The nephrotoxic metal cadmium (Cd) is delivered to the kidneys mainly as CdMT-1 complexes, which are internalized by the PT cells in part via megalin/cubilin-mediated endocytosis (N.A. Wolff et al. 2006 JPET 318:782). In these cells, DMT1, known to also transport Cd, is localized in late endo-/lysosomal compartments (M. Abouhamed et al. 2006 Am J Physiol 290:F1525). Here we investigated the involvement of DMT1 in CdMT-1 cytotoxicity in a rat PT cell line derived from the S1 segment. Transient transfection with a DMT1 shRNA vector construct significantly reduced DMT1 protein expression determined by immunoblotting by ~45% relative to empty vector controls, and attenuated DMT1 immunofluorescence. In MTT cytotoxicity assays, this shRNA significantly decreased 24 h CdMT-1 cytotoxicity by ~30%, while toxicity of free Cd and internalization of labeled MT-1 remained unaltered, indicating intactness of pro-apoptotic signaling and CdMT-1 uptake despite DMT1 knockdown. These data support a role for DMT1 in PT CdMT-1 cytotoxicity, by possibly mediating efflux of Cd released from MT-1 from endo-/lysosomal compartments into the cytosol.

Funded by DFG TH 345/8-1.