Expression of Low Level of VPS35-mCherry Fusion Protein Diminishes Vps35 Depletion Induced Neuron Terminal Differentiation Deficits and Neurodegenerative Pathology, and Prevents Neonatal Death.

Yang Zhao,Daehoon Lee,Wen-Cheng Xiong,Fulei Tang

doi:10.3390/ijms22168394

Abstract

Vps35 (vacuolar protein sorting 35) is a key component of retromer that consists of Vps35, Vps26, and Vps29 trimers, and sortin nexin dimers. Dysfunctional Vps35/retromer is believed to be a risk factor for development of various neurodegenerative diseases. Vps35Neurod6 mice, which selectively knock out Vps35 in Neurod6-Cre+ pyramidal neurons, exhibit age-dependent impairments in terminal differentiation of dendrites and axons of cortical and hippocampal neurons, neuro-degenerative pathology (i.e., increases in P62 and Tdp43 (TAR DNA-binding protein 43) proteins, cell death, and reactive gliosis), and neonatal death. The relationships among these phenotypes and the underlying mechanisms remain largely unclear. Here, we provide evidence that expression of low level of VPS35-mCherry fusion protein in Vps35Neurod6 mice could diminish the phenotypes in an age-dependent manner. Specifically, we have generated a conditional transgenic mouse line, LSL-Vps35-mCherry, which expresses VPS35-mCherry fusion protein in a Cre-dependent manner. Crossing LSL-Vps35-mCherry with Vps35Neurod6 to obtain TgVPS35-mCherry, Vps35Neurod6 mice prevent the neonatal death and diminish the dendritic morphogenesis deficit and gliosis at the neonatal, but not the adult age. Further studies revealed that the Vps35-mCherry transgene expression was low, and the level of Vps35 mRNA comprised only ~5–7% of the Vps35 mRNA of control mice. Such low level of VPS35-mCherry could restore the amount of other retromer components (Vps26a and Vps29) at the neonatal age (P14). Importantly, the neurodegenerative pathology presented in the survived adult TgVps35-mCherry; Vps35Neurod6 mice. These results demonstrate the sufficiency of low level of VPS35-mCherry fusion protein to diminish the phenotypes in Vps35Neurod6 mice at the neonatal age, verifying a key role of neuronal Vps35 in stabilizing retromer complex proteins, and supporting the view for Vps35 as a potential therapeutic target for neurodegenerative diseases.

Highlights

Retromer complex, a key endosomal protein sorting machinery, recognizes specific membrane cargo proteins that are concentrated in discrete regions of the endosomal membranes, and retrieves cargo proteins to the trans-Golgi network or the plasma membrane [1,2,3]
The neurodegenerative pathology appeared in the survived young adult TgVps35-mCherry; Vps35Neurod6 mice. These results suggest the sufficiency of low level of VPS35-mCherry fusion protein to diminish the deficit in neuronal terminal differentiation, cell death, and gliosis at the neonatal age, and to prevent neonatal death, demonstrating the neuronal Vps35 function in stabilizing retromer complex proteins in an age dependent manner, and supporting the view for Vps35 as a potential therapeutic target for neurodegenerative diseases
Retromer dysfunction is involved in pathogenesis of multiple neurodegenerative diseases, including AD and PD, frontotemporal dementia (FTD), and ALS [16,26,27,42]

Summary

Introduction

A key endosomal protein sorting machinery, recognizes specific membrane cargo proteins that are concentrated in discrete regions of the endosomal membranes, and retrieves cargo proteins to the trans-Golgi network or the plasma membrane [1,2,3]. A growing list of retromer cargos has been identified, which includes cation independent mannose 6-phosphate receptors (CI-MRP) [6,7], the Wnt transport protein Wntless/MIG-14 [8,9], sortilin or sortilin-related receptor (SorL1 or SorLA) [10,11,12,13], amyloid precursor protein (APP) [14,15], BACE1 [16,17], TREM2 [18,19], RANK [20] Many of these cargos are involved in the pathogenesis of neurodegenerative diseases. Retromer is implicated in regulation of the development of neurodegenerative disorders

Methods

Results

Conclusion