Bridge-like lipid transfer proteins (BLTPs) play central roles in redistributing lipids from their primary site of synthesis in the endoplasmic reticulum to other organelles. They comprise bridge-doma Show more
Bridge-like lipid transfer proteins (BLTPs) play central roles in redistributing lipids from their primary site of synthesis in the endoplasmic reticulum to other organelles. They comprise bridge-domains spanning between organelles at contact sites that allow lipids to transit the cytosol between adjacent membranes. The assembly of BLTPs into complexes with adaptor proteins enables their lipid transfer ability. To address the mechanisms underlying assembly and regulation of BLTP complexes, we used cryo-EM to resolve the structure of one such BLTP, the Parkinson's protein VPS13C, at near-atomic resolution. The structure identifies a lipid-transfer-nonpermissive conformation, where the built-in C-terminal VAB adaptor module blocks the end of the lipid transfer bridge, interfering with lipid delivery. We also identify calmodulin, central to calcium signaling, as a VPS13 partner, suggesting calcium regulation of VPS13 function. Altogether, this structure of intact VPS13C serves as starting point to understand its regulation and, more broadly, that of other BLTPs. Show less
Mutations in the human VPS13 genes are responsible for neurodevelopmental and neurodegenerative disorders including chorea acanthocytosis (VPS13A) and Parkinson's disease (VPS13C). The mechanisms of t Show more
Mutations in the human VPS13 genes are responsible for neurodevelopmental and neurodegenerative disorders including chorea acanthocytosis (VPS13A) and Parkinson's disease (VPS13C). The mechanisms of these diseases are unknown. Genetic studies in yeast hinted that Vps13 may have a role in lipid exchange between organelles. In this study, we show that the N-terminal portion of VPS13 is tubular, with a hydrophobic cavity that can solubilize and transport glycerolipids between membranes. We also show that human VPS13A and VPS13C bind to the ER, tethering it to mitochondria (VPS13A), to late endosome/lysosomes (VPS13C), and to lipid droplets (both VPS13A and VPS13C). These findings identify VPS13 as a lipid transporter between the ER and other organelles, implicating defects in membrane lipid homeostasis in neurological disorders resulting from their mutations. Sequence and secondary structure similarity between the N-terminal portions of Vps13 and other proteins such as the autophagy protein ATG2 suggest lipid transport roles for these proteins as well. Show less