Morphine Promotes Astrocyte‐Preferential Differentiation of Mouse Hippocampal Progenitor Cells via PKCε‐Dependent ERK Activation and TRBP Phosphorylation

Previously we have shown that morphine regulates adult neurogenesis by modulating miR‐181a maturation and subsequent hippocampal neural progenitor cell (NPC) lineages. Using NPCs cultured from PKCε or β‐arrestin2 knockout mice and the MAPK/ERK kinase inhibitor U0126, we demonstrate that regulation of NPC differentiation via the miR‐181a/Prox1/Notch1 pathway exhibits ligand‐dependent selectivity. In NPCs, morphine and fentanyl activate ERK via the PKCε‐ and β‐arrestin‐dependent pathways, respectively. After fentanyl exposure, the activated phospho‐ERK translocates to the nucleus. Conversely, after morphine treatment, phospho‐ERK remains in the cytosol and is capable of phosphorylating TAR RNA‐binding protein (TRBP), a cofactor of Dicer. This augments Dicer activity and promotes the maturation of miR‐181a. Furthermore, using NPCs transfected with wild‐type TRBP, SΔA, and SΔD TRBP mutants, we confirmed the crucial role of TRBP phosphorylation in Dicer activity, miR‐181a maturation, and finally the morphine‐induced astrocyte‐preferential differentiation of NPCs. Thus, morphine modulates the lineage‐specific differentiation of NPCs by PKCε‐dependent ERK activation with subsequent TRBP phosphorylation and miR‐181a maturation. Stem Cells 2015;33:2762–2772