Abstract: SA-PO0196
Key Residue Drives Pathogenic Light Chain Crystallization in Proximal Tubulopathy
Session Information
- Onconephrology: MGRS, HSCT, Electrolytes, RCC, and More
November 08, 2025 | Location: Exhibit Hall, Convention Center
Abstract Time: 10:00 AM - 12:00 PM
Category: Onconephrology
- 1700 Onconephrology
Authors
- Wang, Xin, Peking-Tsinghua Joint Center for Life Sciences, Beijing, China
- Wang, Shuang, Peking University First Hospital, Beijing, China
- Wang, Chu-qiao, Peking University First Hospital, Beijing, China
- Zhu, Yueyue, Peking University First Hospital, Beijing, China
- Xiaojuan, Yu, Peking University First Hospital, Beijing, China
- Zhang, Xin, Peking University First Hospital, Beijing, China
- Zhou, Fu De, Peking University First Hospital, Beijing, China
- Wang, Su-xia, Peking University First Hospital, Beijing, China
- Zhao, Ming-Hui, Peking University First Hospital, Beijing, China
Background
Light chain proximal tubulopathy (LCPT) results from glomerular-filtered abnormal free light chains (FLCs) that escape endosomal degradation in proximal tubular cells, leading to the formation of intracellular inclusions or excessive lysosomes. Specific FLC amino acid sequences drive tubular injury, highlighting molecular determinants of pathogenesis. Although B-cell receptor (BCR) sequencing of bone marrow samples can provide partial FLC sequence data, de novo sequencing offers a bone marrow-independent method to determine the complete amino acid sequences of FLCs.
Methods
The amino acid sequence of κWJJ, a κ-FLC in crystalline LCPT assigned to IGKV1-33, was determined by de novo sequencing previously. Using this sequence, two engineered FLCs were generated: r-κWJJ and its mutant variant r-κWJJm30 which carried a single amino acid substitution (Lys30→Ser, Fig. 1A). Six-week-old C57BL/6J mice received a single intraperitoneal injection of 100 mg purified protein. Left kidneys were harvested at 72 hours for histopathological analysis by light microscopy and ultrastructural characterization by transmission electron microscopy (TEM).
Results
TEM analysis of proximal tubular cells of r-κWJJ mice showed distinctive rod-shaped crystalline inclusions within cytoplasm as well as in tubular lumen. The crystals observed in mice closely resembled those found in the patient's kidney in terms of morphology (Fig.1B). Mice injected with r-κWJJm30 showed no intracellular or intratubular crystals. Instead, only cytoplasmic droplets were observed, suggesting that FLC was internalized via normal proximal tubular reabsorption without aggregation.
Conclusion
The accumulation of crystals was observed in proximal tubular cells after injection of r-κWJJ into mice. This observation underscores the critical role of residue Lys30 in the variable domain: its substitution to serine disrupts essential molecular interactions for crystallization.
Funding
- Government Support – Non-U.S.