Blancas-Mejía Luis M, Misra Pinaki, Ramirez-Alvarado Marina
Department of Biochemistry and Molecular Biology and ‡Department of Immunology, Mayo Clinic , Rochester, Minnesota 55905, United States.
Biochemistry. 2017 Feb 7;56(5):757-766. doi: 10.1021/acs.biochem.6b01043. Epub 2017 Jan 24.
Light chain (AL) amyloidosis is a lethal disease characterized by the deposition of the immunoglobulin light chain into amyloid fibrils, resulting in organ dysfunction and failure. Amyloid fibrils have the ability to self-propagate, recruiting soluble protein into the fibril by a nucleation-polymerization mechanism, characteristic of autocatalytic reactions. Experimental data suggest the existence of a critical concentration for initiation of fibril formation. As such, the initial concentration of soluble amyloidogenic protein is expected to have a profound effect on the rate of fibril formation. In this work, we present in vitro evidence that fibril formation rates for AL light chains are affected by the protein concentration in a differential manner. De novo reactions of the proteins with the fastest amyloid kinetics (AL-09, AL-T05, and AL-103) do not present protein concentration dependence. Seeded reactions, however, exhibited weak protein concentration dependence. For AL-12, seeded and protein concentration dependence data suggest a synergistic effect for recruitment and elongation at low protein concentrations, while reactions of κI exhibited poor efficiency in nucleating and elongating preformed fibrils. Additionally, co-aggregation and cross seeding of κI variable domain (V) and the κI full length (FL) light chain indicate that the presence of the constant domain in κI FL modulates fibril formation, facilitating the recruitment of κI V. Together, these results indicate that the dominant process in fibril formation varies among the AL proteins tested with a differential dependence of the protein concentration.
轻链（AL）淀粉样变性是一种致命疾病，其特征是免疫球蛋白轻链沉积为淀粉样纤维，导致器官功能障碍和衰竭。淀粉样纤维具有自我增殖能力，通过成核聚合机制将可溶性蛋白招募到纤维中，这是自催化反应的特征。实验数据表明存在纤维形成起始的临界浓度。因此，可溶性淀粉样生成蛋白的初始浓度预计会对纤维形成速率产生深远影响。在这项工作中，我们提供了体外证据，表明AL轻链的纤维形成速率受到蛋白质浓度的不同影响。淀粉样动力学最快的蛋白质（AL-09、AL-T05和AL-103）的从头反应不存在蛋白质浓度依赖性。然而，接种反应表现出较弱的蛋白质浓度依赖性。对于AL-12，接种和蛋白质浓度依赖性数据表明在低蛋白质浓度下招募和延伸存在协同效应，而κI的反应在成核和延伸预先形成的纤维方面效率较低。此外，κI可变结构域（V）和κI全长（FL）轻链的共聚集和交叉接种表明κI FL中恒定结构域的存在调节纤维形成，促进κI V的招募。总之，这些结果表明，在测试的AL蛋白中，纤维形成的主导过程各不相同，且对蛋白质浓度有不同的依赖性。
