Human ISD11 is essential for both iron-sulfur cluster assembly and maintenance of normal cellular iron homeostasis

Abstract

The LYR family consists of proteins of diverse functions that contain the conserved tripeptide 'LYR' near the N-terminus, and it includes Isd11, which was previously observed to have an important role in iron-sulfur (Fe-S) cluster biogenesis in Saccharomyces cerevisiae. Here, we have cloned and characterized human ISD11 and shown that human ISD11 forms a stable complex in vivo with the human cysteine desulfurase (ISCS), which generates the inorganic sulfur needed for Fe-S protein biogenesis. Similar to ISCS, we have found that ISD11 localizes to the mitochondrial compartment, as expected, but also to the nucleus of mammalian cells. Using RNA-interference techniques, we have shown that suppression of human ISD11 inactivated mitochondrial and cytosolic aconitases. In addition, ISD11 suppression activated iron-responsive element-binding activity of iron regulatory protein 1, increased protein levels of iron regulatory protein 2, and resulted in abnormal punctate ferric iron accumulations in cells. These results indicate that ISD11 is important in the biogenesis of Fe-S clusters in mammalian cells, and its loss disrupts normal mitochondrial and cytosolic iron homeostasis.

Evolution of Fe/S cluster biogenesis in the anaerobic parasite Blastocystis

“…S17), likely a consequence of the failure of Bh-IscS to function in the context of the heterologous Tb ISC machinery. Specifically, IscS is known to closely interact with the ISC protein Isd11 in yeast (32,33), humans (33), and probably other eukaryotes (34), including Tb (35). Therefore, it is possible that Bh-IscS is unable to form a functional complex with Tb-Isd11.…”

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

“…Previous studies have shown that deletion of Isd11 in yeast or silencing of ISD11 in mammalian cells leads to impairment of Fe-S cluster biogenesis and reduction in Fe-S cluster containing enzyme activity (20,22). Isd11/ISD11 is an essential protein but its actual role in Fe-S cluster biogenesis by interacting with the sulfur donor Nfs1 is not clear.…”

“…Required for Cell Growth and Survival-Human mitochondrial matrix protein ISD11 (Isd11 in yeast) assists the function of the sulfur donor protein NFS1 (Nfs1 in yeast) (22,23,31). Although there is no bacterial ortholog of the ISD11 protein, it is well conserved in eukaryotes, ranging from yeast to humans as highlighted in multiple sequence alignment (Fig.…”

“…Although Isd11 is not required for desulfurase activity of Nfs1 in vitro, the Nfs1-Isd11 complex represents the functional sulfur donor, in vivo (21). In humans, the Isd11 ortholog ISD11 is believed to play a similar conserved role in Fe-S cluster biogenesis (22) and loss of ISD11 function results in a mitochondrial disorder termed as combined oxidative phosphorylation deficiency 19 (COXPD19) 5 (23). Recent studies on human ISD11 have shown that a homozygous mutation in the LYRM4 gene on chromosome 6p25, which codes for the ISD11 protein, converts a conserved arginine residue at position 68 into leucine (R68L) implicated in the mitochondrial genetic disorder COXPD19.…”

Structure of human Fe–S assembly subcomplex reveals unexpected cysteine desulfurase architecture and acyl-ACP–ISD11 interactions

“…At the center of the complex, the pyridoxal 5′-phosphate (PLP)-dependent cysteine desulfurase NFS1 forms a tight complex with ISD11 (4,8,9,27). The NFS1-ISD11 complex catalyzes the conversion of L-cysteine to L-alanine and generates a persulfide intermediate on a cysteine of the mobile S-transfer loop of NFS1 (S-loop) (24,28).…”