SummaryA minority of individuals experiencing traumatic events develop anxiety disorders. The reason for the lack of correspondence between the prevalence of exposure to psychological trauma and the development of anxiety is unknown. Extracellular proteolysis contributes to fear-associated responses by facilitating neuronal plasticity at the neuron-matrix interface1-4. Here we show that the serine protease neuropsin is critical for stress-related plasticity in the amygdala by regulating the dynamics of EphB2/NMDA receptor interaction, the expression of Fkbp5 and anxiety-like behaviour. Stress results in neuropsin-dependent cleavage of EphB2 in the amygdala causing dissociation of EphB2 from the NR1-subunit of NMDA receptor and promoting membrane turnover of EphB2 receptors. Dynamic EphB2/NR1 interaction enhances NMDA receptor current, induces the Fkbp5 gene expression and enhances behavioural signatures of anxiety. Upon stress, neuropsin-deficient mice do not show EphB2 cleavage and its dissociation from NR1 resulting in a static EphB2/NR1 interaction, attenuated induction of the Fkbp5 gene and low anxiety. The behavioural response to stress can be restored by intra-amygdala injection of neuropsin into neuropsin-deficient mice and disrupted by the injection of either anti-EphB2 antibodies or silencing the Fkbp5 gene in the amygdala of wild-type animals. Our findings establish a novel neuronal pathway linking stress-induced proteolysis of EphB2 in the amygdala to anxiety.

Psychological stress causes adaptive changes in the nervous system directed toward maintaining homoeostasis. These biochemical and structural mechanisms regulate animal behavior, and their malfunction may result in various forms of affective disorders. Here we found that the lipocalin-2 (Lcn2) gene, encoding a secreted protein of unknown neuronal function, was up-regulated in mouse hippocampus following psychological stress. Addition of lipocalin-2 to cultured hippocampal neurons reduced dendritic spine actin's mobility, caused retraction of mushroom spines, and inhibited spine maturation. These effects were further enhanced by inactivating iron-binding residues of Lcn-2, suggesting that they were facilitated by the iron-free form of Lcn-2. Concurrently, disruption of the Lcn2 gene in mice promoted stress-induced increase in spine density and caused an increase in the proportion of mushroom spines. The above changes correlated with higher excitability of CA1 principal neurons and with elevated stress-induced anxiety in Lcn-2 −/− mice.Our study demonstrates that lipocalin-2 promotes stress-induced changes in spine morphology and function to regulate neuronal excitability and anxiety.restraint stress | limbic system | remodeling S tress triggers a variety of adaptive cellular processes that help to maintain nervous system homeostasis and to shape the adequate behavioral response of an animal (1). The nature and extent of these region-specific alterations depends on the duration and severity of the traumatic experience (1-4). Failure to adjust biochemical and structural properties of neurons in stresssensitive brain regions often results in affective disorders that can be as diverse as their underlying causes.Despite considerable effort (1-5), the mechanisms of structural and functional neuronal plasticity underlying the stress response are not well understood. It is known that multiple stress-related pathways affect dendritic structure and spine motility, density, shape, and receptor composition within the spine (6, 7). These changes in dendritic spine morphology and function affecting synaptic and local circuit organization may compose a cellular substrate for altered emotional responses (1-3).Identifying the roles of different pathways involved in stressinduced plasticity is fundamental for our understanding of how diverse mechanisms may result in similar neuronal phenotypes to culminate in a common behavioral outcome-the development of anxiety disorders. In this respect, glucocorticoids and glucocorticoid-regulated genes are instrumental in modulating stress-related neuronal machinery, central nervous system physiology, and animal behavior (8). However, neuronal functions of numerous glucocorticoid-regulated genes are still unclear. Lipocalin-2, a member of the family of over 20 small secreted proteins serving diverse cellular roles (9), caught our attention because it is upregulated by glucocorticoids (10) and has been implicated in tissue restructuring, organ involution, and cellular invasiveness in other sys...

Familial hemiplegic migraine (FHM) is a rare subtype of migraine with aura. Mutations causing FHM type 3 have been identified in SCN1A, the gene encoding the Na v 1.1 Na + channel, which is also a major target of epileptogenic mutations and is particularly important for the excitability of GABAergic neurons. However, functional studies of Na V 1.1 FHM mutations have generated controversial results. In particular, it has been shown that the Na V 1.1-L1649Q mutant is nonfunctional when expressed in a human cell line because of impaired plasma membrane expression, similarly to Na V 1.1 mutants that cause severe epilepsy, but we have observed gain-offunction effects for other Na V 1.1 FHM mutants. Here we show that Na V 1.1-L1649Q is nonfunctional because of folding defects that are rescuable by incubation at lower temperatures or coexpression of interacting proteins, and that a partial rescue is sufficient for inducing an overall gain of function because of the modifications in gating properties. Strikingly, when expressed in neurons, the mutant was partially rescued and was a constitutive gain of function. A computational model showed that 35% rescue can be sufficient for inducing gain of function. Interestingly, previously described folding-defective epileptogenic Na V 1.1 mutants show loss of function also when rescued. Our results are consistent with gain of function as the functional effect of Na V 1.1 FHM mutations and hyperexcitability of GABAergic neurons as the pathomechanism of FHM type 3.spreading depression | Dravet syndrome | generalized epilepsy with febrile seizures plus | calmodulin | ankyrin