SUMO-Specific Protease 2 (SENP2) Is an Important Regulator of Fatty Acid Metabolism in Skeletal Muscle

Small ubiquitin-like modifier (SUMO)-specific proteases (SENPs) that reverse protein modification by SUMO are involved in the control of numerous cellular processes, including transcription, cell division, and cancer development. However, the physiological function of SENPs in energy metabolism remains unclear. Here, we investigated the role of SENP2 in fatty acid metabolism in C2C12 myotubes and in vivo. In C2C12 myotubes, treatment with saturated fatty acids, like palmitate, led to nuclear factor-B-mediated increase in the expression of SENP2. This increase promoted the recruitment of peroxisome proliferator-activated receptor (PPAR) and PPAR, through desumoylation of PPARs, to the promoters of the genes involved in fatty acid oxidation (FAO), such as carnitine-palmitoyl transferase-1 (CPT1b) and long-chain acyl-CoA synthetase 1 (ACSL1). In addition, SENP2 overexpression substantially increased FAO in C2C12 myotubes. Consistent with the cell culture system, muscle-specific SENP2 overexpression led to a marked increase in the mRNA levels of CPT1b and ACSL1 and thereby in FAO in the skeletal muscle, which ultimately alleviated high-fat diet-induced obesity and insulin resistance. Collectively, these data identify SENP2 as an important regulator of fatty acid metabolism in skeletal muscle and further implicate that muscle SENP2 could be a novel therapeutic target for the treatment of obesity-linked metabolic disorders.11116Ysciescopu

Identification of the peptides that inhibit the stimulation of thyrotropin receptor by Graves' immunoglobulin G from peptide libraries

Graves' disease is characterized by the overproduction of thyroid hormones due to the persistent stimulation of TSH receptor by autoantibodies. To determine the epitopes recognized by the autoantibodies, an enzyme-linked immunosorbent assay was developed that uses the human TSH receptor extracellular domain attached to plastic wells. The total IgG from some of the Graves' patients interacted with the bound TSH receptor (TSHR) at a significantly higher level than that in normal individuals. The IgG preparation that showed the highest binding activity was used for the identification of peptide sequences that prevent binding of Graves' IgG to TSHR from positional scanning synthetic peptide combinatorial libraries. A hexapeptide mixture, X1X2FDDA (X1 is a mixture of E, M, and Y; X2 is mixture of E, H, and T), was found to be effective for inhibiting the binding of Graves' IgG to the TSHR. Further fractionation of X1X2FDDA showed that the following three sequences were highly effective: EEFDDA, ETFDDA, and EHFDDA. The second position the three peptides did not appear to be important. The peptides also inhibited the cAMP synthesis induced by IgG of four of eight patients with Graves' disease tested. The synthesis of cAMP by TSH was also inhibited by the peptides to some extent. The peptide sequences most likely mimic a part of the conformational epitopes recognized by a least one class of Graves' IgG.close232

A Systems Approach for Decoding Mitochondrial Retrograde Signaling Pathways

Mitochondrial dysfunctions activate retrograde signaling from mitochondria to the nucleus. To identify transcription factors and their associated pathways that underlie mitochondrial retrograde signaling, we performed gene expression profiling of the cells engineered to have varying amounts of mitochondrial DNA with an A3243G mutation (mt3243) in the leucine transfer RNA (tRNA(Leu)), which reduces the abundance of proteins involved in oxidative phosphorylation that are encoded by the mitochondrial genome. The cells with the mutation exhibited reduced mitochondrial function, including compromised oxidative phosphorylation, which would activate diverse mitochondrial retrograde signaling pathways. By analyzing the gene expression profiles in cells with the mutant tRNA(Leu) and the transcription factors that recognize the differentially regulated genes, we identified 72 transcription factors that were potentially involved in mitochondrial retrograde signaling. We experimentally validated that the mt3243 mutation induced a retrograde signaling pathway involving RXRA (retinoid X receptor alpha), reactive oxygen species, kinase JNK (c-JUN N-terminal kinase), and transcriptional coactivator PGC1 alpha (peroxisome proliferator-activated receptor gamma, coactivator 1 alpha). This RXR pathway contributed to the decrease in mRNA abundances of oxidative phosphorylation enzymes encoded in the nuclear genome, thereby aggravating the dysfunction in oxidative phosphorylation caused by the reduced abundance of mitochondria-encoded enzymes of oxidative phosphorylation. Thus, matching transcription factors to differentially regulated gene expression profiles was an effective approach to understand mitochondrial retrograde signaling pathways and their roles in mitochondrial dysfunction.X117768sciescopu

Groundwater geochemistry of a nitrate-contaminated agricultural site

Groundwater samples were collected from several soil depths down to 50 m below soil surface to investigate vertical profiles of NO3? and hydrogeochemical characteristics of the experimental site. The experimental site is located in the Shimabara City, Nagasaki, Japan, where nitrate contamination in groundwater is severe due to intensive agricultural production. A transition zone regarding dissolved ions was found between specific depths caused by differences in the permeability of soil layers. Though NO3? concentration decreased significantly in the transition zone, the entire soil depth exceeded permissible levels (50 mg L?1) for drinking purposes. Comparing the temporal NO3? fluctuation above the transition zone with that of the below, distinct fluctuations were observed depending on sampling campaign. High rainfall amounts typically lead to initial decrease in NO3? concentration for the shallow groundwater. After some time, however, increase in NO3? concentration occurred due to leaching of accumulated NO3? in the soil matrix. This indicated that temporal NO3? fluctuation is mainly controlled by natural impact and occurring crop system. Results of principal component analysis suggested that application of chemical fertilizers [(NH4)2SO4, NH4NO3, and KCl], dissolution of minerals (feldspar, calcite, and dolomite), and ion exchange are the predominant factors resulting in the observed vertical groundwater chemistry. The relative magnitude of these three principal component scores changed across the transition zone. Below the transition zone, groundwater geochemistry reflected application of NH4NO3 and KCl fertilizer and dissolution of albite and orthoclase