Epidermal growth factor receptor and notch pathways participate in the tumor suppressor function of gamma-secretase

Gamma-secretase, a unique aspartyl protease, is required for the regulated intramembrane proteolysis of Notch and APP, pathways that are implicated, respectively, in the pathogenesis of cancer and Alzheimer disease. However, the mechanism whereby reduction of gamma-secretase causes tumors such as squamous cell carcinoma (SCC) remains poorly understood. Here, we demonstrate that gamma-secretase functions in epithelia as a tumor suppressor in an enzyme activity-dependent manner. Notch signaling is down-regulated and epidermal growth factor receptor (EGFR) is activated in SCC caused by genetic reduction of gamma-secretase. Moreover, the level of EGFR is inversely correlated with the level of gamma-secretase in fibroblasts, suggesting that the up-regulation of EGFR stimulates hyperproliferation in epithelia of mice with genetic reduction of gamma-secretase. Supporting this notion is our finding that the proliferative response of fibroblasts lacking gamma-secretase activity is more sensitive when challenged by either EGF or an inhibitor of EGFR as ompared with wild type cells. Interestingly, the up-regulation of EGFR is independent of Notch signaling, suggesting that the EGFR pathway functions in parallel with Notch in the tumorigenesis of SCC. Collectively, our results establish a novel mechanism linking the EGFR pathway to the tumor suppressor role of gamma-secretase and that mice with genetic reduction of gamma-secretase represent an excellent rodent model for clarifying pathogenesis of SCC and for testing therapeutic strategy to ameliorate this type of human cancer.     

科尔沁草甸生态系统水分利用效率及影响因素

生态系统水分利用效率(WUE)是衡量碳水循环耦合程度的重要指标。利用科尔沁温带草甸草地碳水通量观测数据,对该生态系统总初级生产力水分利用效率(WUEGPP)的日季变化规律及对环境和生理因子的响应进行分析。结果表明:(1)WUEGPP日变化呈下降-稳定-上升的变化趋势,最大值出现在日出后1—2 h,阴天条件下WUEGPP高于晴天,生长中期WUEGPP高于生长初期和末期;(2)总初级生产力、总蒸散和WUEGPP季节变化均呈夏季高、春秋低的形式,生长季平均值分别为0.57 mg m-2s-1、0.08 g m-2s-1和5.97 mg/g,最大值分别为1.49 mg m-2s-1、0.16 g m-2s1和13.62 mg/g;(3)总初级生产力与饱和差、气温和叶面积指数均呈二次曲线关系,与冠层导度呈对数曲线关系;总蒸散与气温呈二次曲线关系,与饱和差、叶面积指数和冠层导度相关性均不显著;(4)WUEGPP与饱和差、气温和叶面积指数均呈二次曲线关系,与冠层导度呈对数曲线关系,饱和差、冠层导度和叶面积指数分别为2.0 k Pa、0.0015 m/s和4.2是控制WUEGPP增加的阈值;(5)净生态系统生产力水分利用效率(WUENEP)和净初级生产力水分利用效率(WUENPP)季节变化规律与WUEGPP一致,均值分别为3.47和5.47 mg/g。     

A dye mixture (Neurobiotin and Alexa 488) reveals extensive dye-coupling among neurons in leeches; physiology confirms the connections

Although the neuronal circuits that generate leech movements have been studied for over 30 years, the list of interneurons (INs) in these circuits remains incomplete. Previous studies showed that some motor neurons (MNs) are electrically coupled to swim-related INs, e.g., rectifying junctions connect IN 28 to MN DI-1 (dorsal inhibitor), so we searched for additional neurons in these behavioral circuits by co-injecting Neurobiotin and Alexa Fluor 488 into segmental MNs DI–1, VI–2, DE–3 and VE–4. The high molecular weight Alexa dye is confined to the injected cell, whereas the smaller Neurobiotin molecules diffuse through gap junctions to reveal electrical coupling. We found that MNs were each dye-coupled to approximately 25 neurons, about half of which are likely to be INs. We also found that (1) dye-coupling was reliably correlated with physiologically confirmed electrical connections, (2) dye-coupling is unidirectional between MNs that are linked by rectifying connections, and (3) there are novel electrical connections between excitatory and inhibitory MNs, e.g. between excitatory MN VE-4 and inhibitory MN DI-1. The INs found in this study provide a pool of novel candidate neurons for future studies of behavioral circuits, including those underlying swimming, crawling, shortening, and bending movements.     

小麦TaMlo基因的原核表达、抗体制备及细胞化学分析(简报)

白粉病菌(Blumeria graminis)是一类高度专化性的寄生真菌,可侵染650多种单子叶植物和 9000多种双子叶植物,能够引起多种麦类作物的白粉病,给农业生产带来巨大的损失。由于白粉病菌生理小种多、变异快,所以利用专化性抗病基因难以解决植物的持久抗病性问题。人们在研究大麦白粉病时．发现大麦Mlo基因的隐性突变可导致大麦对绝大多数白粉病菌生理小种的高效持久的广谱抗病性。Schulze-Lefert等多家实验室合作于1997年成功克隆了野生的 Mlo基因。进一步研究表明．该基因编码一种植物特有的具有7个跨膜区和羧基端长尾的膜蛋白(Mlo),它可能对植物细胞的坏死起负调控作用。但Mlo基因如何表达及其在白粉病菌发育中的作用机制尚不清楚。     

Targeted overexpression of inducible 6-phosphofructo-2-kinase in adipose tissue increases fat deposition but protects against diet-induced insulin resistance and inflammatory responses

Increasing evidence demonstrates the dissociation of fat deposition, the inflammatory response, and insulin resistance in the development of obesity-related metabolic diseases. As a regulatory enzyme of glycolysis, inducible 6-phosphofructo-2-kinase (iPFK2, encoded by PFKFB3) protects against diet-induced adipose tissue inflammatory response and systemic insulin resistance independently of adiposity. Using aP2-PFKFB3 transgenic (Tg) mice, we explored the ability of targeted adipocyte PFKFB3/iPFK2 overexpression to modulate diet-induced inflammatory responses and insulin resistance arising from fat deposition in both adipose and liver tissues. Compared with wild-type littermates (controls) on a high fat diet (HFD), Tg mice exhibited increased adiposity, decreased adipose inflammatory response, and improved insulin sensitivity. In a parallel pattern, HFD-fed Tg mice showed increased hepatic steatosis, decreased liver inflammatory response, and improved liver insulin sensitivity compared with controls. In both adipose and liver tissues, increased fat deposition was associated with lipid profile alterations characterized by an increase in palmitoleate. Additionally, plasma lipid profiles also displayed an increase in palmitoleate in HFD-Tg mice compared with controls. In cultured 3T3-L1 adipocytes, overexpression of PFKFB3/iPFK2 recapitulated metabolic and inflammatory changes observed in adipose tissue of Tg mice. Upon treatment with conditioned medium from iPFK2-overexpressing adipocytes, mouse primary hepatocytes displayed metabolic and inflammatory responses that were similar to those observed in livers of Tg mice. Together, these data demonstrate a unique role for PFKFB3/iPFK2 in adipocytes with regard to diet-induced inflammatory responses in both adipose and liver tissues.     

Effect of luteal-phase support on endometrial microRNA expression following controlled ovarian stimulation

ABSTRACT: BACKGROUND: Studies suggested that microRNAs influence cellular activities in the uterus including cell differentiation and embryo implantation. In assisted reproduction cycles, luteal phase support, given to improve endometrial characteristics and to facilitate the implantation process, has been a standard practice. The effect of different types of luteal phase support using steroid hormones in relation to endometrial miRNA profiles during the peri-implantation period has not seen described. This study was designed to evaluate the expression of miRNAs during the luteal phase following controlled ovarian stimulation for IVF and the influence of different luteal phase support protocols on miRNA profiles. METHODS: The study was approved by the Johns Hopkins Hospital Institutional Review Board. Endometrial biopsies were obtained on the day of oocyte retrieval from 9 oocyte donors (group I). An additional endometrial biopsy was obtained 3-5 days later (Group II) after the donors were randomized into three groups. Group IIa had no luteal-phase support, group IIb had luteal support with micronized progesterone (P), and Group IIc had luteal support with progesterone plus 17-beta-estradiol (P+E). Total RNA was isolated and microarray analysis was performed using an Illumina miRNA expression panel. RESULTS: A total of 526 miRNAs were identified. Out of those, 216 miRNAs were differentially regulated (p<0.05) between the comparison groups. As compared to the day of retrieval, 19, 11 and 6 miRNAs were differentially regulated more than 2 fold in the groups of no support, in the P support only, and in the P+E support respectively, 3-5 days after retrieval. During the peri-implantation period (3-5 days after retrieval) the expression of 33 and 6 miRNAs increased, while the expression of 3 and 0 miRNAs decreased, in the P alone and in the P+E group respectively as compared to the no steroid supplementation group. CONCLUSION: Luteal support following COS has a profound influence on miRNA profiles. Up or down regulation of miRNAs after P or P+E support suggest a role(s) of luteal support in the peri-implantation uterus in IVF cycles through the regulation of associated target genes.     

BALB/c mice produce blister-causing antibodies upon immunization with a recombinant human desmoglein 3

Pemphigus vulgaris (PV) is an Ab-mediated autoimmune blistering disease of mucotaneous surfaces. Over 95% of the patients with PV express DR4 or DRw6, and the disease is characterized by the presence of autoantibodies directed against desmoglein 3 (Dsg 3), a protein expressed on keratinocytes. An appropriate animal model is required to understand immunoregulation and to address the role of immunogenetic components in the production of pathogenic Abs that are characteristic of PV. Therefore, we turned to the development of a mouse model. Four strains of female mice (BALB/c, DBA/1, SJL/J, and HRS/J) were screened for their ability to produce pathogenic anti-Dsg 3 Abs. We demonstrated that only BALB/c mice immunized with a full-length Dsg 3 can produce pathogenic Abs capable of causing acantholysis of human foreskin in culture and blistering in neonatal mice. This observation suggested that either H-2d or the BALB background contains the immunogenetic makeup necessary for the production of pathogenic anti-Dsg 3 Abs. No correlation was noted between a given isotype and the pathogenic potential of autoantibodies from different strains of mice. Similarly, the pattern of reactivity of Abs with a panel of 46 synthetic peptides that span the entire Dsg 3 failed to reveal any association between binding specificity and the pathogenic potential, and suggested that pathogenic Abs might recognize conformational epitopes. Moreover, our studies showed that the epitopes recognized by pathogenic Abs are contained within the extracellular Dsg 3.     

Mitochondrial glycerol-3-phosphate acyltransferase-1 is essential for murine CD4 T cell metabolic activation

Glycerol-3-phosphate acyltransferase-1 is the first rate limiting step in de novo glycerophospholipid synthesis. We have previously demonstrated that GPAT-1 deletion can significantly alter T cell function resulting in a T cell phenotype similar to that seen in aging. Recent studies have suggested that changes in the metabolic profile of T cells are responsible for defining specific effector functions and T cell subsets. Therefore, we determined whether T cell dysfunction in GPAT-1 ^−/− CD4⁺ T cells could be explained by changes in cellular metabolism. We show here for the first time that GPAT-1 ^−/− CD4⁺ T cells exhibit several key metabolic defects. Striking decreases in both the oxygen consumption rate (OCR) and the extracellular acidification rate (ECAR) were observed in GPAT-1 ^−/− CD4⁺ T cells following CD3/CD28 stimulation indicating an inherent cellular defect in energy production. In addition, the spare respiratory capacity (SRC) of GPAT-1 ^−/− CD4 + T cells, a key indicator of their ability to cope with mitochondrial stress was significantly decreased. We also observed a significant reduction in mitochondrial membrane potential in GPAT-1 ^−/− CD4⁺ T cells compared to their WT counterparts, indicating that GPAT-1 deficiency results in altered or dysfunctional mitochondria. These data demonstrate that deletion of GPAT-1 can dramatically alter total cellular metabolism under conditions of increased energy demand. Furthermore, altered metabolic response following stimulation may be the defining mechanism underlying T cell dysfunction in GPAT-1 ^−/− CD4⁺ T cells. Taken together, these results indicate that GPAT-1 is essential for the response to the increased metabolic demands associated with T cell activation.