mTORC1 activation contributes to autophagy inhibition via its recruitment to lysosomes and consequent lysosomal dysfunction in cadmium-exposed rat proximal tubular cells

• Published in: Journal of inorganic biochemistry Vol. 212; p. 111231
• Main Authors: Lian, Cai-Yu, Yang, Heng, Zhai, Zhen-Zhen, Li, Zi-Fa, Han, Dian-Gang, Wang, Lin
• Format: Journal Article
• Language: English
• Published: United States Elsevier Inc 01.11.2020
• Subjects: Autophagy; Cadmium; Kidney; Lysosome; mTORC1; rPT cells; p70S6K; DMSO; Lysosome; rPT cells; PFA; LTR; Autophagy; RIPA; Kidney; 4EBP1; LAMP-2; V-ATPases; DQ-BSA-Green; BCA; Cadmium; Rapa; TFE3; TFEB; DAPI; PVDF; SDS-PAGE; ULK1/ULK2; rPT; RFP-GFP-LC3; ROS; mTORC2; mTORC1
• ISSN: 0162-0134; 1873-3344; 1873-3344
• DOI: 10.1016/j.jinorgbio.2020.111231

Autophagy dysregulation is implicated in cadmium (Cd)-induced nephrotoxicity. The mammalian target of rapamycin complex 1 (mTORC1) is a negative regulator of autophagy, but its role in Cd-induced autophagy inhibition and possible regulatory mechanisms remains poorly understood. In the present study, Cd exposure activated mTORC1 in primary rat proximal tubular (rPT) cells, and two mTORC1 inhibitors (rapamycin and torin 1) were separately utilized to inhibit Cd-induced mTORC1 activation. Data showed that Cd-inhibited autophagic flux was markedly restored by two mTORC1 inhibitors, respectively, as evidenced by immunoblot analysis of autophagy marker proteins and tandem red fluorescent protein-green fluorescent protein-microtubule associated protein light chain 3 (RFP-GFP-LC3) fluorescence microscopy assay. Importantly, Cd exposure triggered the recruitment of mTORC1 onto lysosome membrane assessed by immunofluorescence co-localization analysis, which was obviously inhibited by rapamycin or torin 1. Moreover, Cd-induced lysosomal alkalization, suppressed vacuolar ATPases (V-ATPases) protein levels and impaired lysosomal degradation capacity were markedly reversed by rapamycin or torin 1. In summary, these findings demonstrate that Cd recruits mTORC1 to lysosome membrane to induce its activation, which results in lysosomal dysfunction and resultant autophagy inhibition in rPT cells. Cd-induced mammalian target of rapamycin complex 1 (mTORC1) activation contributes to lysosomal dysfunction and autophagy blockage in primary rat proximal tubular (rPT) cells. [Display omitted] •The definition of mammalian target of rapamycin complex 1 is simplified as mTORC1.•Cadmium (Cd) exposure induces the activation of mTORC1.•Recruitment of mTORC1 to lysosomes contributes to Cd-induced autophagy blockage.•Cd-activated mTORC1 is involved in lysosomal dysfunction.