Hirasaka Katsuya, Mills Edward M, Haruna Marie, Bando Aki, Ikeda Chika, Abe Tomoki, Kohno Shohei, Nowinski Sara M, Lago Cory U, Akagi Ken-Ichi, Tochio Hidehito, Ohno Ayako, Teshima-Kondo Shigetada, Okumura Yuushi, Nikawa Takeshi
Graduate School of Fisheries and Environmental Sciences, Nagasaki University, Nagasaki, Japan; Department of Nutritional Physiology, Institute of Health Biosciences, University of Tokushima, Tokushima, Japan.
Division of Pharmacology/Toxicology, University of Texas at Austin, Austin, TX, USA.
Biochem Biophys Res Commun. 2016 Mar 25;472(1):108-13. doi: 10.1016/j.bbrc.2016.02.075. Epub 2016 Feb 23.
Uncoupling protein 3 (UCP3) is known to regulate energy dissipation, proton leakage, fatty acid oxidation, and oxidative stress. To identify the putative protein regulators of UCP3, we performed yeast two-hybrid screens. Here we report that UCP3 interacted with HS-1 associated protein X-1 (Hax-1), an anti-apoptotic protein that was localized in the mitochondria, and is involved in cellular responses to Ca(2+). The hydrophilic sequences within loop 2, and the matrix-localized hydrophilic domain of mouse UCP3, were necessary for binding to Hax-1 at the C-terminal domain, adjacent to the mitochondrial inner membrane. Interestingly, interaction of these proteins occurred in a calcium-dependent manner. Moreover, the NMR spectrum of the C-terminal domain of Hax-1 was dramatically changed by removal of Ca(2+), suggesting that the C-terminal domain of Hax-1 underwent a Ca(2+)-induced conformational change. In the Ca(2+)-free state, the C-terminal Hax-1 tended to unfold, suggesting that Ca(2+) binding may induce protein folding of the Hax-1 C-terminus. These results suggested that the UCP3-Hax-1 complex may regulate mitochondrial functional changes caused by mitochondrial Ca(2+).
解偶联蛋白3（UCP3）已知可调节能量耗散、质子泄漏、脂肪酸氧化和氧化应激。为了鉴定UCP3的假定蛋白调节因子，我们进行了酵母双杂交筛选。在此我们报告，UCP3与HS-1相关蛋白X-1（Hax-1）相互作用，Hax-1是一种定位于线粒体的抗凋亡蛋白，参与细胞对Ca(2+)的反应。小鼠UCP3的环2内的亲水性序列以及基质定位的亲水性结构域，对于在与线粒体内膜相邻的C末端结构域与Hax-1结合是必需的。有趣的是，这些蛋白的相互作用以钙依赖的方式发生。此外，去除Ca(2+)后，Hax-1的C末端结构域的核磁共振谱发生了显著变化，表明Hax-1的C末端结构域经历了Ca(2+)诱导的构象变化。在无Ca(2+)状态下，C末端Hax-1倾向于展开，表明Ca(2+)结合可能诱导Hax-1 C末端的蛋白折叠。这些结果表明，UCP3-Hax-1复合物可能调节由线粒体Ca(2+)引起的线粒体功能变化。
