Hippocampal TMEM55B overexpression in the 5XFAD mouse model of Alzheimer's disease.

Dysfunction of the endosomal-lysosomal network is a notable feature of Alzheimer's disease (AD) pathology. Dysfunctional endo-lysosomal vacuoles accumulate in dystrophic neurites surrounding amyloid ß (Aß) plaques and may be involved in the pathogenesis and progression of Aß aggregates. Trafficking and thus maturation of these dysfunctional vacuoles is disrupted in the vicinity of Aß plaques. Transmembrane protein 55B (TMEM55B), also known as phosphatidylinositol-4,5-bisphosphate 4-phosphatase 1 (PIP4P1) is an endo-lysosomal membrane protein that is necessary for appropriate trafficking of endo-lysosomes. The present study tested whether overexpression of TMEM55B in the hippocampus could prevent plaque-associated axonal accumulation of dysfunctional endo-lysosomes, reduce Aß plaque load, and prevent hippocampal-dependent learning and memory deficits in the 5XFAD mouse models of Aß plaque pathology. Immunohistochemical analyses revealed a modest but significant reduction in the accumulation of endo-lysosomes in dystrophic neurites surrounding Aß plaques, but there was no change in hippocampal-dependent memory or plaque load. Overall, these data indicate a potential role for TMEM55B in reducing endo-lysosomal dysfunction during AD-like Aß pathology.

The role of nuclear Ca2+ in maintaining neuronal homeostasis and brain health.

Nuclear Ca2+ has emerged as one of the most potent mediators of the dialogue between neuronal synapses and the nucleus that regulates heterochromatin states, transcription factor activity, nuclear morphology and neuronal gene expression induced by synaptic activity. Recent studies underline the importance of nuclear Ca2+ signaling in long-lasting, activity-induced adaptation and maintenance of proper brain function. Diverse forms of neuroadaptation require transient nuclear Ca2+ signaling and cyclic AMP-responsive element-binding protein (CREB1, referred to here as CREB) as its prime target, which works as a tunable switch to drive and modulate specific gene expression profiles associated with memory, pain, addiction and neuroprotection. Furthermore, a reduction of nuclear Ca2+ levels has been shown to be neurotoxic and a causal factor driving the progression of neurodegenerative disorders, as well as affecting neuronal autophagy. Because of its central role in the brain, deficits in nuclear Ca2+ signaling may underlie a continuous loss of neuroprotection in the aging brain, contributing to the pathophysiology of Alzheimer's disease. In this Review, we discuss the principles of the 'nuclear calcium hypothesis' in the context of human brain function and its role in controlling diverse forms of neuroadaptation and neuroprotection. Furthermore, we present the most relevant and promising perspectives for future studies.

Endocytic control of growth factor signalling: multivesicular bodies as signalling organelles.

Signal transduction and endocytosis are intertwined processes. The internalization of ligand-activated receptors by endocytosis has classically been thought to attenuate signals by targeting receptors for degradation in lysosomes, but it can also maintain signals in early signalling endosomes. In both cases, localization to multivesicular endosomesen route to lysosomes is thought to terminate signalling. However, during WNT signal transduction, sequestration of the enzyme glycogen synthase kinase 3 (GSK3) inside multivesicular endosomes results in the stabilization of many cytosolic proteins. Thus, the role of endocytosis during signal transduction may be more diverse than anticipated, and multivesicular endosomes may constitute a crucial signalling organelle.

Rab8 attenuates Wnt signaling and is required for mesenchymal differentiation into adipocytes.

Differentiation of mesenchymal stem cells into adipocyte requires coordination of external stimuli and depends upon the functionality of the primary cilium. The Rab8 small GTPases are regulators of intracellular transport of membrane-bound structural and signaling cargo. However, the physiological contribution of the intrinsic trafficking network controlled by Rab8 to mesenchymal tissue differentiation has not been fully defined in vivo and in primary tissue cultures. Here, we show that mouse embryonic fibroblasts (MEFs) lacking Rab8 have severely impaired adipocyte differentiation in vivo and ex vivo. Immunofluorescent localization and biochemical analyses of Rab8a-deficient, Rab8b-deficient, and Rab8a and Rab8b double-deficient MEFs revealed that Rab8 controls the Lrp6 vesicular compartment, clearance of basal signalosome, traffic of frizzled two receptor, and thereby a proper attenuation of Wnt signaling in differentiating MEFs. Upon induction of adipogenesis program, Rab8a- and Rab8b-deficient MEFs exhibited severely defective lipid-droplet formation and abnormal cilia morphology, despite overall intact cilia growth and ciliary cargo transport. Our results suggest that intracellular Rab8 traffic regulates induction of adipogenesis via proper positioning of Wnt receptors for signaling control in mesenchymal cells.

Enrichment of NPC1-deficient cells with the lipid LBPA stimulates autophagy, improves lysosomal function, and reduces cholesterol storage.

Niemann-Pick C (NPC) is an autosomal recessive disorder characterized by mutations in the NPC1 or NPC2 genes encoding endolysosomal lipid transport proteins, leading to cholesterol accumulation and autophagy dysfunction. We have previously shown that enrichment of NPC1-deficient cells with the anionic lipid lysobisphosphatidic acid (LBPA; also called bis(monoacylglycerol)phosphate) via treatment with its precursor phosphatidylglycerol (PG) results in a dramatic decrease in cholesterol storage. However, the mechanisms underlying this reduction are unknown. In the present study, we showed using biochemical and imaging approaches in both NPC1-deficient cellular models and an NPC1 mouse model that PG incubation/LBPA enrichment significantly improved the compromised autophagic flux associated with NPC1 disease, providing a route for NPC1-independent endolysosomal cholesterol mobilization. PG/LBPA enrichment specifically enhanced the late stages of autophagy, and effects were mediated by activation of the lysosomal enzyme acid sphingomyelinase. PG incubation also led to robust and specific increases in LBPA species with polyunsaturated acyl chains, potentially increasing the propensity for membrane fusion events, which are critical for late-stage autophagy progression. Finally, we demonstrated that PG/LBPA treatment efficiently cleared cholesterol and toxic protein aggregates in Purkinje neurons of the NPC1I1061T mouse model. Collectively, these findings provide a mechanistic basis supporting cellular LBPA as a potential new target for therapeutic intervention in NPC disease.

Mechanical stretch induces myelin protein loss in oligodendrocytes by activating Erk1/2 in a calcium-dependent manner.

Myelin loss in the brain is a common occurrence in traumatic brain injury (TBI) that results from impact-induced acceleration forces to the head. Fast and abrupt head motions, either resulting from violent blows and/or jolts, cause rapid stretching of the brain tissue, and the long axons within the white matter tracts are especially vulnerable to such mechanical strain. Recent studies have shown that mechanotransduction plays an important role in regulating oligodendrocyte progenitors cell differentiation into oligodendrocytes. However, little is known about the impact of mechanical strain on mature oligodendrocytes and the stability of their associated myelin sheaths. We used an in vitro cellular stretch device to address these questions, as well as characterize a mechanotransduction mechanism that mediates oligodendrocyte responses. Mechanical stretch caused a transient and reversible myelin protein loss in oligodendrocytes. Cell death was not observed. Myelin protein loss was accompanied by an increase in intracellular Ca2+ and Erk1/2 activation. Chelating Ca2+ or inhibiting Erk1/2 activation was sufficient to block the stretch-induced loss of myelin protein. Further biochemical analyses revealed that the stretch-induced myelin protein loss was mediated by the release of Ca2+ from the endoplasmic reticulum (ER) and subsequent Ca2+ -dependent activation of Erk1/2. Altogether, our findings characterize an Erk1/2-dependent mechanotransduction mechanism in mature oligodendrocytes that de-stabilizes the myelination program.

Rab8a vesicles regulate Wnt ligand delivery and Paneth cell maturation at the intestinal stem cell niche.

Communication between stem and niche supporting cells maintains the homeostasis of adult tissues. Wnt signaling is a crucial regulator of the stem cell niche, but the mechanism that governs Wnt ligand delivery in this compartment has not been fully investigated. We identified that Wnt secretion is partly dependent on Rab8a-mediated anterograde transport of Gpr177 (wntless), a Wnt-specific transmembrane transporter. Gpr177 binds to Rab8a, depletion of which compromises Gpr177 traffic, thereby weakening the secretion of multiple Wnts. Analyses of generic Wnt/ß-catenin targets in Rab8a knockout mouse intestinal crypts indicate reduced signaling activities; maturation of Paneth cells - a Wnt-dependent cell type - is severely affected. Rab8a knockout crypts show an expansion of Lgr5(+) and Hopx(+) cells in vivo. However, in vitro, the knockout enteroids exhibit significantly weakened growth that can be partly restored by exogenous Wnts or Gsk3ß inhibitors. Immunogold labeling and surface protein isolation identified decreased plasma membrane localization of Gpr177 in Rab8a knockout Paneth cells and fibroblasts. Upon stimulation by exogenous Wnts, Rab8a-deficient cells show ligand-induced Lrp6 phosphorylation and transcriptional reporter activation. Rab8a thus controls Wnt delivery in producing cells and is crucial for Paneth cell maturation. Our data highlight the profound tissue plasticity that occurs in response to stress induced by depletion of a stem cell niche signal.

The amino acid metabolite homocysteine activates mTORC1 to inhibit autophagy and form abnormal proteins in human neurons and mice.

The molecular mechanisms leading to and responsible for age-related, sporadic Alzheimer's disease (AD) remain largely unknown. It is well documented that aging patients with elevated levels of the amino acid metabolite homocysteine (Hcy) are at high risk of developing AD. We investigated the impact of Hcy on molecular clearance pathways in mammalian cells, including in vitro cultured induced pluripotent stem cell-derived forebrain neurons and in vivo neurons in mouse brains. Exposure to Hcy resulted in up-regulation of the mechanistic target of rapamycin complex 1 (mTORC1) activity, one of the major kinases in cells that is tightly linked to anabolic and catabolic pathways. Hcy is sensed by a constitutive protein complex composed of leucyl-tRNA-synthetase and folliculin, which regulates mTOR tethering to lysosomal membranes. In hyperhomocysteinemic human cells and cystathionine ß-synthase-deficient mouse brains, we find an acute and chronic inhibition of the molecular clearance of protein products resulting in a buildup of abnormal proteins, including ß-amyloid and phospho-Tau. Formation of these protein aggregates leads to AD-like neurodegeneration. This pathology can be prevented by inhibition of mTORC1 or by induction of autophagy. We conclude that an increase of intracellular Hcy levels predisposes neurons to develop abnormal protein aggregates, which are hallmarks of AD and its associated onset and pathophysiology with age.-Khayati, K., Antikainen, H., Bonder, E. M., Weber, G. F., Kruger, W. D., Jakubowski, H., Dobrowolski, R. The amino acid metabolite homocysteine activates mTORC1 to inhibit autophagy and form abnormal proteins in human neurons and mice.

Age-Dependent Effects of ALK5 Inhibition and Mechanism of Neuroprotection in Neonatal Hypoxic-Ischemic Brain Injury.

Neonatal encephalopathy due to hypoxic-ischemic (HI) brain injury triggers a wave of neuroinflammatory events attributed to causing the progressive degeneration and functional deficits seen weeks after the initial insult. In a recent set of studies, we evaluated the therapeutic efficacy of a small molecule antagonist for ALK5 (activin-like kinase 5 ), TGF-ß receptor in a rat model of moderate perinatal HI and found significant improvements in neurologic outcomes. Here, we have extended those studies to evaluate the efficacy of delayed TGF-ß receptor antagonism on postnatal day (P) 6 and P9 HI rat pups with and without hypothermia. The ALK5 receptor antagonist SB505124 was administered systemically by osmotic pump beginning 3 days following HI. Extending our earlier data set that showed protection of the hippocampus in P6 pups treated with SB505124, these animals sustained less damage to their hippocampi and had improved performance on the Morris water maze (MWM) when tested on P60 versus vehicle-treated HI animals. By contrast, SB505124 did not improve sensorimotor deficits and exacerbated hippocampal and thalamic volume loss when administered 3 days after HI to P9 pups. SB505124-treated rats injured on P9 tended to perform worse than their vehicle-treated counterparts on MWM, and SB505124 treatment did not preserve hippocampal or thalamic neurons in P9 pups when combined with hypothermia. To elucidate the mechanism whereby ALK5 inhibition reduced neuronal death in the P6 HI model, we assessed levels of autophagy markers in neurons of the neocortex, hippocampus, and thalamus, and in the subcortical white matter, and found that SB505124 increased numbers of autophagosomes and levels of lipidated LC3 (light chain 3), a key protein known to mediate autophagy. Altogether, our results demonstrate that there is a dynamic switch in the CNS response to TGF-ß1 that occurs around P9 in rats where TGF-ß signaling inhibition worsens functional outcomes. This response is similar to the outcome of antagonizing TGF-ß signaling in adult stroke and other CNS disease models. We conclude that attenuating TGF-ß1 signaling will likely be an effective treatment for HI-related encephalopathy in moderately preterm infants, offering protection of the neocortex, hippocampus, and thalamus with enhanced cerebral autophagy contributing to the decrease in the extent of progressive neuronal cell death.

Familial Alzheimer's disease-associated PSEN1 mutations affect neurodevelopment through increased Notch signaling.

Alzheimer's disease (AD) is the most common neurodegenerative disorder, but its root cause may lie in neurodevelopment. PSEN1 mutations cause the majority of familial AD, potentially by disrupting proper Notch signaling, causing early unnoticed cellular changes that affect later AD progression. While rodent models are useful for modeling later stages of AD, human induced pluripotent stem cell-derived cortical spheroids (hCSs) allow access to studying the human cortex at the cellular level over the course of development. Here, we show that the PSEN1 L435F heterozygous mutation affects hCS development, increasing size, increasing progenitors, and decreasing post-mitotic neurons as a result of increased Notch target gene expression during early hCS development. We also show altered Aß expression and neuronal activity at later hCS stages. These results contrast previous findings, showing how individual PSEN1 mutations may differentially affect neurodevelopment and may give insight into fAD progression to provide earlier time points for more effective treatments.

The connexin 40 A96S mutation causes renin-dependent hypertension.

Deletion of the gap-junction-forming protein connexin40 leads to renin-dependent hypertension in mice, but whether observed human variants in connexin40, such as A96S, promote hypertension is unknown. Here, we generated mice with the A96S variant in the mouse connexin40 gene. Although mice homozygous for the A96S mutations had normal expression patterns of connexin40 in the kidney, they were hypertensive, had sixfold higher plasma renin concentrations, and had 40% higher levels of renin mRNA than controls. Renin-expressing cells were aberrantly located outside the media layer of afferent arterioles, and increased renal perfusion pressure did not inhibit renin secretion from kidneys isolated from homozygous A96S mice. Treatment with a low-salt diet in combination with an ACE inhibitor increased renin mRNA levels, plasma renin concentrations, and the number of aberrantly localized renin-producing cells. Taken together, these findings suggest that the A96S mutation in connexin40 leads to renin-dependent hypertension in mice. Modulation of renin secretion by BP critically depends on functional connexin40; with the A96S mutation, the aberrant extravascular localization of renin-secreting cells in the kidney likely impairs the pressure-mediated inhibition of renin secretion.

Mechanisms of Tertiary Neurodegeneration after Neonatal Hypoxic-Ischemic Brain Damage.

Neonatal encephalopathy linked to hypoxia-ischemia (H-I) which is regarded as the most important neurological problem of the newborn, can lead to a spectrum of adverse neurodevelopmental outcomes such as cerebral palsy, epilepsy, hyperactivity, cognitive impairment and learning difficulties. There have been numerous reviews that have focused on the epidemiology, diagnosis and treatment of neonatal H-I; however, a topic that is less often considered is the extent to which the injury might worsen over time, which is the focus of this review. Similarly, there have been numerous reviews that have focused on mechanisms that contribute to the acute or subacute injury; however, there is a tertiary phase of recovery that can be defined by cellular and molecular changes that occur many weeks and months after brain injury and this topic has not been the focus of any review for over a decade. Therefore, in this article we review both the clinical and pre-clinical data that show that tertiary neurodegeneration is a significant contributor to the final outcome, especially after mild to moderate injuries. We discuss the contributing roles of apoptosis, necroptosis, autophagy, protein homeostasis, inflammation, microgliosis and astrogliosis. We also review the limited number of studies that have shown that significant neuroprotection and preservation of neurological function can be achieved administering drugs during the period of tertiary neurodegeneration. As the tertiary phase of neurodegeneration is a stage when interventions are eminently feasible, it is our hope that this review will stimulate a new focus on this stage of recovery towards the goal of producing new treatment options for neonatal hypoxic-ischemic encephalopathy.

Moderately Inducing Autophagy Reduces Tertiary Brain Injury after Perinatal Hypoxia-Ischemia.

Recent studies of cerebral hypoxia-ischemia (HI) have highlighted slowly progressive neurodegeneration whose mechanisms remain elusive, but if blocked, could considerably improve long-term neurological function. We previously established that the cytokine transforming growth factor (TGF)ß1 is highly elevated following HI and that delivering an antagonist for TGFß receptor activin-like kinase 5 (ALK5)-SB505124-three days after injury in a rat model of moderate pre-term HI significantly preserved the structural integrity of the thalamus and hippocampus as well as neurological functions associated with those brain structures. To elucidate the mechanism whereby ALK5 inhibition reduces cell death, we assessed levels of autophagy markers in neurons and found that SB505124 increased numbers of autophagosomes and levels of lipidated light chain 3 (LC3), a key protein known to mediate autophagy. However, those studies did not determine whether (1) SB was acting directly on the CNS and (2) whether directly inducing autophagy could decrease cell death and improve outcome. Here we show that administering an ALK5 antagonist three days after HI reduced actively apoptotic cells by ~90% when assessed one week after injury. Ex vivo studies using the lysosomal inhibitor chloroquine confirmed that SB505124 enhanced autophagy flux in the injured hemisphere, with a significant accumulation of the autophagic proteins LC3 and p62 in SB505124 + chloroquine treated brain slices. We independently activated autophagy using the stimulatory peptide Tat-Beclin1 to determine if enhanced autophagy is directly responsible for improved outcomes. Administering Tat-Beclin1 starting three days after injury preserved the structural integrity of the hippocampus and thalamus with improved sensorimotor function. These data support the conclusion that intervening at this phase of injury represents a window of opportunity where stimulating autophagy is beneficial.

14-3-3 targets keratin intermediate filaments to mechanically sensitive cell-cell contacts.

Intermediate filament (IF) cytoskeletal networks simultaneously support mechanical integrity and influence signal transduction pathways. Marked remodeling of the keratin IF network accompanies collective cellular morphogenetic movements that occur during early embryonic development in the frog Xenopus laevis. While this reorganization of keratin is initiated by force transduction on cell-cell contacts mediated by C-cadherin, the mechanism by which keratin filament reorganization occurs remains poorly understood. In this work, we demonstrate that 14-3-3 proteins regulate keratin reorganization dynamics in embryonic mesendoderm cells from Xenopus gastrula. 14-3-3 colocalizes with keratin filaments near cell-cell junctions in migrating mesendoderm. Coimmunoprecipitation, mass spectrometry, and bioinformatic analyses indicate 14-3-3 is associated with Keratin 19 (K19) in the whole embryo and, more specifically, mesendoderm tissue. Inhibition of 14-3-3 results in both the decreased exchange of keratin subunits into filaments and blocks keratin filament recruitment toward cell-cell contacts. Synthetically coupling 14-3-3 to K19 through a unique fusion construct conversely induces the localization of this keratin population to the region of cell-cell contacts. Taken together, these findings indicate that 14-3-3 acts on keratin IFs and is involved in their reorganization to sites of cell adhesion.

Pathogenic Tau Causes a Toxic Depletion of Nuclear Calcium.

Synaptic activity-induced calcium (Ca2+) influx and subsequent propagation into the nucleus is a major way in which synapses communicate with the nucleus to regulate transcriptional programs important for activity-dependent survival and memory formation. Nuclear Ca2+ shapes the transcriptome by regulating cyclic AMP (cAMP) response element-binding protein (CREB). Here, we utilize a Drosophila model of tauopathy and induced pluripotent stem cell (iPSC)-derived neurons from humans with Alzheimer's disease to study the effects of pathogenic tau, a pathological hallmark of Alzheimer's disease and related tauopathies, on nuclear Ca2+. We find that pathogenic tau depletes nuclear Ca2+ and CREB to drive neuronal death, that CREB-regulated genes are over-represented among differentially expressed genes in tau transgenic Drosophila, and that activation of big potassium (BK) channels elevates nuclear Ca2+ and suppresses tau-induced neurotoxicity. Our studies identify nuclear Ca2+ depletion as a mechanism contributing to tau-induced neurotoxicity, adding an important dimension to the calcium hypothesis of Alzheimer's disease.

TFEB-driven endocytosis coordinates MTORC1 signaling and autophagy.

The mechanistic target of rapamycin kinase complex 1 (MTORC1) is a central cellular kinase that integrates major signaling pathways, allowing for regulation of anabolic and catabolic processes including macroautophagy/autophagy and lysosomal biogenesis. Essential to these processes is the regulatory activity of TFEB (transcription factor EB). In a regulatory feedback loop modulating transcriptional levels of RRAG/Rag GTPases, TFEB controls MTORC1 tethering to membranes and induction of anabolic processes upon nutrient replenishment. We now show that TFEB promotes expression of endocytic genes and increases rates of cellular endocytosis during homeostatic baseline and starvation conditions. TFEB-mediated endocytosis drives assembly of the MTORC1-containing nutrient sensing complex through the formation of endosomes that carry the associated proteins RRAGD, the amino acid transporter SLC38A9, and activate AKT/protein kinase B (AKT p-T308). TFEB-induced signaling endosomes en route to lysosomes are induced by amino acid starvation and are required to dissociate TSC2, re-tether and activate MTORC1 on endolysosomal membranes. This study characterizes TFEB-mediated endocytosis as a critical process leading to activation of MTORC1 and autophagic function, thus identifying the importance of the dynamic endolysosomal system in cellular clearance. Abbreviations: CAD: central adrenergic tyrosine hydroxylase-expressing-a-differentiated; ChIP-seq: chromosome immunoprecipitation sequencing; DAPI: 4',6-diamidino-2-phenylindole; DMSO: dimethyl sulfoxide; EDTA: ethylenediaminetetraacetic acid; EEA1: early endosomal antigen 1; EGF: epidermal growth factor; FBS: fetal bovine serum; GFP: green fluorescent protein; GTPase: guanosine triphosphatase; HEK293T: human embryonic kidney 293 cells expressing a temperature-sensitive mutant of the SV40 large T antigen; LAMP: lysosomal-associated membrane protein; LYNUS: lysosomal nutrient-sensing complex; MAP1LC3/LC3: microtubule associated protein 1 light chain 3 alpha/beta; MTOR: mechanistic target of rapamycin kinase; MTORC: mechanistic target of rapamycin kinase complex; OE: overexpression; PH: pleckstrin homology; PtdIns(3,4,5)P3: phosphatidylinositol 3,4,5-trisphosphate; RRAGD: Ras related GTPase binding D; RHEB: Ras homolog enriched in brain; SLC38A9: solute carrier family 38 member 9; SQSTM1: sequestosome 1; TFEB: transcription factor EB; TSC2: tuberous sclerosis 2; TMR: tetramethylrhodamine; ULK1: unc-51 like kinase 1; WT: wild type.

Subacute Transplantation of Native and Genetically Engineered Neural Progenitors Seeded on Microsphere Scaffolds Promote Repair and Functional Recovery After Traumatic Brain Injury.

There is intense interest and effort toward regenerating the brain after severe injury. Stem cell transplantation after insult to the central nervous system has been regarded as the most promising approach for repair; however, engrafting cells alone might not be sufficient for effective regeneration. In this study, we have compared neural progenitors (NPs) from the fetal ventricular zone (VZ), the postnatal subventricular zone, and an immortalized radial glia (RG) cell line engineered to conditionally secrete the trophic factor insulin-like growth factor 1 (IGF-1). Upon differentiation in vitro, the VZ cells were able to generate a greater number of neurons than subventricular zone cells. Furthermore, differentiated VZ cells generated pyramidal neurons . In vitro, doxycycline-driven secretion of IGF-1 strongly promoted neuronal differentiation of cells with hippocampal, interneuron and cortical specificity. Accordingly, VZ and engineered RG-IGF-1-hemagglutinin (HA) cells were selected for subsequent in vivo experiments. To increase cell survival, we delivered the NPs attached to a multifunctional chitosan-based scaffold. The microspheres containing adherent NPs were injected subacutely into the lesion cavity of adult rat brains that had sustained controlled cortical impact injury. At 2 weeks posttransplantation, the exogenously introduced cells showed a reduction in stem cell or progenitor markers and acquired mature neuronal and glial markers. In beam walking tests assessing sensorimotor recovery, transplanted RG cells secreting IGF-1 contributed significantly to functional improvement while native VZ or RG cells did not promote significant recovery. Altogether, these results support the therapeutic potential of chitosan-based multifunctional microsphere scaffolds seeded with genetically modified NPs expressing IGF-1 to promote repair and functional recovery after traumatic brain injuries.

TOR-mediated regulation of metabolism in aging.

Cellular metabolism is regulated by the mTOR kinase, a key component of the molecular nutrient sensor pathway that plays a central role in cellular survival and aging. The mTOR pathway promotes protein and lipid synthesis and inhibits autophagy, a process known for its contribution to longevity in several model organisms. The nutrient-sensing pathway is regulated at the lysosomal membrane by a number of proteins for which deficiency triggers widespread aging phenotypes in tested animal models. In response to environmental cues, this recently discovered lysosomal nutrient-sensing complex regulates autophagy transcriptionally through conserved factors, such as the transcription factors TFEB and FOXO, associated with lifespan extension. This key metabolic pathway strongly depends on nucleocytoplasmic compartmentalization, a cellular phenomenon gradually lost during aging. In this review, we discuss the current progress in understanding the contribution of mTOR-regulating factors to autophagy and longevity. Furthermore, we review research on the regulation of metabolism conducted in multiple aging models, including Caenorhabditis elegans, Drosophila and mouse, and human iPSCs. We suggest that conserved molecular pathways have the strongest potential for the development of new avenues for treatment of age-related diseases.