Theo Rein and colleagues examine the role of FKBP51 in the actions of antidepressants, with a particular focus on pathways of autophagy. Please see later in the article for the Editors' Summary

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Stress impairs cognition via corticotropin-releasing hormone receptor 1 (CRHR1), but the molecular link between abnormal CRHR1 signaling and stress-induced cognitive impairments remains unclear. We investigated whether the cell adhesion molecule nectin-3 is required for the effects of CRHR1 on cognition and structural remodeling after early-life stress exposure. Postnatally stressed adult mice had decreased hippocampal nectin-3 levels, which could be attenuated by CRHR1 inactivation and mimicked by corticotropin-releasing hormone (CRH) overexpression in forebrain neurons. Acute stress dynamically reduced hippocampal nectin-3 levels, which involved CRH-CRHR1, but not glucocorticoid receptor, signaling. Suppression of hippocampal nectin-3 caused spatial memory deficits and dendritic spine loss, whereas enhancing hippocampal nectin-3 expression rescued the detrimental effects of early-life stress on memory and spine density in adulthood. Our findings suggest that hippocampal nectin-3 is necessary for the effects of stress on memory and structural plasticity and indicate that the CRH-CRHR1 system interacts with the nectin-afadin complex to mediate such effects.

Chronic stress evokes profound structural and molecular changes in the hippocampus, which may underlie spatial memory deficits. Corticotropin-releasing hormone (CRH) and CRH receptor 1 (CRHR1) mediate some of the rapid effects of stress on dendritic spine morphology and modulate learning and memory, thus providing a potential molecular basis for impaired synaptic plasticity and spatial memory by repeated stress exposure. Using adult male mice with CRHR1 conditionally inactivated in the forebrain regions, we investigated the role of CRH-CRHR1 signaling in the effects of chronic social defeat stress on spatial memory, the dendritic morphology of hippocampal CA3 pyramidal neurons, and the hippocampal expression of nectin-3, a synaptic cell adhesion molecule important in synaptic remodeling. In chronically stressed wild-type mice, spatial memory was disrupted, and the complexity of apical dendrites of CA3 neurons reduced. In contrast, stressed mice with forebrain CRHR1 deficiency exhibited normal dendritic morphology of CA3 neurons and mild impairments in spatial memory. Additionally, we showed that the expression of nectin-3 in the CA3 area was regulated by chronic stress in a CRHR1-dependent fashion and associated with spatial memory and dendritic complexity. Moreover, forebrain CRHR1 deficiency prevented the down-regulation of hippocampal glucocorticoid receptor expression by chronic stress but induced increased body weight gain during persistent stress exposure. These findings underscore the important role of forebrain CRH-CRHR1 signaling in modulating chronic stress-induced cognitive, structural and molecular adaptations, with implications for stress-related psychiatric disorders.