Abstract
Melanosomes are lysosome-related organelles that produce and accumulate melanin. Their maturation is regulated through interactions with mitochondria and involves the export and recycling of proteins via tubular transport and fission events whose mechanisms are unknown. Here, we demonstrate that the mitochondrial fission factor protein (MFF) is involved in melanosome fission. MFF is trafficked between mitochondria and melanosomes and locates at melanosome fission events. Upon downregulation of MFF, but not of dynamin-related protein 1 (DRP1), melanosomes enlarge, intracellular melanin accumulates, and melanosomal lumenal catabolism increases, indicating that MFF-dependent melanosome fission is required for their maturation. We show that MFF interacts with regulators of the ARP2/3 complex, which drives F-actin nucleation. Actin filaments accumulate between melanosomes at MFF-enriched membrane constriction sites, and silencing of ARP2/3 subunits mimics the increase in melanosome size. MFF regulates actin-dependent fission of melanosomes via the ARP2/3 complex, indicating an extramitochondrial function for MFF in the regulation of melanosome homeostasis.
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Data availability
The MS data generated in this study have been deposited in the ProteomeXchange database with the identifier PXD051372. Raw reads have been deposited in the NCBI SRA database and are available through the Bioproject ID PRJNA1092600. Raw files from imaging experiments will be available on request. The processed data and W.blot images generated in this study are provided in the Supplementary Information/Source Data file. The unpublished melan-c2 cells, as well as the wild type cells melan-a, will be readily available on request from the Functional Genomics Cell Bank at City St. George’s, University of London, UK. Source data are provided with this paper.
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Acknowledgements
We thank all members of the Dibio Imaging facility (https://www.biologia.unipd.it/servizi/servizi-alla-ricerca/imaging-facility/) for technical assistance on sample preparation and image acquisition. Sequencing services were performed by the NGS facility of the Department of Biology, University of Padua. This work was supported by the following grants: LEO Foundation Open Competition grant LF-OC-20-000630 (M.G.), LEO Foundation Serendipity grant LF-SE-23-800010 (M.G.) and Wellcome Trust grant 108429/Z/15/Z (E.V.S.); European Union Next Generation EU, Mission 4 Component 2 B73C22001250006 (L.S.), Ministry of University and Research PRIN P2022JZ9RE_002 and PRIN 20222Y9X43 (L.S.); European Union's Horizon 2020 research and innovation program under the Marie Sklodowska-Curie grant agreement (no. 896745, T.K.) and the Italian Ministry of University and Research within the framework of the National Recovery and Resilience Plan (no. MSCA2024_0000047, T.K.).
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Conceptualization: A.P.M.R. and M.Gi. Methodology: A.P.M.R., A.M., A.P., F.D.B., M.Ge., M.Gi., S.G. and S.S. Formal analysis: A.P.M.R., S.G., L.Sa., M.Ge. and P.Gru. Investigation: A.P.M.R., A.M., P.Gru. and T.K. Resources: E.V.S., P.Goff, L.Sc., M.Gi. and C.F. Data curation: A.P.M.R., S.G. and L.Sa. Writing—original draft: A.P.M.R. and M.Gi. Writing—review and editing: all authors. Supervision: M.Gi. Funding acquisition: M.Gi., T.K., L.S. and E.V.S.
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Magalhães Rebelo, A.P., Maracani, A., Greco, S. et al. MFF budding from mitochondria regulates melanosome size and maturation. Nat Commun (2026). https://doi.org/10.1038/s41467-026-70572-3
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DOI: https://doi.org/10.1038/s41467-026-70572-3
