RESUMEN
GRN mutations cause frontotemporal dementia (GRN-FTD) due to deficiency in progranulin (PGRN), a lysosomal and secreted protein with unclear function. Here, we found that Grn-/- mice exhibit a global deficiency in bis(monoacylglycero)phosphate (BMP), an endolysosomal phospholipid we identified as a pH-dependent PGRN interactor as well as a redox-sensitive enhancer of lysosomal proteolysis and lipolysis. Grn-/- brains also showed an age-dependent, secondary storage of glucocerebrosidase substrate glucosylsphingosine. We investigated a protein replacement strategy by engineering protein transport vehicle (PTV):PGRN-a recombinant protein linking PGRN to a modified Fc domain that binds human transferrin receptor for enhanced CNS biodistribution. PTV:PGRN rescued various Grn-/- phenotypes in primary murine macrophages and human iPSC-derived microglia, including oxidative stress, lysosomal dysfunction, and endomembrane damage. Peripherally delivered PTV:PGRN corrected levels of BMP, glucosylsphingosine, and disease pathology in Grn-/- CNS, including microgliosis, lipofuscinosis, and neuronal damage. PTV:PGRN thus represents a potential biotherapeutic for GRN-FTD.
Asunto(s)
Productos Biológicos/uso terapéutico , Encéfalo/metabolismo , Enfermedades por Almacenamiento Lisosomal/terapia , Progranulinas/uso terapéutico , Animales , Proteínas Morfogenéticas Óseas/metabolismo , Endosomas/metabolismo , Femenino , Demencia Frontotemporal/sangre , Demencia Frontotemporal/líquido cefalorraquídeo , Gliosis/complicaciones , Gliosis/patología , Humanos , Células Madre Pluripotentes Inducidas/metabolismo , Inflamación/patología , Metabolismo de los Lípidos , Lipofuscina/metabolismo , Lisosomas/metabolismo , Macrófagos/metabolismo , Masculino , Glicoproteínas de Membrana/metabolismo , Ratones , Ratones Endogámicos C57BL , Ratones Transgénicos , Microglía/metabolismo , Degeneración Nerviosa/patología , Fenotipo , Progranulinas/deficiencia , Progranulinas/metabolismo , Receptores Inmunológicos/metabolismo , Receptores de Transferrina/metabolismo , Distribución TisularRESUMEN
Members of the solute carrier 17 (SLC17) family use divergent mechanisms to concentrate organic anions. Membrane potential drives uptake of the principal excitatory neurotransmitter glutamate into synaptic vesicles, whereas closely related proteins use proton cotransport to drive efflux from the lysosome. To delineate the divergent features of ionic coupling by the SLC17 family, we determined the structure of Escherichia coli D-galactonate/H+ symporter D-galactonate transporter (DgoT) in 2 states: one open to the cytoplasmic side and the other open to the periplasmic side with substrate bound. The structures suggest a mechanism that couples H+ flux to substrate recognition. A transition in the role of H+ from flux coupling to allostery may confer regulation by trafficking to and from the plasma membrane.