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Updated: Jul 9, 2026
A Model Membrane Platform for Reconstituting Mitochondrial Membrane Dynamics
Published on: September 2, 2020
Metalloprotease-mediated OPA1 processing is modulated by the mitochondrial membrane potential
Olwenn Guillery1, Florence Malka, Thomas Landes
1Inserm U582, 75651 Paris cedex 13, France.
Background Information:
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.
Insights
Mitochondrial OPA1 processing into short isoforms is regulated by inner membrane potential and mediated by the YME1L metalloprotease, impacting mitochondrial dynamics but not apoptosis.
Area of Science:
- Mitochondrial biology
- Protein processing
- Cellular dynamics
Background:
- Optic atrophy type 1 (OPA1) is a mitochondrial intermembrane space protein crucial for membrane fusion.
- OPA1 exists in multiple isoforms generated by alternative splicing and proteolytic processing, similar to its yeast counterpart Mgm1p.
- This study investigates the specific mechanisms and regulators of OPA1 proteolytic processing.
Purpose of the Study:
- To identify the proteases responsible for OPA1 processing.
- To determine the cellular conditions that regulate OPA1 processing.
- To elucidate the functional consequences of OPA1 processing on mitochondrial dynamics and apoptosis.
Main Methods:
- Analysis of OPA1 isoform patterns in various mammalian cell types.
- Investigation of OPA1 processing kinetics under conditions of altered mitochondrial membrane potential, oxidative phosphorylation, and glycolysis.
- Inhibition studies using heavy-metal chelators and genetic manipulation (knock-down, mutations) of candidate proteases (PARL, paraplegin, YME1L).
- Assessment of OPA1 interactions with mitofusins (Mfn1, Mfn2) and effects of OPA1 processing on apoptotic release of OPA1 and cytochrome c.
Main Results:
- Mammalian cells exhibit distinct long (L-OPA1) and short (S-OPA1) OPA1 isoforms.
- Loss of inner mitochondrial membrane potential triggers rapid L-OPA1 to S-OPA1 conversion.
- OPA1 processing is mediated by a metalloprotease, with YME1L identified as the likely protease, while PARL and paraplegin are not directly involved.
- OPA1 processing is stimulated during apoptosis but does not influence the release of OPA1 or cytochrome c.
- All OPA1 isoforms interact with Mfn1 and Mfn2, irrespective of membrane potential or processing state.
Conclusions:
- Metalloprotease-dependent processing of OPA1 is modulated by the mitochondrial inner membrane potential.
- The YME1L metalloprotease is the primary mediator of OPA1 processing.
- OPA1 processing is distinct from its role in apoptotic mitochondrial outer membrane permeabilization.
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