title: Copper and Zinc Ions Specifically Promote Nonamyloid Aggregation of the Highly Stable Human γ-D Crystallin.
abstract: Cataract is the leading cause of blindness in the world. It results from aggregation of eye lens proteins into high-molecular-weight complexes, causing light scattering and lens opacity. Copper and zinc concentrations in cataractous lens are increased significantly relative to a healthy lens, and a variety of experimental and epidemiological studies implicate metals as potential etiological agents for cataract. The natively monomeric, β-sheet rich human γD (HγD) crystallin is one of the more abundant proteins in the core of the lens. It is also one of the most thermodynamically stable proteins in the human body. Surprisingly, we found that both Cu(II) and Zn(II) ions induced rapid, nonamyloid aggregation of HγD, forming high-molecular-weight light-scattering aggregates. Unlike Zn(II), Cu(II) also substantially decreased the thermal stability of HγD and promoted the formation of disulfide-bridged dimers, suggesting distinct aggregation mechanisms. In both cases, however, metal-induced aggregation depended strongly on temperature and was suppressed by the human lens chaperone αB-crystallin (HαB), implicating partially folded intermediates in the aggregation process. Consistently, distinct site-specific interactions of Cu(II) and Zn(II) ions with the protein and conformational changes in specific hinge regions were identified by nuclear magnetic resonance. This study provides insights into the mechanisms of metal-induced aggregation of one of the more stable proteins in the human body, and it reveals a novel and unexplored bioinorganic facet of cataract disease.
authors.affiliation: Departamento de Química, Centro de Investigación y de Estudios Avanzados (Cinvestav) , 07360 Mexico City, México.
authors.forename: Liliana
authors.initials: L
authors.lastname: Quintanar
authors.affiliation: Departamento de Química, Centro de Investigación y de Estudios Avanzados (Cinvestav) , 07360 Mexico City, México.
authors.forename: José A
authors.initials: JA
authors.lastname: Domínguez-Calva
authors.affiliation: Department of Biology, Massachusetts Institute of Technology , Cambridge, Massachusetts 02139, United States.
authors.forename: Eugene
authors.initials: E
authors.lastname: Serebryany
authors.affiliation: Centro de Investigaciones Químicas, Instituto de Investigación en Ciencias Básicas y Aplicadas, Universidad Autónoma del Estado de Morelos , 62209 Cuernavaca, México.
authors.forename: Lina
authors.initials: L
authors.lastname: Rivillas-Acevedo
authors.affiliation: Department of Biology, Massachusetts Institute of Technology , Cambridge, Massachusetts 02139, United States.
authors.forename: Cameron
authors.initials: C
authors.lastname: Haase-Pettingell
authors.affiliation: Centro de Investigaciones Químicas, Instituto de Investigación en Ciencias Básicas y Aplicadas, Universidad Autónoma del Estado de Morelos , 62209 Cuernavaca, México.
authors.forename: Carlos
authors.initials: C
authors.lastname: Amero
authors.affiliation: Department of Biology, Massachusetts Institute of Technology , Cambridge, Massachusetts 02139, United States.
authors.forename: Jonathan A
authors.initials: JA
authors.lastname: King
mesh_terms: D003300:Copper / Q000737:chemistry / Q000494:pharmacology*; D003459:Crystallins / Q000378:metabolism*; D004591:Electrophoresis, Polyacrylamide Gel; D006801:Humans; D007477:Ions; D009682:Magnetic Resonance Spectroscopy; D046529:Microscopy, Electron, Transmission; D008958:Models, Molecular; D066263:Protein Aggregation, Pathological / Q000139:chemically induced*; D017510:Protein Folding; D055550:Protein Stability; D013696:Temperature; D015032:Zinc / Q000737:chemistry / Q000494:pharmacology*
chemical_list: D003459:Crystallins; D007477:Ions; D003300:Copper; D015032:Zinc