Uncoupling protein 3 attenuates generation of reactive oxygen species by interacting with thioredoxin 2 in the mitochondrial intermembrane space

Katsuya Hirasaka1*, Edward M Mills2, Shohei Kohno1, Tomoki Abe1, Chika Ikeda1, Tasuku Maeda1, Shigetada Kondo1, Ayako Maita1, Yuushi Okumura1 and Takeshi Nikawa1 Author Affiliations 1 Department of Nutritional Physiology, Institute of Health Biosciences, University of Tokushima, Tokushima, 770-8503, Japan 2 Division of Pharmacology/Toxicology, University of Texas at Austin, Austin, TX 78712, USAPoster presentation Uncoupling protein 3 (UCP3) is primarily expressed in the inner membrane of skeletal muscle mitochondria. It has been proposed that UCP3 reduces production of reactive oxygen species (ROS) and oxidative damage. However, the mechanisms by which UCP3 attenuates ROS production are not well understood. Here we report that UCP3 interacts with the non-processed form of thioredoxin 2 (Trx2), a redox protein that is localized in mitochondria, but not processed Trx2, which is involved in cellular responses to ROS. The hydrophilic sequences within the N-terminal tail of UCP3, which faces the intermembrane space, are necessary for binding to Trx2. In addition, Trx2 directly associated with UCP3 through a mitochondrial targeting signaling sequence, was processed in the intermembrane space, and thereby allowing redox reactions. A bimolecular fluorescence complementation analysis demonstrated that the interaction of these proteins occurs in the mitochondrial intermembrane space. Furthermore, increased UCP3 expression significantly attenuated ROS production in isolated mitochondrial without effects on membrane potential, however this effect is lost by Trx2 knock down. These results suggest that UCP3 binds to Trx2 in the mitochondrial intermembrane space and attenuates ROS production.Pharmac

Structure of MSPL–inhibitor complex

Infection of certain influenza viruses is triggered when its HA is cleaved by host cell proteases such as proprotein convertases and type II transmembrane serine proteases (TTSP). HA with a monobasic motif is cleaved by trypsin-like proteases, including TMPRSS2 and HAT, whereas the multibasic motif found in high pathogenicity avian influenza HA is cleaved by furin, PC5/6, or MSPL. MSPL belongs to the TMPRSS family and preferentially cleaves [R/K]-K-K-R↓ sequences. Here, we solved the crystal structure of the extracellular region of human MSPL in complex with an irreversible substrate-analog inhibitor. The structure revealed three domains clustered around the C-terminal α-helix of the SPD. The inhibitor structure and its putative model show that the P1-Arg inserts into the S1 pocket, whereas the P2-Lys and P4-Arg interacts with the Asp/Glu-rich 99-loop that is unique to MSPL. Based on the structure of MSPL, we also constructed a homology model of TMPRSS2, which is essential for the activation of the SARS-CoV-2 spike protein and infection. The model may provide the structural insight for the drug development for COVID-19

ハイヨウセイ キン イシュク オ フセグ コウユビキチンカ ペプチド Cblin Cbl-b inhibitor ノ コウキノウカ

Skeletal muscle atrophy caused by unloading is characterized by both decreased responsiveness to myogenic growth factors and increased proteolysis. In our previous studies, it has been shown that ubiquitin ligase Cbl-b interacted and degraded the IGF-1 signaling intermediate IRS-1. We also reported that a peptide mimetic of tyrosin608-phosphorylated IRS-1 （DGpYMP）, named Cblin, Cbl-b inhibitor. However, Cblin may tend to be degraded by aminopeptidase in vivo. We aimed to confirm whether Cblin inhibiter muscle atrophy caused by glucocorticoids in mouse C2C12 myotubes, and effects of the modified Cblin N-terminus to prevent it from degradation. Pretreatment with Cblin significantly prevented the decrease in diameters of C2C12 myotubes treated with dexamethasone, and IRS-1 degradation, expression of atrogenes mRNA was repressed, and phosphorylation of Akt/mTOR was also protected. Moreover, the 50％ inhibitory concentration of N -myristoylated Cblin and Cblin for Cbl-b-mediated IRS-1 ubiquitination was 35μM and 120μM, respectively. In addition, N -myristoylated Cblin significantly inhibited the dexamethasone-induced reduction of myotube diameter. Taken together, these results suggest that Cblin Cblin prevented the dexamethasone induced myotube atrophy, and N -myristoyled Cblin is more effective than nonmodified Cblin in prevention of muscle atrophy