Surface plasmon resonance analysis of interactions between diacylglycerol acyltransferase and its interacting molecules

To measure the interactions of diacylglycerol acyltransferase (DGAT) by surface plasmon resonance (SPR), we immobilized Saccharomyces cerevisiae DGAT2 encoded by DGA1 on a BIACORE sensor chip surface. We used N-terminally truncated Dga1p with a FLAG tag at the C-terminus, which was purified to apparent homogeneity, maintaining significant DGAT activity (Kamisaka et al., Appl. Microbiol. Biotechnol., 88, 105-115 (2010)). Truncated Dga1p with a FLAG tag was immobilized with an anti-FLAG antibody that had been coupled with an L1 chip surface consisting of a carboxymethyl dextran matrix with additional hydrophobic alkane groups. The Dga1p-immobilized chip surface was analyzed for interactions of Dga1p with oleoyl-CoA, its substrate, and anti-Dga1p IgG, its interacting protein, by SPR. The binding of these analytes with the Dga1p-immobilized chip surface was specific, because butyryl-CoA, which cannot be used as a substrate for DGAT, and anti-glyceraldehyde-3-phosphate dehydrogenase IgG, did not induce any signals on SPR. Furthermore, injection of organic compounds such as xanthohumol, a DGAT inhibitor, into the Dga1p-immobilized chip surface induced significant SPR signals, probably due to interaction with DGAT. Another DGAT inhibitor, piperine, did not induce SPR signals on application, but induced them due to piperine on application together with oleoyl-CoA, in which piperine can be incorporated into the micelles of oleoyl-CoA. The results indicate that the Dga1p-immobilized L1 chip surface recognized DGAT inhibitors. Taking all this together, SPR measurement using the Dga1p-immobilized L1 chip surface provided a useful system to elucidate the structure-function relationships of DGAT and screen DGAT inhibitors.     

Development of drug-loaded protein nanoparticles displaying enzymatically-conjugated DNA aptamers for cancer cell targeting

Molecular Biology Reports - Modification of protein-based drug carriers with tumor-targeting properties is an important area of research in the field of anticancer drug delivery. To this end, we...     

Immunosuppressive effect of a non-proteinogenic amino acid from Streptomyces through inhibiting allogeneic T cell proliferation

The immunosuppressive activity of myriocin (ISP-1), a lead compound of fingolimod (FTY720), is derived from its 2-amino-1,3-propandiol structure. A non-proteinogenic amino acid, (2S,6R)-diamino-(5R,7)-dihydroxy-heptanoic acid (DADH), that contains this structure, was recently identified as a biosynthetic intermediate of a dipeptide secondary metabolite, vazabitide A, in Streptmyces sp. SANK 60404; however its effect on adaptive immunity has not yet been examined. In this study, we examined whether DADH suppresses mixed lymphocyte reaction using mouse bone marrow-derived dendritic cells (BMDCs) and allogeneic splenic T cells. Although T cell proliferation induced by cross-linking CD3 and CD28 were not suppressed by DADH unlike ISP-1, the pre-incubation of BMDCs with DADH but not ISP-1 significantly decreased allogeneic CD8⁺ T cell expansion. Based on these results, we concluded that DADH suppresses DC-mediated T cell activation by targeting DCs.     

Trait-dependent resemblance of the flowering phenology and floral morphology of the allopolyploid Cardamine flexuosa to those of the parental diploids in natural habitats

Allopolyploids possess complete sets of genomes derived from different parental species and exhibit a range of variation in various traits. Reproductive traits may play a key role in the reproductive isolation between allopolyploids and their parental species, thus affecting the thriving of allopolyploids. However, empirical data, especially in natural habitats, comparing reproductive trait variation between allopolyploids and their parental species remain rare. Here, we documented the flowering phenology and floral morphology of the allopolyploid wild plant Cardamine flexuosa and its diploid parents C. amara and C. hirsuta in their native range in Switzerland. The flowering of C. flexuosa started at an intermediate time compared with those of the parents and the flowering period of C. flexuosa overlapped with those of the parents. Cardamine flexuosa resembled C. hirsuta in the size of flowers and petals and the length/width ratio of petals, while it resembled C. amara in the length/width ratio of flowers. These results provide empirical evidence of the trait-dependent variation of allopolyploid phenotypes in natural habitats at the local scale. They also suggest that the variation in some reproductive traits in C. flexuosa is associated with self-fertilization. Therefore, it is helpful to consider the mating system in furthering the understanding of the processes that may have shaped trait variation in polyploids in nature.

     

Cerebellum size is related to fear memory and domestication of chickens

Red Junglefowl (Gallus gallus) were selected for divergent levels of fear of humans during eight generations, causing the selection lines to differ in fear levels as well as in the proportional brain and cerebellum masses. Birds from the two lines were then crossed to obtain an F3 intercross in order to study the correlations between brain mass and fear learning. We exposed 105 F3-animals individually to a fear habituation and memory test at 8 days of age, where the reactions to repeated light flashes were assessed on 2 consecutive days. After culling, the absolute and relative sizes of each of four brain regions were measured. Stepwise regression was used to analyse the effects of the size of each brain region on habituation and memory. There were no effects of any brain region on the habituation on day one. However, birds with a larger absolute size of cerebellum had significantly reduced reactions to the fearful stimuli on day two, indicating a better memory of the stimuli. No other regions had significant effects. We conclude that increased cerebellum size may have been important in facilitating chicken domestication, allowing them to adapt to a life with humans.     

A flipped ion pair at the dynein–microtubule interface is critical for dynein motility and ATPase activation

Dynein is a motor protein that moves on microtubules (MTs) using the energy of adenosine triphosphate (ATP) hydrolysis. To understand its motility mechanism, it is crucial to know how the signal of MT binding is transmitted to the ATPase domain to enhance ATP hydrolysis. However, the molecular basis of signal transmission at the dynein–MT interface remains unclear. Scanning mutagenesis of tubulin identified two residues in α-tubulin, R403 and E416, that are critical for ATPase activation and directional movement of dynein. Electron cryomicroscopy and biochemical analyses revealed that these residues form salt bridges with the residues in the dynein MT-binding domain (MTBD) that work in concert to induce registry change in the stalk coiled coil and activate the ATPase. The R403-E3390 salt bridge functions as a switch for this mechanism because of its reversed charge relative to other residues at the interface. This study unveils the structural basis for coupling between MT binding and ATPase activation and implicates the MTBD in the control of directional movement.     

Ghrelin Augments the Expressions and Secretions of Proinflammatory Adipokines,VEGF120 and MCP‐1, in Differentiated 3T3‐L1 Adipocytes

Ghrelin is a physiological‐active peptide with growth hormone‐releasing activity, orexigenic activity, etc. In addition, the recent study has also suggested that ghrelin possesses the pathophysiological abilities related with type 2 diabetes. However, the ghrelin‐direct‐effects implicated in type 2 diabetes on peripheral tissues have been still unclear, whereas its actions on the central nervous system (CNS) appear to induce the development of diabetes. Thus, to assess its peripheral effects correlated with diabetes, we investigated the regulatory mechanisms about adipokines, which play a central role in inducing peripheral insulin resistance, secreted from mature 3T3‐L1 adipocytes stimulated with ghrelin in vitro . The stimulation with 50 nmol/L ghrelin for 24 h resulted in the significant 1.9‐fold increase on vascular endothelial growth factor‐120 (VEGF₁₂₀) releases (p < 0.01) and the 1.7‐fold on monocyte chemoattractant protein‐1 (MCP‐1) (p < 0.01) from 3T3‐L1 adipocytes, respectively, while ghrelin failed to enhance tumor necrosis factor‐α (TNF‐α), interleukin‐1β (IL‐1β), IL‐6, IL‐10 and adiponectin secretions. In addition, Akt phosphorylation on Ser473 and c‐Jun NH₂‐terminal protein kinase (JNK) phosphorylation on Thr183/Tyr185 were markedly enhanced 1.4‐fold (p < 0.01) and 1.6‐fold (p < 0.01) in the ghrelin‐stimulated adipocytes, respectively. Furthermore, the treatment with LY294002 (50 μmol/L) and Wortmannin (10nmol/L), inhibitors of phosphatidylinositol 3‐kinase (PI3K), significantly decreased the amplified VEGF₁₂₀ secretion by 29% (p < 0.01) and 28% (p < 0.01) relative to the cells stimulated by ghrelin alone, respectively, whereas these inhibitors had no effects on increased MCP‐1 release. On the other hand, JNK inhibitor SP600125 (10 μmol/L) clearly reduced the increased MCP‐1, but not VEGF₁₂₀, release by 35% relative to the only ghrelin‐stimulated cells (p < 0.01). In conclusion, ghrelin can enhance the secretions of proinflammatory adipokines, VEGF₁₂₀ and MCP‐1, but fails to affect IL‐10 and adiponectin which are considered to be anti‐inflammatory adipokines. Moreover, this augmented VEGF₁₂₀ release is invited through the activation of PI3K pathways and the MCP‐1 is through JNK pathways. Consequently, our results strongly suggest that ghrelin can induce the development of diabetes via its direct‐action in peripheral tissues as well as via in CNS. J. Cell. Physiol. 230: 199–209, 2015. © 2014 The Authors. Journal of Cellular Physiology Published by Wiley Periodicals, Inc.     

ATP11C mutation is responsible for the defect in phosphatidylserine uptake in UPS-1 cells

Type IV P-type ATPases (P4-ATPases) translocate phospholipids from the exoplasmic to the cytoplasmic leaflets of cellular membranes. We and others previously showed that ATP11C, a member of the P4-ATPases, translocates phosphatidylserine (PS) at the plasma membrane. Twenty years ago, the UPS-1 (uptake of fluorescent PS analogs) cell line was isolated from mutagenized Chinese hamster ovary (CHO)-K1 cells with a defect in nonendocytic uptake of nitrobenzoxadiazole PS. Due to its defect in PS uptake, the UPS-1 cell line has been used in an assay for PS-flipping activity; however, the gene(s) responsible for the defect have not been identified to date. Here, we found that the mRNA level of ATP11C was dramatically reduced in UPS-1 cells relative to parental CHO-K1 cells. By contrast, the level of ATP11A, another PS-flipping P4-ATPase at the plasma membrane, or CDC50A, which is essential for delivery of most P4-ATPases to the plasma membrane, was not affected in UPS-1 cells. Importantly, we identified a nonsense mutation in the ATP11C gene in UPS-1 cells, indicating that the intact ATP11C protein is not expressed. Moreover, exogenous expression of ATP11C can restore PS uptake in UPS-1 cells. These results indicate that lack of the functional ATP11C protein is responsible for the defect in PS uptake in UPS-1 cells and ATP11C is crucial for PS flipping in CHO-K1 cells.