Glucose transporter 3 is a rab11-dependent trafficking cargo and its transport to the cell surface is reduced in neurons of CAG140 Huntington's disease mice.

Hollis Mcclory,Dana Williams,Ping Wang,Ellen Sapp,Leah W Gatune,Marian Difiglia,Xueyi Li

doi:10.1186/s40478-014-0178-7

Abstract

Huntington’s disease (HD) disturbs glucose metabolism in the brain by poorly understood mechanisms. HD neurons have defective glucose uptake, which is attenuated upon enhancing rab11 activity. Rab11 regulates numerous receptors and transporters trafficking onto cell surfaces; its diminished activity in HD cells affects the recycling of transferrin receptor and neuronal glutamate/cysteine transporter EAAC1. Glucose transporter 3 (Glut3) handles most glucose uptake in neurons. Here we investigated rab11 involvement in Glut3 trafficking. Glut3 was localized to rab11 positive puncta in primary neurons and immortalized striatal cells by immunofluorescence labeling and detected in rab11-enriched endosomes immuno-isolated from mouse brain by Western blot. Expression of dominant active and negative rab11 mutants in clonal striatal cells altered the levels of cell surface Glut3 suggesting a regulation by rab11. About 4% of total Glut3 occurred at the cell surface of primary WT neurons. HD140Q/140Q neurons had significantly less cell surface Glut3 than did WT neurons. Western blot analysis revealed comparable levels of Glut3 in the striatum and cortex of WT and HD140Q/140Q mice. However, brain slices immunolabeled with an antibody recognizing an extracellular epitope to Glut3 showed reduced surface expression of Glut3 in the striatum and cortex of HD140Q/140Q mice compared to that of WT mice. Surface labeling of GABAα1 receptor, which is not dependent on rab11, was not different between WT and HD140Q/140Q mouse brain slices. These data define Glut3 to be a rab11-dependent trafficking cargo and suggest that impaired Glut3 trafficking arising from rab11 dysfunction underlies the glucose hypometabolism observed in HD.

Highlights

Huntington’s disease (HD) is a progressive neurodegenerative disorder caused by a mutation in huntingtin (Htt) [1]
Defective trafficking of Glucose transporter 3 (Glut3) to cell surfaces in primary HD neurons We previously showed that primary neurons cultured from embryonic cortex of HD140Q/140Q mice took up significantly less glucose than did primary neurons cultured from WT mice [25]
We found that the signal for biotinylated Glut3 was extremely low in both WT and HD140Q/140Q neurons, and was hardly detected in some experiments (Figure 1A and data not shown)

Summary

Introduction

Huntington’s disease (HD) is a progressive neurodegenerative disorder caused by a mutation in huntingtin (Htt) [1]. Positron emission tomography brain imaging with [18 F]-fluorodeoxyglucose has revealed a regional decrease of glucose usage in the striatum (caudate and putamen) and cortex (frontal and temporal lobes) of persons symptomatic and at risk for HD [3,4,5,6,7,8]. Decreased activity of brain glucose metabolism correlates with the progression of HD [9]. On the other hand, is expressed in neurons in all layers of neocortex, the striatum, the thalamus, midbrain, cerebellum and the ependymal layer of all ventricles [14,15,16]. In the brain and in cultured neurons, Glut protein is detected in somata and neural processes [12,15]. HD patients at early stages of striatal degeneration (grade I [17]) have normal levels of McClory et al Acta Neuropathologica Communications (2014) 2:179

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