VGF及其衍生肽

神经肽VGF广泛存在于中枢神经系统和外周神经系统中,在垂体、肾上腺髓质、胃肠内分泌细胞和胰岛B细胞中亦有表达。神经细胞／内分泌细胞表达VGF多肽受到神经营养因子、神经元活性等因素的调控。目前证实,VGF及其衍生肽参与生物体的能量平衡、新陈代谢以及生殖发育等的凋节。在神经系统变性病及情感性精神障碍的相关研究也日益受到关注。本文就神经肽VGF及其衍生肽的生化、生理特性及病理生理作用做一综述。     

神经肽拮抗剂

由于肽的分离纯化、结构分析、化学合成、放射免疫、组织化学定位以及重组DNA等技术的应用,已发现的神经肽的数目与日俱增;但其中多数神经肽的生理功能尚不清楚,原因之一是缺乏特异性的拮抗剂。在神经系统中,神经肽可能起神经递质或神经调节物的作用;在神经内分泌、旁分泌及内分泌系统,又可能起激素的作用。神经肽拮抗剂能在受体水平阻断神经肽的作用,因而可用来推测神经肽在生理及病理状态下的功能;它们又可用于神经肽受体性质的研究以及受体亚型的分型。它们可能发展成为新型的诊断药或治疗药。     

高通量质谱法用于小鼠器官内源性肽的鉴定

内源性肽以细胞因子、生长激素、激素肽等形式在人体的内分泌、神经、细胞生长和生殖各个领域发挥功能。神经肽是一种内源性肽,与痛觉、睡眠、情绪、学习与记忆等生理活动相关,不但存在于脑部神经细胞,也存在于其他体液和器官内并发挥重要作用。目前对器官内源性肽的研究仍不足,尤其是其中的神经肽。文中应用液质联用串联质谱高通量鉴定胰腺、心脏、肝脏和肾脏中内源性肽的分布以及神经肽的种类。鉴定结果显示,在肝脏中内源性肽和神经肽的数目最多,而胰腺中最少;所鉴定到的内源性肽具有器官特异性,在4个器官中分别呈现不同的动态分布;4个器官中神经肽的LPV(最长肽变异体)数目差异较大,而且基因家族的分布也各不相同,比如胰腺中的神经肽多属于Glucagon家族,心脏中的神经肽分别属于ACBD7、Granins、PEBP等几个家族。鉴定结果将为疾病的机制研究和治疗药物的研发提供参考。     

调控型分泌的分子机制研究进展

调控型分泌途径对于维持内分泌细胞和神经元的功能非常重要。内分泌和神经系统的细胞将神经递质、神经肽和激素等包装在分泌囊泡内,然后在受到刺激时将这些物质释放到细胞外。调控型分泌囊泡,从生成、转运到与细胞膜的融合都需要许多蛋白质的参与和调节。简要总结参与这些过程的一些重要蛋白质的研究进展。     

高通量质谱法用于小鼠脑部神经肽的鉴定

神经肽在参与调控人体各种生理功能上发挥着重要的作用,如痛觉、睡眠、情绪、学习与记忆等生理活动都受到神经肽的影响。神经肽主要存在于机体的神经组织内,其他体液和器官中也有少量的分布。目前对全脑组织神经肽高通量鉴定的研究仍不足,高通量检测这些神经肽对了解神经肽的组成和功能具有重要的意义。本研究通过对小鼠全脑组织内源性肽段的萃取,运用液相串联质谱(LC-MS/MS)技术对全脑组织的神经肽进行检测,共鉴定到1 830条内源性肽段和99条预测神经肽肽段。这些内源性肽段的鉴定在疾病的治疗和机制研究以及药物的研发方面提供了参考价值,也为研究新的神经肽及其功能奠定了基础。     

下丘脑室旁核内雌激素受体的表达与意义

下丘脑室旁核 (paraventricularnucleus ,PVN)包括大细胞部、小细胞部和背侧帽部等几个部分 ,其中大细胞部主要合成催产素和加压素 ,小细胞部主要合成促肾上腺皮质激素释放激素、甘丙肽等多种神经肽。研究发现PVN的神经内分泌活动受到雌激素的调节 ,进而影响动物的分娩、摄食、脂肪代谢、体重增加等生理功能。雌激素有α和 β两种受体 (即ER α和ER β)。在不同种属动物的PNV内两种雌激素受体的表达水平不同 ,如大鼠PVN主要表达ER β ,而小鼠PVN内除了表达ER β以外也能表达少量ER α ,提示两种ER在不同动物的PVN内功能可能不同 ,它们单独或协同介导雌激素在PVN内参与多种肽能神经元有关的生理功能。     

胃肠内分泌学的新进展

本文对胃肠内分泌学的特点以及胃肠激素和肽类的化学、生理学的新进展作了简要的介绍。胃肠内分泌学近十余年来进展迅速,一些老激素的分离、提纯、阐明化学结构和人工合成,一些新激素和肽类的发现,使这一部分科学的面貌为之一新。胃肠激素和肽类是由个别地散处于胃肠道粘膜上皮细胞之间的内分泌细胞所分泌。由于胃肠道粘膜的面积特别大,胃肠内分泌细胞的总数超过机体所有其它内分泌细胞的总和,因而消化道粘膜被认为是机体内最大最复杂的内分泌器官。另一值得注意的现象是:有些存在于神经系统中的肽类,也在消化道内发现;而原先在消化道内发现的,现在也在神经系统中找到。此现象的生理意义,尚有待进一步明确。     

甲胎蛋白衍生肽作为抗原表位在肝癌免疫治疗中的作用

甲胎蛋白(AFP)作为一种肝癌诊断的标志物,一直受到人们的广泛关注。通过对AFP衍生肽的研究,已经发现AFP衍生肽作为抗原表位在肝癌的生长和发展过程中对T细胞有刺激作用。我们通过阐述AFP衍生肽抗原表位的分布及其对肝细胞癌中T细胞活动的影响,进一步说明AFP衍生肽作为抗原表位在肝癌免疫治疗中的作用。     

Galanin（甘丙肽）及其受体在成年小鼠脑内神舭部位的表达及对神经干细胞分化的作用

Galallin（甘丙肽）是一种在中枢神经系统中广泛分布的神经肽,功能涉及摄食、睡眠和觉醒、疼痛、认知和生殖等各方面。我们在成年小鼠脑的神经细胞新生部位如SVZ,DG和RMS发现有galanin及其受体的mRNA表达,同时在SVZ来源的神经干细胞中也检测到有galanin及其受体的表达。细胞实验中．在分化后特定时间段GALKO小鼠来源的神经干细胞产生神经突的细胞比例及神经突的长度明显小于正常小鼠来源的神经干细胞．而加入galanin或受体激动剂GAL2—11后．该神经干细胞则在产生神经突的细胞比例及神经突的长度都明显上升。受体拮抗剂M35的添加可减弱galanin或GAL2-11所产生的作用。这些结果表明galanin及其受体与神经干细胞的分化及神经突的生长有着密切的联系．并可能参与了神经系统的发育。     

动物进化中神经肽样物质和神经系统关系之探讨

用免疫组织化学方法,研究和追踪神经肽样物质在原生动物、水螅及蝾螈胚胎发育过程中分布的变化,试图探索在动物早期进化过程中神经肽样物质和神经系统之间的关系。实验结果表明：（1）从系统发育看神经肽样物质比神经系统先出现并行使在细胞内的功能。（2）在随后的进化中神经肽样物质先分布于非神经系统部位,如肠道外缘及表皮,并逐渐进入神经系统,这无论从系统发育和个体发育中都能找到依据。（3）在神经系统,神经肽样物质先出现在周边神经,之后;才出现在中枢神经,实验中表明NPY是随着神经嵴细胞的迁移而进入周边神经系统,之后,随着胶质细胞的出现而出现在中枢神经系统。（4）原生动物和蝾螈胚胎均由皮膜或表皮细胞中囊泡状结构直接分泌神经肽祥物质进入胞质内或细胞外。     

Isolation and characterization of VGF peptides in rat brain. Role of PC1/3 and PC2 in the maturation of VGF precursor

The neurotrophin responsive gene vgf is widely expressed in central and peripheral neurones, and in certain neuroendocrine cell populations. Its encoded VGF precursor protein (proVGF1: 617 amino acids in rat, 615 in man, > 85% homology) gives rise to several low molecular weight species. We studied a range of neuroendocrine and neuronal cells, in which VGF-processing products were prominent with an apparent molecular weight of 20 and 10 kDa (VGF20 and VGF10, respectively). Such peptides were recognized by antibodies specific for the C-terminal rat VGF nonapeptide, thus indicating that they included the C-terminus of proVGF. Ectopic expression of the neuroendocrine-specific prohormone convertases PC1/3 or PC2 in GH3 cells showed that both could generate VGF20, while VGF10 was preferentially produced by PC1/3. Site-directed mutagenesis was used to identify the KRKRKK(488) motif as the target within VGF sequence which leads to the production of VGF20. Molecular characterization of rat VGF10, on the other hand, revealed that this peptide is produced by cleavage at the RPR(555) site. By the combined use of high-resolution separation techniques, matrix-assisted laser desorption/ionization time of flight (MALDI-ToF) mass spectrometry and manual Edman degradation we identified in rat brain a VGF fragment analogous to bovine peptide V and two novel peptides also derived from the C-terminal region of proVGF.     

VGF metabolic-related gene: distribution of its derived peptides in mammalian pancreatic islets.

The vgf gene has been shown to be involved in several metabolic pathways. Because the pancreas is crucial to metabolism and food intake, we studied the VGF peptides in bovine, rat, and pig Langherans islets using antisera raised against specific sites along the primary sequence of the rat/mouse and human VGF protein precursor. Whereas almost all of the pancreatic endocrine cells expressed vgf mRNA, when using the VGF antisera a different staining pattern became apparent. VGF(556-565) and VGF(282-291) immunoreactivity were exclusively found in delta somatostatin-producing cells, whereas the human C-terminus antiserum selectively immunolabeled alpha glucagon and pancreatic polypeptide cells. The same cells were decorated with the VGF(443-588) antiserum, which also weakly labeled beta insulin-secreting cells. Finally, the VGF(298-306) peptide and the rat C terminus were found in virtually all pancreatic endocrine cells. Using bovine, swine, and rat pancreatic extracts, data from chromatography and ELISA assay showed the presence of a high molecular mass form compatible with the proVGF and lower molecular mass fractions corresponding to short VGF peptides. In conclusion, selective VGF distribution may suggest a multifaceted cell type-specific processing of proVGF, resulting in different peptides probably involved in neuroendocrine regulatory metabolic mechanisms.     

Nucleotide Sequence and Regulatory Studies of VGF, a Nervous System-Specific mRNA That Is Rapidly and Relatively Selectively Induced by Nerve Growth Factor

A nervous system-specific mRNA that is rapidly induced in PC12 cells to a greater extent by nerve growth factor (NGF) than by epidermal growth factor treatment has been cloned. The polypeptide deduced from the nucleic acid sequence of the NGF33.1 cDNA clone contains regions of amino acid sequence identity with that predicted by the cDNA clone VGF, and further analysis suggests that both NGF33.1 and VGF cDNA clones very likely correspond to the same mRNA (VGF). In this report both the nucleic acid sequence that corresponds to VGF mRNA and the polypeptide predicted by the NGF33.1 cDNA clone are presented. Genomic Southern analysis and database comparison did not detect additional sequences with high homology to the VGF gene. Induction of VGF mRNA by depolarization and phorbol 12-myristate 13-acetate treatment was greater than by serum stimulation or protein kinase A pathway activation. These studies suggest that VGF mRNA is induced to the greatest extent by NGF treatment and that VGF is one of the most rapidly regulated neuronal mRNAs identified in PC12 cells.     

Immune cells express endocrine markers

Evidence are now given that immune cells expressed endocrine markers like neuropeptides, biogenic amine, neuropeptide processing enzymes, regulated secretion pathway. In clear, immune cells expressed like the nervous system an endocrine phenotype. This give the following question: what can we now consider as immune or endocrine?     

A mosquito neuropeptide in a moth larva (Helicoverpa zea): relation to FMRF-amide immunoreactivity.

The cerebral nervous and midgut endocrine systems of the larval corn earworm, Helicoverpa zea, were examined using light microscopy and immunocytochemistry for RF-amide family peptides. Immunoreactivity for a mosquito neuropeptide, Aedes Head Peptide-I (Aea-HP-I,pERPhPSLKTRFa), is widely distributed in this lepidopteran. Immunostaining for Aea-HP-I is localized (1a) in perikarya and axons of the brain, the subesophageal ganglion, and the first thoracic ganglion, (b) in peripheral axons innervating muscles of the midgut, and (2) in numerous midgut endocrine cells. Aea-HP-I-associated activity generally occurs as a subset of FMRF-amide (FMRFa; a molluscan cardioactive peptide) immunoreactivity. Cross-reactivity studies indicate that Aea-HP-I and FMRFa immunoreactivities are heterogeneous in the cerebral nervous system and in axons innervating the muscles of the midgut, but may be homogeneous in midgut endocrine cells. Radioimmunoassay for Aea-HP-I reveals immunoreactivity in hemolymph, as well as in extracts of midguts and heads.