These findings identify miR-212 as a novel cocaine-responsive gene that is up regulated in the striatum in response to cocaine overconsumption that serves to promote CREB activity through positive feedback and thereby attenuate the motivational properties of the drug. Based on these findings, we next investigated the mechanisms by which miR-212 may amplify CREB signaling. We found that miR-212 increases activity-dependent production of cAMP by sensitizing adenylyl cyclase activity. This stimulatory action on adenylyl cyclase results in accumulation of phosphorylated CREB and increased activity of the core CREB co-activators CREB-regulated transcription co-activator-1 and -2 (CRTC1 and CRTC2), also known as TORC1 and TORC2. Further investigation of the mechanism by which miR-212 enhances CREB signaling revealed that the kinase Raf1 was activated by miR-212, and was found to play a key role in sensitizing adenylyl cyclase activity. Finally, computational and biochemical analysis showed that Sprouty-related EVH1 domain-containing protein 1 (SPRED1), a known negative regulator of Raf1 signaling, is a miR-212 target mRNA transcript and SPRED1 repression by miR-212 contributes to its stimulatory effects on Raf1 and CREB activity (Hollander et al., 2010).
