Structure-activity relationship of synthetic branched-chain distearoylglycerol (distearin) as protein kinase C activators

Several representative branched-chain analogues of distearin (DS) were synthesized and tested for their abilities to activate protein kinase C (PKC) and to compete for the binding of [3H]phorbol 12,13-dibutyrate (PDBu) to the enzyme. Substitutions of stearoyl moieties at sn-1 and sn-2 with 8-methylstearate decreased activities on these parameters, relative to those of the parental diacylglycerol DS, a weak PKC activator. Substitutions with 8-butyl, 4-butyl, or 8-phenyl derivatives, on the other hand, increased activities of the resulting analogues to levels comparable to those seen for diolein (DO), a diacylglycerol prototype shown to be a potent PKC activator. Kinetic analysis indicated that 8-methyldistearin (8-MeDS) acted by decreasing, whereas 8-butyldistearin (8-BuDS) and 8-phenyldistearin (8-PhDS) acted by increasing, the affinities of PKC for phosphatidylserine (PS, a phospholipid cofactor) and Ca2+ compared to the values seen in the absence or presence of DS. The stimulatory effect of 8-BuDS and 8-PhDS on PKC, as DO, was additive to that of 1,2-(8-butyl)distearoylphosphatidylcholine [1,2(8-Bu)DSPC] and, moreover, they abolished the marked inhibition of the enzyme activity caused by high concentrations of 1,2(8-Bu)DSPC. The present findings demonstrated a structure-activity relationship of the branched-chain DS analogues in the regulation of PKC, perhaps related to their abilities to specifically modify interactions of PKC with PS and/or Ca2+ critically involved in enzyme activation/inactivation.     

Genetic diversity and relationship of Fritillaria thunbergii Miq. landraces and related taxa

Genetic diversity and differentiation of four landraces of Fritillaria thunbergii Miq. and two congeners Fritillaria cirrhosa D. Don and Fritillaria anhuiensis S. C. Chen et S. F. Yin were evaluated using ISSR markers. The results showed that the genetic diversity of F. thunbergii was high at the specie level but relatively lower at the landrace level. A high level of genetic differentiation among four F. thunbergii landraces was detected based on the gene differentiation coefficient and the AMOVA, in line with the low inter-landrace gene flow. MS-tree analysis showed that the four F. thunbergii landraces were clustered on adjacent positions of the tree, and that Kuanye (Ft-KY) landrace was relatively distantly related to other landraces. In line with the MS-tree analysis, PCoA revealed that the three species of Fritillaria can be divided into two groups and three subgroups, among which there occurred a remarkable genetic differentiation.     

Phospho-regulated ACAP4-Ezrin Interaction Is Essential for Histamine-stimulated Parietal Cell Secretion

The ezrin-radixin-moesin proteins provide a regulated linkage between membrane proteins and the cortical cytoskeleton and also participate in signal transduction pathways. Ezrin is localized to the apical membrane of parietal cells and couples the protein kinase A activation cascade to the regulated HCl secretion. Our recent proteomic study revealed a protein complex of ezrin-ACAP4-ARF6 essential for volatile membrane remodeling (Fang, Z., Miao, Y., Ding, X., Deng, H., Liu, S., Wang, F., Zhou, R., Watson, C., Fu, C., Hu, Q., Lillard, J. W., Jr., Powell, M., Chen, Y., Forte, J. G., and Yao, X. (2006) Mol. Cell Proteomics 5, 1437–1449). However, knowledge of whether ACAP4 physically interacts with ezrin and how their interaction is integrated into membrane-cytoskeletal remodeling has remained elusive. Here we provide the first evidence that ezrin interacts with ACAP4 in a protein kinase A-mediated phosphorylation-dependent manner through the N-terminal 400 amino acids of ACAP4. ACAP4 locates in the cytoplasmic membrane in resting parietal cells but translocates to the apical plasma membrane upon histamine stimulation. ACAP4 was precipitated with ezrin from secreting but not resting parietal cell lysates, suggesting a phospho-regulated interaction. Indeed, this interaction is abolished by phosphatase treatment and validated by an in vitro reconstitution assay using phospho-mimicking ezrin^S66D. Importantly, ezrin specifies the apical distribution of ACAP4 in secreting parietal cells because either suppression of ezrin or overexpression of non-phosphorylatable ezrin prevents the apical localization of ACAP4. In addition, overexpressing GTPase-activating protein-deficient ACAP4 results in an inhibition of apical membrane-cytoskeletal remodeling and gastric acid secretion. Taken together, these results define a novel molecular mechanism linking ACAP4-ezrin interaction to polarized epithelial secretion.     

Characterization and mapping of a novel mutant sms1 (senescence and male sterility 1) in rice

Plant senescence plays diverse important roles in development and environmental responses.However,the molecular basis of plant senescence is remained largely unknown.A rice spontaneous mutant with the character of early senescence and male sterility (sms) was found in the breeding line NT10-748.In order to identify the gene SMS1 and the underlying mechanism,we preliminarily analyzed physiological and biochemical phenotypes of the mutant.The mutant contained lower chlorophyll content compared with the wild t...     

Genetic diversity and population structure of Swertia tetraptera (Gentianaceae), an endemic species of Qinghai-Tibetan Plateau

Swertia tetraptera Maxim is an annual alpine herb endemic to the Qinghai-Tibetan Plateau (QTP). Its populations are locally scattered as isolated patches throughout this region. Genetic variation within and among thirty-four populations of this species was assessed using ISSR fingerprinting with 10 primers. High levels of genetic diversity exist within species (P = 98.9%, I = 0.3475; He = 0.2227), while the within-population diversity is low (P = 32.7%, I = 0.177; He = 0.12). High levels of genetic differentiation were detected among populations based on various statistics, including Nei’s genetic diversity analysis (G_ST = 0.4608), Bayesian analysis (θ^B = 0.476) and AMOVA (F_ST = 0.57). That is, populations shared low levels of genetic identity (I = 0.2622–0.0966). This genetic structure was probably due to severe genetic drift, breeding system and limited gene flow. The observed genetic structure of the populations implies that different populations across the distribution range of the species should be sampled to maintain high genetic diversity when a conservation strategy is implemented.     

Early Mixed Farming of Millet and Rice 7800 Years Ago in the Middle Yellow River Region,China

The Peiligang Culture (9000-7000 cal. yr BP) in the Middle Yellow River region, North China, has long been considered representative of millet farming. It is still unclear, however, if broomcorn millet or foxtail millet was the first species domesticated during the Peiligang Culture. Furthermore, it is also unknown whether millet was cultivated singly or together with rice at the same period. In this study, phytolith analysis of samples from the Tanghu archaeological site reveals early crop information in the Middle Yellow River region, China. Our results show that broomcorn millet was the early dry farming species in the Peiligang Culture at 7800 cal. yr BP, while rice cultivation took place from 7800 to 4500 cal. yr BP. Our data provide new evidence of broomcorn millet and rice mixed farming at 7800 cal. yr BP in the Middle Yellow River region, which has implications for understanding the domestication process of the two crops, and the formation and continuance of the Ancient Yellow River Civilization.     

Development of an Automated and Sensitive Microfluidic Device for Capturing and Characterizing Circulating Tumor Cells (CTCs) from Clinical Blood Samples

Current analysis of circulating tumor cells (CTCs) is hindered by sub-optimal sensitivity and specificity of devices or assays as well as lack of capability of characterization of CTCs with clinical biomarkers. Here, we validate a novel technology to enrich and characterize CTCs from blood samples of patients with metastatic breast, prostate and colorectal cancers using a microfluidic chip which is processed by using an automated staining and scanning system from sample preparation to image processing. The Celsee system allowed for the detection of CTCs with apparent high sensitivity and specificity (94% sensitivity and 100% specificity). Moreover, the system facilitated rapid capture of CTCs from blood samples and also allowed for downstream characterization of the captured cells by immunohistochemistry, DNA and mRNA fluorescence in-situ hybridization (FISH). In a subset of patients with prostate cancer we compared the technology with a FDA-approved CTC device, CellSearch and found a higher degree of sensitivity with the Celsee instrument. In conclusion, the integrated Celsee system represents a promising CTC technology for enumeration and molecular characterization.