RESUMEN
Progranulin (PGRN) haploinsufficiency is a major risk factor for frontotemporal lobar degeneration with TAR DNA-binding protein 43 (TDP-43) pathology (FTLD-GRN). Multiple therapeutic strategies are in clinical development to restore PGRN in the CNS, including gene therapy. However, a limitation of current gene therapy approaches aimed to alleviate FTLD-associated pathologies may be their inefficient brain exposure and biodistribution. We therefore developed an adeno-associated virus (AAV) targeting the liver (L) to achieve sustained peripheral expression of a transferrin receptor (TfR) binding, brain-penetrant (b) PGRN variant [AAV(L):bPGRN] in two mouse models of FTLD-GRN, namely, Grn knockout and GrnxTmem106b double knockout mice. This therapeutic strategy avoids potential safety and biodistribution issues of CNS-administered AAVs and maintains sustained concentrations of PGRN in the brain after a single dose. AAV(L):bPGRN treatment reduced several FTLD-GRN-associated pathologies including severe motor function deficits, aberrant TDP-43 phosphorylation, dysfunctional protein degradation, lipid metabolism, gliosis, and neurodegeneration in the brain. The potential translatability of our findings was tested in an in vitro model using cocultured human induced pluripotent stem cell (hiPSC)-derived microglia lacking PGRN and TMEM106B and wild-type hiPSC-derived neurons. As in mice, aberrant TDP-43, lysosomal dysfunction, and neuronal loss were ameliorated after treatment with exogenous TfR-binding protein transport vehicle fused to PGRN (PTV:PGRN). Together, our studies suggest that peripherally administered brain-penetrant PGRN replacement strategies ameliorate FTLD-GRN relevant phenotypes including TDP-43 pathology, neurodegeneration, and behavioral deficits. Our data provide preclinical proof of concept for the use of this AAV platform for treatment of FTLD-GRN and potentially other CNS disorders.
Asunto(s)
Encéfalo , Dependovirus , Modelos Animales de Enfermedad , Degeneración Lobar Frontotemporal , Ratones Noqueados , Progranulinas , Animales , Humanos , Ratones , Encéfalo/metabolismo , Encéfalo/patología , Dependovirus/metabolismo , Proteínas de Unión al ADN/metabolismo , Proteínas de Unión al ADN/genética , Degeneración Lobar Frontotemporal/metabolismo , Degeneración Lobar Frontotemporal/patología , Terapia Genética , Fosforilación , Progranulinas/metabolismo , Progranulinas/genética , Receptores de Transferrina/metabolismoRESUMEN
Loss-of-function variants of TREM2 are associated with increased risk of Alzheimer's disease (AD), suggesting that activation of this innate immune receptor may be a useful therapeutic strategy. Here we describe a high-affinity human TREM2-activating antibody engineered with a monovalent transferrin receptor (TfR) binding site, termed antibody transport vehicle (ATV), to facilitate blood-brain barrier transcytosis. Upon peripheral delivery in mice, ATV:TREM2 showed improved brain biodistribution and enhanced signaling compared to a standard anti-TREM2 antibody. In human induced pluripotent stem cell (iPSC)-derived microglia, ATV:TREM2 induced proliferation and improved mitochondrial metabolism. Single-cell RNA sequencing and morphometry revealed that ATV:TREM2 shifted microglia to metabolically responsive states, which were distinct from those induced by amyloid pathology. In an AD mouse model, ATV:TREM2 boosted brain microglial activity and glucose metabolism. Thus, ATV:TREM2 represents a promising approach to improve microglial function and treat brain hypometabolism found in patients with AD.
Asunto(s)
Enfermedad de Alzheimer , Células Madre Pluripotentes Inducidas , Humanos , Animales , Ratones , Microglía , Barrera Hematoencefálica , Distribución Tisular , Anticuerpos , Encéfalo , Modelos Animales de Enfermedad , Glicoproteínas de Membrana , Receptores Inmunológicos/genéticaRESUMEN
Increasing levels of the cold-shock protein, RNA-binding motif 3 (RBM3), either through cooling or by ectopic over-expression, prevents synapse and neuronal loss in mouse models of neurodegeneration. To exploit this process therapeutically requires an understanding of mechanisms controlling cold-induced RBM3 expression. Here, we show that cooling increases RBM3 through activation of TrkB via PLCγ1 and pCREB signaling. RBM3, in turn, has a hitherto unrecognized negative feedback on TrkB-induced ERK activation through induction of its specific phosphatase, DUSP6. Thus, RBM3 mediates structural plasticity through a distinct, non-canonical activation of TrkB signaling, which is abolished in RBM3-null neurons. Both genetic reduction and pharmacological antagonism of TrkB and its downstream mediators abrogate cooling-induced RBM3 induction and prevent structural plasticity, whereas TrkB inhibition similarly prevents RBM3 induction and the neuroprotective effects of cooling in prion-diseased mice. Conversely, TrkB agonism induces RBM3 without cooling, preventing synapse loss and neurodegeneration. TrkB signaling is, therefore, necessary for the induction of RBM3 and related neuroprotective effects and provides a target by which RBM3-mediated synapse-regenerative therapies in neurodegenerative disorders can be used therapeutically without the need for inducing hypothermia.
Asunto(s)
Glicoproteínas de Membrana/metabolismo , Neuroprotección , Proteínas Tirosina Quinasas/metabolismo , Proteínas de Unión al ARN/metabolismo , Transducción de Señal , Animales , Biomarcadores , Factor Neurotrófico Derivado del Encéfalo/metabolismo , Frío , Glicoproteínas de Membrana/agonistas , Ratones , Fosforilación , Enfermedades por Prión/genética , Enfermedades por Prión/metabolismo , Enfermedades por Prión/patología , Priones/metabolismo , Unión Proteica , Células Piramidales/efectos de los fármacos , Células Piramidales/metabolismo , Transducción de Señal/efectos de los fármacos , Sinapsis/efectos de los fármacos , Sinapsis/metabolismo , Sinapsis/ultraestructuraRESUMEN
Recent interest in astrocyte activation states has raised the fundamental question of how these cells, normally essential for synapse and neuronal maintenance, become pathogenic. Here, we show that activation of the unfolded protein response (UPR), specifically phosphorylated protein kinase R-like endoplasmic reticulum (ER) kinase (PERK-P) signaling-a pathway that is widely dysregulated in neurodegenerative diseases-generates a distinct reactivity state in astrocytes that alters the astrocytic secretome, leading to loss of synaptogenic function in vitro. Further, we establish that the same PERK-P-dependent astrocyte reactivity state is harmful to neurons in vivo in mice with prion neurodegeneration. Critically, targeting this signaling exclusively in astrocytes during prion disease is alone sufficient to prevent neuronal loss and significantly prolongs survival. Thus, the astrocyte reactivity state resulting from UPR over-activation is a distinct pathogenic mechanism that can by itself be effectively targeted for neuroprotection.
Asunto(s)
Astrocitos/metabolismo , Factor 2B Eucariótico de Iniciación/metabolismo , Enfermedades Neurodegenerativas/metabolismo , Enfermedades por Prión/metabolismo , Sinapsis/metabolismo , Respuesta de Proteína Desplegada/fisiología , eIF-2 Quinasa/metabolismo , Animales , Estrés del Retículo Endoplásmico/efectos de los fármacos , Inhibidores Enzimáticos/farmacología , Técnicas In Vitro , Memoria , Ratones , Fosforilación , Biosíntesis de Proteínas , Proteína Fosfatasa 1/genética , Proteína Fosfatasa 1/metabolismo , Transducción de Señal , Tapsigargina/farmacología , Transcriptoma , Tunicamicina/farmacología , Respuesta de Proteína Desplegada/efectos de los fármacosRESUMEN
Organisms live on a budget; hence, they cannot maximize all their activities at the same time. Instead, they must prioritize how they spend limiting resources on the many processes they rely on in their lives. Among others, they are thought to economize on the maintenance and repair processes required for survival in favour of maximizing reproduction, with ageing as a consequence. We investigate the biological mechanisms of neuronal ageing. Using Lymnaea stagnalis, we have previously described various aspects of age-associated neuronal decline and appetitive long-term memory failure. In view of postulated trade-offs between somatic maintenance and reproduction, we tested for interactions between resource allocation mechanisms and brain function. We show that removal of the lateral lobes, which are key regulators of energy balance in L. stagnalis, increases body mass and enhances appetitive learning, raising the possibility that the lateral lobes are one of the sites where the 'why' and 'how' of (neuronal) ageing meet.