Investigation of metal-ion induced aggregation of human eye lens proteins by combination of X-ray spectroscopy, site-directed mutagenesis and quantum chemistry
Biochemistry
Final Report Abstract
The remarkable increase in global life expectancy has highlighted the need to address age-related diseases, particularly cataracts—the leading cause of blindness worldwide. Cataracts result from the aggregation of damaged lens proteins (crystallins), which scatter light and cause lens opacity. Current treatments are limited to surgery, creating a financial burden. Research into the mechanisms of crystallin aggregation could pave the way for cost-effective preventative therapies, enhancing quality of life and reducing healthcare costs globally. Crystallins, highly stable proteins responsible for lens transparency, can lose structural integrity due to factors like UV exposure, glycation, and metal ion interactions. Metals, such as copper (Cu) and zinc (Zn), play role in cataract formation. Workers in metal industries exhibit a heightened risk, underscoring the impact of these interactions. Notably, Cu and Zn induce non-amyloid aggregation in crystallins, forming highmolecular-weight complexes. Mechanisms include partial protein unfolding, metalbridging, and disulfide-bridging. Research revealed novel bio-inorganic aspects of cataract formation. Cu(II) and Zn(II) ions interact with γ-crystallins and β-crystallins, inducing structural destabilization and aggregation. Cu(II) binding sites in γ-crystallins, identified through spectroscopy and calorimetry, exhibit redox activity, generating protein-based free radicals. These findings suggest that metal-induced aggregation of γcrystallins could play a role in opacification in the aging lens. A related study on βB2-crystallin identified an ATCUN-like copper-binding site at its N- terminus. This site stabilizes the protein, reducing susceptibility to copper-induced aggregation. The research also highlighted the role of redox activity in forming disulfidebridged oligomers, emphasizing the metal’s contribution to cataractogenesis. In a parallel investigation, the zinc-binding roles of tryptophan metabolites were explored in Drosophila melanogaster. The kynurenine pathway, regulated by dietary tryptophan, was found to control systemic zinc homeostasis. Kynurenine promotes zinc storage granules in Malpighian tubules, functioning as a zinc-regulating hormone. This discovery establishes a physiological link between zinc and the kynurenine pathway, critical for immunity, aging, and neurodegeneration. Despite challenges, including pandemic restrictions, the project achieved notable success. Collaborative efforts led to publications in high-impact journals and breakthroughs in understanding metal-crystallin interactions. These findings provide a foundation for future studies to develop physiologically relevant applications, advancing cataract prevention and treatment.
Publications
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Chloroquine disrupts zinc storage granules in primary Malpighian tubule cells of Drosophila melanogaster. Metallomics, 14(10).
Campos-Blázquez, Jessica P.; Schuth, Nils; Garay, Erika; Clark, Adam H.; Vogelsang, Urs; Nachtegaal, Maarten; Contreras, Rubén G.; Quintanar, Liliana & Missirlis, Fanis
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Molecular Dynamics and Structural Studies of Zinc Chloroquine Complexes. Journal of Chemical Information and Modeling, 63(1), 161-172.
Paulikat, Mirko; Vitone, Daniele; Schackert, Florian K.; Schuth, Nils; Barbanente, Alessandra; Piccini, GiovanniMaria; Ippoliti, Emiliano; Rossetti, Giulia; Clark, Adam H.; Nachtegaal, Maarten; Haumann, Michael; Dau, Holger; Carloni, Paolo; Geremia, Silvano; De Zorzi, Rita; Quintanar, Liliana & Arnesano, Fabio
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Tryptophan regulatesDrosophilazinc stores. Proceedings of the National Academy of Sciences, 119(16).
Garay, Erika; Schuth, Nils; Barbanente, Alessandra; Tejeda-Guzmán, Carlos; Vitone, Daniele; Osorio, Beatriz; Clark, Adam H.; Nachtegaal, Maarten; Haumann, Michael; Dau, Holger; Vela, Alberto; Arnesano, Fabio; Quintanar, Liliana & Missirlis, Fanis
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ATCUN-like Copper Site in βB2-Crystallin Plays a Protective Role in Cataract-Associated Aggregation. Inorganic Chemistry, 62(27), 10592-10604.
Tovar-Ramírez, Martin E.; Schuth, Nils; Rodríguez-Meza, Oscar; Kroll, Thomas; Saab-Rincon, Gloria; Costas, Miguel; Lampi, Kirsten & Quintanar, Liliana
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Cataracts and copper: A spectroscopic perspective of copper-induced aggregation of betaB2-crystallin. Biophysical Journal, 122(3), 286a.
Tovar, Martin E.; Schuth, Nils; Kroll, Thomas; Saab-Rincon, Gloria; Lampi, Kirsten & Quintanar, Liliana
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Copper Reductase Activity and Free Radical Chemistry by Cataract-Associated Human Lens γ-Crystallins. Journal of the American Chemical Society, 145(12), 6781-6797.
Palomino-Vizcaino, Giovanni; Schuth, Nils; Domínguez-Calva, José A.; Rodríguez-Meza, Oscar; Martínez-Jurado, Eduardo; Serebryany, Eugene; King, Jonathan A.; Kroll, Thomas; Costas, Miguel & Quintanar, Liliana
