Throughout the review, the synergy of combined "omics" technologies such as genomics and epigenomics, proteomics, and metabolomics is highlighted. These are anticipated to lead to new hypotheses to understand IR effects on biological systems and improve IR-based therapies.

Activation of ferroptosis, a recently described mechanism of regulated cell death, dramatically inhibits growth of ovarian cancer cells. Given the importance of lipid metabolism in ferroptosis and the key role of lipids in ovarian cancer, we examined the contribution to ferroptosis of steroyl CoA desaturase (SCD1), an enzyme that catalyzes the rate-limiting step in monounsaturated fatty acid synthesis, in ovarian cancer cells. SCD1 was highly expressed in ovarian cancer tissue, cell lines, and a genetic model of ovarian cancer stem cells. Inhibition of SCD1 induced lipid oxidation and cell death. Conversely, over-expression of SCD1 or exogenous administration of its C16:1 and C18:1 products, palmitoleic acid or oleate, protected cells from death. Inhibition of SCD1 induced both ferroptosis and apoptosis: inhibition of SCD1 decreased CoQ 10 , an endogenous membrane antioxidant whose depletion has been linked to ferroptosis, while concomitantly decreasing unsaturated fatty acyl chains in membrane phospholipids and increasing long chain saturated ceramides, changes previously linked to apoptosis. Simultaneous triggering of two death pathways suggests SCD1 inhibition may be an effective component of anti-tumor therapy, since overcoming this dual mechanism of cell death may present a significant barrier to the emergence of drug resistance. Supporting this concept, we observed that inhibition of SCD1 significantly potentiated the anti-tumor effect of ferroptosis inducers in both ovarian cancer cell lines and a mouse orthotopic xenograft model. Our results suggest that the use of combined treatment with SCD1

Tyrosine phosphorylation of cellular proteins induced by extracellular cues serves as a critical mediator in the control of a great variety of cellular processes. Here, we describe an integrated experimental approach including rapid quench methodology and ESI-LC-MS/MS as well as time-resolved ESI-MS to demonstrate that tyrosine autophosphorylation of the catalytic tyrosine kinase domain of FGF-receptor-1 (FGFR1) is mediated by a sequential and precisely ordered reaction. We also demonstrate that the rate of catalysis of two FGFR substrates is enhanced by 50- to 100-fold after autophosphorylation of Y653 in the activation loop, whereas autophosphorylation of the second site in the activation loop (Y654) results in 500- to 1,000-fold increase in the rate of substrate phosphorylation. We propose that FGFR1 is activated by a two-step mechanism mediated by strictly ordered and regulated autophosphorylation, suggesting that distinct phosphorylation states may provide both temporal and spatial resolution to receptor signaling.

Cysteine sulfenic acid formation in proteins results from the oxidative modification of susceptible cysteine residues by hydrogen peroxide, alkyl hydroperoxides and peroxynitrite. This species represents a biologically-significant modification occurring during oxidant signaling or oxidative stress and it can modulate protein function. Most methods to identify such oxidatively-modified proteins rely on monitoring the loss of one or more thiol group(s) or on selective labeling of nascent thiol groups following reduction of oxidized proteins. Our previous work reported the direct labeling of these chemically distinct modifications with a dimedone analogue, 1,3-cyclohexadione, to which a linker and functional group (an alcohol) had been added; further addition of a fluorescent isatoic acid or methoxycoumarin reporter allowed detection of the incorporated tag by fluorescence techniques [Poole, L. B., Zeng, B. B., Knaggs, S. A., Yakubu, M., and King, S. B. (2005) Synthesis of chemical probes to map sulfenic acid modifications on proteins. Bioconjug Chem 16, 1624Chem 16, -1628. We have now expanded our arsenal of tagging reagents to include two fluorescein-, two rhodamineand three biotin-conjugated probes based on the original approach. The new tools provide readily detectable fluorescent and affinity probes to identify sulfenic acid modifications in proteins and have been used in subsequent mass spectrometric analyses to confirm covalent attachment of the conjugates and directly determine the site of modification. Keywordscysteine sulfenic acid; reactive oxygen species; oxidized cysteine; papain; peroxiredoxins; peroxide; redox sensor; redox signaling Given the significant role played by formation of cysteine sulfenic acid (S-hydroxycysteine, R-SOH) in the redox regulation of enzymes and transcription regulators (1-3) and its general instability toward protein analytical methods (4), there is a critical need for better reagents to trap and identify these modifications in proteins. Based on a known alkylator of R-SOH, *To whom correspondence should be addressed: Department of Biochemistry, Center for Structural Biology, Medical Center Boulevard, Winston-Salem, NC 27157; Telephone: 336-716-6711 (Poole), 336-758-5774 (King); Fax: 336-777-3242 (Poole), 336-758-4656 (King); E-mail: lbpoole@wfubmc.edu, kingsb@wfu.edu. NIH Public Access Author ManuscriptBioconjug Chem. Author manuscript; available in PMC 2008 November 1. Published in final edited form as:Bioconjug Chem. 2007 ; 18(6): 2004-2017. doi:10.1021/bc700257a. NIH-PA Author ManuscriptNIH-PA Author Manuscript NIH-PA Author Manuscript dimedone (5,5-dimethyl-1,3-cyclohexanedione), we previously designed, synthesized and validated the use of two fluorescent reagents linked to the reactive core of dimedone, 1,3-cyclohexadione, as detectable markers of R-SOH formation in proteins (5). These reagents were shown to specifically trap only the R-SOH modification in a test protein, AhpC (a cysteine-based peroxidase from bacteria), leaving underivatized the other protein...

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