Sternke-Hoffmann Rebecca, Boquoi Amelie, Lopez Y Niedenhoff David, Platten Florian, Fenk Roland, Haas Rainer, Buell Alexander K
Institute of Physical Biology, Heinrich-Heine Universität Düsseldorf, Düsseldorf, Germany.
Department of Hematology, Oncology and Clinical Oncology, Heinrich-Heine Universität Düsseldorf, Düsseldorf, Germany.
PeerJ. 2020 Mar 17;8:e8771. doi: 10.7717/peerj.8771. eCollection 2020.
In light chain (LC) diseases, monoclonal immunoglobulin LCs are abundantly produced with the consequence in some cases to form deposits of a fibrillar or amorphous nature affecting various organs, such as heart and kidney. The factors that determine the solubility of any given LC in vivo are still not well understood. We hypothesize that some of the biochemical properties of the LCs that have been shown to correlate with amyloid fibril formation in patients also can be used as predictors for the degree of kidney damage in a patient group that is only biased by protein availability. We performed detailed biochemical and biophysical investigations of light chains extracted and purified from the urine of a group of 20 patients with light chain disease. For all samples that contained a sufficiently high concentration of LC, we quantified the unfolding temperature of the LCs, the monomer-dimer distribution, the digestibility by trypsin and the formation of amyloid fibrils under various conditions of pH and reducing agent. We correlated the results of our biophysical and biochemical experiments with the degree of kidney damage in the patient group and found that most of these parameters do not correlate with kidney damage as defined by clinical parameters. However, the patients with the greatest impairment of kidney function have light chains which display very poor digestibility by trypsin. Most of the LC properties reported before to be predictors of amyloid formation cannot be used to assess the degree of kidney damage. Our finding that poor trypsin digestibility correlates with kidney damage warrants further investigation in order to probe a putative mechanistic link between these factors.
在轻链（LC）疾病中，单克隆免疫球蛋白轻链大量产生，在某些情况下会形成影响心脏和肾脏等各种器官的纤维状或无定形沉积物。决定任何给定轻链在体内溶解度的因素仍未完全清楚。我们假设，在患者中已显示与淀粉样纤维形成相关的轻链的一些生化特性，也可作为仅受蛋白质可用性影响的患者组中肾脏损伤程度的预测指标。我们对从20名轻链病患者尿液中提取和纯化的轻链进行了详细的生化和生物物理研究。对于所有含有足够高浓度轻链的样品，我们量化了轻链的解折叠温度、单体-二聚体分布、胰蛋白酶消化率以及在不同pH值和还原剂条件下淀粉样纤维的形成。我们将生物物理和生化实验结果与患者组的肾脏损伤程度进行了关联，发现这些参数中的大多数与临床参数所定义的肾脏损伤无关。然而，肾功能损害最严重的患者的轻链对胰蛋白酶的消化性非常差。之前报道的大多数可作为淀粉样形成预测指标的轻链特性，不能用于评估肾脏损伤程度。我们发现胰蛋白酶消化性差与肾脏损伤相关，这一发现值得进一步研究，以探究这些因素之间可能的机制联系。
