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Activating transcription factor 6 (ATF6) is an endoplasmic reticulum (ER) stress-regulated transcription factor that induces expression of major molecular chaperones in the ER. We recently reported that ATF6β, a subtype of ATF6, promoted survival of hippocampal neurons exposed to ER stress and excitotoxicity, at least in part by inducing expression of calreticulin, an ER molecular chaperone with high Ca2+-binding capacity. In the present study, we demonstrate that ATF6β deficiency in mice also decreases calreticulin expression and increases expression of glucose-regulated protein 78, another ER molecular chaperone, in emotional brain regions such as the prefrontal cortex (PFC), hypothalamus, hippocampus, and amygdala. Comprehensive behavioral analyses revealed that Atf6b−/− mice exhibit anxiety-like behavior in the light/dark transition test and hyperactivity in the forced swim test. Consistent with these results, PFC and hypothalamic corticotropin-releasing hormone (CRH) expression was increased in Atf6b−/− mice, as was circulating corticosterone. Moreover, CRH receptor 1 antagonism alleviated anxiety-like behavior in Atf6b−/− mice. These findings suggest that ATF6β deficiency produces anxiety-like behavior and hyperactivity via a CRH receptor 1-dependent mechanism. ATF6β could play a role in psychiatric conditions in the emotional centers of the brain. [ABSTRACT FROM AUTHOR]

While ATF6α plays a central role in the endoplasmic reticulum (ER) stress response, the function of its paralogue ATF6β remains elusive, especially in the central nervous system (CNS). Here, we demonstrate that ATF6β is highly expressed in the hippocampus of the brain, and specifically regulates the expression of calreticulin (CRT), a molecular chaperone in the ER with a high Ca2+-binding capacity. CRT expression was reduced to ~ 50% in the CNS of Atf6b−/− mice under both normal and ER stress conditions. Analysis using cultured hippocampal neurons revealed that ATF6β deficiency reduced Ca2+ stores in the ER and enhanced ER stress-induced death. The higher levels of death in Atf6b−/− neurons were recovered by ATF6β and CRT overexpressions, or by treatment with Ca2+-modulating reagents such as BAPTA-AM and 2-APB, and with an ER stress inhibitor salubrinal. In vivo, kainate-induced neuronal death was enhanced in the hippocampi of Atf6b−/− and Calr+/− mice, and restored by administration of 2-APB and salubrinal. These results suggest that the ATF6β-CRT axis promotes neuronal survival under ER stress and excitotoxity by improving intracellular Ca2+ homeostasis. [ABSTRACT FROM AUTHOR]

We study the collapse of a many-body system which is used to model two-component Bose–Einstein condensates with attractive intra-species interactions and either attractive or repulsive inter-species interactions. Such a system consists a mixture of two different species for N identical bosons in R 2 , interacting with potentials rescaled in the mean-field manner - N 2 β - 1 w (σ) (N β x) with ∫ R 2 w (σ) (x) d x = 1 . Assuming that 0 < β < 1 / 2 , we first show that the leading order of the quantum energy is captured correctly by the Gross–Pitaevskii energy. Secondly, we investigate the blow-up behavior of the quantum energy as well as the ground states when N → ∞ , and either the total interaction strength of intra-species and inter-species or the strengths of intra-species interactions of each component approach sufficiently slowly a critical value, which is the critical strength for the focusing Gross–Pitaevskii functional. We prove that the many-body ground states fully condensate on the (unique) Gagliardo–Nirenberg solution. [ABSTRACT FROM AUTHOR]

We study minimizers of the pseudo-relativistic Hartree functional $${\mathcal {E}}_{a}(u):=\Vert (-\varDelta +m^{2})^{1/4}u\Vert _{L^{2}}^{2}+\int _{{\mathbb {R}}^{3}}V(x)|u(x)|^{2}\mathrm{d}x-\frac{a}{2}\int _{{\mathbb {R}}^{3}}(\left| \cdot \right| ^{-1}\star |u|^{2})(x)|u(x)|^{2}\mathrm{d}x$$ under the mass constraint $$\int _{{\mathbb {R}}^3}|u(x)|^2\mathrm{d}x=1$$ . Here $$m>0$$ is the mass of particles and $$V\ge 0$$ is an external potential. We prove that minimizers exist if and only if a satisfies $$0\le a0$$ . [ABSTRACT FROM AUTHOR]

We consider the gravitational collapse for neutron stars in the Hartree–Fock–Bogoliubov theory. We prove that when the number particle becomes large and the gravitational constant is small such that the attractive interaction strength approaches the Chandrasekhar limit mass slowly, the minimizers develop a universal blow-up profile. It is given by the Lane–Emden solution. [ABSTRACT FROM AUTHOR]