Sumoylation of PPARγ contributes to vascular endothelium insulin resistance through stabilizing the PPARγ-NcoR complex.

Sumoylation of peroxisome proliferator-activated receptor Î³ (PPARγ) affects its stabilization, sublocalization, and transcriptional activity. However, it remains largely unknown whether PPARγ sumoylation inhibits the transactivation effect, leading to endothelium insulin resistance (IR). To test this possibility, human umbilical vascular endothelial cells (HUVECs) with a 90% confluence were randomly allocated to two batches. One batch was first pretreated with or without vitamin E for 24 hr and the other infected with adenoviruses containing either PIAS1-shRNA (protein inhibitor of activated STAT1-short hairpin RNA) or scramble shRNA. Cells were suffered from high glucose and palmitic acid (PA) exposure for further 48 hr. The levels of PPARγ, p-IKK, IKK, and NcoR (nuclear corepressors) were measured by western blot analysis. The interaction of IKK and PIAS1, as well as the PPARγ sumoylation, were examined by coimmunoprecipitation. The results showed that the exposure of high glucose and PA induced reactive oxygen species (ROS) production and IKK activation in HUVECs, promoting the interaction of IKK and PIAS1 and the sumoylation of PPARγ. However, vitamin E and PIAS1-shRNA partially decreased ROS production and IKK activation induced by high glucose and PA exposure. These data indicate that ROS-IKK-PIAS1 pathway mediates PPARγ sumoylation, leading to endothelium IR via stabilizing PPARγ-NcoR complex. These findings benefit understanding of regulatory networks of insulin signaling, which might provide a potential target to prevent and cure IR-related diseases.

Osteopontin-induced brown adipogenesis from white preadipocytes through a PI3K-AKT dependent signaling.

Recent studies have shown that OPN (osteopontin) plays critical roles in cell survival, differentiation, bio-mineralization, cancer and cardiovascular remodeling. However, its roles in the differentiation of brown adipocytes and the underlying mechanisms remain unclear. Therefore, the aim of this study was to investigate the roles of OPN in the brown adipogenesis and the underlying mechanisms. It was shown that the OPN successfully induced the differentiation of 3T3-L1 white preadipocytes into the PRDM16(+) (PRD1-BF1-RIZ1 homologous domain containing 16) and UCP-1(+) (uncoupling protein-1) brown adipocytes in a concentration and time-dependent manner. Also, activation of PI3K (phosphatidylinositol 3-kinase)-AKT pathway was required for the OPN-induced brown adipogenesis. The findings suggest OPN plays an important role in promoting the differentiation of the brown adipocytes and might provide a potential novel therapeutic approach for the treatment of obesity and related disorders.

Ultrasensitive Detection of Testosterone Using Microring Resonator with Molecularly Imprinted Polymers.

We report ultrasensitive and highly selective detection of testosterone based on microring resonance sensor using molecularly imprinted polymers (MIP). A silicon-on-insulator (SOI) micoring resonator was modified by MIP films (MIPs) on a surface. The MIPs was synthesized by thermopolymerization using methacrylic acid as functional monomer and ethylene glycol dimethacrylate as crosslinking agent. The concentration of detected testosterone varies from 0.05 ng/mL to 10 ng/mL. The detection limit reaches 48.7 pg/mL. Ultrahigh sensitivity, good specificity and reproducibility have been demonstrated, indicating the great potential of making a cost effective and easy to operate lab-on-Chip and down scaling micro-fluidics devices in biosensing.

The N-terminal zinc finger domain of Tgf2 transposase contributes to DNA binding and to transposition activity.

Active Hobo/Activator/Tam3 (hAT) transposable elements are rarely found in vertebrates. Previously, goldfish Tgf2 was found to be an autonomously active vertebrate transposon that is efficient at gene-transfer in teleost fish. However, little is known about Tgf2 functional domains required for transposition. To explore this, we first predicted in silico a zinc finger domain in the N-terminus of full length Tgf2 transposase (L-Tgf2TPase). Two truncated recombinant Tgf2 transposases with deletions in the N-terminal zinc finger domain, S1- and S2-Tgf2TPase, were expressed in bacteria from goldfish cDNAs. Both truncated Tgf2TPases lost their DNA-binding ability in vitro, specifically at the ends of Tgf2 transposon than native L-Tgf2TPase. Consequently, S1- and S2-Tgf2TPases mediated gene transfer in the zebrafish genome in vivo at a significantly (p < 0.01) lower efficiency (21%-25%), in comparison with L-Tgf2TPase (56% efficiency). Compared to L-Tgf2TPase, truncated Tgf2TPases catalyzed imprecise excisions with partial deletion of TE ends and/or plasmid backbone insertion/deletion. The gene integration into the zebrafish genome mediated by truncated Tgf2TPases was imperfect, creating incomplete 8-bp target site duplications at the insertion sites. These results indicate that the zinc finger domain in Tgf2 transposase is involved in binding to Tgf2 terminal sequences, and loss of those domains has effects on TE transposition.

Identification of nuclear localization signal within goldfish Tgf2 transposase.

The structure of goldfish (Carassius auratus) Tgf2 transposase is still poorly understood, although it can mediate efficient gene transfer in teleost fish. We hypothesized the existence of a nuclear localization signal (NLS) within Tgf2 transposase to assist transport into the nucleus. To explore this, 15 consecutive amino acid residues (656-670 aa) within the C-terminus of Tgf2 transposase were predicted in silico to be a NLS domain. The pEGFP-C1-Tgf2TP(△31C) plasmid encoding the NLS-domain-deleted Tgf2 transposase fused to EGFP was constructed, and transfected into 293T cells. After transfection with pEGFP-C1-Tgf2TP(△31C), EGFP was not detected in the nucleus alone, while 67.0% of cells expressed EGFP only in the cytoplasm. In contrast, after transfection with control plasmids containing C- or N-terminal truncated Tgf2 transposases with an intact NLS domain, EGFP was not detected in the cytoplasm alone, while approximately 40% of cells expressed EGFP only in the nucleus, and the remaining 60% expressed EGFP in both the nucleus and cytoplasm. Our results demonstrated that loss of the NLS domain results in expression in the cytoplasm but not in the nucleus. These findings suggest that 15 aa residues located from 656 to 670 aa within the C-terminus of Tgf2 transposase can function as a NLS to assist the transfer of the transposase into the nucleus where it mediates DNA transposition.

Prokaryotic expression and purification of soluble goldfish Tgf2 transposase with transposition activity.

Goldfish Tgf2 transposon of Hobo/Activator/Tam3 (hAT) family can mediate gene insertion in a variety of aquacultural fish species by transposition; however, the protein structure of Tgf2 transposase (TPase) is still poorly understood. To express the goldfish Tgf2 TPase in Escherichia coli, the 2061-bp coding region was cloned into pET-28a(+) expression vector containing an N-terminal (His)6-tag. The pET-28a(+)-Tgf2 TPase expression cassette was transformed into Rosetta 1 (DE3) E. coli lines. A high yield of soluble proteins with molecular weight of ~80 kDa was obtained by optimized cultures including low-temperature (22 °C) incubation and early log phase (OD600 = 0.3-0.4) induction. Mass spectrometry analysis following trypsin digestion of the recombinant proteins confirmed a Tgf2 TPase component in the eluate of Ni(2+)-affinity chromatography. When co-injected into 1-2 cell embryos with a donor plasmid harboring a Tgf2 cis-element, the prokaryotic expressed Tgf2 TPase can mediate high rates (45 %) of transposition in blunt snout bream (Megalobrama amblycephala). Transposition was proved by the presence of 8-bp random direct repeats at the target sites, which is the signature of hAT family transposons. Production of the Tgf2 Tpase protein in a soluble and active form not only allows further investigation of its structure, but provides an alternative tool for fish transgenesis and insertional mutagenesis.