2-Nitroimidazole-tricarbocyanine conjugate as a near-infrared fluorescent probe for in vivo imaging of tumor hypoxia

We developed a novel near-infrared (NIR) fluorescent probe, GPU-167, for in vivo imaging of tumor hypoxia. GPU-167 comprises a tricarbocyanine dye as an NIR fluorophore and two 2-nitroimidazole moieties as exogenous hypoxia markers that undergo bioreductive activation and then selective entrapment in hypoxic cells. After treatment with GPU-167, tumor cells contained significantly higher levels of fluorescence in hypoxia than in normoxia. In vivo fluorescence imaging specifically detected GPU-167 in tumors 24 h after administration. Ex vivo analysis revealed that fluorescence showed a strong correlation with hypoxia inducible factor (HIF)-1 active hypoxic regions. These data suggest that GPU-167 is a promising in vivo optical imaging probe for tumor hypoxia.     

Crystal structure of Arabidopsis thaliana RabA_(1a)

RabGTPase is a member of the Ras superfamily of small GTPases, which share a GTP-binding pocket containing highly conserved motifs that promote GTP hydrolysis. In Arabidopsis, the RabA group, which corresponds to the Rab_(11) group in animals, functions in the recycling of endosomes that control docking and fusion during vesicle transport. However, their molecular mechanisms remain unknown. In this study, we determined the crystal structures of the GDP-bound inactive form and both GppNHp-and GTP-bound active forms of RabA1a, at resolutions of 2.8, 2.6, and 2.6 A?,respectively. A bound sulfate ion in the active site of the GDP-bound structure stabilized Switch Ⅱ by bridging the interaction between a magnesium ion and Arg74.Comparisons of the two states of RabA1a with Rab_(11) proteins revealed clear differences in the Switch Ⅰ and Ⅱ loops. These results suggested that conformational change of the Switch regions of RabA1a, derived by GTP or GDP binding, could maintain subcellular membrane traffic through the specific interaction of effector molecules.     

The effect of the <Emphasis Type="Italic">cwf14</Emphasis> gene of fission yeast on cell wall integrity is associated with rho1

In all eukaryotic organisms, a wide range of morphologies are responsible for critical cellular function and development. In particular, the Rho GTPases, which are highly conserved from yeast to mammals, are key molecules in signaling pathways that control cell polarity processes and cell wall biosynthesis, which are fundamental aspects of morphogenesis. Therefore, using haploinsufficiency deletion mutants of the fission yeast Schizosaccharomyces pombe, we screened the slow-growing mutants and their morphogenesis, specifically focusing on regulation of their Rho GTPases. Based on this screening, we found that the cwf14 mutant of S. pombe exhibited the slow growth and abnormal phenotypes with an elongated cell shape and thicker cell wall when compared with wild-type cells. In particular, cells with the cwf14 deletion showed excessive Rho1 expression. However, the wildtype strain with ectopically expressed Rho1 did not exhibited any significant change in the level of cwf14, suggesting that cwf14 may act on the upstream of Rho1. Furthermore, the cells with a cwf14 deletion also have increased sensitivity to β-glucanase, a cell wall-digesting enzyme, which is also seen in Rho1-overexpressing cells. Overall, our results suggest that the cwf14 plays a key role in fission yeast morphogenesis and cell wall biosynthesis and/or degradation possibly via the regulation of Rho1 expression.     

Identification of a potent and noncytotoxic inhibitor of melanin production

On the basis of a hit from random screening, biaryl amide derivatives were prepared in a combinatorial manner via parallel solution-phase synthesis, and their effects on melanocytes were investigated to discover new effective skin depigmenting agents. Among the 120 derivatives prepared, five members exhibited a >30% reduction of melanin production at 30 μM with a cell viability of >90%. In particular, compound A₃/B₅ exhibited effective inhibitory activity on melanin synthesis. Although the inhibition percentage of A₃/B₅ was slightly lower than that of the positive reference compound, phenylthiourea (PTU), A₃/B₅ demonstrated a much better cell viability than PTU. In vivo evaluation of A₃/B₅ also showed a significant decrease of melanin pigments. In addition, the in silico classification model was built based on the experimental data of library members. Our results suggest that these biaryl amide derivatives may act as potent skin depigmenting agents.