Structure-based rational design of staurosporine-based fluorescent probe with broad-ranging kinase affinity for kinase panel application

Selectivity profiling of compounds is important for kinase drug discovery. To this end, we aimed to develop a broad-range protein kinase assay by synthesizing a novel staurosporine-derived fluorescent probe based on staurosporine and kinase-binding related structural information. Upon structural analysis of staurosporine with kinases, a 4′-methylamine moiety of staurosporine was found to be located on the solvent side of the kinases, to which several linker units can be conjugated by either alkylation or acylation. However, such conjugation was suggested to reduce the binding affinities of the modified compound for several kinases, owing to the elimination of hydrogen bond donor moiety of NH-group from 4′-methylamine and/or steric hindrance by acyl moiety. Based on this structural information, we designed and synthesized a novel staurosporine-based probe without methyl group in order to retain the hydrogen bond donor, similar to unmodified staurosporine. The broad range of the kinase binding assay demonstrated that our novel fluorescent probe is an excellent tool for developing broad-ranging kinase binding assay.     

Production of crystallins and lens-like structures in differentiation-induced neoplastic pigment cells (goldfish erythrophoroma cells) in vitro

Abstract. We examined the crystallins present in lens-like cell aggregates produced by goldfish erythrophoroma (tumors of integumental erythrophores) cells in vitro using a combination of Sephadex-G-200 gel filtration, one- and two-dimensional sodium-dodecyl-sulfate/poly-acryl-amide gel electrophoresis, immunoblotting, and indirect immunofluorescence assays. The two studied neoplastic pigment cell lines, GEM 81 and GEM 218, formed small, spherical, transparent cell aggregates, resembling lentoid bodies. within the cell mounds of monolayer cultures after treatment with dimethylsulfoxide (DMSO) and autologous serum. Partial purification of a water-soluble extract of such lens-like cell aggregates and subsequent immunoblotting using antibodies (polyclonal) against newt whole lens proteins revealed the presence of about 20 unequivocally conjugated peptides with molecular masses of 19-27 kilodaltons. From their antigenicity and their behavior during gel filtration and electrophoresis, most of these peptides were identified as either α or β-form crystallins. Immunofluorescence microscopy using antibodies to newt whole lens proteins revealed intense fluorescence in the lens-like cell aggregates formed by these erythrophoroma cells, whereas the cell mounds in cultures of the same cell lines that had not been subjected to differentiation induction were almost unlabeled. Thus, goldfish erythrophoroma cells appear to be capable of crystallin production as well as the formation of lens-like cell aggregates upon the induction of differentiation. There is little available information indicating that normal pigment cells are capable of lens formation and crystallin synthesis during vertebrate ontogeny, and thus it is possible that neoplastic transformation of pigment cells is associated with the acquisition of the ability to produce crystallins.     

Selective expansion of foxp3-positive regulatory T cells and immunosuppression by suppressors of cytokine signaling 3-deficient dendritic cells

Dendritic cells (DCs) induce immunity and immunological tolerance as APCs. It has been shown that DCs secreting IL-10 induce IL-10(+) Tr1-type regulatory T (Treg) cells, whereas Foxp3-positive Treg cells are expanded from naive CD4(+) T cells by coculturing with mature DCs. However, the regulatory mechanism of expansion of Foxp3(+) Treg cells by DCs has not been clarified. In this study, we demonstrated that suppressors of cytokine signaling (SOCS)-3-deficient DCs have a strong potential as Foxp3(+) T cell-inducing tolerogenic DCs. SOCS3(-/-) DCs expressed lower levels of class II MHC, CD40, CD86, and IL-12 than wild-type (WT)-DCs both in vitro and in vivo, and showed constitutive activation of STAT3. Foxp3(-) effector T cells were predominantly expanded by the priming with WT-DCs, whereas Foxp3(+) Treg cells were selectively expanded by SOCS3(-/-) DCs. Adoptive transfer of SOCS3(-/-) DCs reduced the severity of experimental autoimmune encephalomyelitis. Foxp3(+) T cell expansion was blocked by anti-TGF-beta Ab, and SOCS3(-/-) DCs produced higher levels of TGF-beta than WT-DCs, suggesting that TGF-beta plays an essential role in the expansion of Foxp3(+) Treg cells. These results indicate an important role of SOCS3 in determining on immunity or tolerance by DCs.     

Light-induced structural changes in the LOV2 domain of Adiantum phytochrome3 studied by low-temperature FTIR and UV-visible spectroscopy

Phototropin (Phot) is a blue-light receptor in plants. The molecule has two FMN (flavin mononucleotide) binding domains named LOV (light-, oxygen-, and voltage-sensing), which is a subset of the PAS (Per-Arnt-Sim) superfamily. Illumination of the phot-LOV domains in the dark state (D447) produces a covalent C(4a) flavin-cysteinyl adduct (S390) via a triplet excited state (L660), which reverts to D447 in the dark. In this work, we studied the light-induced structural changes in the LOV2 domain of Adiantum phytochrome3 (phy3), which is a fusion protein of phot containing the phytochrome chromophoric domain, by low-temperature UV-visible and FTIR spectroscopy. UV-visible spectroscopy detected only one intermediate state, S390, in the temperature range from 77 to 295 K, indicating that the adduct is produced even at temperatures as low as 77 K, although a portion of D447 cannot be converted to S390 at low temperatures possibly because of motional freezing. In the whole temperature range, FTIR spectra in the S-H stretching frequency region showed that Cys966 of phy3-LOV2 is protonated in D447 and unprotonated on illumination, supporting adduct formation. The pK(a) of the S-H group in D447 is estimated to be >10. FTIR spectra also showed the light-induced appearance of a positive peak around 3621 cm(-1) in the whole temperature range, indicating that adduct formation accompanies rearrangement of a hydrogen bond of a water molecule(s), which can be either water25, water45, or both, near the chromophore. In contrast to the weak temperature dependence of the spectral changes in the UV-visible absorption and the FTIR of both S-H and O-H stretching bands, light-induced changes in the amide I vibration that probes protein backbone structure vary significantly with the increase in temperature. The spectral changes suggest that light excitation of FMN loosens the local structure around it, particularly in turns, in the early stages and that another change subsequently takes place to tighten it, mainly in beta-structure, but some occur in the alpha-helical structure of the protein moiety as well. Interestingly, these changes proceed without altering the shape of UV-visible spectra, suggesting the presence of multiple conformation states in S390.     

Somatic embryogenesis induced by the simple application of abscisic acid to carrot (Daucus carota L.) seedlings in culture

Seedlings of carrot (Daucus carota L. cv. Red Cored Chantenay) formed somatic embryos when cultured on medium containing abscisic acid (ABA) as the sole source of growth regulator. The number of embryos per number of seedlings changed depending on the concentration of ABA added to the medium, with a maximum embryo number at 1 × 10⁻⁴M ABA. Seedling age was critical for response to exogenous ABA; no seedling with a hypocotyl longer than 3.0 cm was able to form an embryo. Removal of shoot apices from seedlings completely inhibited the embryogenesis induced by application of exogenous ABA, suggesting that the action of ABA requires some substance(s) that is translocated basipetally from shoot apices through hypocotyls. Histologically, somatic embryos shared common epidermal cells and differentiated not through the formation of embryogenic cell clumps, but directly from epidermal cells. These morphological traits are distinct from those of embryogenesis via formation of embryogenic cell clumps, which has been found in embryogenic carrot cultures established using 2,4-dichlorophenoxyacetic acid or other auxins. These results suggest that ABA acts as a signal substance in stress-induced carrot seedling somatic embryogenesis. Received: 22 April 2000 / Accepted: 8 June 2000     

Coffee polyphenols suppress diet-induced body fat accumulation by downregulating SREBP-1c and related molecules in C57BL/6J mice

The prevalence of obesity is increasing globally, and obesity is a major risk factor for type 2 diabetes and cardiovascular disease. We investigated the effects of coffee polyphenols (CPP), which are abundant in coffee and consumed worldwide, on diet-induced body fat accumulation. C57BL/6J mice were fed either a control diet, a high-fat diet, or a high-fat diet supplemented with 0.5 to 1.0% CPP for 2-15 wk. Supplementation with CPP significantly reduced body weight gain, abdominal and liver fat accumulation, and infiltration of macrophages into adipose tissues. Energy expenditure evaluated by indirect calorimetry was significantly increased in CPP-fed mice. The mRNA levels of sterol regulatory element-binding protein (SREBP)-1c, acetyl-CoA carboxylase-1 and -2, stearoyl-CoA desaturase-1, and pyruvate dehydrogenase kinase-4 in the liver were significantly lower in CPP-fed mice than in high-fat control mice. Similarly, CPP suppressed the expression of these molecules in Hepa 1-6 cells, concomitant with an increase in microRNA-122. Structure-activity relationship studies of nine quinic acid derivatives isolated from CPP in Hepa 1-6 cells suggested that mono- or di-caffeoyl quinic acids (CQA) are active substances in the beneficial effects of CPP. Furthermore, CPP and 5-CQA decreased the nuclear active form of SREBP-1, acetyl-CoA carboxylase activity, and cellular malonyl-CoA levels. These findings indicate that CPP enhances energy metabolism and reduces lipogenesis by downregulating SREBP-1c and related molecules, which leads to the suppression of body fat accumulation.