D-glucosamine inhibits proliferation of human cancer cells through inhibition of p70S6K

Although D-glucosamine has been reported as an inhibitor of tumor growth both in vivo and in vitro, the mechanism for the anticancer effect of D-glucosamine is still unclear. Since there are several reports suggesting D-glucosamine inhibits protein synthesis, we examined whether D-glucosamine affects p70S6K activity, an important signaling molecule involved in protein translation. In the present study, we found D-glucosamine inhibited the activity of p70S6K and the proliferation of DU145 prostate cancer cells and MDA-MB-231 breast cancer cells. D-glucosamine decreased phosphorylation of p70S6K, and its downstream substrates RPS6, and eIF-4B, but not mTOR and 4EBP1 in DU145 cells, suggesting that D-glucosamine induced inhibition of p70S6K is not through the inhibition of mTOR. In addition, D-glucosamine enhanced the growth inhibitory effects of rapamycin, a specific inhibitor of mTOR. These findings suggest that D-glucosamine can inhibit growth of cancer cells through dephosphorylation of p70S6K.     

Heat shock augments myosin phosphatase target-subunit phosphorylation

Our previous study demonstrated that heat shock augmented vascular contraction. In the present study, we hypothesized that heat shock augments myosin phosphatase target-subunit (MYPT1) phosphorylation resulting in augmented vascular contraction. Endothelium-denuded rat aortic rings were mounted in organ baths, exposed to heat shock (42 degrees C for 45 min), and subjected to contraction 4 h after the heat shock followed by Western blot analysis for MLC(20) (the 20 kDa light chains of myosin II) or MYPT1. The contractile responses in both control and heat shock-treated aorta were inhibited by Y27632, an inhibitor of Rho-kinase. The level of the MLC(20) and MYPT1(Thr855) phosphorylation in response to KCl was higher in heat shock-treated aorta than that in timed-control. The increased MYPT1(Thr855) phosphorylation was inhibited by Y27632 (1.0 microM) in parallel with inhibition of MLC(20) phosphorylation and vascular contraction. These results indicate that heat shock augments MYPT1 phosphorylation resulting in augmented vascular contraction.     

Probing the local conformational change of alpha1-antitrypsin

The native form of serpins (serine protease inhibitors) is a metastable conformation, which converts into a more stable form upon complex formation with a target protease. It has been suggested that movement of helix-F (hF) and the following loop connecting to strand 3 of beta-sheet A (thFs3A) is critical for such conformational change. Despite many speculations inferred from analysis of the serpin structure itself, direct experimental evidence for the mobilization of hF/thFs3A during the inhibition process is lacking. To probe the mechanistic role of hF and thFs3A during protease inhibition, a disulfide bond was engineered in alpha(1)-antitrypsin, which would lock the displacement of thFs3A from beta-sheet A. We measured the inhibitory activity of each disulfide-locked mutant and its heat stability against loop-sheet polymerization. Presence of a disulfide between thFs3A and s5A but not between thFs3A and s3A caused loss of the inhibitory activity, suggesting that displacement of hF/thFs3A from strand 5A but not from strand 3A is required during the inhibition process. While showing little influence on the inhibitory activity, the disulfide between thFs3A and s3A retarded loop-sheet polymerization significantly. This successful protein engineering of alpha(1)-antitrypsin is expected to be of value in clinical applications. Based on our current studies, we propose that the reactive-site loop of a serpin glides through between s5A and thFs3A for the full insertion into beta-sheet A while a substantial portion of the interactions between hF and s3A is kept intact.     

Stem cells act through multiple mechanisms to benefit mice with neurodegenerative metabolic disease

Intracranial transplantation of neural stem cells (NSCs) delayed disease onset, preserved motor function, reduced pathology and prolonged survival in a mouse model of Sandhoff disease, a lethal gangliosidosis. Although donor-derived neurons were electrophysiologically active within chimeric regions, the small degree of neuronal replacement alone could not account for the improvement. NSCs also increased brain beta-hexosaminidase levels, reduced ganglioside storage and diminished activated microgliosis. Additionally, when oral glycosphingolipid biosynthesis inhibitors (beta-hexosaminidase substrate inhibitors) were combined with NSC transplantation, substantial synergy resulted. Efficacy extended to human NSCs, both to those isolated directly from the central nervous system (CNS) and to those derived secondarily from embryonic stem cells. Appreciating that NSCs exhibit a broad repertoire of potentially therapeutic actions, of which neuronal replacement is but one, may help in formulating rational multimodal strategies for the treatment of neurodegenerative diseases.     

Dominance Relationship between Two Self-Incompatible<Emphasis Type="Italic">Brassica campestris</Emphasis> Haplotypes in Response to CO<Subscript>2</Subscript> Gas

InBrassica, self-incompatibility (SI) can be overcome by CO₂ application, an effective method for obtaining numerous inbred lines for F, commercial seed. We previously reported two different S-alleles ofBrassica campestris, S⁷³³ and S⁷³⁴, with extremely different degrees of susceptibility to this gas. In the current study, we raised a cross-population between those two genetic lines, and analyzed their reaction level of self-incompatibility to CO₂ (RLSICO₂). Here, all 40 of our progeny from the F₁ cross-population were susceptible, maintaining high values of RLSICO₂. This suggests that the susceptible line, S⁷³⁴, is dominant to the insusceptible line, S⁷³³. We also generated an F₂ selfing-population of each crossed progeny, S⁷³³♀ S⁷³⁴♂ and S⁷³³♂ S⁷³⁴♀, to assess the RLSICO₂ of each individual. PCR-RFLP analysis was performed to determine the S-genotype of the F₂ population. The S⁷³⁴ allele segregated in a theoretical ratio of the dominant trait, and the RLSICO₂ was consistent with the dominance relationship. Therefore, we have now demonstrated that high RLSICO₂ in β.campestris is controlled by a dominant gene. Both authors contributed equally to this work     

Photolithographic fabrication of poly(ethylene glycol) microstructures for hydrogel-based microreactors and spatially addressed microarrays

We describe the fabrication of poly(ethylene glycol) diacrylate (PEG-DA) hydrogel microstructures with a high aspect ratio and the use of hydrogel microstructures containing the enzyme beta-galactosidase (beta-Gal) or glucose oxidase (GOx)/horseradish peroxidase (HRP) as biosensing components for the simultaneous detection of multiple analytes. The diameters of the hydrogel microstructures were almost the same at the top and at the bottom, indicating that no differential curing occurred through the thickness of the hydrogel microstructure. Using the hydrogel microstructures as microreactors, beta-Gal or GOx/HRP was trapped in the hydrogel array, and the time-dependent fluorescence intensities of the hydrogel array were investigated to determine the dynamic uptake of substrates into the PEG-DA hydrogel. The time required to reach steady-state fluorescence by glucose diffusing into the hydrogel and its enzymatic reactions with GOx and HRP was half the time required for resorufin beta-D-galactopyranoside (RGB) when used as the substrate for beta-Gal. Spatially addressed hydrogel microarrays containing different enzymes were micropatterned for the simultaneous detection of multiple analytes, and glucose and RGB solutions were incubated as substrates. These results indicate that there was no cross-talk between the beta-Gal-immobilizing hydrogel micropatches and the GOx/HRP-immobilizing micropatches.     

Increasing production in Korean shrimp farms with white-spot syndrome virus PCR-negative brood stock

White-spot syndrome virus (WSSV) is a devastating, infectious virus affecting shrimp. Although sensitive techniques involving PCR have been developed to assist farmers in screening shrimp (brood stock) for WSSV prior to stocking ponds, such practices have not yet been applied in Korea. Despite the rationality of implementing screening, there has been some doubt as to whether the stocking of WSSV-PCR-negative fry epidemiologically decreases white-spot disease outbreaks. Here, we report a retrospective analysis of data from shrimp farms in the western coast of Korea where WSSV-PCR-negative brood stocks were used to stock rearing ponds. A total of 366 shrimp from Heuksan Island were sampled for WSSV with PCR. Of the tested shrimp, 7.2% (28 brood stocks) were identified as WSSV positive; only WSSV-PCR-negative shrimp were used for brood stocks. Total unit production (final shrimp production/ the area of the ponds) was higher, at 1.96, in ponds where WSSV-PCR-negative shrimp were used, as compared with 1.02 in other ponds in Korea in 2004. This retrospective analysis of WSSV in Korea may be useful to the shrimp aquaculture industry, suggesting a testable hypothesis that may contribute to the eventual control of WSSV outbreaks.     

Redifferentiation of dedifferentiated chondrocytes on chitosan membranes and involvement of PKCalpha and P38 MAP kinase

To investigate the effects of chitosan on the redifferentiation of dedifferentiated chondrocytes, we used chondrocytes obtained from a micromass culture system. Micromass cultures of chick wing bud mesenchymal cells yielded differentiated chondrocytes, but these dedifferentiated during serial monolayer subculture. When the dedifferentiated chondrocytes were cultured on chitosan membranes they regained the phenotype of differentiated chondrocytes. Expression of protein kinase C (PKC) increased during chondrogenesis, decreased during dedifferentiation, and increased again during redifferentiation. Treatment of the cultures with phorbol 12-myristate 13-acetate (PMA) inhibited redifferentiation and down-regulated PKC. In addition, the expression of p38 mitogen-activated protein (MAP) kinase increased during redifferentiation, and its inhibition suppressed redifferentiation. These findings establish a culture system for producing chondrocytes, point to a new role of chitosan in the redifferentiation of dedifferentiated chondrocytes, and show that PKC and p38 MAP kinase activities are required for chondrocyte redifferentiation in this model system.