SAT1, A Glutamine Transporter, is Preferentially Expressed in GABAergic Neurons

Subsets of GABAergic neurons are able to maintain high frequency discharge patterns, which requires efficient replenishment of the releasable pool of GABA. Although glutamine is considered a preferred precursor of GABA, the identity of transporters involved in glutamine uptake by GABAergic neurons remains elusive. Molecular analyses revealed that SAT1 (Slc38a1) features system A characteristics with a preferential affinity for glutamine, and that SAT1 mRNA expression is associated with GABAergic neurons. By generating specific antibodies against SAT1 we show that this glutamine carrier is particularly enriched in GABAergic neurons. Cellular SAT1 distribution resembles that of GAD67, an essential GABA synthesis enzyme, suggesting that SAT1 can be involved in translocating glutamine into GABAergic neurons to facilitate inhibitory neurotransmitter generation

The Glutamine Transporter Slc38a1 Regulates GABAergic Neurotransmission and Synaptic Plasticity

GABA signaling sustains fundamental brain functions, from nervous system development to the synchronization of population activity and synaptic plasticity. Despite these pivotal features, molecular determinants underscoring the rapid and cell-autonomous replenishment of the vesicular neurotransmitter GABA and its impact on synaptic plasticity remain elusive. Here, we show that genetic disruption of the glutamine transporter Slc38a1 in mice hampers GABA synthesis, modifies synaptic vesicle morphology in GABAergic presynapses and impairs critical period plasticity. We demonstrate that Slc38a1-mediated glutamine transport regulates vesicular GABA content, induces high-frequency membrane oscillations and shapes cortical processing and plasticity. Taken together, this work shows that Slc38a1 is not merely a transporter accumulating glutamine for metabolic purposes, but a key component regulating several neuronal functions

Two Late Pleistocene human femora from Trinil, Indonesia: Implications for body size and behavior in Southeast Asia

Late Pleistocene hominin postcranial specimens from Southeast Asia are relatively rare. Here we describe and place into temporal and geographic context two partial femora from the site of Trinil, Indonesia, which are dated stratigraphically and via Uranium-series direct dating to ca. 37–32 ka. The specimens, designated Trinil 9 and 10, include most of the diaphysis, with Trinil 9 being much better preserved. Microcomputed tomography is used to determine cross-sectional diaphyseal properties, with an emphasis on midshaft anteroposterior to mediolateral bending rigidity (Ix/Iy), which has been shown to relate to both body shape and activity level in modern humans. The body mass of Trinil 9 is estimated from cortical area and reconstructed length using new equations based on a Pleistocene reference sample. Comparisons are carried out with a large sample of Pleistocene and Holocene East Asian, African, and European/West Asian femora. Our results show that Trinil 9 has a high Ix/Iy ratio, most consistent with a relatively narrow-bodied male from a mobile hunting-gathering population. It has an estimated body mass of 55.4 kg and a stature of 156 cm, which are small relative to Late Pleistocene males worldwide, but larger than the penecontemporaneous Deep Skull femur from Niah Cave, Malaysia, which is very likely female. This suggests the presence of small-bodied active hunter-gatherers in Southeast Asia during the later Late Pleistocene. Trinil 9 also contrasts strongly in morphology with earlier partial femora from Trinil dating to the late Early-early Middle Pleistocene (Femora II–V), and to a lesser extent with the well-known complete Femur I, most likely dating to the terminal Middle-early Late Pleistocene. Temporal changes in morphology among femoral specimens from Trinil parallel those observed in Homo throughout the Old World during the Pleistocene and document these differences within a single site

Environmental influences on reproductive health: the importance of chemical exposures

Chemical exposures during pregnancy can have a profound and life-long impact on human health. Due to the omnipresence of chemicals in our daily life, there is continuous contact with chemicals in food, water, air and consumer products. Consequently, human biomonitoring studies show that pregnant women around the globe are exposed to a variety of chemicals. In this review, we provide a summary of current data on maternal and fetal exposure as well as health consequences from these exposures. We review several chemical classes including polychlorinated biphenyls (PCBs), perfluoroalkyl substances (PFAS), polybrominated diphenyl ethers (PBDEs), phenols, phthalates, pesticides, and metals. Additionally, we discuss environmental disparities and vulnerable populations, and future research directions. We conclude by providing some recommendations for prevention of chemical exposure and its adverse reproductive health consequences

Brain-derived neurotrophic factor and endocannabinoid functions in gabaergic interneuron development

Formation of the cerebral cortex is controlled by tightly regulated processes: the proliferation and survival decisions of neural progenitors, radial and tangential migration of neuronal precursors, axon guidance and dendritic growth underpinning the formation of synapses. Patterning of the neocortex has been extensively studied and significant progress has been made in understanding the principles of cortical neuronal circuit formation. However, the cellular and molecular factors that coordinate the establishment of specialized neuronal subnetworks remain unclear. In this thesis the roles of brain-derived neurotrophic factor (BDNF) and endocannabinoids, critical regulators of synaptic plasticity, were studied for their functions in corticogenesis. We showed that BDNF, along with membrane depolarization, is critical for fast-spiking interneurons (FS cells) to establish functional inhibitory microcircuits. In enriched FS cell cultures, BDNF promoted interneuron differentiation by increasing the somatic diameter, neurite outgrowth and branching, and the frequency of action potential firing. BDNF treatment led to a significant up-regulation of synaptophysin and vesicular GABA transporter expressions reflecting the accelerated maturation of functional synapses. Next, we addressed the role of BDNF and its receptor TrkB in the differentiation of GABAergic interneurons in the main olfactory bulb in vivo. We used mice lacking BDNF, mice carrying neurotrophin-3 (NT3) in the place of BDNF, and TrkB signaling mutant mice with a receptor that exclusively activates phospholipase Cgamma (PLCgamma). The absence of BDNF resulted in a compressed olfactory bulb. A significant loss of parvalbumin (PV) immunoreactive GABAergic interneurons in the external plexiform layer was dependent on the recruitment of the adaptor proteins Shc/Frs2 to the TrkB receptor. In contrast, PLCgamma signaling was sufficient for dendrite growth. Since in utero exposure to delta9 -tetrahydrocannabinol, the active component from marijuana, induces cognitive deficits, we asked whether endocannabinoids can alter the BDNF-dependent maturation of cortical GABAergic interneurons. We identified endocannabinoids as chemoattractants for migrating GABAergic interneurons with their effect mediated by Src-dependent TrkB receptor transactivation. Simultaneously, endocannabinoids suppressed BDNF-stimulated neurite outgrowth. Based on the findings that interneurons arbors were affected by endocannabinoids, we studied the mechanisms involved in endocannabinoid-regulated axonal growth and guidance. We identified a selective enrichment of CB 1Rs in isolated growth cone particles. Agonist stimulation induced CB 1R trafficking in motile growth cones and activated the Erk1/2 pathway. Endocannabinoids were identified as repellant cues for cultured rodent GABAergic interneurons through the activation of the small GTPase RhoA. Similarly, endocannabinoids diminished galvanotropism of Xenopus laevis spinal neurons. These results are consistent with the increased density of inhibitory afferents in the neocortex in mice lacking CB 1Rs in forebrain GABAergic interneurons. Overall, this thesis provides compelling data showing that the antagonism of BDNF and endocannabinoid signaling during the late embryonic and perinatal periods of cortical development is essential for the establishment of the cortical microarchitecture

The role of cover and pattern of installed resource sinks in the recovery of degraded patchy drylands

A low-cost restoration in patchy drylands aiming at recovering the ability of the ecosystem to capture and store water and nutrients is the installation of obstructions to break runoff pathways and retain these resources (hereafter, resource sinks). Field works in drylands worldwide have studied how the effectiveness of this action depends on the materials used to build the obstructions. However, the spatial pattern attributes of the resource sinks can also affect the effectiveness of the restoration and has not yet been investigated. In this work, we cover this knowledge gap by using a well-known dryland model to investigate how different initial amounts of cover and spatial distribution of installed resource sinks (i.e., random vs. regular) affects the recovery of the system. In agreement with field-work studies, our model results confirm that the installation of resource sinks can restore degraded drylands that are not able to recover naturally. More importantly, we found that a very small cover of resource sinks was sufficient to trigger the recovery of vegetation, while a high cover could lead to a complete failure of vegetation recovery. This was found for both random and regular distributions of resource sinks. However, a distribution similar to that of vegetation in the reference healthy system (i.e., regular distribution in our study system) was more effective: higher plant densities were reached for a given initial cover of resource sinks. Given the high efficiency of low covers of resource sinks suggested by our work, combined with the low-cost materials needed, the installation of resource sinks in severely degraded drylands has the potential to be a key contributor to the large restoration efforts needed to achieve land-degradation neutrality in the coming decades, particularly in developing countries

More is not necessarily better: The role of cover and spatial organization of resource sinks in the restoration of patchy drylands

A low-cost restoration action in patchy drylands worldwide is the installation of obstructions (hereafter, resource sinks) to break runoff pathways and retain resources. Field-works have studied how the effectiveness of this action depends on the materials installed. However, the influence and effectiveness of the cover and spatial organization of resource sinks have not been widely investigated. In this work, we use a well-known dryland model to study how different initial cover and spatial organization of installed resource sinks affect the recovered ecosystem. In agreement with field-work studies, our results confirm that the installation of resource sinks can restore degraded drylands that would not recover naturally. More importantly, a very small cover of resource sinks was sufficient to trigger vegetation recovery, while a high cover would lead to complete failure. Higher plant densities were reached when distribution and cover were similar to that of spatial self-organized vegetation in the reference healthy system (i.e., regular spatial distribution in our study system). Given the effectiveness of low cover installations, suggested by our work, combined with the low-cost materials needed, resource sinks have the potential to be a key contributor to the large restoration efforts needed to achieve land-degradation neutrality, particularly in developing countries

Crystal structures of homoserine dehydrogenase suggest a novel catalytic mechanism for oxidoreductases

The structure of the antifungal drug target homoserine dehydrogenase (HSD) was determined from Saccharomyces cerevisiae in apo and holo forms, and as a ternary complex with bound products, by X-ray diffraction. The three forms show that the enzyme is a dimer, with each monomer composed of three regions, the nucleotide-binding region, the dimerization region and the catalytic region. The dimerization and catalytic regions have novel folds, whereas the fold of the nucleotide-binding region is a variation on the Rossmann fold. The novel folds impose a novel composition and arrangement of active site residues when compared to all other currently known oxidoreductases. This observation, in conjunction with site-directed mutagenesis of active site residues and steady-state kinetic measurements, suggest that HSD exhibits a new variation on dehydrogenase chemistry

Mechanism of aminoglycoside antibiotic kinase APH(3\u27)-IIIa: role of the nucleotide positioning loop

The aminoglycoside antibiotic resistance kinases (APHs) and the Ser/Thr/Tyr protein kinases share structural and functional homology but very little primary sequence conservation ( \u3c 5%). A region of structural, but not amino acid sequence, homology is the nucleotide positioning loop (NPL) that closes down on the enzyme active site upon binding of ATP. This loop region has been implicated in facilitating phosphoryl transfer in protein kinases; however, there is no primary sequence conservation between APHs and protein kinases in the NPL. There is an invariant Ser residue in all APH NPL regions, however. This residue in APH(3\u27)-IIIa (Ser27), an enzyme widespread in aminoglycoside-resistant Enterococci, Streptococci, and Staphylococci, directly interacts with the beta-phosphate of ATP through the Ser hydroxymethyl group and the amide hydrogen in the 3D structure of the enzyme. Mutagenesis of this residue to Ala and Pro supported a role for the Ser amide hydrogen in nucleotide capture and phosphoryl transfer. A molecular model of the proposed dissociative transition state, which is consistent with all of the available mechanistic data, suggested a role for the amide of the adjacent Met26 in phosphoryl transfer. Mutagenesis studies confirmed the importance of the amide hydrogen and suggest a mechanism where Ser27 anchors the ATP beta-phosphate facilitating bond breakage with the gamma-phosphate during formation of the metaphosphate-like transition, which is stabilized by interaction with the amide hydrogen of Met26. The APH NPL therefore acts as a lever, promoting phosphoryl transfer to the aminoglycoside substrate, with the biological outcome of clinically relevant antibiotic resistance

Visualizing dual downregulation of IGF-1R and VEGF by Hsp90 inhibition effect in triple negative breast cancer

Purpose Triple negative breast cancer (TNBC) is biologically characterized by heterogeneous presence of molecular pathways underlying it. Insulin-like growth factor receptor-1 (IGF-1R) expression and vascular endothelial growth factor-A (VEGF-A) have been identified as key factors in these pathways in TNBC. In this study, we aimed at in vivo PET imaging the effect of heat shock protein (Hsp) 90 inhibition by means of NVP-AUY922 on these pathways, with zirconium-89 (89Zr) labeled antibodies targeting IGF-1R and VEGF. Experimental design In vitro NVP-AUY922 effects on cellular IGF-1R expression and VEGF-A secretion were determined in MCF-7 and MDA-MB-231 cell lines. Moreover human TNBC bearing MDA-MB-231 mice received 50 mg/kg NVP-AUY922 or vehicle q3d intraperitoneally for 21 days. PET scans with 89Zr-MAB391 and 89Zr-bevacizumab for visualization of IGF-1R and VEGF were performed before and during treatment. Ex vivo biodistribution and correlative tissue analyses were performed. Results NVP-AUY922 treatment reduced IGF-1R expression and VEGF-A excretion in both cell lines. Hsp90 inhibition lowered tumor uptake on 89Zr-MAB391-PET by 37.3% (P < 0.01) and on 89Zr-bevacizumab-PET by 44.4% (P < 0.01). This was confirmed by ex vivo biodistribution with a reduction of 41.3 % injected dose (ID)/g for 89Zr-MAB391 and 37.8 %ID/g for 89Zr-bevacizumab, while no differences were observed for other tissues. This coincided with reduced IGF-1R expression and mean vessel density in the NVP-AUY922 treated tumors. Conclusion 89Zr-MAB391 and 89Zr-bevacizumab PET reflect effect of Hsp90 inhibitors and can therefore potentially be used to monitor therapeutic effects of Hsp90 inhibitor therapy in TNBC