UAS domain of Ubxd8 and FAF1 polymerizes upon interaction with long-chain unsaturated fatty acids

Hyeonwoo Kim,Hong Zhang,David Meng,Geoffrey Russell,Joon No Lee,Jin Ye

doi:10.1194/jlr.m037218

Abstract

Ubxd8, a multidomain protein sensor for long-chain unsaturated fatty acids (FAs), plays a crucial role to maintain cellular homeostasis of FAs. Ubxd8 polymerizes upon interaction with long-chain unsaturated FAs, but the molecular mechanism involved in this polymerization remains unclear. Here we report that the UAS domain of Ubxd8 mediates this polymerization. We show that a positively charged surface area in the domain is required for the reaction. Mutations changing the positively charged residues in this area to glutamates prevented long-chain unsaturated FAs from inducing oligomerization of Ubxd8. Consequently, the mutant protein no longer responded to regulation by long-chain unsaturated FAs in cultured cells. Long-chain unsaturated FAs also induced polymerization of Fas-associated factor 1 (FAF1), the only other mammalian protein that contains a UAS domain homologous to that of Ubxd8. These results provide further insights into protein-FA interactions by identifying the UAS domain as a motif interacting with long-chain unsaturated FAs.

Highlights

Ubxd8, a multidomain protein sensor for longchain unsaturated fatty acids (FAs), plays a crucial role to maintain cellular homeostasis of Fatty acids (FA)
To identify the region in Ubxd8 that is required for long-chain unsaturated FAs to induce polymerization of the protein, we made various deletion mutants in Ubxd8(⌬90–118) fused with a His6-tag at the NH2 terminus, purified the recombinant protein expressed in sf9 cells to homogeneity using Ni2+-affinity followed by size exclusion chromatography, and analyzed the effect of FAs on polymerization of the proteins through blue native PAGE, a technique that allows detection of protein complexes in their native state [2, 14]
While long-chain unsaturated FAs failed to induce oligomerization of the purified UBA domain (Fig. 1D), they were effective in stimulating polymerization of the purified UAS domain (Fig. 1E)

Summary

Introduction

Ubxd8, a multidomain protein sensor for longchain unsaturated fatty acids (FAs), plays a crucial role to maintain cellular homeostasis of FAs. Long-chain unsaturated FAs induced polymerization of Fas-associated factor 1 (FAF1), the only other mammalian protein that contains a UAS domain homologous to that of Ubxd8.

Results

Conclusion