Chronic exposure to paclitaxel diminishes phosphoinositide signaling by calpain-mediated neuronal calcium sensor-1 degradation

Abstract

Paclitaxel (Taxol) is a well established chemotherapeutic agent for the treatment of solid tumors, but it is limited in its usefulness by the frequent induction of peripheral neuropathy. We found that prolonged exposure of a neuroblastoma cell line and primary rat dorsal root ganglia with therapeutic concentrations of Taxol leads to a reduction in inositol trisphosphate (InsP 3)-mediated Ca 2؉ signaling. We also observed a Taxol-specific reduction in neuronal calcium sensor 1 (NCS-1) protein levels, a known modulator of InsP 3 receptor (InsP3R) activity. This reduction was also found in peripheral neuronal tissue from Taxol treated animals. We further observed that short hairpin RNA-mediated NCS-1 knockdown had a similar effect on phosphoinositide-mediated Ca 2؉ signaling. When NCS-1 protein levels recovered, so did InsP 3-mediated Ca 2؉ signaling. Inhibition of the Ca 2؉ -activated protease -calpain prevented alterations in phosphoinositide-mediated Ca 2؉ signaling and NCS-1 protein levels. We also found that NCS-1 is readily degraded by -calpain in vitro and that -calpain activity is increased in Taxol but not vehicle-treated cells. From these results, we conclude that prolonged exposure to Taxol activates -calpain, which leads to the degradation of NCS-1, which, in turn, attenuates InsP 3-mediated Ca 2؉ signaling. These findings provide a previously undescribed approach to understanding and treating Taxolinduced peripheral neuropathy.calcium imaging ͉ dorsal root ganglia ͉ endoplasmic reticulum ͉ polyneuropathy ͉ inositol 1,4,5-trisphosphate receptor

Inhibition of Paclitaxel-induced Decreases in Calcium Signaling

“…Taxol has been previously shown to interact with NCS-1 (10,11). This study confirmed that Taxol, as well as two other chemotherapeutic drugs, docetaxel and vincristine, bind to NCS-1 in the low micromolar range.…”

“…The lower NCS-1 levels in the cell, in turn, leads to decreased activation of the InsP 3 R, resulting in an attenuated calcium signal (12) as seen in the calcium signaling experiments in this study. Earlier studies have shown that Taxol diminishes the InsP 3 R-dependent calcium signal through calpain degradation of NCS-1 (11,12). This study confirmed this finding and then showed that the addition of either lithium or ibudilast to SHSY-5Y cells, a neuroblastoma cell line, treated with Taxol resulted in a protection of NCS-1 levels.…”

“…Interestingly, Taxol increases the interaction between NCS-1 and the InsP 3 R (11) which enhances intracellular calcium signaling. Treatment with Taxol also activates calpain, a calciumdependent enzyme, which cleaves a number of substrates, including NCS-1 (11,16) and the InsP 3 R (32). This cleavage of NCS-1 results in a decrease in the activity of the InsP 3 R, resulting in a decrease in the generation of intracellular calcium signals (10,11,15,17).…”

“…Treatment with Taxol also activates calpain, a calciumdependent enzyme, which cleaves a number of substrates, including NCS-1 (11,16) and the InsP 3 R (32). This cleavage of NCS-1 results in a decrease in the activity of the InsP 3 R, resulting in a decrease in the generation of intracellular calcium signals (10,11,15,17). Inhibition of calpain with calpastatin, its endogenous inhibitor, or with small molecule inhibitors, protects NCS-1 levels and intracellular calcium signals in neuroblastoma cells treated with Taxol (12).…”

Integrating Image-Based High-Content Screening with Mouse Models Identifies 5-Hydroxydecanoate as a Neuroprotective Drug for Paclitaxel-Induced Neuropathy

“…The mitoK ATP channel regulates both internal Ca 2þ concentration and the inner membrane potential upon the onset of cellular energy crisis (34). Chronic paclitaxel treatments have been reported to decrease Ca 2þ signaling (14,35) and impair SOCE (36), which is related to peripheral neuropathy (37). Our data showing that pretreatment with 5-HD significantly reversed the paclitaxel-induced decreases in SOCE implying that 5-HD may prevent chemotherapy-induced peripheral neuropathy by restoring [Ca 2þ ] i homeostasis in DRG neurons.…”