Binding,internalization, and degradation of antiproliferative heparan sulfate by human embryonic lung fibroblasts

Binding, internalization, and degradation of ¹²⁵I-labeled, antiproliferative, or nonantiproliferative heparan sulfate by human embryonic lung fibroblasts was investigated. Both L-iduronate-rich, antiproliferative heparan sulfate species as well as L-iduronate-poor, inactive ones were bound to trypsin-releasable, cell-surface sites. Both heparan sulfate types were bound with approximately the same affinity to one high-affinity site (K_d approximately 10⁻⁸ M) and to one (K_d approximately 10⁻⁶ M), respectively. Results of Hill-plot analysis suggested that the two sites are independent. Competition experiments with unlabeled glycosaminoglycans indicated that the binding sites had a selective specificity for sulfated, L-iduronate-rich heparan sulfate. Dermatan sulfate, which is also antiproliferative, was weakly bound to the cells. The antiproliferative effects of heparan and dermatan sulfate appeared to be additive. Hence, the two glycosaminoglycans probably exert their effect through different mechanisms. At concentrations above 5 μg/ml (approximately 10⁻⁷ M), heparan sulfate was taken up by human embryonic lung fibroblasts, suggesting that the low-affinity site represents an endocytosis receptor. The antiproliferative effect of L-iduronate-rich heparan sulfate species was also exerted at the same concentrations. The antiproliferative species was taken up to a greater degree than the inactive one, suggesting a requirement for internalization. However, competition experiments with dextran sulfate suggested that both the high-affinity and the low-affinity sites are involved in mediating the antiproliferative effect. Structural analysis of the inactive and active heparan sulphate preparations indicated that although sulphated L-iduronate appears essential for antiproliferative activity, it is not absolutely required for binding to the cells. Degradation of internalized heparan sulfate was analyzed by polyacrylamide gel electrophoresis using a sensitive detection technique. The inactive species was partially degraded, whereas the antiproliferative one was only marginally affected. J. Cell. Biochem. 64:595–604. © 1997 Wiley-Liss, Inc.     

Sphingosine kinase type 1 induces G12/13-mediated stress fiber formation,yet promotes growth and survival independent of G protein-coupled receptors

Sphingosine 1-phosphate (S1P) is the ligand for a family of specific G protein-coupled receptors (GPCRs) that regulate a wide variety of important cellular functions, including growth, survival, cytoskeletal rearrangements, and cell motility. However, whether it also has an intracellular function is still a matter of great debate. Overexpression of sphingosine kinase type 1, which generated S1P, induced extensive stress fibers and impaired formation of the Src-focal adhesion kinase signaling complex, with consequent aberrant focal adhesion turnover, leading to inhibition of cell locomotion. We have dissected biological responses dependent on intracellular S1P from those that are receptor-mediated by specifically blocking signaling of Galphaq, Galphai, Galpha12/13, and Gbetagamma subunits, the G proteins that S1P receptors (S1PRs) couple to and signal through. We found that intracellular S1P signaled "inside out" through its cell-surface receptors linked to G12/13-mediated stress fiber formation, important for cell motility. Remarkably, cell growth stimulation and suppression of apoptosis by endogenous S1P were independent of GPCRs and inside-out signaling. Using fibroblasts from embryonic mice devoid of functional S1PRs, we also demonstrated that, in contrast to exogenous S1P, intracellular S1P formed by overexpression of sphingosine kinase type 1 promoted growth and survival independent of its GPCRs. Hence, exogenous and intracellularly generated S1Ps affect cell growth and survival by divergent pathways. Our results demonstrate a receptor-independent intracellular function of S1P, reminiscent of its action in yeast cells that lack S1PRs.     

Protein Kinase LTRPK1 Influences Cold Adaptation and Microtubule Stability in Rice

Rice LTRPK1, which encodes a member of the casein kinase I family, has been reported to be involved in root development, hormone response, and metabolic processes. Here we further show that LTRPK1 participates in stress resistance by regulating cytoskeleton rearrangement and formation of cold tolerance and adaptation. Semiquantitative RT-PCR analysis revealed enhanced expression of LTRPK1 in plants subject to low-temperature stress at 4 °C, suggesting a role in low-temperature-related cell responses and signal transduction pathways. Further analysis of LTRPK1-deficient transgenic plants showed that under low-temperature treatment, the growth rate of transgenic plant primary roots, which is commonly used as an indicator for cold stress response abilities, was less inhibited than that of control plants. Moreover, damage to the plasma membrane of root cells in LTRPK1-deficient plants was greater than that of controls as measured by relative electrical conductivity (REC). The malondialdehyde (MDA) content of LTRPK1-deficient plants also increased over that of the control, indicating increased plasma membrane permeability. Further immunofluorescence localization observations indicated that microtubules of transgenic plants subject to low temperature disassembled more rapidly, whereas the control plant microtubules in most cells of the root elongation zone kept their normal habitus, which suggested that LTRPK1-deficient plants had reduced capacity to resist low-temperature stress through regulation of microtubule assembly. These results demonstrate involvement of LTRPK1 in low-temperature stress and provide new insight for rice breeding and germplasm innovation to improve crop cold tolerance.     

干细胞与再生医学技术发展态势研究

20世纪以来,干细胞与再生医学技术一直是国际生物医学领域的热点前沿之一,它为保障人类生命健康、改善人类生存质量和延长人类寿命发挥不可替代的巨大作用。因此,美国、欧洲国家、日本和中国等科技大国均将该领域纳入了国家科研与产业发展的重点战略中,并通过专项扶持、政策补贴、立法保障等方式激励该领域的创新发展。通过对近年来国际科技战略和科技研发态势的梳理分析,发现该领域的国际战略布局规律,揭示我国在该领域的领先优势与弱点,为我国未来干细胞与再生医学技术发展提出相关参考建议。     

甘露醇对渗透胁迫下的鱼腥藻(Anabaena)固氮活性的增效作用

外源甘露醇可在一定程度上增强鱼腥藻Anabaenasp．7120固氮的抗渗透胁迫能力．厌氧（Ar中）、能量供应受阻（暗处理、添加ATP形成的抑制剂）、合成固氮酶蛋白所需物质供应不足（单加N2不加CO2）以及分子氧下,甘露醇的有益作用减小或消失,反之（正常光照、通气环境、提高CO2浓度,同时供应H2和O2或CO2和N2）则这一作用增大。渗透胁迫下,外源蔗糖对甘露醇支持蓝藻固氮的作用不明显。     

Differential effects of paraoxonase 1 (PON1) polymorphisms on cancer risk: evidence from 25 published studies

Paraoxonase is an HDL-associated enzyme that plays a preventive role against oxidative stress, which is thought to contribute to cancer development. PON1 activity varies widely among individuals, which is in part related to two common nonsynonymous polymorphisms in the PON1 gene (Q192R and L55M). The polymorphisms in PON1 have been implicated in cancer risk. However, results from the studies to date have been conflicting. To clarify the association, a meta-analysis was performed for 7,073 cases and 9,520 controls from 25 published case–control studies. Odds ratios (ORs) with 95% confidence intervals (CIs) were used to assess the strength of the association. Significant associations between PON1-L55M but not Q192R polymorphism and total cancer were observed from all the comparisons. In stratified analyses, PON1-55M allele was a risk factor for breast cancer. Similarly, increased risk was observed for prostate cancer (OR = 1.18, 95% CI: 1.01–1.36, P _{heterogeneity} = 0.260) and Caucasian population (OR = 1.18, 95% CI: 1.02–1.38, P _{heterogeneity} = 0.1) of the LM genotype, compared with the LL genotype. For PON1-Q192R polymorphism, PON1-192R allele was a decreased risk factor for cancer in the Asian group (RR vs QQ: OR = 0.61, 95% CI: 0.38–0.98, P _{heterogeneity} = 0.268; QR vs QQ: OR = 0.71, 95% CI: 0.52–0.96, P _{heterogeneity} = 0.130; RR + QR vs QQ: OR = 0.71, 95% CI: 0.53–0.95, P _{heterogeneity} = 0.135). Although some modest bias could not be eliminated, this meta-analysis suggests that the PON1-55M allele is a risk factor for the development of cancer, in particular for breast cancer. Future studies with larger sample sizes are warranted to further evaluate these associations.     

Late-acting self-incompatibility in tea plant (<Emphasis Type="Italic">Camellia sinensis</Emphasis>)

The self-incompatibility of tea plant (Camellia sinensis (L.) O. Kuntze) was studied with the methods of aniline blue fluorescence assay and paraffin sections. The characteristics of pollen tube elongation after hand pollination was analyzed in 4 tea cultivars, including ‘Keemenzhong’, ‘Longjing-changye’, ‘Fuding-dabaicha’ and ‘Yabukita’, under self-pollination and cross-pollination, respectively. Although there were some difference among cultivars, pollen tubes elongated through the style and reach the ovary successfully at 48 h after pollination for both cross- and self-pollen tubes in all the four cultivars of tea. Pollen tubes entered into the ovule micropyles, however, only for cross-pollination, but not for self-pollination. Pollen tubes of selfing plants, failed in fertilizing, seemed have some difficulties to enter the ovule. All of which indicated that the self-incompatibility of tea plant is a late-acting self-incompatibility system (LSI) or an ovarian sterility (OS), in which the self incompatibility was due to none self pollen tube penetrating into the ovule and no fertilization.     

Potential Applications in Sewage Bioremediation of the Highly Efficient Pyridine-Transforming Paenochrobactrum sp.

Applied Biochemistry and Microbiology - A pyridine-transforming strain P2 was isolated from sewage collected from Guangzhou oil stain field(China).According to the system analysis, it was...