Impaired XK recycling for importing manganese underlies striatal vulnerability in Huntington's disease.

Mutant huntingtin, which causes Huntington's disease (HD), is ubiquitously expressed but induces preferential loss of striatal neurons by unclear mechanisms. Rab11 dysfunction mediates homeostatic disturbance of HD neurons. Here, we report that Rab11 dysfunction also underscores the striatal vulnerability in HD. We profiled the proteome of Rab11-positive endosomes of HD-vulnerable striatal cells to look for protein(s) linking Rab11 dysfunction to striatal vulnerability in HD and found XK, which triggers the selective death of striatal neurons in McLeod syndrome. XK was trafficked together with Rab11 and was diminished on the surface of immortalized HD striatal cells and striatal neurons in HD mouse brains. We found that XK participated in transporting manganese, an essential trace metal depleted in HD brains. Introducing dominantly active Rab11 into HD striatal cells improved XK dynamics and increased manganese accumulation in an XK-dependent manner. Our study suggests that impaired Rab11-based recycling of XK onto cell surfaces for importing manganese is a driver of striatal dysfunction in Huntington's disease.