Interleukin-4 alters early phagosome phenotype by modulating class I PI3K dependent lipid remodeling and protein recruitment

Phagocytosis is a complex process that involves membranelipid remodeling and the attraction and retention of key effector proteins. Phagosome phenotype depends on the type of receptor engaged and can be influenced by extracellular signals. Interleukin 4 (IL-4) is a cytokine that induces the alternative activation of macrophages (MΦs) upon prolonged exposure, triggering a different cell phenotype that has an altered phagocytic capacity. In contrast, the direct effects of IL-4 during phagocytosis remain unknown. Here, we investigate the impact of short-term IL-4 exposure (1 hour) during phagocytosis of IgG-opsonized yeast particles by MΦs. By time-lapse confocal microscopy of GFP-tagged lipid-sensing probes, we show that IL-4 increases the negative charge of the phagosomal membrane by prolonging the presence of the negatively charged second messenger PI(3,4,5)P3. Biochemical assays reveal an enhanced PI3K/Akt activity upon phagocytosis in the presence of IL-4. Blocking the specific class I PI3K after the onset of phagocytosis completely abrogates the IL-4-induced changes in lipid remodeling and concomitant membrane charge. Finally, we show that IL-4 direct signaling leads to a significantly prolonged retention profile of the signaling molecules Rac1 and Rab5 to the phagosomal membrane in a PI3K-dependent manner. This protracted early phagosome phenotype suggests an altered maturation, which is supported by the delayed phagosome acidification measured in the presence of IL-4. Our findings reveal that molecular differences in IL-4 levels, in the extracellular microenvironment, influence the coordination of lipid remodeling and protein recruitment, which determine phagosome phenotype and, eventually, fate. Endosomal and phagosomal membranes provide topological constraints to signaling molecules. Therefore, changes in the phagosome phenotype modulated by extracellular factors may represent an additional mechanism that regulates the outcome of phagocytosis and could have significant impact on the net biochemical output of a cell.     

A case with de novo interstitial deletion of chromosome 7q21.1-q22

A case with de novo interstitial deletion of chromosome 7q21.1-q22: A patient with multiple congenital anomalies was found to have a de novo proximal interstitial deletion of chromosome 7q21.1-q22. The patient was 10.5 years of age, and manifestations include growth retardation (below 3rd percentile), mental retardation, mild microcephaly, hypersensitivity to noise, mild spasticity, short palpebral fissures, alternant exotropia, compensated hypermetropic astigmatism, hypotelorism, hypoplastic labia majora and minora, clinodactyly of fingers 4 and 5. Molecular studies revealed that the deletion had a paternal origin, while chromosomes of both parents cytogenetically were shown to be normal. Molecular, and fluorescence in situ hybridization (FISH) analyses confirmed no deletion at the Williams-Beuren Syndrome region. Some of the heterogeneous clinical findings were consistent with previously reported cases of same chromosomal breakpoints.     

植物Cation/H~+反向转运蛋白研究进展

CAX是一种通过质子梯度产生的能量运输协调再分配钙离子(Ca2+)等阳离子的转运蛋白,是Ca2+/Cation antiporter(CaCA)大家族的一个分化枝。植物CAXs属于CAX三大类的Ⅰ型CAX。大部分植物CAXs有11个跨膜区(TM)和5个典型的功能域,即N-端自抑制区域(NRR)、C-端功能区域、Ca2+功能域(CaD)、C功能域和D功能域。其中NRR存在于大部分CAX中,调节CAX的功能。以下综述了近年来国内外对CAX类蛋白的研究成果与进展,涉及到CAX家族的命名,亚家族的分类,CAX组织表达及亚细胞定位,特别是CAX的转运活性等研究。加强对CAX的研究对调节植物生长、提高农作物养分吸收和减轻土壤中污染物等有重要作用。     

Plasma membrane cholesterol: a possible barrier to intracellular oxygen in normal and mutant CHO cells defective in cholesterol metabolism

The effect of the cholesterol content of the plasma membrane on the intracellular concentration of oxygen in Chinese hamster ovary (CHO) cells and their mutants was investigated by EPR oximetry. Total and free cholesterol content was significantly higher in 25 RA CHO cells as compared to wild-type and M 19 CHO cells, with most of the free cholesterol in normal and mutant CHO cells located in the plasma membrane. The plasma membrane cholesterol content also was altered by various biochemical means, and the effect on the oxygen gradient was studied. Comparing the three cell lines, the gradient was larger with increased content of cholesterol in the plasma cell membrane. This result also is supported by an additional increase in the oxygen gradients with the incorporation of additional cholesterol in the plasma membrane and a decrease in the oxygen gradient when the cholesterol was depleted from the plasma membrane. The results indicate that the concentration of cholesterol in the plasma membrane can be an important factor for the magnitude of the oxygen gradient observed across the cell membrane.     

The little bacteria that can – diversity,genomics and ecophysiology of ‘Dehalococcoides’ spp. in contaminated environments

The fate and persistence of chlorinated organics in the environment have been a concern for the past 50 years. Industrialization and extensive agricultural activities have led to the accumulation of these pollutants in the environment, while their adverse impact on various ecosystems and human health also became evident. This review provides an update on the current knowledge of specialized anaerobic bacteria, namely ‘Dehalococcoides’ spp., which are dedicated to the transformation of various chlorinated organic compounds via reductive dechlorination. Advances in microbiology and molecular techniques shed light into the diversity and functioning of Dehalococcoides spp. in several different locations. Recent genome sequencing projects revealed a large number of genes that are potentially involved in reductive dechlorination. Molecular approaches towards analysis of diversity and expression especially of reductive dehalogenase-encoding genes are providing a growing body of knowledge on biodegradative pathways active in defined pure and mixed cultures as well as directly in the environment. Moreover, several successful field cases of bioremediation strengthen the notion of dedicated degraders such as Dehalococcoides spp. as key players in the restoration of contaminated environments.     

Capacitation suppression by mouse seminal vesicle autoantigen involves a decrease in plasma membrane Ca2+‐ATPase (PMCA)‐mediated intracellular calcium

Successful fertilization is tightly regulated by capacitation and decapacitation processes. Without appropriate decapacitation regulation, sperm would undergo a spontaneous acrosome reaction which leads to loss of fertilization ability. Seminal plasma is known to negatively regulate sperm capacitation. However, the suppressive mechanisms still remain unclear. In this study, we demonstrate the decapacitation mechanism of mouse seminal vesicle autoantigen (SVA) might target membrane sphingomyelin (SPM) and regulate plasma membrane Ca²⁺‐ATPase (PMCA) activity. The SVA was shown to suppress sperm capacitation induced by a broad panel of capacitation factors (bovine serum albumin (BSA), PAF, and cyclodextrin (CD)). Furthermore, SVA significantly decreased [Ca²⁺]_i and NaHCO₃‐induced [cAMP]_i. Cyclic AMP agonists bypassed the SVA's suppressive ability. Importantly, the SVA may regulate PMCA activity which was evidenced by the fact that the SVA decreased the [Ca²⁺]_i and intracellular pH (pH_i) of sperm; meanwhile, a PMCA inhibitor (carboxyeosin) could reverse SVA's suppression of [Ca²⁺]_i. The potential target of the SVA on membrane SPM/lipid rafts was highlighted by the high binding affinity of SPM–SVA (with a K_d of ～3 µM) which was close to the IC₅₀ of SVA's suppressive activity. Additionally, treatment of mink lung epithelial cells with the SVA enhanced plasminogen activator inhibitor (PAI)‐1 expression stimulated by tumor growth factor (TGF)‐β and CD. These observations supported the membrane lipid‐raft targeting of SVA. In summary, in this paper, we demonstrate that the decapacitation mechanism of the SVA might target membrane sphingolipid SPM and regulate PMCA activity to lower [Ca²⁺]_i, thereby decreasing the [cAMP]_i level and preventing sperm pre‐capacitation. J. Cell. Biochem. 111: 1188–1198, 2010. © 2010 Wiley‐Liss, Inc.     

苦荞麦麸皮的化学成分研究

从苦荞麦麸皮浸膏中分离得到7个化合物,经波谱分析确定结构分别为：β—谷甾醇(1)、过氧化麦角甾醇(2)、大黄素(3)、胡萝卜甙(4)、山奈酚(5)、异山奈酚(6)和槲皮素(7)。化合物1—6为首次从苦荞麦麸皮中分离得到。     

Localization of the Netherton syndrome gene to chromosome 5q32, by linkage analysis and homozygosity mapping

Netherton syndrome (NS [MIM 256500]) is a rare and severe autosomal recessive disorder characterized by congenital ichthyosis, a specific hair-shaft defect (trichorrhexis invaginata), and atopic manifestations. Infants with this syndrome often fail to thrive; life-threatening complications result in high postnatal mortality. We report the assignment of the NS gene to chromosome 5q32, by linkage analysis and homozygosity mapping in 20 families affected with NS. Significant evidence for linkage (maximum multipoint LOD score 10.11) between markers D5S2017 and D5S413 was obtained, with no evidence for locus heterogeneity. Analysis of critical recombinants mapped the NS locus between markers D5S463 and D5S2013, within an <3.5-cM genetic interval. The NS locus is telomeric to the cytokine gene cluster in 5q31. The five known genes encoding casein kinase Ialpha, the alpha subunit of retinal rod cGMP phosphodiesterase, the regulator of mitotic-spindle assembly, adrenergic receptor beta2, and the diastrophic dysplasia sulfate-transporter gene, as well as the 38 expressed-sequence tags mapped within the critical region, are not obvious candidates. Our study is the first step toward the positional cloning of the NS gene. This finding promises a better understanding of the molecular mechanisms that control epidermal differentiation and immunity.