Role of human mitochondrial Nfs1 in cytosolic iron-sulfur protein biogenesis and iron regulation.
The biogenesis of iron-sulfur (Fe/S) proteins in eukaryotes is a complex process involving more than 20 components. So far, functional investigations have mainly been performed in Saccharomyces cerevisiae. Here, we have analyzed the role of the human cysteine desulfurase Nfs1 (huNfs1), which serves as a sulfur donor in biogenesis. The protein is located predominantly in mitochondria, but small amounts are present in the cytosol/nucleus. huNfs1 was depleted efficiently in HeLa cells by a small interfering RNA (siRNA) approach, resulting in a drastic growth retardation and striking morphological changes of mitochondria. The activities of both mitochondrial and cytosolic Fe/S proteins were strongly impaired, demonstrating that huNfs1 performs an essential function in Fe/S protein biogenesis in human cells. Expression of murine Nfs1 (muNfs1) in huNfs1-depleted cells restored both growth and Fe/S protein activities to wild-type levels, indicating the specificity of the siRNA depletion approach. No complementation of the growth retardation was observed, when muNfs1 was synthesized without its mitochondrial presequence. This extramitochondrial muNfs1 did not support maintenance of Fe/S protein activities, neither in the cytosol nor in mitochondria. In conclusion, our study shows that the essential huNfs1 is required inside mitochondria for efficient maturation of cellular Fe/S proteins. The results have implications for the regulation of iron homeostasis by cytosolic iron regulatory protein 1.
Biederbick
Annette
A
Institut für Zytobiologie, Philipps Universität Marburg, Robert-Koch-Str. 6, 35037 Marburg, Germany.
Stehling
Oliver
O
Rösser
Ralf
R
Niggemeyer
Brigitte
B
Nakai
Yumi
Y
Elsässer
Hans-Peter
HP
Lill
Roland
R
D000595:Amino Acid Sequence; D000818:Animals; D013437:Carbon-Sulfur Lyases / Q000235:genetics / Q000378:metabolism*; D003600:Cytosol / Q000201:enzymology*; D005822:Genetic Vectors; D006367:HeLa Cells; D006706:Homeostasis; D006801:Humans; D007501:Iron / Q000378:metabolism*; D007506:Iron-Sulfur Proteins / Q000096:biosynthesis* / Q000235:genetics; D051379:Mice; D008928:Mitochondria / Q000201:enzymology* / Q000648:ultrastructure; D024101:Mitochondrial Proteins; D008969:Molecular Sequence Data; D034741:RNA, Small Interfering / Q000235:genetics / Q000378:metabolism; D029701:Saccharomyces cerevisiae Proteins / Q000235:genetics / Q000378:metabolism; D016415:Sequence Alignment; D013466:Sulfurtransferases
D007506:Iron-Sulfur Proteins; D024101:Mitochondrial Proteins; D034741:RNA, Small Interfering; D029701:Saccharomyces cerevisiae Proteins; D007501:Iron; D013466:Sulfurtransferases; C115912:NFS1 protein, S cerevisiae; D013437:Carbon-Sulfur Lyases; C513492:NFS1 protein, human; C513493:Nfs1 protein, mouse; C080546:cysteine desulfurase