Abstract
Exosomes are increasingly recognized as vehicles of intercellular communication. However, the role of exosome in maintaining cellular homeostasis under stress conditions remained unclear. Here we show that Rab27a expression was upregulated exclusively in tubular epithelial cells (TECs) during proteinuria nephropathy established by adriamycin (ADR) injection and 5/6 nephrectomy as well as in chronic kidney disease patients, leading to the increased secretion of exosomes carrying albumin. The active exosome production promoted tubule injury and inflammation in neighboring and the producing cells. Interferon regulatory factor 1 (IRF-1) was found as the transcription factor contributed to the upregulation of Rab27a. Albumin could be detected in exosome fraction and co-localized with exosome marker CD63 indicating the secretion of albumin into extracellular space by exosomes. Interestingly, inhibition of exosome release accelerated albumin degradation which reversed tubule injury with albumin overload, while lysosome suppression augmented exosome secretion and tubule inflammation. Our findings revealed that IRF-1/Rab27a mediated exosome secretion constituted a coordinated approach to lysosome degradation for albumin handling, which lead to the augment of albumin toxicity as a maladaptive response to maintain cell homeostasis. The findings may suggest a novel therapeutic strategy for proteinuric kidney disease by targeting exosome secretion.