👤 Mooradian AD

Stimulation of plasma membrane receptor tyrosine kinases (RTKs), such as the epidermal growth factor receptor (EGFR), locally increases the abundance of reactive oxygen species (ROS). These ROS then oxidize cysteine residues in proteins to potentiate downstream signaling. Spatial confinement of ROS is an important regulatory mechanism of redox signaling that enables the stimulation of different RTKs to oxidize distinct sets of downstream proteins. To uncover additional mechanisms that specify cysteines that are redox regulated by EGF stimulation, we performed time-resolved quantification of the EGF-dependent oxidation of 4200 cysteine sites in A431 cells. Fifty-one percent of cysteines were statistically significantly oxidized by EGF stimulation. Furthermore, EGF induced three distinct spatiotemporal patterns of cysteine oxidation in functionally organized protein networks, consistent with the spatial confinement model. Unexpectedly, protein crystal structure analysis and molecular dynamics simulations indicated widespread redox regulation of cryptic cysteine residues that are solvent exposed only upon changes in protein conformation. Phosphorylation and increased flux of nucleotide substrates served as two distinct modes by which EGF specified the cryptic cysteine residues that became solvent exposed and redox regulated. Because proteins that are structurally regulated by different RTKs or cellular perturbations are largely unique, these findings suggest that solvent exposure and redox regulation of cryptic cysteine residues contextually delineate redox signaling networks. Show less

Organometallic ruthenium(II) complexes of the general formula [Ru(eta6-p-cymene)Cl2(L)] and [Ru(eta6-p-cymene)Cl(L)2][BPh4] with modified phenoxazine- and anthracene-based multidrug resistance (MDR) modulator ligands (L) have been synthesized, spectroscopically characterized, and evaluated in vitro for their cytotoxic and MDR reverting properties in comparison with the free ligands. For an anthracene-based ligand, coordination to a ruthenium(II) arene fragment led to significant improvement of cytotoxicity as well as Pgp inhibition activity. A similar, but weaker effect was also observed when using a benzimidazole-phenoxazine derivative as Pgp inhibitor. The most active compound in terms of both Pgp inhibition and cytotoxicity is [Ru(eta6-p-cymene)Cl2(L)], where L is an anthracene-based ligand. Studies show that it induces cell death via inhibition of DNA synthesis. Moreover, because the complex is fluorescent, its uptake in cells was studied, and relative to the free anthracene-based ligand, uptake of the complex is accelerated and accumulation of the complex in the cell nucleus is observed. Show less