A zebrafish luminescent biosensor for kidney tubulopathy, metal toxicity and drug screening.

An efficient endolysosomal pathway is crucial to mediate the reabsorption and processing of ultrafiltered solutes including low-molecular-weight (LMW) proteins by epithelial cells lining the proximal tubule (PT) of the kidney. The zebrafish pronephros is used as a model system for congenital or acquired disorders that impair endolysosomal processing in PT cells, causing inappropriate loss of solutes and LMW proteins in urine. Here, we describe a new reporter ½vdbp-NanoLuc zebrafish line, in which vitamin D-binding protein is coupled to NanoLuc luciferase for detection of PT dysfunction and LMW proteinuria. We demonstrate the reliability and value of the ½vdbp-NanoLuc biosensor in fish models of monogenic endolysosomal diseases, gentamicin and cisplatin-induced nephrotoxicity, and metal contamination. This novel reporter system yields mechanistic insights into cadmium- and copper-induced PT dysfunction and provides a platform for drug screening.