Dipartimento di Fisiopatologia Medico-Chirurgica e Dei Trapianti, Università Degli Studi di Milano, 20090 Segrate, Italy.
Dipartimento di Biochimica e Farmacologia Molecolare, Istituto di Ricerche Farmacologiche Mario Negri IRCCS, 20156 Milan, Italy.
Int J Mol Sci. 2022 Jan 16;23(2):950. doi: 10.3390/ijms23020950.
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 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 Cu 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 Cu-induced toxicity; moreover, they also show that copper binding is just one of the several biochemical traits contributing to LC soluble in vivo toxicity.
轻链淀粉样变（AL）是由免疫球蛋白轻链（LC）异常过度产生引起的。由此导致血液中异常高浓度的 LC 导致在心脏和其他靶器官中形成沉积物。器官损伤不仅是由大量淀粉样沉积物的积累引起的，而且广泛的临床数据表明，循环可溶性 LC 也会产生心脏毒性作用。线虫已被验证可在体内重现 LC 可溶性毒性，并且在该模型中已报道铜离子在增加 LC 可溶性毒性方面的作用。在这里，我们应用了微量热泳动、等温量热法和热融解来证明 Cu 与淀粉样变 H7 的可变结构域的特异性结合，亲和力为亚毫摩尔。LC 序列中存在的组氨酸残基不参与结合，但它们突变为 Ala 会降低 H7 的可溶性毒性。铜离子结合并使可变结构域不稳定，并在该结构域中诱导有限的稳定。总之，这里报道的数据阐明了 Cu 诱导毒性的生化基础；此外，它们还表明铜结合只是导致 LC 体内可溶性毒性的几个生化特征之一。
