Depression, a devastating psychiatric disorder, is a leading cause of disability worldwide. Current antidepressants address specific symptoms of the disease, but there is vast room for improvement . In this respect, new compounds that act beyond classical antidepressants to target signal transduction pathways governing synaptic plasticity and cellular resilience are highly warranted. The extracellular signal-regulated kinase (ERK) pathway is implicated in mood regulation, but its pleiotropic functions and lack of target specificity prohibit optimal drug development. Here, we identified the transcription factor ELK-1, an ERK downstream partner , as a specific signaling module in the pathophysiology and treatment of depression that can be targeted independently of ERK. ELK1 mRNA was upregulated in postmortem hippocampal tissues from depressed suicides; in blood samples from depressed individuals, failure to reduce ELK1 expression was associated with resistance to treatment. In mice, hippocampal ELK-1 overexpression per se produced depressive behaviors; conversely, the selective inhibition of ELK-1 activation prevented depression-like molecular, plasticity and behavioral states induced by stress. Our work stresses the importance of target selectivity for a successful approach for signal-transduction-based antidepressants, singles out ELK-1 as a depression-relevant transducer downstream of ERK and brings proof-of-concept evidence for the druggability of ELK-1.

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Drug addiction involves profound modifications of neuronal plasticity in the nucleus accumbens, which may engage various cell types. Here, we report prominent effects of cocaine on calcium signals in astrocytes characterized by in vivo fiber photometry. Astrocyte calcium signals in the nucleus accumbens are sufficient and necessary for the acquisition of cocaine seeking behavior. We identify the astrocyte-secreted matricellular protein hevin as an effector of the action of cocaine and calcium signals on reward and neuronal plasticity.

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