RNF213 Formed and Decorated Membrane-Based Structures in U-2 OS Cells

RING protein 213 (RNF213), the susceptibility gene for Moyamoya disease (MMD), possesses two active AAA+ ATPase (ATPases Associated with diverse cellular Activities) modules, a RING, and RNF213-ZNFX1 finger (RZ finger) domains. Several RNF213 variants have been reported in MMD patients, including the p.R4810K variant (rs112735431), which is a founder polymorphism associated with MMD in East Asia. To elucidate the function of RNF213 and its variant, we investigated the localization of RNF213 and the R4810K variant in this study. RNF213 induced circular hole structures near the nucleus, similar to lipid droplets (LDs), in U-2 OS cells. The holes decorated with tagged RNF213 protein were colocalized with mCherry-RAB5A and mCherry-peroxisome, but not mCherry-RAB9A and other organelles. RNF213 decorated the holes, and the structures were growing and changing to cylindrical objects, but not the R4810K variant efficiently. Furthermore, both AAA+ ATPase modules and the ubiquitin ligase domain of RNF213 were required for the formation of the hole structures and cylindrical objects. These findings suggest that RNF213 activity may be involved in the formation of organelle-like structures, and this structure formation by RNF213 may be responsible for vascular functions.