Figure 2.

Cisplatin exposure activates both the c-Jun N-terminal kinase (JNK) and mammalian target of rapamycin (mTOR) pathways in sensory hair cells. (A) Cisplatin exposure resulted in a coordinated increase in phosphorylated JNK (p-JNK) and phosphorylated ribosomal protein S6 (p-rpS6) immunoreactivity, indicating an activation of the JNK and mTOR pathways. When explant cultures were exposed to both cisplatin and the multikinase inhibitor sorafenib (500 nM), the activation of JNK and mTOR pathways were inhibited. Rapamycin exposure did not alter the cisplatin-induced activation of JNK, but prevented activation of mTOR. When cultures were incubated with 100 nM insulin for 4 h, it resulted in robust activation of mTOR but not the JNK pathway (bottom panel). (B) AHA-biotin immunoblot showing that when administered with cisplatin, insulin lead to a 34% increase (p-value 0.004) in overall cellular protein synthesis, when compared to cisplatin alone. (C) Immunoblot confirming cisplatin-induced activation of the JNK pathway (as measured by p-c-Jun) and mTOR (as measured by p-rpS6), and the modulation of this response by sorafenib, rapamycin and insulin. Scale bar 20 μm.