Dysfunction Of Rab7 Is Involved In The Neurodegneration Of Alzheimer's Disease

Objective:Dysregulation of EAL pathway is one of the early changes in AD.Rab7,a small GTPase,plays a key role in EAL pathway via regulating maturation of late endosome and fusion of vesicles.In this study,we aimed to explore the molecular mechanism underlying Rab7 related EAL dysregulation in APP/PS1 model mice.Methods:12-month-old APP/PS1 mice were used to model AD and their wild-type littermates were employed as controls.Markers of EAL pathway,Rab5,Rab7,LC3 B and Lamp1,and PI3KC3 complex components,UVRAG,Beclin1 and Rubicon,were detected in cortex and hippocampus respectively by Immunohistochemistry and Western blot.Results:1.Abnormal expression of Rab7 and markers of EAL pathway were observed in APP/PS1 mice brain.Expression patterns of those markers in APP/PS1 cortex and hippocampus were different.Rab5,Rab7,LC3 B and Lamp1 were increased in APP/PS1 cortex,while Rab7 was decreased with other markers increased in APP/PS1 hippocampus.2.Expression of UVRAG,Beclin1 and Rubicon was investigated and manifested different expression patterns in APP/PS1 cortex and hippocampus respectively.UVRAG and Beclin1 were upregulated,and more UVRAG-Beclin1 positive cells were observed in APP/PS1 cortex,with no significant changes of Rubicon,compared to that of wild-type mice.However,Beclin1 was decreased accompanied by upregulated Rubicon and less UVRAG-Beclin1 positive cells in APP/PS1 hippocampus.Conclusions:1.Rab7 related EAL pathway is dysregulated in APP/PS1 brain.2.Dysregulation of EAL pathway manifests different expression patterns in different regions of APP/PS1 brain,which indicated that lesions of neurons in these regions may not be simultaneous.Autophagy flux is a dynamic condition and could change during the course of AD.Early in the neurodegenerative process,accelerated endocytosis leads to upregulation of Rab7 and the EAL pathway and increased recruitment of endosomes and autophagosomes in neurons.As the disease progresses to the later stage,exhaustion of Rab7 and its related proteins leading to a marked accumulation of AVs,finally collapse of EAL pathway and death of neurons due to a deficiency in lysosomal clearance.3.Rab7 may participate in EAL dysregulation by interacting with UVRAG,Beclin1 and Rubicon in APP/PS1 mice.Objective:To access the effect of lentivirus encoding constitutive active Rab7 on AD mouse model and further confirm that the dysfunction of Rab7 is involved in neurodegeneration in AD.Methods:Genotype of 5x FAD mice is identified by PCR and then,deposition of A? in 5x FAD mice is detected by Immunohistochemistry.Lentivirus encoding constitutive active Rab7 mutant Rab7Q67L and control virus were successfully packaged and harvested.Stereotactic intracerebroventricular injection of lentivirus was performed on 1-month-old5 x FAD mice.And then their spatial memory and brain glucose metabolism were accessed by Water maze and18FDG-PET respectively when they were 6 months old.Results:1.5x FAD mice were successfully bred.Considerable intracellular and extracellular A? deposition could be observed in the brains of 6-month-old mice.2.Lentivirus encoding constitutive active Rab7 mutant(Rab7Q67L)was successfully packaged and harvested.3.Neurons in cortex and hippocampus of 5x AD were infected efficiently by intracerebroventricularly injected lentivirus.4.Escape latency of lenti-Rab7Q67 L group was significantly shortened when compared with that of the uninjected 5xAD group and control lentivirus injected group.5.18FDG-PET revealed that Rab7Q67L-lentivirus injection improved glucose metabolism in 5xFAD brain.Conclusions:1.Dysfunction of Rab7 is involved in neurodegeneration of AD.2.Overexpression of active Rab7 could improve behavioral performance and brain glucose metabolism of 5x FAD mice.3.Rab7 may be a novel therapeutic target for AD.