TSPO/PBR, a component of mPTP, modulates ethanol-related behaviors in Drosophila. Ran Lin, Douglas Wallace. Children's Hospital of Philadelphia Research Institute, Philadelphia, PA.

   The translocator protein 18kDa (TSPO), formerly named peripheral benzodiazepine receptor (PBR), is a putative component of mitochondrial permeability transition pore (mPTP). As the binding site of benzodiazepine, a psychoactive drug that induces tolerance and addiction, TSPO is hypothesized as an essential factor involved in addiction of benzodiazepine and other abusive substances. By pharmacological and genetic inactivation, we analyzed the function of dTSPO in Drosophila, concentrating on mPTP and behavioral responses to the most commonly used abusive substance, ethanol. Inactivation of dTSPO by ligands (PK11195 and Ro5-4864), P-element insertion in the genomic region, and transgenic expression of dsRNA all inhibited mPTP opening, based on recording for swelling in isolated mitochondria from adult flies. In living cells of larval brain, mPTP opening was also shown to be attenuated by PK11195, or in dTSPO-/- flies, based on Cobalt/Calcein quenching assay. Thus dTSPO is required for mPTP opening in flies. To monitor the sensitivity to ethanol, we measured the time to sedation in flies exposed to ethanol vapor. The dTSPO-/- flies were more sensitive, while neuronal-specific dTSPO knock-down flies were more resistant, than control flies. After 6 hours of first exposure to ethanol, flies exhibited resistance if exposed to ethanol again, indicating the formation of tolerance. However, dTSPO-/- flies were not able to form tolerance in this condition, while neuronal-specific dTSPO knock-down flies were more tolerant than control. Moreover, neither dTSPO-/- nor neuronal-specific dTSPO knock-down Drosophila performed strong preference to ethanol-containing food over regular food in two-choice feeding assay, as control flies did. Taken together, dTSPO is an important component of mPTP in Drosophila, and modulates multiple ethanol-related behaviors in tissue-specific manner.