Dolichol biosynthesis and its effects on the unfolded protein response and abiotic stress resistance in Arabidopsis

Dolichols are long-chain unsaturated polyisoprenoids with multiple cellular functions, such as serving as lipid carriers of sugars used for protein glycosylation, which affects protein trafficking in the endoplasmic reticulum. The biological functions of dolichols in plants are largely unknown. We isolated an Arabidopsis thaliana mutant, lew1 (for leaf wilting1), that showed a leaf-wilting phenotype under normal growth conditions. LEW1 encoded a cis-prenyltransferase, which when expressed in Escherichia coli catalyzed the formation of dolichol with a chain length around C(80) in an in vitro assay. The lew1 mutation reduced the total plant content of main dolichols by approximately 85% and caused protein glycosylation defects. The mutation also impaired plasma membrane integrity, causing electrolyte leakage, lower turgor, reduced stomatal conductance, and increased drought resistance. Interestingly, drought stress in the lew1 mutant induced higher expression of the unfolded protein response pathway genes BINDING PROTEIN and BASIC DOMAIN/LEUCINE ZIPPER60 as well as earlier expression of the stress-responsive genes RD29A and COR47. The lew1 mutant was more sensitive to dark treatment, but this dark sensitivity was suppressed by drought treatment. Our data suggest that LEW1 catalyzes dolichol biosynthesis and that dolichol is important for plant responses to endoplasmic reticulum stress, drought, and dark-induced senescence in Arabidopsis.     

Clathrin-independent internalization and recycling

The functionality of receptor and channel proteins depends directly upon their expression level on the plasma membrane. Therefore, the ability to selectively adjust the surface level of a particular receptor or channel protein is pivotal to many cellular signaling events. The internalization and recycling pathway plays a major role in the regulation of protein surface level, and thus has been a focus of research for many years. Although several endocytic pathways have been identified, most of our knowledge has come from the clathrin-dependent pathway, while the other pathways remain much less well defined. Considering that clathrin-independent internalization may account for as much as 50% of the total endocytic activity in the cell, the lack of such knowledge constitutes a major gap in our efforts to understand how different internalization pathways are utilized and coordinated. Recent studies have provided valuable insights into this area, yet many more questions still remain. In this review, we will give a panoramic introduction to the current knowledge of various internalization and recycling pathways, with an emphasis on the latest findings that have broadened our view of the clathrin-independent pathways. We will also dedicate one section to the emerging studies of the clathrin-independent internalization pathways in neuronal cells.     

Prevalence of obesity and correlations with lifestyle and dietary factors in Chinese men

Objective: To estimate the age‐adjusted prevalence of general and centralized obesity among Chinese men living in urban Shanghai. Methods and Procedures: A cross‐sectional study was conducted in 61,582 Chinese men aged 40–75. BMI (kg/m²) was used to measure overweight (23 ≤ BMI < 27.4) and obesity (BMI ≥ 27.5) based on the World Health Organization (WHO) recommended criteria for Asians. Waist‐to‐hip ratio (WHR) was used to measure moderate (75th ≤ WHR < 90th percentile) and severe (WHR ≥ 90th percentile) centralized obesity. Results: The average BMI and WHR were 23.7 kg/m² and 0.90, respectively. The prevalence of overweight was 48.6% and obesity was 10.5%. The prevalence of general and centralized obesity was higher in men with high income or who were retired, tea drinkers, or nonusers of ginseng than their counterparts. Men with high education had a higher prevalence of overweight and centralized obesity, but had a lower prevalence of obesity and severe centralized obesity compared to those with less education. Current smokers or alcohol drinkers had a lower prevalence of general obesity but higher prevalence of centralized obesity than nonsmokers or nondrinkers of alcohol. Ex‐smokers and ex‐alcohol drinkers had a higher prevalence of general and centralized obesity compared to nonsmokers and nondrinkers of alcohol. Prevalence of obesity was associated with high energy intake and less daily physical activity. Discussion: The prevalence of obesity among Chinese men in urban Shanghai was lower than that observed in Western countries but higher than that in other Asian countries, and the prevalence of general and centralized obesity differed by demographic, lifestyle, and dietary factors.     

A-type GABA receptor as a central target of TRPM8 agonist menthol

Menthol is a widely-used cooling and flavoring agent derived from mint leaves. In the peripheral nervous system, menthol regulates sensory transduction by activating TRPM8 channels residing specifically in primary sensory neurons. Although behavioral studies have implicated menthol actions in the brain, no direct central target of menthol has been identified. Here we show that menthol reduces the excitation of rat hippocampal neurons in culture and suppresses the epileptic activity induced by pentylenetetrazole injection and electrical kindling in vivo. We found menthol not only enhanced the currents induced by low concentrations of GABA but also directly activated GABA(A) receptor (GABA(A)R) in hippocampal neurons in culture. Furthermore, in the CA1 region of rat hippocampal slices, menthol enhanced tonic GABAergic inhibition although phasic GABAergic inhibition was unaffected. Finally, the structure-effect relationship of menthol indicated that hydroxyl plays a critical role in menthol enhancement of tonic GABA(A)R. Our results thus reveal a novel cellular mechanism that may underlie the ambivalent perception and psychophysical effects of menthol and underscore the importance of tonic inhibition by GABA(A)Rs in regulating neuronal activity.     

Closing the Gaps in Paediatric Reference Intervals: The CALIPER Initiative

Screening, diagnosis and monitoring of paediatric diseases relies on the measurement of a spectrum of disease biomarkers in clinical laboratories to guide important clinical decisions. Physicians rely on the availability of suitable and reliable reference intervals to accurately interpret laboratory test results with data collected during medical history and physical examination. However, critical gaps currently exist in accurate and up-to-date reference intervals (normal values) for accurate interpretation of laboratory tests performed in children and adolescents. These gaps in the available paediatric laboratory reference intervals have the clear potential of contributing to erroneous diagnosis or misdiagnosis of many diseases of childhood and adolescence. Most of the available reference intervals for laboratory tests were determined over two decades ago on older instruments and technologies, and are no longer relevant considering the current testing technology used by clinical laboratories. It is thus critical and of utmost urgency that a more acceptable and comprehensive database be established. There are however many challenges when attempting to establish paediatric reference intervals. Paediatric specimen collection is a major concern for health care providers as it is frequently difficult to obtain sufficient volumes of blood or urine from paediatric patients. Common reference intervals have not been widely implemented due to lack of harmonisation of methods and differences in patient populations. Consequently, clinical laboratory accreditation organisations and licensing agencies require that each laboratory verify or establish reference intervals for each method. To provide such reference intervals requires selection criteria for suitable reference individuals, defined conditions for specimen collection and analysis, method selection to determine reference limits and validation of the reference interval. The current review will provide a brief introduction to the current approach to establishment of reference intervals, will highlight the current gaps in data available in paediatric populations, and review a recent Canadian initiative, CALIPER (Canadian Laboratory Initiative on Paediatric Reference Intervals), to establish a comprehensive database for both traditional and emerging biomarkers of paediatric disease.     

Effect of TGF-β/Smad signaling on sertoli cell and possible mechanism related to complete sertoli cell-only syndrome

Chicken Riboflavin Carrier Protein (cRCP) transports riboflavin from the maternal circulation to the egg yolk for fetal development. The cRCP is a globular protein and structurally very stable due to the presence of nine intra-molecular disulphide bonds. The cRCP comprises of two domains; the larger riboflavin binding, and the smaller, oocyte receptor binding domain. With the objective to study domain folding in cRCP, these two domains of the corresponding gene were amplified, cloned, and expressed in a eukaryotic expression system to obtain soluble product. Our studies on the biochemical characterization of the recombinant proteins indicated that though the ligand binding domain assumed near-native conformation, as determined by immunological methods, it did not bind riboflavin, suggesting the interdependence of the two domains for proper organization of the riboflavin binding pocket.     

Alkaline pH- and cAMP-induced V-ATPase membrane accumulation is mediated by protein kinase A in epididymal clear cells

In the epididymis, low luminal bicarbonate and acidic pH maintain sperm quiescent during maturation and storage. The vacuolar H(+)-ATPase (V-ATPase) in epididymal clear cells plays a major role in luminal acidification. We have shown previously that cAMP, luminal alkaline pH, and activation of the bicarbonate-regulated soluble adenylyl cyclase (sAC) induce V-ATPase apical accumulation in these cells, thereby stimulating proton secretion into the epididymal lumen. Here we examined whether protein kinase A (PKA) is involved in this response. Confocal immunofluorescence labeling on rat epididymis perfused in vivo showed that at luminal acidic pH (6.5), V-ATPase was distributed between short apical microvilli and subapical endosomes. The specific PKA activator N(6)-monobutyryl-3'-5'-cyclic monophosphate (6-MB-cAMP, 1 mM) induced elongation of apical microvilli and accumulation of V-ATPase in these structures. The PKA inhibitor myristoylated-PKI (mPKI, 10 microM) inhibited the apical accumulation of V-ATPase induced by 6-MB-cAMP. Perfusion at pH 6.5 with 8-(4-chlorophenylthio)-2-O-methyl-cAMP (8CPT-2-O-Me-cAMP; 10 microM), an activator of the exchange protein activated by cAMP (Epac), did not induce V-ATPase apical accumulation. When applied at a higher concentration (100 microM), 8CPT-2-O-Me-cAMP induced V-ATPase apical accumulation, but this effect was completely inhibited by mPKI, suggesting crossover effects on the PKA pathway with this compound at high concentrations. Importantly, the physiologically relevant alkaline pH-induced apical V-ATPase accumulation was completely inhibited by pretreatment with mPKI. We conclude that direct stimulation of PKA activity by cAMP is necessary and sufficient for the alkaline pH-induced accumulation of V-ATPase in clear cell apical microvilli.     

贵州兴义发现最原始弓鳍鱼

记述在贵州兴义著名的贵州龙化石层（上三叠统卡尼介）中发现的最原始弓鳍鱼而建立了一新属新种－优美贵州弓鳍鱼（Guizhouamia bellula gen.et sp.nov.)。