Sphingolipid regulation of ezrin,radixin, and moesin proteins family: Implications for cell dynamics

A key but poorly studied domain of sphingolipid functions encompasses endocytosis, exocytosis, cellular trafficking, and cell movement. Recently, the ezrin, radixin and moesin (ERM) family of proteins emerged as novel potent targets regulated by sphingolipids. ERMs are structural proteins linking the actin cytoskeleton to the plasma membrane, also forming a scaffold for signaling pathways that are used for cell proliferation, migration and invasion, and cell division. Opposing functions of the bioactive sphingolipid ceramide and sphingosine-1-phosphate (S1P), contribute to ERM regulation. S1P robustly activates whereas ceramide potently deactivates ERM via phosphorylation/dephosphorylation, respectively. This recent dimension of cytoskeletal regulation by sphingolipids opens up new avenues to target cell dynamics, and provides further understanding of some of the unexplained biological effects mediated by sphingolipids. In addition, these studies are providing novel inroads into defining basic mechanisms of regulation and action of bioactive sphingolipids. This review describes the current understanding of sphingolipid regulation of the cytoskeleton, it also describes the biologies in which ERM proteins have been involved, and finally how these two large fields have started to converge. This article is part of a Special Issue entitled New Frontiers in Sphingolipid Biology.     

兼性CAM植物长叶景天叶片在C3和CAM型时的光氧化作用

通过停止浇水产生水分胁迫使兼性CAM植物长叶景天(Sedum spectabile Boreau)叶片光合途径由C3型转为CAM型.干旱15 d时观察到典型的CAM生理特征,且叶片的δ13C值与含水量成线性相关.水分胁迫改变了叶绿素荧光参数和抗氧化能力,ΦPSⅡ和qP降低50%和34%,NPQ提高约180%,SOD活性和清除DPPH@ 自由基能力也明显下降, 但膜半透性变化不大.当将处于C3(浇水)和诱导为CAM(缺水)型的叶圆片用外源甲基紫精(MV)和强光作光氧化处理后,与C3型叶片相比,诱导CAM型叶片的NPQ不能提高,qP和ΦPSⅡ降至很低水平,光系统处于高还原态,光能供给与消耗失衡(1-qP=0.86和(1-qP)/NPQ>1),膜系统几乎失去完整性.这种严重的光氧化损伤表明,与我们以前报告的专性CAM植物不同,以兼性CAM植物诱导表达的CAM型未能显示比C3型较强的耐光氧化优势.讨论了出现这种光氧化敏感性差别的可能原因.     

大气CO2浓度升高对八宝景天生长及光合生理的影响

利用开顶式气室(OTC)系统,设正常大气CO₂浓度和CO₂浓度升高200 μmol·mol^-12个CO₂浓度处理,模拟大气CO₂浓度升高对八宝景天光合生理和生长发育的影响.结果表明: 大气CO₂浓度升高使八宝景天叶片上、下表皮气孔密度分别显著下降16.1%和16.7%,使叶片维管束增粗,导管增多,靠近上表皮细胞增大;CO₂浓度升高可以显著增加傍晚时八宝景天叶片光合色素含量,使夜间净光合速率、气孔导度和蒸腾速率显著增加.初花期傍晚,CO₂浓度升高使叶片苹果酸含量显著下降64.0%,纤维素含量显著增加20.8%.盛花期清晨,CO₂浓度升高使叶片苹果酸含量显著增加27.0%,对糖类物质含量影响不显著,植株的分枝数、单株茎质量和单株总生物量显著增加.CO₂浓度升高可以促进八宝景天光合作用,有利于植株生长.     

14‐3‐3 Proteins regulate K2P5.1 surface expression on T lymphocytes

K_2P5.1 channels (also called TASK‐2 or Kcnk5) have already been shown to be relevant in the pathophysiology of autoimmune disease because they are known to be upregulated on peripheral and central T lymphocytes of multiple sclerosis (MS) patients. Moreover, overexpression of K_2P5.1 channels in vitro provokes enhanced T‐cell effector functions. However, the molecular mechanisms regulating intracellular K_2P5.1 channel trafficking are unknown so far. Thus, the aim of the study is to elucidate the trafficking of K_2P5.1 channels on T lymphocytes. Using mass spectrometry analysis, we have identified 14‐3‐3 proteins as novel binding partners of K_2P5.1 channels. We show that a non‐classical 14‐3‐3 consensus motif (R‐X‐X‐pT/S‐x) at the channel's C‐terminus allows the binding between K_2P5.1 and 14‐3‐3. The mutant K_2P5.1/S266A diminishes the protein‐protein interaction and reduces the amplitude of membrane currents. Application of a non‐peptidic 14‐3‐3 inhibitor (BV02) significantly reduces the number of wild‐type channels in the plasma membrane, whereas the drug has no effect on the trafficking of the mutated channel. Furthermore, blocker application reduces T‐cell effector functions. Taken together, we demonstrate that 14‐3‐3 interacts with K_2P5.1 and plays an important role in channel trafficking.      

GPCRs 组成性活性的研究进展及意义

GPCRs是体内最大的蛋白质亚家族,其活性涉及体内绝大部分重要的生理和病理进程。研究表明,GPCRs或其突变体能在无配体结合的情况下自发产生部分甚至完全活性程度的生理活性,称之为组成性活性。据此研究者提出了GPCRs激活过程中存在多个中间激活态的观点,从而丰富了配体受体相互作用的经典模型,并使组成性活性突变体(constitutive active mutant,CAM)成为研究GPCRs的新方法。本文系统介绍了组成性活性的研究历程,以及近年来利用CAM的方法研究GPCRs的结构、激活机制和活性调节的历程和进展,和体内组成性活性突变的成因和与疾病的关系,以及CAM在研究药物作用机理和新药研发中的意义。     

An Instruction on the In Vivo Shell-Less Chorioallantoic Membrane 3-Dimensional Tumor Spheroid Model

The traditional shell chicken chorioallantoic membrane (CAM) model has been used extensively in cancer research to study tumor growth and angiogenesis. Here we present a combined in vivo tumor spheroid and shell-less CAM three-dimensional model for use in quantitative and qualitative analysis. With this model, the angiogenic and tumorigenic environments can be generated locally without exogenous growth factors. This physiological model offers a stable, static and flat environment that features a large working area and wider field of view useful for imaging and biomedical engineering applications. The short experimental time frame allows for rapid data acquisition, screening and validation of biomedical devices. The method and application of this shell-less model are discussed in detail, providing a useful tool for biomedical engineering research.     

Considering the role of pyruvate in tumor cells during hypoxia

Impairment of oxygen supply occurs in many pathological situations. In the case of cancer, both chronic and acute hypoxic areas are found in the tumor. Tumor hypoxia is associated with poor clinical prognoses and is correlated with tumor growth and metastasis development.     

Evaluation of an Allosteric BACE Inhibitor Peptide to Identify Mimetics that Can Interact with the Loop F Region of the Enzyme and Prevent APP Cleavage

The aspartyl protease BACE1 (BACE) has emerged as an appealing target for reduction of amyloid-β in Alzheimer's disease. The clinical fate of active-site BACE inhibitors may depend on potential side effects related to enzyme and substrate selectivity. One strategy to reduce this risk is through development of allosteric inhibitors that interact with and modulate the Loop F region unique to BACE1. Previously, a BACE-inhibiting antibody (Ab) was shown by co-crystallization to bind and induce conformational changes of Loop F, resulting in backbone perturbations at the distal S6 and S7 subsites, preventing proper binding of a long APP-like substrate to BACE and inhibiting its cleavage. In an effort to discover small Loop F-interacting molecules that mimic the Ab inhibition, we evaluated a peptide series with a YPYF(I/L)P(L/Y) motif that was reported to bind a BACE exosite. Our studies show that the most potent inhibitor from this series, peptide 65007, has a similar substrate cleavage profile to the Ab and reduces sAPPβ levels in cell models and primary neurons. As our modeling indicates, it interacts with the Loop F region causing a conformational shift of the BACE protein backbone near the distal subsites. The peptide-bound enzyme adopts a conformation that closely overlays with the crystal structure (PDB: 3R1G) from Ab binding. Importantly, peptide 65007 appears to be BACE substrate and enzyme selective, showing little inhibition of NRG1, PSGL1, CHL1, or Cat D. Thus, peptide 65007 is a promising lead for discovery of Loop F-interacting small-molecule mimetics as allosteric inhibitors of BACE.