BSKs mediate signal transduction from the receptor kinase BRI1 in Arabidopsis

Brassinosteroids (BRs) bind to the extracellular domain of the receptor kinase BRI1 to activate a signal transduction cascade that regulates nuclear gene expression and plant development. Many components of the BR signaling pathway have been identified and studied in detail. However, the substrate of BRI1 kinase that transduces the signal to downstream components remains unknown. Proteomic studies of plasma membrane proteins lead to the identification of three homologous BR-signaling kinases (BSK1, BSK2, and BSK3). The BSKs are phosphorylated by BRI1 in vitro and interact with BRI1 in vivo. Genetic and transgenic studies demonstrate that the BSKs represent a small family of kinases that activate BR signaling downstream of BRI1. These results demonstrate that BSKs are the substrates of BRI1 kinase that activate downstream BR signal transduction.     

Brassinosteroids regulate dissociation of BKI1, a negative regulator of BRI1 signaling, from the plasma membrane

Brassinosteroids, the steroid hormones of plants, are perceived at the plasma membrane by a leucine-rich repeat receptor serine/threonine kinase called BRI1. We report a BRI1-interacting protein, BKI1, which is a negative regulator of brassinosteroid signaling. Brassinosteroids cause the rapid dissociation of BKI1-yellow fluorescent protein from the plasma membrane in a process that is dependent on BRI1-kinase. BKI1 is a substrate of BRI1 kinase and limits the interaction of BRI1 with its proposed coreceptor, BAK1, suggesting that BKI1 prevents the activation of BRI1.     

植物LRR类受体蛋白激酶的研究进展

植物中富亮氨酸重复片断类受体蛋白激酶(LRR RLK)属于跨膜类受体蛋白激酶,由胞外LRR结构域、单次跨膜区以及胞内激酶结构域三部分组成。在不同植物中,LRR RLK作为信号识别受体参与CLV、BR、Ax21等信号转导过程,在植物生长发育、激素调节以及逆境应答反应等方面中发挥重要的作用。综述了近年来LRR RLK的相关调控功能及其作用机制的研究进展,并为进一步探索LRR RLK的功能及应用提供参考。     

油菜素内酯参与调控植物生长发育与抗逆性的机制及其育种应用研究

油菜素内酯（brassinosteroids,BRs）是一类重要的植物促生激素,参与调控植物生长发育。最近的研究表明,BRs能增加作物产量和增强作物抗逆性。在BRs信号转导过程中,蛋白激酶的磷酸化功能与转录因子的磷酸化和脱磷酸化过程是BRs信号重要的生化调控机制,其中起始BRs信号由胞外向胞内转导的蛋白激酶BRI1和 BAK1,以及BRs信号下游调控不同性状基因表达的转录因子BZR1和BZR2/BES1,是BRs信号途径中关键的功能基因。基于重要蛋白激酶和转录因子的蛋白结构和功能分析,通过不同氨基酸功能位点的基因定点突变和修饰技术,能实现BRs信号途径的功能研究与植物性状改良,从而提高植物对环境的适应性。综述了BRs信号途径与植物生长发育和环境胁迫的研究,期望为植物分子育种提供很好的借鉴。     

水稻富亮氨酸类受体蛋白激酶参与外界胁迫应答的研究进展

水稻是我国重要的粮食作物,随着外界环境条件的恶化和降水的减少,水稻生产遭到严重威胁。植物类受体蛋白激酶作为一种对植物生长发育激素信号转导以及生物与非生物胁迫反应中具有重要调控功能的膜蛋白,目前已成为研究的热点之一。该文对富亮氨酸类受体蛋白激酶的结构和功能以及水稻富亮氨酸类受体蛋白激酶家族与外界环境胁迫的关系进行了综述,以期为探究水稻LRK基因家族与外界环境关系提供参考。     

Essential cytoplasmic translocation of a cytokine receptor-assembled signaling complex

Cytokine signaling is thought to require assembly of multicomponent signaling complexes at cytoplasmic segments of membrane-embedded receptors, in which receptor-proximal protein kinases are activated. Indeed, CD40, a tumor necrosis factor receptor (TNFR) family member, forms a complex containing adaptor molecules TRAF2 and TRAF3, ubiquitin-conjugating enzyme Ubc13, cellular inhibitor of apoptosis proteins 1 and 2 (c-IAP1/2), IkappaB kinase regulatory subunit IKKgamma (also called NEMO), and mitogen-activated protein kinase (MAPK) kinase kinase MEKK1 upon ligation. TRAF2, Ubc13, and IKKgamma were required for complex assembly and activation of MEKK1 and MAPK cascades. However, these kinases were not activated unless the multicomponent signaling complex translocated from CD40 to the cytosol upon c-IAP1/2-induced degradation of TRAF3. This two-stage signaling mechanism may apply to other innate immune receptors, accounting for spatial and temporal separation of MAPK and IKK signaling.     

Role of the kinase MST2 in suppression of apoptosis by the proto-oncogene product Raf-1

The ablation of the protein kinase Raf-1 renders cells hypersensitive to apoptosis despite normal regulation of extracellular signal-regulated kinases, which suggests that apoptosis protection is mediated by a distinct pathway. We used proteomic analysis of Raf-1 signaling complexes to show that Raf-1 counteracts apoptosis by suppressing the activation of mammalian sterile 20-like kinase (MST2). Raf-1 prevents dimerization and phosphorylation of the activation loop of MST2 independently of its protein kinase activity. Depletion of MST2 from Raf-1-/- mouse or human cells abrogated sensitivity to apoptosis, whereas overexpression of MST2 induced apoptosis. Conversely, depletion of Raf-1 from Raf-1+/+ mouse or human cells led to MST2 activation and apoptosis. The concomitant depletion of both Raf-1 and MST2 prevented apoptosis.     

云南3种野生稻中抗病基因同源序列的克隆及序列分析

 根据已报道的NBS LRR类和STK类抗病基因结构中的氨基酸保守区域 ,设计简并引物 ,通过PCR扩增及克隆 ,从普通野生稻 (OryzarufipogonGriff.)、药用野生稻 (OryzaofficinalisWall.)、疣粒野生稻 (Oryzameye rianaBaill.)中共获得 14类NBS LRR类抗病基因同源序列 ,其中普通野生稻中的有 7类 ,药用野生稻中的有 2类 ,疣粒野生稻中的有 6类。药用野生稻中TO12代表序列与普通野生稻中TR19代表序列 ,同属一类 ,且具有 10 0 %的同源性 ,说明不同种野生稻中的同一类 (聚类 )抗病基因同源序列是完全一致的。同时 ,还获得 5类STK类抗病基因同源序列 ,其中普通野生稻中的有 4类 ;药用野生稻中的有 1类。通过氨基酸同源性比较分析 ,发现笔者克隆到的抗病基因同源序列与已克隆的抗病基因L6、N、Bs2、Prf、Pto、Lr10和Xa2 1等的氨基酸同源性都相当低 (均低于 2 5 % ) ,暗示了这些抗病基因同源序列可能是目前尚未报道的抗病基因的同源序列。     

MAP激酶在植物信号传递网络中的功能

促分裂素原活化蛋白激酶(mitogen-activated protein kinases,MAP激酶,MAPK)链是真核生物信号传递网络中的重要途径之一.MAPK链由3类蛋白激酶MAP3K-MAP2K-MAPK组成,通过依次磷酸化将上游信号传递至下游应答分子.本文主要阐述MAPK链在植物的逆境反应、抗病反应和激素调控等信号传递网络中的功能.     

Structure of nerve growth factor complexed with the shared neurotrophin receptor p75

Neurotrophins are secreted growth factors critical for the development and maintenance of the vertebrate nervous system. Neurotrophins activate two types of cell surface receptors, the Trk receptor tyrosine kinases and the shared p75 neurotrophin receptor. We have determined the 2.4 A crystal structure of the prototypic neurotrophin, nerve growth factor (NGF), complexed with the extracellular domain of p75. Surprisingly, the complex is composed of an NGF homodimer asymmetrically bound to a single p75. p75 binds along the homodimeric interface of NGF, which disables NGF's symmetry-related second p75 binding site through an allosteric conformational change. Thus, neurotrophin signaling through p75 may occur by disassembly of p75 dimers and assembly of asymmetric 2:1 neurotrophin/p75 complexes, which could potentially engage a Trk receptor to form a trimolecular signaling complex.     

Keeping G proteins at bay: a complex between G protein-coupled receptor kinase 2 and Gbetagamma

The phosphorylation of heptahelical receptors by heterotrimeric guanine nucleotide-binding protein (G protein)-coupled receptor kinases (GRKs) is a universal regulatory mechanism that leads to desensitization of G protein signaling and to the activation of alternative signaling pathways. We determined the crystallographic structure of bovine GRK2 in complex with G protein beta1gamma2 subunits. Our results show how the three domains of GRK2-the RGS (regulator of G protein signaling) homology, protein kinase, and pleckstrin homology domains-integrate their respective activities and recruit the enzyme to the cell membrane in an orientation that not only facilitates receptor phosphorylation, but also allows for the simultaneous inhibition of signaling by Galpha and Gbetagamma subunits.     

水稻蛋白激酶OsCIPK5的亚细胞定位分析及RNAi转基因水稻的获得

在植物生长发育中,CIPKs(CBL-interacting protein kinases)在胁迫信号转导和增强抗逆途径中发挥着重要作用,而OsCIPK5的具体功能还未知。为了研究OsCIPK5的功能,本研究从日本晴水稻中成功克隆了OsCIPK5基因。用生物信息学方法对其编码的蛋白进行分析,结果表明OsCIPK5含有2个功能区即激酶活性区和NAF区,OsCIPK5与5种植物的CIPK5同源性较高,而与短花药野生稻CIPK5的同源性最高(94%),亲缘关系最近。利用植物生理学方法对水稻进行低钾处理,结果表明水稻根中OsCIPK5受低钾诱导表达,而叶片中OsCIPK5表达量没有变化;同时构建了OsCIPK5与黄色荧光蛋白基因融合的植物瞬时表达载体,共聚焦显微镜观察显示,OsCIPK5编码的蛋白主要定位在细胞核、细胞膜,还以颗粒状结构不规则分布在细胞质中。进一步构建了OsCIPK5的RNAi载体,通过水稻遗传转化体系获得26株阳性转基因水稻。荧光定量PCR(Real-time qPCR)分析表明,T1代转基因水稻中OsCIPK5的表达量与野生型相比显著降低。OsCIPK5的生物信息学分析、植物生理学分析、亚细胞定位以及RNAi转基因水稻的获得为研究OsCIPK5的功能奠定了基础。     

An insulin-stimulated protein kinase similar to yeast kinases involved in cell cycle control

A protein kinase characterized by its ability to phosphorylate microtubule-associated protein-2 (MAP2), is thought to be an early intermediate in an insulin-stimulated phosphorylation cascade and in a variety of other mammalian cell responses to extracellular signals. A complementary DNA that encodes this protein serine-threonine kinase has been cloned, and the protein designated extracellular signal-regulated kinase 1 (ERK1). ERK1 has striking similarity to two protein kinases, KSS1 and FUS3, from yeast. The yeast kinases function in an antagonistic manner to regulate the cell cycle in response to mating factors. Thus, ERK1 and the two yeast kinases constitute a family of evolutionarily conserved enzymes involved in regulating the response of eukaryotic cells to extracellular signals.     

Requirement for Tec kinases Rlk and Itk in T cell receptor signaling and immunity

T cell receptor (TCR) signaling requires activation of Zap-70 and Src family tyrosine kinases, but requirements for other tyrosine kinases are less clear. Combined deletion in mice of two Tec kinases, Rlk and Itk, caused marked defects in TCR responses including proliferation, cytokine production, and apoptosis in vitro and adaptive immune responses to Toxoplasma gondii in vivo. Molecular events immediately downstream from the TCR were intact in rlk-/-itk-/- cells, but intermediate events including inositol trisphosphate production, calcium mobilization, and mitogen-activated protein kinase activation were impaired, establishing Tec kinases as critical regulators of TCR signaling required for phospholipase C-gamma activation.     

植物抗病基因类似序列的研究进展及应用策略

植物抗病基因克隆对抗病育种和抗病机制的研究具有重要意义。对已克隆出的基因研究表明,大多数的抗病基因都具有高度保守的结构域(如NBS,LRR,LZ,STK和TIR等)。根据这些保守区域设计核苷酸引物,通过PCR技术已经获得很多的RGA,然后以此为探针筛选DNA或cDNA文库,最终可获得抗病基因的候选克隆,这就是新近发展起来的同源序列克隆技术。文章简述了对抗病基因的结构特征,同源序列克隆技术及其应用策略。     

Brassinosteroid signaling: a paradigm for steroid hormone signaling from the cell surface

Plants use the coordinated action of several small-molecule hormones to grow and develop optimally in response to a changing environment. Among these hormones are the brassinosteroids (BRs), the polyhydroxylated steroid hormones of plants. BRs bind a small family of leucine-rich repeat receptor kinases at the cell surface, thereby initiating an intracellular signal transduction cascade that results in the altered expression of hundreds of genes.     

Four-jointed is a Golgi kinase that phosphorylates a subset of cadherin domains

The atypical cadherin Fat acts as a receptor for a signaling pathway that regulates growth, gene expression, and planar cell polarity. Genetic studies in Drosophila identified the four-jointed gene as a regulator of Fat signaling. We show that four-jointed encodes a protein kinase that phosphorylates serine or threonine residues within extracellular cadherin domains of Fat and its transmembrane ligand, Dachsous. Four-jointed functions in the Golgi and is the first molecularly defined kinase that phosphorylates protein domains destined to be extracellular. An acidic sequence motif (Asp-Asn-Glu) within Four-jointed was essential for its kinase activity in vitro and for its biological activity in vivo. Our results indicate that Four-jointed regulates Fat signaling by phosphorylating cadherin domains of Fat and Dachsous as they transit through the Golgi.     

高脂日粮对初情期小鼠乳腺发育的影响及分子机制

【目的】研究高脂日粮对初情期小鼠乳腺发育的影响及可能机制。【方法】选用20只4周龄昆明雌性小鼠,设对照组和高脂日粮组,试验期4周,每周称体质量并统计采食量。试验结束后采集小鼠乳腺并称质量,采用wholemount及HE染色观察小鼠乳腺组织形态结构及导管数量。利用Western blot检测初情期小鼠乳腺组织胰岛素样生长因子1(Insulin-like growth factor1,IGF-1)、增殖相关信号通路关键蛋白蛋白激酶B(Protein kinase B,Akt)、胞外调控的蛋白激酶(Extracellular regulated protein kinase,Er K)以及炎症信号通路关键蛋白Toll样受体4(Toll-like receptor 4,TLR4)、c-Jun氨基末端激酶(c-Jun N-terminal kinase,JNK)和核因子κB激酶抑制剂(Inhibitor of nuclear factor kappa-B kinase,IKK)的表达。【结果】高脂日粮组小鼠采食量极显著低于对照组(P0.01),但在能量摄入方面与对照组无显著差异。高脂日粮组小鼠的体质量增加显著高于对照组(P0.05)。高脂日粮组小鼠在乳腺质量、乳腺质量与体质量的比值上均极显著高于对照组(P0.01)。乳腺组织的whole-mount及HE染色结果表明,高脂日粮组小鼠乳腺导管发育明显被抑制,其乳腺组织的导管数和密度明显降低,乳腺组织的终末乳芽数量也极显著低于对照组(P0.01)。高脂日粮能够显著抑制小鼠乳腺组织IGF-I的蛋白表达以及Akt、Erk和IKK的磷酸化水平(P0.01或0.05),极显著促进小鼠乳腺组织TLR4的蛋白表达(P0.01)和显著促进JNK的磷酸化水平(P0.05)。【结论】高脂日粮能够抑制初情期小鼠乳腺发育,这可能是通过抑制乳腺增殖的相关信号和促进乳腺组织炎症的相关信号来实现。     

The phosphothreonine lyase activity of a bacterial type III effector family

Pathogenic bacteria use the type III secretion system to deliver effector proteins into host cells to modulate the host signaling pathways. In this study, the Shigella type III effector OspF was shown to inactivate mitogen-activated protein kinases (MAPKs) [extracellular signal-regulated kinases 1 and 2 (Erk1/2), c-Jun N-terminal kinase, and p38]. OspF irreversibly removed phosphate groups from the phosphothreonine but not from the phosphotyrosine residue in the activation loop of MAPKs. Mass spectrometry revealed a mass loss of 98 daltons in p-Erk2, due to the abstraction of the alpha proton concomitant with cleavage of the C-OP bond in the phosphothreonine residue. This unexpected enzymatic activity, termed phosphothreonine lyase, appeared specific for MAPKs and was shared by other OspF family members.