ABSTRACT
In the developing brain, immature synapses contain calcium-permeable AMPA glutamate receptors (AMPARs) that are subsequently replaced with GluA2-containing calcium-impermeable AMPARs as synapses stabilize and mature. Here, we show that this essential switch in AMPARs and neuronal synapse maturation is regulated by astrocytes. Using biochemical fractionation of astrocyte-secreted proteins and mass spectrometry, we identified that astrocyte-secreted chordin-like 1 (Chrdl1) is necessary and sufficient to induce mature GluA2-containing synapses to form. This function of Chrdl1 is independent of its role as an antagonist of bone morphogenetic proteins (BMPs). Chrdl1 expression is restricted to cortical astrocytes in vivo, peaking at the time of the AMPAR switch. Chrdl1 knockout (KO) mice display reduced synaptic GluA2 AMPARs, altered kinetics of synaptic events, and enhanced remodeling in an in vivo plasticity assay. Studies have shown that humans with mutations in Chrdl1 display enhanced learning. Thus astrocytes, via the release of Chrdl1, promote GluA2-dependent synapse maturation and thereby limit synaptic plasticity.
Subject(s)
Astrocytes/metabolism , Eye Proteins/physiology , Nerve Tissue Proteins/physiology , Neuronal Plasticity , Receptors, AMPA/metabolism , Synapses/physiology , Animals , Cells, Cultured , Eye Proteins/metabolism , Female , Male , Mice, Inbred C57BL , Mice, Knockout , Nerve Tissue Proteins/metabolism , Rats, Sprague-DawleyABSTRACT
gp78 is a membrane-anchored ubiquitin ligase mediating the degradation of HMG-CoA reductase (HMGCR) and Insig-1. As a rate-limiting enzyme in cholesterol biosynthesis, HMGCR undergoes rapid sterol-promoted degradation. In contrast, destruction of Insig-1 releases its inhibition on SREBP and stimulates the expression of lipogenic genes. Thus, gp78 has opposite effects on lipid biosynthesis. We here generated liver-specific gp78 knockout (L-gp78(-/-)) mice and showed that although the degradation of HMGCR was blunted, SREBP was suppressed due to the elevation of Insig-1/-2, and therefore the lipid biosynthesis was decreased. The L-gp78(-/-) mice were protected from diet-/age-induced obesity and glucose intolerance. The livers of L-gp78(-/-) mice produced more FGF21, which activated thermogenesis in brown adipocytes and enhanced energy expenditure. Together, the major function of gp78 in liver is regulating lipid biosynthesis through SREBP pathway. Ablation of gp78 decreases the lipid levels and increases FGF21, and is beneficial to patients with metabolic diseases.
Subject(s)
Hyperlipidemias/genetics , Insulin Resistance/genetics , Lipids/biosynthesis , Liver/metabolism , Receptors, Autocrine Motility Factor/deficiency , Sterol Regulatory Element Binding Proteins/antagonists & inhibitors , Animals , Blood Glucose , Chromatography, Liquid , Fibroblast Growth Factors/metabolism , Hydroxymethylglutaryl CoA Reductases/metabolism , Membrane Proteins/metabolism , Mice , Mice, Knockout , Receptors, Autocrine Motility Factor/metabolismABSTRACT
The title compouand {[Zn(C(4)H(4)O(6))(C(12)H(8)N(2))]·6H(2)O}(n), has a linear chain structure parallel to [100] with Zn(C(4)H(4)O(6))(C(12)H(8)N(2)) repeat units; the asymmetric unit consists of one Zn(2+) cation, one l-tartrate dianion, one 1,10-phenanthroline and six free water mol-ecules. The Zn atom is in a distorted octa-hedral ZnN(2)O(4) coordination environment. The crystal structure is stabilized by O-Hâ¯O hydrogen bonds and π-π stacking of the phenanthroline units [centroid-centroid distances in the range 3.552â (2)-3.625â (2)Å] occurs between the chains. The title compound is isotypic with the Cu and Mn analogues.
ABSTRACT
The title salt, (C(6)H(11)N(2))(2)[Cd(C(7)H(3)NO(4))(2)], displays a discrete mononuclear structure, in which the central Cd(II) atom is six-coordinated in a distorted octa-hedral coordination geometry by two N and four O atoms from two different pyridine-2,6-dicarboxyl-ate anions in an O(2),N,O(6)-tridentate chelation mode. The crystal packing is stabilized by N-Hâ¯O hydrogen bonds and π-π inter-actions [centroid-centroid distance = 3.576â (5)â Å].
ABSTRACT
In the title compound, [Mn(C(10)H(10)N(2))(6)](ClO(4))(2), the Mn(II) ion, located on an inversion center, is coordinated by six N atoms from three pairs of symmetry-related 1-benzyl-1H-imidazole ligands in a distorted octa-hedral geometry. In the crystal, weak inter-molecular C-Hâ¯O hydrogen bonds link the complex cations and perchlorate anions.
ABSTRACT
In the title compound, C(14)H(14)N(4), the center of the phenyl-ene group is a crystallographic center of inversion. The compound is composed of three aromatic rings displaying a Z-like conformation. The dihedral angle between the pyrazole rings and the central phenyl ring is 83.84â (9)°.
ABSTRACT
In the dication of the title compound, C(16)H(20)N(4) (2+)·C(10)H(4)O(8) (2-)·H(2)O, the dihedral angles formed by mean planes of the imidazolium rings and the benzene ring are 69.05â (18) and 89.1â (2)°. In the crystal, the components are linked into a three-dimensional network by inter-molecular N-Hâ¯O and O-Hâ¯O hydrogen bonds.
ABSTRACT
In the pseudo-centrosymmetric mol-ecule of the title compound, C(18)H(16)N(4), two benzimidazole fragments form the dihedral angles of 83.49â (7) and 79.37â (7)°, with the mean plane of the linking butene chain. No classical inter-molecular inter-actions are observed. The porous crystal packing exhibits voids of 85â Å(3).
ABSTRACT
The asymmetric unit of the title compound, C(14)H(16)N(4) (2+)·2C(7)H(4)NO(4) (-)·2C(7)H(5)NO(4), comprises one-half of the 3,3'-(p-phenyl-enedimethyl-ene)di-1H-imidazol-1-ium dication, which lies on an inversion centre, one 4-nitro-benzoate anion and one 4-nitro-benzoic acid mol-ecule. In the crystal, the components are linked into a two-dimensional network parallel to (110) by O-Hâ¯O, N-Hâ¯O and C-Hâ¯O hydrogen bonds.
