Translin deletion impairs cocaine-induced locomotor sensitization and RGS8 expression in the nucleus accumbens

Multiple lines of evidence show that the microRNA system plays a prominent role in regulating behavioral responses to psychostimulants. Suppressing microRNA degradation is an effective strategy for elucidating the impact of these intracellular messengers on cellular function. The translin/trax complex is an RNase that appears to mediate degradation of a small number of microRNAs. In this study we investigated the effect of deleting the translin/trax microRNA-degrading enzyme on cocaine-induced behavioral responses in mice. Wild type and Translin (Tsn) KO mice were injected with cocaine and their open-field locomotor activity was monitored. We found that the locomotor activity in response to repeated (5, 10 and 20 mg/kg, i.p.), but not acute (20 mg/kg, i.p.), cocaine exposure was significantly impaired in Tsn KO mice. We identified several microRNAs (412-5p, 412-3p, 93-3p, 7b-3p, and 204-5p) that were significantly increased in the NAc of Tsn KO mice. As regulator of G-protein signaling 8 (RGS8) is a predicted target gene shared by three of these microRNAs, and expressed in the NAc, we confirmed its reduced expression in this region in Tsn KO mice. Moreover, shRNA-mediated knockdown of RGS8 in the NAc attenuated locomotor sensitization to repeated cocaine administration. Taken together, our results suggest that microRNAs targeted by the translin/trax RNase inhibit cocaine-induced locomotor sensitization, in part, by silencing expression of RGS8.