Biology subjects

Janer, A.

Publications and source records attributed to Janer, A..

4 recordsLinked to original sources

bioRxiv2023

BOLA3 and NFU1 link mitoribosome iron-sulfur cluster assembly to multiple mitochondrial dysfunctions syndrome

The human mitochondrial ribosome contains three [2Fe-2S] clusters whose assembly pathway, role, and implications for mitochondrial and metabolic diseases are unknown. Here, structure-function correlation studies show that the clusters play a structural role during mitoribosome assembly. To uncover the assembly pathway, we have examined the effect of silencing the expression of Fe-S cluster biosynthetic and delivery factors on mitoribosome stability. We find that the mitoribosome receives its [2Fe-2S] clusters from the GLRX5-BOLA3 node. Additionally, the assembly of the small subunit depends on the mitoribosome biogenesis factor METTL17, recently reported containing a [4Fe-4S] cluster, which we propose is inserted via the ISCA1-NFU1 node. Consistently, fibroblasts from subjects suffering from "multiple mitochondrial dysfunction" syndrome due to mutations in BOLA3 or NFU1 display previously unrecognized attenuation of mitochondrial protein synthesis that contributes to their cellular and pathophysiological phenotypes. Finally, we report that, in addition to their structural role, one of the mitoribosomal [2Fe-2S] clusters and the [4Fe-4S] cluster in mitoribosome assembly factor METTL17 sense changes in the redox environment, thus providing a way to regulate organellar protein synthesis accordingly.

biochemistry↗

bioRxiv2022

SLC25A46 localizes to sites of mitochondrial fission and fusion and loss of function variants alter the oligomerization states of MFN2 and OPA1

Mutations in SLC25A46, coding for an outer mitochondrial membrane protein, underlie a wide spectrum of neurodegenerative diseases associated with alterations in mitochondrial morphology, but the precise role of the protein remains unknown. We established an SLC25A46 knock-out cell line in human fibroblasts and studied the pathogenicity of three different variants (p.T142I, p.R257Q, p.E335D) introduced into the null background. Mitochondria were fragmented in the knock-out cell line and hyperfused in all pathogenic variants. The loss of SLC25A46 led to impaired cellular proliferation and striking abnormalities in mitochondrial cristae ultrastructure that were not rescued by expression of the pathogenic variants. SLC25A46 was present in discrete puncta at mitochondrial branch points and at tips of mitochondrial tubules, co-localizing with DRP1 and OPA1. Virtually all fission/fusion events were demarcated by the presence of an SLC25A46 focus. SLC25A46 co-immunoprecipitated with the fusion machinery, and loss of function altered the oligomerization state of OPA1 and MFN2. Proximity interaction mapping identified components of the ER membrane, lipid transfer proteins, and mitochondrial outer membrane proteins indicating that it is present at interorganellar contact sites important for lipid exchange. Consistent with this, SLC25A46 loss of function led to altered mitochondrial lipid composition, suggesting that it may facilitate interorganellar lipid flux or play a role in membrane remodeling associated with mitochondrial fusion and fission.

cell biology↗

bioRxiv2022

Loss of mitochondrial Chchd10 or Chchd2 in zebrafish leads to an ALS-like phenotype and Complex I deficiency independent of the mt-ISR

Mutations in CHCHD10 and CHCHD2, coding for two paralogous mitochondrial proteins, have been identified in amyotrophic lateral sclerosis (ALS), frontotemporal lobar degeneration (FTD), and Parkinsons disease (PD). Here we investigated the biological roles of these proteins during vertebrate development using knockout (KO) models in zebrafish. We demonstrate that loss of either or both proteins leads to a motor impairment, reduced survival, and compromised neuromuscular junction (NMJ) integrity in larval zebrafish. Compensation by Chchd10 was observed in the chchd2-/- model, but not by Chchd2 in the chchd10 -/- model. The assembly of mitochondrial respiratory chain Complex I was impaired in chchd10 -/- and chchd2 -/- zebrafish larvae, but unexpectedly not in the double chchd10 -/- & chchd2 -/- model, suggesting that reduced mitochondrial Complex I cannot be solely responsible for the observed phenotypes, which are generally more severe in the double KO. Activation of the mitochondrial integrated stress response (mt-ISR) was only observed in the double KO model, possibly implicating this pathway in the recovery of the Complex I defect, and suggesting that Complex I assembly defect in our single KO is independent of the mt-ISR. Our results demonstrate that both proteins are required for normal vertebrate development, but their precise molecular function in the mitochondrial biology of motor neurons remains to be discovered.

developmental biology↗

bioRxiv2020

A high-density human mitochondrial proximity interaction network.

We used BioID, a proximity-dependent biotinylation assay, to interrogate 100 mitochondrial baits from all mitochondrial sub-compartments to create a high resolution human mitochondrial proximity interaction network. We identified 1465 proteins, producing 15626 unique high confidence proximity interactions. Of these, 528 proteins were previously annotated as mitochondrial, nearly half of the mitochondrial proteome defined by Mitocarta 2.0. Bait-bait analysis showed a clear separation of mitochondrial compartments, and correlation analysis among preys across all baits allowed us to identify functional clusters involved in diverse mitochondrial functions, and to assign uncharacterized proteins to specific modules. We demonstrate that this analysis can assign isoforms of the same mitochondrial protein to different mitochondrial sub-compartments, and show that some proteins may have multiple cellular locations. Outer membrane baits showed specific proximity interactions with cytosolic proteins and proteins in other organellar membranes, suggesting specialization of proteins responsible for contact site formation between mitochondria and individual organelles. This proximity network will be a valuable resource for exploring the biology of uncharacterized mitochondrial proteins, the interactions of mitochondria with other cellular organelles, and will provide a framework to interpret alterations in sub-mitochondrial environments associated with mitochondrial disease. Bullet pointsO_LIWe created a high resolution human mitochondrial protein proximity map using BioID C_LIO_LIBait-bait analysis showed that the map has sub-compartment resolution and correlation analysis of preys identified functional clusters and assigned proteins to specific modules C_LIO_LIWe identified isoforms of matrix and IMS proteins with multiple cellular localizations and an endonuclease that localizes to both the matrix and the OMM C_LIO_LIOMM baits showed specific interactions with non-mitochondrial proteins reflecting organellar contact sites and protein dual localization C_LI

cell biology↗