Mapping Key Residues of ISD11 Critical for NFS1-ISD11 Subcomplex Stability

• Published in: The Journal of biological chemistry Vol. 290; no. 43; pp. 25876 - 25890
• Main Authors: Saha, Prasenjit Prasad, Srivastava, Shubhi, Kumar S. K., Praveen, Sinha, Devanjan, D'Silva, Patrick
• Format: Journal Article
• Language: English
• Published: Elsevier Inc 23.10.2015
• Subjects: electron transfer; iron-sulfur protein; mitochondria; mitochondrial disease; molecular chaperone; protein-protein interaction; reactive oxygen species (ROS); respiration; molecular chaperone; electron transfer; mitochondria; iron-sulfur protein; protein-protein interaction; respiration; reactive oxygen species (ROS); mitochondrial disease
• ISSN: 0021-9258; 1083-351X
• DOI: 10.1074/jbc.M115.678508

Biogenesis of the iron-sulfur (Fe-S) cluster is an indispensable process in living cells. In mammalian mitochondria, the initial step of the Fe-S cluster assembly process is assisted by the NFS1-ISD11 complex, which delivers sulfur to scaffold protein ISCU during Fe-S cluster synthesis. Although ISD11 is an essential protein, its cellular role in Fe-S cluster biogenesis is still not defined. Our study maps the important ISD11 amino acid residues belonging to putative helix 1 (Phe-40), helix 3 (Leu-63, Arg-68, Gln-69, Ile-72, Tyr-76), and C-terminal segment (Leu-81, Glu-84) are critical for in vivo Fe-S cluster biogenesis. Importantly, mutation of these conserved ISD11 residues into alanine leads to its compromised interaction with NFS1, resulting in reduced stability and enhanced aggregation of NFS1 in the mitochondria. Due to altered interaction with ISD11 mutants, the levels of NFS1 and Isu1 were significantly depleted, which affects Fe-S cluster biosynthesis, leading to reduced electron transport chain complex (ETC) activity and mitochondrial respiration. In humans, a clinically relevant ISD11 mutation (R68L) has been associated in the development of a mitochondrial genetic disorder, COXPD19. Our findings highlight that the ISD11 R68A/R68L mutation display reduced affinity to form a stable subcomplex with NFS1, and thereby fails to prevent NFS1 aggregation resulting in impairment of the Fe-S cluster biogenesis. The prime affected machinery is the ETC complex, which showed compromised redox properties, causing diminished mitochondrial respiration. Furthermore, the R68L ISD11 mutant displayed accumulation of mitochondrial iron and reactive oxygen species, leading to mitochondrial dysfunction, which correlates with the phenotype observed in COXPD19 patients. Background: NFS1-ISD11 complex is essential for the Fe-S cluster assembly process and the homozygous R68L ISD11 mutation causes the mitochondrial disorder, COXPD19. Results: Putative helix-3 and the C terminus of ISD11 are critical for NFS1-ISD11 subcomplex formation and Fe-S cluster biogenesis. Conclusion: ISD11 interaction is critical for NFS1 stability and its steady-state levels, in vivo. Significance: Identified important ISD11 residues will provides valuable information to understand COXPD19 progression.