New Insights of the NEET Protein CISD2 Reveals Distinct Features Compared to Its Close Mitochondrial Homolog mitoNEET.
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ABSTRACT:
SUBMITTER: Salameh M
PROVIDER: S-EPMC8067432 | biostudies-literature |
REPOSITORIES: biostudies-literature
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Project description:Identification of novel drug targets and chemotherapeutic agents is a high priority in the fight against cancer. Here, we report that MAD-28, a designed cluvenone (CLV) derivative, binds to and destabilizes two members of a unique class of mitochondrial and endoplasmic reticulum (ER) 2Fe-2S proteins, mitoNEET (mNT) and nutrient-deprivation autophagy factor-1 (NAF-1), recently implicated in cancer cell proliferation. Docking analysis of MAD-28 to mNT/NAF-1 revealed that in contrast to CLV, which formed a hydrogen bond network that stabilized the 2Fe-2S clusters of these proteins, MAD-28 broke the coordinative bond between the His ligand and the cluster's Fe of mNT/NAF-1. Analysis of MAD-28 performed with control (Michigan Cancer Foundation; MCF-10A) and malignant (M.D. Anderson-metastatic breast; MDA-MB-231 or MCF-7) human epithelial breast cells revealed that MAD-28 had a high specificity in the selective killing of cancer cells, without any apparent effects on normal breast cells. MAD-28 was found to target the mitochondria of cancer cells and displayed a surprising similarity in its effects to the effects of mNT/NAF-1 shRNA suppression in cancer cells, causing a decrease in respiration and mitochondrial membrane potential, as well as an increase in mitochondrial iron content and glycolysis. As expected, if the NEET proteins are targets of MAD-28, cancer cells with suppressed levels of NAF-1 or mNT were less susceptible to the drug. Taken together, our results suggest that NEET proteins are a novel class of drug targets in the chemotherapeutic treatment of breast cancer, and that MAD-28 can now be used as a template for rational drug design for NEET Fe-S cluster-destabilizing anticancer drugs.
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Project description:MitoNEET is a protein of unknown function present in the mitochondrial membrane that was recently shown to bind specifically the antidiabetic drug pioglizatone. Here, we report the crystal structure of the soluble domain (residues 32-108) of human mitoNEET at 1.8-A resolution. The structure reveals an intertwined homodimer, and each subunit was observed to bind a [2Fe-2S] cluster. The [2Fe-2S] ligation pattern of three cysteines and one histidine differs from the known pattern of four cysteines in most cases or two cysteines and two histidines as observed in Rieske proteins. The [2Fe-2S] cluster is packed in a modular structure formed by 17 consecutive residues. The cluster-binding motif is conserved in at least seven distinct groups of proteins from bacteria, archaea, and eukaryotes, which show a consensus sequence of (hb)-C-X(1)-C-X(2)-(S/T)-X(3)-P-(hb)-C-D-X(2)-H, where hb represents a hydrophobic residue; we term this a CCCH-type [2Fe-2S] binding motif. The nine conserved residues in the motif contribute to iron ligation and structure stabilization. UV-visible absorption spectra indicated that mitoNEET can exist in oxidized and reduced states. Our study suggests an electron transfer function for mitoNEET and for other proteins containing the CCCH motif.
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Project description:Members of the thiazolidinedione (TZD) class of insulin-sensitizing drugs are extensively used in the treatment of type 2 diabetes. Pioglitazone, a member of the TZD family, has been shown to bind specifically to a protein named mitoNEET [Colca JR, McDonald WG, Waldon DJ, Leone JW, Lull JM, Bannow CA, Lund ET, Mathews WR (2004) Am J Physiol 286:E252-E260]. Bioinformatic analysis reveals that mitoNEET is a member of a small family of proteins containing a domain annotated as a CDGSH-type zinc finger. Although annotated as a zinc finger protein, mitoNEET contains no zinc, but instead contains 1.6 mol of Fe per mole of protein. The conserved sequence C-X-C-X(2)-(S/T)-X(3)-P-X-C-D-G-(S/A/T)-H is a defining feature of this unique family of proteins and is likely involved in iron binding. Localization studies demonstrate that mitoNEET is an integral protein present in the outer mitochondrial membrane. An amino-terminal anchor sequence tethers the protein to the outer membrane with the CDGSH domain oriented toward the cytoplasm. Cardiac mitochondria isolated from mitoNEET-null mice demonstrate a reduced oxidative capacity, suggesting that mito- NEET is an important iron-containing protein involved in the control of maximal mitochondrial respiratory rates.
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