing by a mitochondrial metalloprotease. The pattern of OPA1 isoforms and its processing kinetics were normal in mitochondria devoid of the serine protease PARL (presenilins-associated rhomboid-like protein) - the human orthologue of Pcp1/Rbd1 - and in cells from patients carrying homozygous mutations in SPG7 (spastic paraplegia type 7), a gene encoding the matrix-oriented metalloprotease paraplegin. In contrast, OPA1 processing kinetics were delayed upon knock-down of YME1L (human yme1-like protein), an IMS-oriented metalloprotease. OPA1 processing was also stimulated during apoptosis, but inhibition of this processing did not affect apoptotic release of OPA1 and cytochrome c. Finally, we show that all OPA1 isoforms interact with Mfn1 (mitofusin 1) and Mfn2 and that these interactions are not affected by dissipation of DeltaPsim (inner mitochondrial membrane potential) or OPA1 processing.


CONCLUSIONS
Metalloprotease-mediated processing of OPA1 is modulated by the inner membrane potential and is likely to be mediated by the YME1L protease.
Guillery
Olwenn
O
Inserm U582, 75651 Paris cedex 13, France.
Malka
Florence
F
Landes
Thomas
T
Guillou
Emmanuelle
E
Blackstone
Craig
C
Lombès
Anne
A
Belenguer
Pascale
P
Arnoult
Damien
D
Rojo
Manuel
M
D000074183:ATPases Associated with Diverse Cellular Activities; D020558:GTP Phosphohydrolases / Q000378:metabolism*; D006367:HeLa Cells; D006801:Humans; D053078:Membrane Potential, Mitochondrial / Q000502:physiology*; D008565:Membrane Proteins / Q000378:metabolism; D026901:Membrane Transport Proteins / Q000378:metabolism; D008666:Metalloendopeptidases / Q000378:metabolism*; D045726:Metalloproteases / Q000378:metabolism*; D033681:Mitochondrial Membrane Transport Proteins; D051336:Mitochondrial Membranes / Q000201:enzymology*; D024101:Mitochondrial Proteins / Q000378:metabolism; D008969:Molecular Sequence Data; D020033:Protein Isoforms / Q000378:metabolism; D011499:Protein Processing, Post-Translational; D034622:RNA Interference / Q000502:physiology; D020133:Reverse Transcriptase Polymerase Chain Reaction
D008565:Membrane Proteins; D026901:Membrane Transport Proteins; D033681:Mitochondrial Membrane Transport Proteins; D024101:Mitochondrial Proteins; D020033:Protein Isoforms; D045726:Metalloproteases; D008666:Metalloendopeptidases; C410807:YME1L1 protein, human; D020558:GTP Phosphohydrolases; C470018:MFN2 protein, human; C415198:OPA1 protein, human; D000074183:ATPases Associated with Diverse Cellular Activities; C470017:Mfn1 protein, human