Cu(II) Binding Increases the Soluble Toxicity of Amyloidogenic Light Chains

Russo R, Romeo M, Schulte T, Maritan M, Oberti L, Barzago MM, Barbiroli A, Pappone C, Anastasia L, Palladini G, Diomede L, Ricagno S. Cu(II) Binding Increases the Soluble Toxicity of Amyloidogenic Light Chains. Int J Mol Sci. 2022 Jan 16;23(2):950. doi: 10.3390/ijms23020950. PMID: 35055136; PMCID: PMC8780072.

Abstract

Light chain amyloidosis (AL) is caused by the aberrant overproduction of immunoglobulin light chains (LCs). The resulting abnormally high LC concentrations in blood lead to deposit formation in the heart and other target organs. Organ damage is caused not only by the accumulation of bulky amyloid deposits, but extensive clinical data indicate that circulating soluble LCs also exert cardiotoxic effects. The nematode C. elegans has been validated to recapitulate LC soluble toxicity in vivo, and in such a model a role for copper ions in increasing LC soluble toxicity has been reported. Here, we applied microscale thermophoresis, isothermal calorimetry and thermal melting to demonstrate the specific binding of Cu2+ to the variable domain of amyloidogenic H7 with a sub-micromolar affinity. Histidine residues present in the LC sequence are not involved in the binding, and yet their mutation to Ala reduces the soluble toxicity of H7. Copper ions bind to and destabilize the variable domains and induce a limited stabilization in this domain. In summary, the data reported here, elucidate the biochemical bases of the Cu2+-induced toxicity; moreover, they also show that copper binding is just one of the several biochemical traits contributing to LC soluble in vivo toxicity.

Russo R、Romeo M、Schulte T、Maritan M、Oberti L、Barzago MM、Barbiroli A、Pappone C、Anastasia L、Palladini G、Diomede L、Ricagno S. 铜(II)结合增强淀粉样变性轻链的可溶性毒性. 《国际分子科学杂志》（Int J Mol Sci）. 2022年1月16日;23(2):950. DOI: 10.3390/ijms23020950. PMID: 35055136; PMCID: PMC8780072.

摘要

轻链淀粉样变性（light chain amyloidosis, AL）由免疫球蛋白轻链（immunoglobulin light chains, LCs）的异常过度生成所引发。血液中异常升高的轻链浓度会导致心脏及其他靶器官形成沉积。器官损伤不仅由大量淀粉样沉积的蓄积所导致，大量临床数据表明，循环中的可溶性轻链同样会产生心脏毒性。秀丽隐杆线虫（C. elegans）模型已被验证可在体内重现轻链的可溶性毒性，且已有研究报道铜离子在该模型中可增强轻链的可溶性毒性。本研究采用微量热泳动技术（microscale thermophoresis）、等温滴定量热法（isothermal calorimetry）及热融解实验，证实Cu²⁺可与淀粉样变性H7的可变域以亚微摩尔亲和力特异性结合。轻链序列中的组氨酸残基并未参与该结合过程，然而将其突变为丙氨酸（Ala）会降低H7的可溶性毒性。铜离子可结合该可变域并使其去稳定，同时在该域内诱导有限的稳定作用。综上，本研究报道的数据阐明了Cu²⁺诱导毒性的生化基础；此外，研究结果还表明，铜离子结合仅是促成轻链在体内产生可溶性毒性的多种生化特性之一。