Endoplasmic reticulum membrane adapter protein XK
endoplasmic reticulum membrane
XK is a partner for VPS13A: a molecular link between Chorea-Acanthocytosis and McLeod Syndrome.
Vps13 is a highly conserved lipid transfer protein found at multiple interorganelle membrane contact sites where it mediates distinct processes. In yeast, recruitment of Vps13 to different contact sites occurs via various partner proteins. In humans, four VPS13 family members, A-D, are associated with different diseases. In particular, <i>vps13A</i> mutants result in the neurodegenerative disorder Chorea-Acanthocytosis (ChAc). ChAc phenotypes resemble those of McLeod Syndrome, caused by mutations in the <i>XK</i> gene, suggesting that XK could be a partner protein for VPS13A. XK does, in fact, exhibit hallmarks of a VPS13A partner: it forms a complex with VPS13A in human cells and, when overexpressed, relocalizes VPS13A from lipid droplets to subdomains of the endoplasmic reticulum. Introduction of two different ChAc disease-linked missense mutations into VPS13A prevents this XK-induced relocalization. These results suggest that dysregulation of a VPS13A-XK complex is the common basis for ChAc and McLeod Syndrome.