Gustducin is a taste-cell-specific G protein closely related to the transducins.

A novel G protein alpha-subunit (alpha-gustducin) has been identified and cloned from taste tissue. alpha-Gustducin messenger RNA is expressed in taste buds of all taste papillae (circumvallate, foliate and fungiform); it is not expressed in non-sensory portions of the tongue, nor is it expressed in the other tissues examined. alpha-Gustducin most closely resembles the transducins (the rod and cone photoreceptor G proteins), suggesting that gustducin's role in taste transduction is analogous to that of transducin in light transduction.     

The development of taste transduction and taste chip technology

Taste is one of important sensations. The primary taste sensations commonly are categorized as sweet, acid, bitter, salty and umami, of which various tastes are composed. The sensation of taste is initiated by the interaction of tas- tants with receptors and ion channels in the apical micro- villi of taste receptor cells (TRCs) when some sapid molecules (tastants) dissolve in saliva. Subsequently, through a cellular signaling pathway (TRC depolarization and Ca2+ release) gustatory signals a…     

黑鲷化学感觉发育和摄食关系

研究了黑鲷（Ｓｐａｒｕｓｍａｃｒｏｃｅｐｈａｌｕｓ）仔、稚、幼鱼嗅觉和味觉器官的基本结构及嗅觉、味觉与摄食的关系，初孵仔鱼的嗅囊很小、很浅，细胞没有分化。５ｄ的嗅囊细胞开始分化，２４ｄ嗅囊分化完毕，嗅觉开始功能化，参与摄食反应。初孵仔鱼味蕾没分化，５ｄ的仔鱼味蕾分化形成，参与摄食反应。随发育的进行，先后从口咽腔、头部、躯干、尾部、鳍等处依次出现味蕾。嗅觉和味觉是鱼类的化学感觉，嗅觉可以对远、近距离的食物发生反应，而味觉只能对接触的或几乎接触的食物发生反应。化学感觉对摄食的作用是对黑暗条件下视觉摄食的补充。     

小熊猫舌粘膜和口腔粘膜的组织学研究

小熊猫的舌粘膜由角化的复层扁平上皮和固有层构成，无粘膜肌层．舌腹面粘膜平滑，未形成舌乳头．舌背面的粘膜特化为舌乳头．舌乳头有丝状乳头、菌状乳头和轮廓乳头几种，未见典型的叶状乳头．味腺仅分布于轮廓乳头和舌根部位，主要由粘液性腺泡组成．硬腭粘膜形成光滑的弓形腭褶．软腭和口腔底部粘膜的固有层内有发达的腺体，几乎全是粘液性腺泡．     

Odorant-sensitive adenylate cyclase may mediate olfactory reception

The mechanism of the sense of smell has long been a subject for theory and speculation. More recently, the notion of odorant recognition by stereospecific protein receptors has gained wide acceptance, but the receptor molecules remained elusive. The recognition molecules are believed to be quite diverse, which would partly explain the unusual difficulties encountered in their isolation by conventional ligand-binding techniques. An alternative approach would be to probe the receptors through transductory components that may be common to all receptor types. Here we report the identification of one such transductory molecular component. This is an odorant-sensitive adenylate cyclase, present in very large concentrations in isolated dendritic membranes of olfactory sensory neurones. Odorant activation of the enzyme is ligand and tissue specific, and occurs only in the presence of GTP, suggesting the involvement of receptor(s) coupled to a guanine nucleotide binding protein (G-protein). The olfactory G-protein is independently identified by labelling with bacterial toxins, and found to be similar to stimulatory G-proteins in other systems. Our results suggest a role for cyclic nucleotides in olfactory transduction, and point to a molecular analogy between olfaction and visual, hormone and neurotransmitter reception. Most importantly, the present findings reveal new ways to identify and isolate olfactory receptor proteins.     

The S-locus receptor kinase is inhibited by thioredoxins and activated by pollen coat proteins

The self-incompatibility response in Brassica allows recognition and rejection of self-pollen by the stigmatic papillae. The transmembrane S-locus receptor kinase (SRK), a member of the receptor-like kinase superfamily in plants, mediates recognition of self-pollen on the female side, whereas the S-locus cysteine-rich protein (SCR) is the male component of the self-incompatibility response. SCR is presumably located in the pollen coat, and is thought to be the SRK ligand. Although many receptor-like kinases have been isolated in plants, the mechanisms of signal transduction mediated by these molecules remain largely unknown. Here we show that SRK is phosphorylated in vivo within one hour of self-pollination. We also show that, in vitro, autophosphorylation of SRK is prevented by the stigma thioredoxin THL1 in the absence of a ligand. This inhibition is released in a haplotype-specific manner by the addition of pollen coat proteins. Our data indicate that SRK is inhibited by thioredoxins and activated by pollen coat proteins.     

Rapid kinetics of second messenger formation in olfactory transduction

Olfactory transduction is thought to be mediated by a membrane-bound receptor protein initiating a multistep reaction cascade which ultimately leads to a depolarizing generator current. There is considerable evidence for the involvement of adenylate cyclase in vertebrate olfactory transduction, and some data indicate that phospholipase C may have a central role in insect olfaction. However, one must show that odorants not only stimulate enzyme activity but also induce changes in concentrations of relevant second messengers. One important criterion for a candidate second messenger of chemo-electrical transduction is that its formation must precede the onset of the odorant-induced membrane permeability changes which proceed on a subsecond time-scale. Here we report an odorant-induced, transient accumulation of cyclic AMP in isolated olfactory cilia from rats, and the generation of inositol trisphosphate in antennal preparations from insects, both of which show subsecond time courses that are sufficiently rapid to mediate the odorant-regulated permeability of olfactory receptor cells.     

Hyperpolarization-activated channels HCN1 and HCN4 mediate responses to sour stimuli.

Sour taste is initiated by protons acting at receptor proteins or channels. In vertebrates, transduction of this taste quality involves several parallel pathways. Here we examine the effects of sour stimuli on taste cells in slices of vallate papilla from rat. From a subset of cells, we identified a hyperpolarization-activated current that was enhanced by sour stimulation at the taste pore. This current resembled Ih found in neurons and cardio-myocytes, a current carried by members of the family of hyperpolarization-activated and cyclic-nucleotide-gated (HCN) channels. We show by in situ hybridization and immunohistochemistry that HCN1 and HCN4 are expressed in a subset of taste cells. By contrast, gustducin, the G-protein involved in bitter and sweet taste, is not expressed in these cells. Lowering extracellular pH causes a dose-dependent flattening of the activation curve of HCN channels and a shift in the voltage of half-maximal activation to more positive voltages. Our results indicate that HCN channels are gated by extracellular protons and may act as receptors for sour taste.     

TRPA1 is a candidate for the mechanosensitive transduction channel of vertebrate hair cells

Mechanical deflection of the sensory hair bundles of receptor cells in the inner ear causes ion channels located at the tips of the bundle to open, thereby initiating the perception of sound. Although some protein constituents of the transduction apparatus are known, the mechanically gated transduction channels have not been identified in higher vertebrates. Here, we investigate TRP (transient receptor potential) ion channels as candidates and find one, TRPA1 (also known as ANKTM1), that meets criteria for the transduction channel. The appearance of TRPA1 messenger RNA expression in hair cell epithelia coincides developmentally with the onset of mechanosensitivity. Antibodies to TRPA1 label hair bundles, especially at their tips, and tip labelling disappears when the transduction apparatus is chemically disrupted. Inhibition of TRPA1 protein expression in zebrafish and mouse inner ears inhibits receptor cell function, as assessed with electrical recording and with accumulation of a channel-permeant fluorescent dye. TRPA1 is probably a component of the transduction channel itself.     

LysM蛋白在植物免疫中的作用

溶解素基序（LysM）是在多种蛋白质中普遍存在的结构域.植物LysM蛋白能够感知几丁质及其寡糖等分子配体，从而启动植物对病原菌的免疫反应.在水稻、拟南芥等植物免疫应答过程中，LysM蛋白作为一种重要的模式识别受体，通过不同形式的寡聚化，激活多种类受体胞质激酶及其下游的MAPK（mitogen activated protein kinase）级联反应传递信号.同时，蛋白质可逆磷酸化和蛋白质降解途径可以负调节LysM蛋白介导的防御信号转导.文章综述了植物免疫过程中LysM蛋白介导的信号转导分子机制.     

嗅觉与感觉信息整合

 嗅觉作为重要的化学感官,对生命的生存和繁衍起着重要作用。本文阐述了嗅觉感觉的发生,说明了嗅觉在社会信息交流和媒介情绪中发挥独特作用,分析了嗅觉与其他感觉通道进行信息整合,构建了人脑对环境的生动表征。未来仍需进一步研究揭示嗅觉与感觉信息整合更为完整深入的图景。     

Cyclic nucleotides may mediate taste transduction

Taste stimulus adsorption is believed to occur at the taste cell microvillous membrane. But due to technical difficulties of inserting glass electrodes into the mammalian taste cell, little is known about the mechanisms of taste transduction. Reliable intracellular recordings are necessary to determine the characteristics of taste cells. This has been accomplished previously in the mouse and is reported here. Recent experiments indicated that cyclic nucleotides can act on the inner surface of the membranes of a variety of cells to alter their ion-channel activity, and these substances might act as intracellular transmitters in taste cells. But tight junctions found at the apical membrane of mammalian taste cells do not allow stimuli to enter the taste bud, making it difficult to alter the environment of the taste cell by perfusing with chemical solutions. Here we report that cyclic AMP, cyclic GMP, EGTA or tetraethyl-ammonium electrophoretically injected into the mouse taste cell induce membrane depolarization and increased membrane resistance. These results suggest that a cyclic nucleotide enzymatic cascade, modulated by calcium ions, may mediate the potassium permeability that controls taste, in a way analogous to visual and olfactory transduction.     

Molecular basis of mechanosensory transduction

Mechanotransduction - a cell's conversion of a mechanical stimulus into an electrical signal - reveals vital features of an organism's environment. From hair cells and skin mechanoreceptors in vertebrates, to bristle receptors in flies and touch receptors in worms, mechanically sensitive cells are essential in the life of an organism. The scarcity of these cells and the uniqueness of their transduction mechanisms have conspired to slow molecular characterization of the ensembles that carry out mechanotransduction. But recent progress in both invertebrates and vertebrates is beginning to reveal the identities of proteins essential for transduction.     

The bcl-2 gene encodes a novel G protein

Little is known about the biochemical or functional nature of the proteins encoded by the bcl-2 gene, which undergoes chromosomal translocation in approximately 85% of follicular lymphoma, 20% of diffuse large cell lymphoma and 10% of chronic lymphocytic leukaemia of B cells. Translocation of bcl-2 sequences from chromosome 18 to the JH segment of the immunoglobulin gene at chromosome band 14q32 in B cells results in deregulated expression of this gene, causing high steady state levels of bcl-2 messenger RNA2. DNA sequence data indicate that bcl-2 encodes two proteins by virtue of alternative splicing, designated as Bcl-2 alpha and Bcl-2 beta, with relative molecular masses of 26,000 and 22,000 respectively. Cell fractionation experiments indicate that the bcl-2 alpha gene product is located at the inner surface of the cell membrane, suggesting a possible role in mitogenic signal transduction. We report here that Bcl-2 alpha has GTP-binding activity and a protein sequence that suggests it belongs to the small molecular weight GTP-binding protein (G protein) family.     

Stimulation of specific GTP binding and hydrolysis activities in lymphocyte membrane by interleukin-2

Interleukin-2 (IL-2) is a polypeptide growth factor which stimulates the proliferation and differentiation of T lymphocytes. The receptor for IL-2 is expressed on activated T lymphocytes, cloned IL-2 dependent cells and several other cell types. Analysis of the primary structure and of immune-precipitated receptor suggests that this molecule has no intrinsic signal transduction function, unlike other growth factors. IL-2 interaction with a high affinity receptor has been shown, however, to activate the calcium/phospholipid-dependent protein kinase C (PK-C) presumably via phosphoinositide hydrolysis. Members of a family of closely related guanine nucleotide binding proteins (G proteins) regulate a diverse group of metabolic events. Two of them, Gs and Gi, stimulate and inhibit adenylate cyclase activity respectively, and other G proteins are involved in diverse signal transduction system. Another member, Go, has no known function and activation of phospholipase C has been attributed to the action of an unidentified G protein, Gp. Since it has been observed that IL-2 inhibits the catalytic activity of adenylate cyclase and that agents such as PGE2 which stimulate adenylate cyclase activity inhibit the lymphoproliferative response to IL-2, association of GTP binding proteins with IL-2 signal transduction was investigated. In this report we describe for the first time the participation of a GTP binding protein in the action of a polypeptide growth factor, interleukin-2.     

癌症相关促凋亡蛋白Par-4的信号转导途径预测研究

利用支持向量机(SVM)技术构建Par-4关联的蛋白质相互作用网络,预测出与Par-4有相互作用的蛋白质82个;这些蛋白质按照功能划分为8大类,主要包括:蛋白激酶、泛素化蛋白酶、死亡受体相关因子、与细胞周期或DNA复制相关蛋白质、调节蛋白质、与疾病相关蛋白质、具有特定结构域结合蛋白质和其他蛋白质等。结合文献挖掘和数据库检索信息,推断出了Par-4的2条可能新的信号转导途径。首次预测到Par-4与一大类泛素化蛋白有密切的关系。研究发现,Par-4与多种蛋白质具有复杂的相互作用,并且,在多个细胞凋亡途径中扮演了重要角色。     

arrow encodes an LDL-receptor-related protein essential for Wingless signalling

The Wnt family of secreted molecules functions in cell-fate determination and morphogenesis during development in both vertebrates and invertebrates (reviewed in ref. 1). Drosophila Wingless is a founding member of this family, and many components of its signal transduction cascade have been identified, including the Frizzled class of receptor. But the mechanism by which the Wingless signal is received and transduced across the membrane is not completely understood. Here we describe a gene that is necessary for all Wingless signalling events in Drosophila. We show that arrow gene function is essential in cells receiving Wingless input and that it acts upstream of Dishevelled. arrow encodes a single-pass transmembrane protein, indicating that it may be part of a receptor complex with Frizzled class proteins. Arrow is a low-density lipoprotein (LDL)-receptor-related protein (LRP), strikingly homologous to murine and human LRP5 and LRP6. Thus, our data suggests a new and conserved function for this LRP subfamily in Wingless/Wnt signal reception.     

A family of candidate taste receptors in human and mouse

The gustatory system of mammals can sense four basic taste qualities, bitter, sweet, salty and sour, as well as umami, the taste of glutamate. Previous studies suggested that the detection of bitter and sweet tastants by taste receptor cells in the mouth is likely to involve G-protein-coupled receptors. Although two putative G-protein-coupled bitter/sweet taste receptors have been identified, the chemical diversity of bitter and sweet compounds leads one to expect that there is a larger number of different receptors. Here we report the identification of a family of candidate taste receptors (the TRBs) that are members of the G-protein-coupled receptor superfamily and that are specifically expressed by taste receptor cells. A cluster of genes encoding human TRBs is located adjacent to a Prp gene locus, which in mouse is tightly linked to the SOA genetic locus that is involved in detecting the bitter compound sucrose octaacetate. Another TRB gene is found on a human contig assigned to chromosome 5p15, the location of a genetic locus (PROP) that controls the detection of the bitter compound 6-n-propyl-2-thiouracil in humans.     

果蝇NOMPC相互作用蛋白的筛选与鉴定

NOMPC是果蝇感受触觉的机械力敏感离子通道,属于瞬时受体电位(TRP)离子通道家族,机械力敏感离子通道通过怎样的机制被机械力激活?与NOMPC相互作用的蛋白有哪些?为了研究这些问题,本研究从果蝇NOMPC全长cDNA中扩增得到其N端的29个锚蛋白重复序列(ARs),ORF长度为3 039bp.然后将这29个ARs构建到表达载体pUAST-EGFP上,转染果蝇S2细胞后,通过免疫沉淀、质谱分析和Western blot筛选和鉴定NOMPC相互作用的蛋白,实验筛选出NOMPC N端的29ARs和NOMPC全长的相互作用蛋白,通过免疫共沉淀(Co-IP)实验,对可能与NOMPC存在相互作用的蛋白质进行验证,鉴定出Annexin B9、CG3195、CG3731、CG5374与NOMPC存在相互作用,为进一步研究NOMPC介导触觉转导的分子机制提供了基础.