In cystinosis, renal proximal tubule (RPT) function is compromised, due to mutations in ctns, which encodes for the transporter cystinosin, which removes cystine from lysosomes. Altered RPT function in cystinosis has been attributed to decreased ATP, as well as increased apoptosis. In this report, the role of AMPK was examined. AMPK was activated in primary rabbit RPT cells with a cystinosin knockdown, using cystinosin siRNA. The activation of AMPK was associated with a 50% decrease in ATP and a 1.7-fold increase in the ADP/ATP level. Cisplatin-induced apoptosis also increased in primary RPT cells with a cystinosin knockdown. The role of AMPK in the increased sensitivity to cisplatin was examined. The increased sensitivity to cisplatin was prevented in primary RPT cells with a cystinosin knockdown by the AMPK inhibitor Compound C. The effect of siRNAs against AMPK alpha 1 and AMPK alpha 2 was also studied. The siRNAs knocked down AMPK alpha, and prevented AMPK alpha activation by 5-aminoimidazole-4-carboxamide-1-beta-D-ribofuranoside (AICAR). The siRNAs against AMPK alpha 1 and AMPK alpha 2 also prevented the increased sensitivity to cisplatin in the primary RPT cells with a cystinosin knockdown. These results suggest that signaling through AMPK plays a role in the enhanced apoptosis in the RPT in cystinosis. (C) 2012 Elsevier Inc. All rights reserved.